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Posted: 6/6/2024 8:18:40 AM EDT
[#1]
Quote HistoryQuoted: OK, yes I did miss where you stated "new piston". So I should disassemble an engine that runs, and has only ran a couple minutes at the most? That doesn't make any sense to me. @AR15Texan Quote HistoryQuoted: Quoted: Quoted: Quoted: That piston is awful. Did you do a compression test? Did you take the head and cylinder off and check the new piston's condition? Did you check the condition of the reeds? Did you install new reeds? If the reeds don't seal correctly the scavenging won't work right. Did you confirm the jets were the correct ones? Is there an intake boot between the carburetor and the reed cage? What is its condition? Did you miss this portion of the OP?: Quoted: So I get the bike, go thru everything, rebuilt the top end, clean the carb, etc, I'll spare you the gritty details. This isn't my first rodeo, and I'm picky when I do these builds/rebuilds The piston in the pics is the piston that was in it before I rebuilt the top end. I'm the one who put in the new piston. I verified piston to cylinder specs from the piston manufacturer. Verified ring end gap twice. Reeds are new and met spec. The jetting is set to the baseline spec of the dynojet kit. The intake boot is a new OEM installed my me and is fine. This engine has not been run on the road yet. I'm trying to eliminate any possible issues before I run it down the road. As far as I'm concerned, the first issue is eliminating the exhaust leak. Which is why I asked about stacking gaskets. Once I have the exhaust leak fixed, then I can move on to eliminating the slight bog at idle and get it on the road to finish jetting the carb. No, I didn't miss it, but you missed this: "Did you take the head and cylinder off and check the new piston's condition?" Why go through any more diagnosis and throwing parts at it if you smoked yet another piston. Best of luck with it OK, yes I did miss where you stated "new piston". So I should disassemble an engine that runs, and has only ran a couple minutes at the most? That doesn't make any sense to me. @AR15Texan Yes you should. If you suspect the same problem still exists that destroyed the last piston then how long of a run time do you think it takes to ruin a new piston. And you're on your way to splitting the case anyways. |
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Posted: 6/6/2024 8:21:54 AM EDT
[#2]
Anytime I'm working on a two stroke my first order of business is to plug all opening and pressure test the engine to check the crank seals and the case halves for air leaks. Start there.
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Posted: 6/6/2024 11:15:53 AM EDT
[#3]
Quote HistoryQuoted: So, which is it? If the factory didn't use any type of stupid RTV on parts you certainly shouldn't when you rebuild it, very simple. Quote HistoryQuoted: Quoted: Avoid aftermarket seals and gaskets and stick to cast pistons. Seal the exhaust with high temp RTV besides the gasket. Leaking a little is not a big deal. So, which is it? If the factory didn't use any type of stupid RTV on parts you certainly shouldn't when you rebuild it, very simple. What Jeff said. Also, there are aftermarket gaskets and seals that are OEM quality and better, and not from China. I typically take the numbers off seals and bearing and get the same as OEM at a lower price. I've used Wiseco forged pistons in previous 2-stroke (and 4-stroke) builds over the years with no issues. |
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Posted: 6/6/2024 11:17:28 AM EDT
[#4]
Quote HistoryQuoted: Sounds like you need to fix the leak, I despise rtv. What does the plug read for fuel mixture? Did you pressure test your engine after rebuild? Haven't gotten to the point of jetting yet. No, not yet. |
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Posted: 6/6/2024 11:19:45 AM EDT
[#5]
Quote HistoryQuoted: If it is a split case, did you check the bottom end for leaks? No leaks I can see at the case seams, but it's only ran for a couple minutes so far since I found the exhaust leak. |
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Posted: 6/6/2024 11:22:15 AM EDT
[#6]
Quote HistoryQuoted: Certainly not you, it was more of a general statement about when people are selling a bike and proudly tell you it's been rebuilt. I have always asked to see receipts. Bike wasn't sold to me, it was brought to me for repair. Last time it was rebuilt was 20 years ago, he didn't have any receipts, and he couldn't remember who did the work. The guy who rebuilt it probably isn't in the business anymore and wouldn't remember this project after that amount of time anyway. |
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Posted: 6/6/2024 11:31:20 AM EDT
[#7]
Quote HistoryQuoted: You obviously know more than a lot people about 2 strokes and have covered pretty much everything I can think of. With everything you have done I would be looking at crank seals for the leak. I don't think the exhaust is the cause. Quote HistoryQuoted: You obviously know more than a lot people about 2 strokes and have covered pretty much everything I can think of. With everything you have done I would be looking at crank seals for the leak. I don't think the exhaust is the cause. Quoted: Sounds like crank seals. The extra smoke can be crank oil Keep a eye on crank oil fill. I had that issue on a kx65 Dammit beat Quoted: +1 for crank seals. I'd have replaced those at the rebuild. I will be keeping an eye on the crankcase oil level, this bike just has a cap no dipstick (OEM), so I'm going to try a Honda dipstick if it fits the threads just so I can monitor the oil level, either that or I'll come up with a homemade dipstick for that purpose. I didn't do a full rebuild, just the top end. Crank seals were replaced in the previous build, they used Yamabond on the seal O.D. to seal bore surface, that's not factory. Crank seals are in mint condition and looked brand new, can be replaced without tearing down the engine. ETA: I'll need to come up with a way to seal the exhaust flange. It's a threaded collar style fitting, not a flat flange with the ball/socket style. I'm thinking a flat piece of medium thick rubber cut to the I.D. of the threaded collar, similar to the ex gasket, but no hole in the middle, will do the trick. Intake side will be easy. How many PSI do I pump the cylinder up to? |
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Posted: 6/6/2024 12:10:41 PM EDT
[#8]
Quote HistoryQuoted: No leaks I can see at the case seams, but it's only ran for a couple minutes so far since I found the exhaust leak. Quote HistoryQuoted: Quoted: If it is a split case, did you check the bottom end for leaks? No leaks I can see at the case seams, but it's only ran for a couple minutes so far since I found the exhaust leak. Pretty sure he's talking about the crank seals leaking and sucking air and not the transmission leaking. |
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Posted: 6/6/2024 12:39:39 PM EDT
[#9]
Quote HistoryQuoted: Does it sputter when it bogs? Rich. Bogs down like lack of fuel no sputter? Lean. But now to figure out WHY it is this way. Lots of case seal recommendations, exhaust leak should be an easy fix, check carb boots for cracks. Reed valves for sealing. 32:1 sounds a bit much for modern oils. Is the bogging better or worse with the choke on vs off? That might help diagnose. ETA: I did not read every response. Yup, know all of this. 32:1 is the factory manual specified ratio and I used the factory manual specified oil. |
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Posted: 6/6/2024 12:42:40 PM EDT
[#10]
Quote HistoryQuoted: Pretty sure he's talking about the crank seals leaking and sucking air and not the transmission leaking. Quote HistoryQuoted: Quoted: Quoted: If it is a split case, did you check the bottom end for leaks? No leaks I can see at the case seams, but it's only ran for a couple minutes so far since I found the exhaust leak. Pretty sure he's talking about the crank seals leaking and sucking air and not the transmission leaking. A crankcase seam can leak once someone else has had it apart. Since others have covered crank seals and wildearp specified split case, I covered the other option. 
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Posted: 6/6/2024 1:06:19 PM EDT
[#11]
Educate me...
Are the last few seconds of sputtering when an engine is intentionally run out of fuel enough to cause excessively lean type damage over time? Or does it have to go for some time before? |
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Posted: 6/6/2024 1:57:34 PM EDT
[#12]
The piston looks horrible. Very lean and not enough oil. The aftermarket pipe might be a suspect. You can't use stock jetting with a different pipe. I'd get a big fat jet in there, then work my way back down.
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Posted: 6/6/2024 1:59:54 PM EDT
[#13]
are there any mods that can effectively make 2-stroke engines quieter?
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Posted: 6/6/2024 2:08:13 PM EDT
[#14]
I have seen pistons like that and 90% of the time it was because they have been out on backwards or ring not gapped correctly, since its piston ported I would lean towards not gapped ring.
Red rtv is your friend with exhaust leaks |
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Posted: 6/6/2024 2:11:17 PM EDT
[#15]
Quote HistoryQuoted: Educate me... Are the last few seconds of sputtering when an engine is intentionally run out of fuel enough to cause excessively lean type damage over time? Or does it have to go for some time before? I would say no, only due to my experience in the construction trades and years of myself and others running 2-stroke equipment out of fuel repeatedly, year after year, without killing an engine. The equipment I saw killed was when someone, usually a rookie, put unmixed fuel in the tank. Yes, we always had clearly marked fuel cans. I think most of those guys were Millennials....... 
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Posted: 6/6/2024 2:17:54 PM EDT
[#16]
Quote HistoryQuoted: I have seen pistons like that and 90% of the time it was because they have been out on backwards or ring not gapped correctly, since its piston ported I would lean towards not gapped ring. Red rtv is your friend with exhaust leaks The toasted piston was correctly oriented when I disassembled the engine. I can't verify what the ring gap was, I didn't put it together the first time. I can however guarantee that the new piston is properly oriented and the rings are properly gapped, and verified twice. |
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Posted: 6/6/2024 2:36:55 PM EDT
[#17]
Quote HistoryQuoted: are there any mods that can effectively make 2-stroke engines quieter? The factory exhaust on any of the 2-stroke ATVs I've owned was fairly quiet, like stock Polaris Sportsman and Trail Boss. Hell, even the stock pipe on my Polaris 400 Scrambler is pretty quiet. FMF sells this. I have no idea how well it works.: FMF Q Stealth silencer Modifying the muffler, installing a spark arrestor. I've been told, but never heard one modified like this, that a section of inner tube slipped over the end of the pipe and hanging 8-10 inches down off of the end of the pipe works.   ETA: Then there's homemade:  Homemade Db Killer |
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Posted: 6/6/2024 2:41:15 PM EDT
[#18]
I would look at the crank seals. I had an engine on an 89 CR 80 that had new crank seals installed.
Never could get it to run right. Bog, low power, plug fouling. Come to find out, I had nicked the deal ir it was defective. Changed that one seal, and boom. Fixed all the problems. Check the case halves, and crank seals. |
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Posted: 6/6/2024 3:08:33 PM EDT
[#19]
Quote HistoryQuoted: Yup, I know that, thanks. Followed the Yamaha pre-mix guidelines pertqaining to type of oil and amount measure with a 2 stroke oil measuring cup, no guessing. Carb was rebuilt with a dynojet kit, jetted per manufacturers instructions for this engine. I have not driven this bike yet. It has only been run in a couple of short cycles to verify that it would start at first, now I'm making sure that this exhaust leak is corrected before I move ahead to tuning the carb. Quote HistoryQuoted: Quoted: Also, regarding fuel:oil mix… “richer” mix i.e. greater oil concentration leans out the air:fuel ratio, so ensure it’s jetted for the pre-mix ratio you are running. Yup, I know that, thanks. Followed the Yamaha pre-mix guidelines pertqaining to type of oil and amount measure with a 2 stroke oil measuring cup, no guessing. Carb was rebuilt with a dynojet kit, jetted per manufacturers instructions for this engine. I have not driven this bike yet. It has only been run in a couple of short cycles to verify that it would start at first, now I'm making sure that this exhaust leak is corrected before I move ahead to tuning the carb. Didn't you say it had a special pipe on it? Those "kits" just get you close....I've never used one that still didn't need some adjustment in the jetting and/or needle position. Altitude/temps/oil ratio all affect jetting. |
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Posted: 6/6/2024 3:18:20 PM EDT
[#20]
Quote HistoryQuoted: Didn't you say it had a special pipe on it? Those "kits" just get you close....I've never used one that still didn't need some adjustment in the jetting and/or needle position. Altitude/temps/oil ratio all affect jetting. Quote HistoryQuoted: Quoted: Quoted: Also, regarding fuel:oil mix… “richer” mix i.e. greater oil concentration leans out the air:fuel ratio, so ensure it’s jetted for the pre-mix ratio you are running. Yup, I know that, thanks. Followed the Yamaha pre-mix guidelines pertqaining to type of oil and amount measure with a 2 stroke oil measuring cup, no guessing. Carb was rebuilt with a dynojet kit, jetted per manufacturers instructions for this engine. I have not driven this bike yet. It has only been run in a couple of short cycles to verify that it would start at first, now I'm making sure that this exhaust leak is corrected before I move ahead to tuning the carb. Didn't you say it had a special pipe on it? Those "kits" just get you close....I've never used one that still didn't need some adjustment in the jetting and/or needle position. Altitude/temps/oil ratio all affect jetting. Yes, you are correct sir. Proper jetting procedure is a PITA, but necessary. Gonna seal up that exhaust leak first. The pipe is from a place called Team Calamari, and they specialize(d) in these pit bikes for a long time. It appears they are revamping the website. |
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Posted: 6/6/2024 4:17:40 PM EDT
[#21]
Quote HistoryQuoted: are there any mods that can effectively make 2-stroke engines quieter? I've seen stealth exhaust parts for wheelers that are used for hunting but have no experience with them. I've repacked a couple silencers on older 2-strokes but not even sure if newer ones use the same type of packing. Not many manufacturers even make a 2-stroke anymore. Husky, KTM, Beta and maybe Yamaha might be the only ones left. I don't think Honda has made a 2-stroke in 12 or 15 years. Silencer Packing |
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Posted: 6/6/2024 4:23:31 PM EDT
[#22]
Quote HistoryQuoted: Gonna seal up that exhaust leak first. Post a pic of where it's leaking and someone will probably come up with a solution. |
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Posted: 6/6/2024 5:03:12 PM EDT
[#23]
Quote HistoryQuoted: Post a pic of where it's leaking and someone will probably come up with a solution. I had several options for sealing the leak before I posted the thread, the purpose of the thread was the question: "Would a leak like this cause the engine to burn down like it did?" There have been some proposed solutions, but my belief was and is, and as another poster pointed out: "If they didn't use RTV from the factory, it shouldn't need it now". I'm going to try double stacking OEM gaskets first, I also have some longer than OEM crushable exhaust gaskets I can try if needed. |
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Posted: 6/7/2024 8:10:30 AM EDT
[#24]
Quote HistoryQuoted: I had several options for sealing the leak before I posted the thread, the purpose of the thread was the question: "Would a leak like this cause the engine to burn down like it did?" No. There have been some proposed solutions, but my belief was and is, and as another poster pointed out: "If they didn't use RTV from the factory, it shouldn't need it now". Correct. I'm going to try double stacking OEM gaskets first, I also have some longer than OEM crushable exhaust gaskets I can try if needed. I've been building 2 t's for +-40 years, but never this one. That old piston is very troubling. If it only ran a few minutes, I'm betting the exhaust port didn't get chamfered. Does the exhaust port have a bridge? If so see "exhaust bridge lube holes". |
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Posted: 6/7/2024 8:25:48 AM EDT
[#25]
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Posted: 6/7/2024 9:47:10 AM EDT
[#26]
Quote HistoryQuoted: This. I've been building 2 t's for +-40 years, but never this one. That old piston is very troubling. If it only ran a few minutes, I'm betting the exhaust port didn't get chamfered. Does the exhaust port have a bridge? If so see "exhaust bridge lube holes". There was a definite increase in the amount of exhaust port chamfer when I got it back from my machinist.
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Posted: 6/7/2024 9:47:40 AM EDT
[#27]
Quote HistoryQuoted: I know a guy that's in to them in a big way. https://www.ar15.com/media/mediaFiles/279984/Rotary_valve_jpg-3234569.JPG That's impressive! |
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Posted: 6/7/2024 10:12:04 AM EDT
[#28]
Quote HistoryQuoted: I have no idea. I have no information on who rebuilt the engine 20 years ago or what was done, nor do I have a factory an OEM un-modified cylinder to compare to, so I have to start right from scratch. Since you know nothing about what was done, and don’t have any idea what the problem is why don’t you take it to a motorcycle mechanic who works on dirt bikes and pay them to fix the errors of multiple people not knowing what is going on? |
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Posted: 6/7/2024 10:55:50 AM EDT
[#29]
Quote HistoryQuoted: Since you know nothing about what was done, and don’t have any idea what the problem is why don’t you take it to a motorcycle mechanic who works on dirt bikes and pay them to fix the errors of multiple people not knowing what is going on? Quote HistoryQuoted: Quoted: I have no idea. I have no information on who rebuilt the engine 20 years ago or what was done, nor do I have a factory an OEM un-modified cylinder to compare to, so I have to start right from scratch. Since you know nothing about what was done, and don’t have any idea what the problem is why don’t you take it to a motorcycle mechanic who works on dirt bikes and pay them to fix the errors of multiple people not knowing what is going on? Because the going shop rate around here is $125-$150/hour plus parts. Because I've been doing this for decades. It saves me money and makes me money. It's fun, challenging, tests my skills, I learn new skills, and it's very satisfying when the engine that I got as junk is up and running again. Even more so if the engine has been modified like this one to have more power and go faster than the original design, even if it's only 50cc's. I've never had this issue with an exhaust leak on a 2-stroke so I was looking for knowledge. Contrary to popular belief, there is some intelligence in GD.   I've repaired or rebuilt everything from weed whips and push mowers to Harleys and other motorcycles, three wheelers and ATVs, Harley transmissions, manual car and truck transmissions, automotive engines, etc. Hell, once I even got a washing machine from 1915 repaired and running for a little old neighbor lady that belonged to her mother. The smile on her face when she saw it running again was well worth the moderate effort it took to get it running. Identical machine to this one: The biggest benefit is if I'm on the road or on the trail and there's an issue, I can fix it there and not have to be towed out of the woods or hauled home. We've also never had any kind of repairman in this house. I've researched, diagnosed, and repaired any of the appliance issues we've had since we built this home almost 30 years ago, saving us more money. That's why. 
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Posted: 6/7/2024 11:00:37 AM EDT
[#30]
Looks like a cold seizure to me. The bike wasn’t warmed up properly and the piston expanded faster than the cylinder.
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Posted: 6/8/2024 9:50:12 AM EDT
[#31]
Quote HistoryQuoted: Yes, you are correct sir. Proper jetting procedure is a PITA, but necessary. Gonna seal up that exhaust leak first. The pipe is from a place called Team Calamari, and they specialize(d) in these pit bikes for a long time. It appears they are revamping the website. Team Calamari are really good people-I spent a weekend with the owner and her partner who also worked there back in ‘94. Suzan is retired now, but those folks really know small bore two strokes. |
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Posted: 6/8/2024 9:51:33 AM EDT
[#32]
Quote HistoryQuoted: I know a guy that's in to them in a big way. https://www.ar15.com/media/mediaFiles/279984/Rotary_valve_jpg-3234569.JPG RS125 or shifter kart engine? |
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Posted: 6/8/2024 10:05:04 AM EDT
[#33]
Quote HistoryQuoted: RS125 or shifter kart engine? It's for some sort of franken bike he is building. All his projects involve motorcycles, mostly dirt bikes and ice racers. |
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Posted: 6/8/2024 10:07:58 AM EDT
[#34]
Quote HistoryQuoted: Team Calamari are really good people-I spent a weekend with the owner and her partner who also worked there back in ‘94. Suzan is retired now, but those folks really know small bore two strokes. Quote HistoryQuoted: Quoted: Yes, you are correct sir. Proper jetting procedure is a PITA, but necessary. Gonna seal up that exhaust leak first. The pipe is from a place called Team Calamari, and they specialize(d) in these pit bikes for a long time. It appears they are revamping the website. Team Calamari are really good people-I spent a weekend with the owner and her partner who also worked there back in ‘94. Suzan is retired now, but those folks really know small bore two strokes. Yes they do. When I tried calling I got "The line has been disconnected or is no longer in service", website says they're upgrading. I hope they don't go away. |
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Posted: 6/8/2024 10:09:11 AM EDT
[#35]
Quote HistoryQuoted: Looks like a cold seizure to me. The bike wasn’t warmed up properly and the piston expanded faster than the cylinder. I've never seen a suspected cold seizure where a ring did the damage to the piston like the one in the OP. YMMV |
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Posted: 6/8/2024 1:17:39 PM EDT
[#36]
Shine a light in the exhaust port and verify that the ring ends are fully supported through the stroke.
Verify that the old piston was the correct one for that motor, not another Yamaha 50. You stated about not finding a dipstick for crankcase oil. I assume you meant transmission oil since there is no standing oil in the crankcase. There will be a level bolt or screw in the left side of the transmission about a third of the way from the bottom. With the bike level oil should just run out of the hole with the bolt out. I'm sure you are aware that Wisecos need to be run .001/.002" looser than OEM pistons. |
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Posted: 6/8/2024 10:27:33 PM EDT
[#37]
Quote HistoryQuoted: Because the going shop rate around here is $125-$150/hour plus parts. Because I've been doing this for decades. It saves me money and makes me money. It's fun, challenging, tests my skills, I learn new skills, and it's very satisfying when the engine that I got as junk is up and running again. Even more so if the engine has been modified like this one to have more power and go faster than the original design, even if it's only 50cc's. I've never had this issue with an exhaust leak on a 2-stroke so I was looking for knowledge. Contrary to popular belief, there is some intelligence in GD. I've repaired or rebuilt everything from weed whips and push mowers to Harleys and other motorcycles, three wheelers and ATVs, Harley transmissions, manual car and truck transmissions, automotive engines, etc. Hell, once I even got a washing machine from 1915 repaired and running for a little old neighbor lady that belonged to her mother. The smile on her face when she saw it running again was well worth the moderate effort it took to get it running. Identical machine to this one: https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Ftse1.mm.bing.net%2Fth%3Fid%3DOIP.1q9q3O2q5qhEO8qwg9p5uAAAAA%26pid%3DApi&f=1&ipt=2ec0746f8a2d597fedc8b318b48c72ca57be842a31a38622202de0fdba6d48ce&ipo=images The biggest benefit is if I'm on the road or on the trail and there's an issue, I can fix it there and not have to be towed out of the woods or hauled home. We've also never had any kind of repairman in this house. I've researched, diagnosed, and repaired any of the appliance issues we've had since we built this home almost 30 years ago, saving us more money. That's why. If you’ve been doing it for decades then you should be able to identify when it is time to pay for it to be done right. Maybe the knowledge you’re looking for comes at $150/hr. Just like people paying for an hour or two of a lawyer’s time. You just keep on riding the struggle bus and eventually you’ll figure it out I guess. Maybe for a few bucks less and plenty of days longer than paying for it to be done.
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Posted: 6/10/2024 2:42:01 PM EDT
[#38]
Quote HistoryQuoted: Shine a light in the exhaust port and verify that the ring ends are fully supported through the stroke. Verify that the old piston was the correct one for that motor, not another Yamaha 50. You stated about not finding a dipstick for crankcase oil. I assume you meant transmission oil since there is no standing oil in the crankcase. There will be a level bolt or screw in the left side of the transmission about a third of the way from the bottom. With the bike level oil should just run out of the hole with the bolt out. I'm sure you are aware that Wisecos need to be run .001/.002" looser than OEM pistons. Did the light thing already, one of the first thing I did after reassembling the motor. Yes, you are correct, transmission oil. Yamaha calls it the crankcase in the manual. Yes on the Wiseco pistons. No oil level screw on this one. I located a factory dipstick. It wasn't attached to the fill cap, it came in the tool kit. 
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Posted: 6/11/2024 2:40:26 PM EDT
[#39]
Quote HistoryQuoted: If you’ve been doing it for decades then you should be able to identify when it is time to pay for it to be done right. Maybe the knowledge you’re looking for comes at $150/hr. Just like people paying for an hour or two of a lawyer’s time. You just keep on riding the struggle bus and eventually you’ll figure it out I guess. Maybe for a few bucks less and plenty of days longer than paying for it to be done. Quote HistoryQuoted: Quoted: Because the going shop rate around here is $125-$150/hour plus parts. Because I've been doing this for decades. It saves me money and makes me money. It's fun, challenging, tests my skills, I learn new skills, and it's very satisfying when the engine that I got as junk is up and running again. Even more so if the engine has been modified like this one to have more power and go faster than the original design, even if it's only 50cc's. I've never had this issue with an exhaust leak on a 2-stroke so I was looking for knowledge. Contrary to popular belief, there is some intelligence in GD. I've repaired or rebuilt everything from weed whips and push mowers to Harleys and other motorcycles, three wheelers and ATVs, Harley transmissions, manual car and truck transmissions, automotive engines, etc. Hell, once I even got a washing machine from 1915 repaired and running for a little old neighbor lady that belonged to her mother. The smile on her face when she saw it running again was well worth the moderate effort it took to get it running. Identical machine to this one: https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Ftse1.mm.bing.net%2Fth%3Fid%3DOIP.1q9q3O2q5qhEO8qwg9p5uAAAAA%26pid%3DApi&f=1&ipt=2ec0746f8a2d597fedc8b318b48c72ca57be842a31a38622202de0fdba6d48ce&ipo=images The biggest benefit is if I'm on the road or on the trail and there's an issue, I can fix it there and not have to be towed out of the woods or hauled home. We've also never had any kind of repairman in this house. I've researched, diagnosed, and repaired any of the appliance issues we've had since we built this home almost 30 years ago, saving us more money. That's why. If you’ve been doing it for decades then you should be able to identify when it is time to pay for it to be done right. Maybe the knowledge you’re looking for comes at $150/hr. Just like people paying for an hour or two of a lawyer’s time. You just keep on riding the struggle bus and eventually you’ll figure it out I guess. Maybe for a few bucks less and plenty of days longer than paying for it to be done. F'n LOL A person is not a failure until they give up. Do you really think that if I take this to a shop they are going to give me a full, clear explanation of how they repaired this, and why? Repair shops aren't in the business of educating customers. They get paid to do the work, not tell customers how to do it. Your assumption of "plenty of days longer" is  There is no time frame on this, it's a hobby, and I haven't spent "days" reassembling and figuring this out. Have you ever rebuilt any kind of an engine before? Maybe you should be in this thread instead of here: https://www.ar15.com/forums/general/Why-do-people-feel-compelled-to-comment-about-stuff-they-don-t-know-about-/5-2728858/ |
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Posted: 6/11/2024 7:32:11 PM EDT
[#40]
Quote HistoryQuoted: ...located a factory dipstick. It wasn't attached to the fill cap, it came in the tool kit. Holy crap! I remember those. Fuck, I'm old. |
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Posted: 6/11/2024 8:21:35 PM EDT
[#41]
Quote HistoryQuoted: Threads like that go in that direction because most of the answers are from people who couldn't buy a clue and shouldn't be responding. It's pretty crazy the answers I'm seeing here. It has got to be frustrating to be the OP trying to wade through 90% of posts from guys that don't have a clue. One guy is ripping on him to take it to a shop. Yeah, ok. Take your 1980's mini bike that blew up once to a shop and see what they say. That's probably the same guy that takes his 40 year old craftsman chainsaw to a small engine shop and gets pissed when they say they wont touch it. |
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Posted: 6/11/2024 8:25:17 PM EDT
[#42]
Quote HistoryQuoted: Looks like a cold seizure to me. The bike wasn’t warmed up properly and the piston expanded faster than the cylinder. My man, there is a CHUNK missing from the piston around the piston rings. This is not a cold seizure. |
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Posted: 6/12/2024 12:59:48 AM EDT
[#43]
Quote HistoryQuoted: Yup, know all of this. 32:1 is the factory manual specified ratio and I used the factory manual specified oil. There is no factory specified ratio for a YSR-50…. These were autolube injection engines. |
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Posted: 6/12/2024 1:18:57 AM EDT
[#44]
https://www.scribd.com/doc/12154807/1987-YAMAHA-YSR-50T-Service-Manual
(Free download) I only mention this because I see no mention of the factory service manual. Separate lubrication: (Yamaha Autolube) Engine Oil Type: Yamalube "2" or air cooled 2 stroke engine oil with BIA certified for service TC-W |
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Posted: 6/12/2024 1:25:31 AM EDT
[#45]
Most of the time "smoke" coming out of the exhaust port connection with a pipe is no big deal.
Any spooge coming out with the smoke? Is it dripping premix? Did you replace the exhaust gasket? GASKET, EXSTPIPE 3MT-14613-00-00 In Stock Partzilla Did you seal off the exhaust port (pipe to gasket to port connection) with red hi-temp RTV? This is where I would start. |
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Posted: 6/12/2024 2:30:49 AM EDT
[#46]
Smoke is partially normal on these especially if you’ve got the oil injector removed and you’re using premix. That piston looks terrible to me though. How does the plug look?
I’ve had a few YSRs, for a while I had two- an ‘89 that had custom candy blue paint and the whole Calimari catalog thrown at it, with a bored/ported/polished top end and a bigger carb and a White Brothers pipe, it was jetted and tuned for 40:1 and it ran a little hot but it was a blast. The other was a full custom ‘89 drag YSR with aftermarket plastics that was lowered, reinforced and stretched 8” and had a 12” car tire out back. I had a YZ250 motor for that one but handed that project over to a buddy when I got in over my head with a fox body project instead. I wish I had more input to add on yours, I’m mainly tagging this because those little bikes make me feel nostalgic as heck. My blue one was my only functioning transportation for a while back in like 1994/1995, I was living at Motel 6 at the time and always got a downstairs room so I could pull it inside.  If you’ve got any full pics of the bike, post them. |
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Posted: 6/12/2024 11:28:29 AM EDT
[#47]
Quote HistoryQuoted: There is no factory specified ratio for a YSR-50…. These were autolube injection engines. Quote HistoryQuoted: Quoted: Yup, know all of this. 32:1 is the factory manual specified ratio and I used the factory manual specified oil. There is no factory specified ratio for a YSR-50…. These were autolube injection engines. Yes, you are correct, I mistyped. 32:1 is the recommended ratio when autolube pump is eliminated, and I used the factory manual specified oil. The 32:1 ratio is also recommended by Team Calimari and multiple vintage 2-stroke websites. |
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Posted: 6/12/2024 11:29:09 AM EDT
[#48]
Quote HistoryQuoted: https://www.scribd.com/doc/12154807/1987-YAMAHA-YSR-50T-Service-Manual (Free download) I only mention this because I see no mention of the factory service manual. Separate lubrication: (Yamaha Autolube) Engine Oil Type: Yamalube "2" or air cooled 2 stroke engine oil with BIA certified for service TC-W Yup, I have a copy of the factory manual. |
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Posted: 6/12/2024 11:38:26 AM EDT
[#49]
Quote HistoryQuoted: It's pretty crazy the answers I'm seeing here. It has got to be frustrating to be the OP trying to wade through 90% of posts from guys that don't have a clue. One guy is ripping on him to take it to a shop. Yeah, ok. Take your 1980's mini bike that blew up once to a shop and see what they say. That's probably the same guy that takes his 40 year old craftsman chainsaw to a small engine shop and gets pissed when they say they wont touch it. Quote HistoryQuoted: Quoted: Threads like that go in that direction because most of the answers are from people who couldn't buy a clue and shouldn't be responding. It's pretty crazy the answers I'm seeing here. It has got to be frustrating to be the OP trying to wade through 90% of posts from guys that don't have a clue. One guy is ripping on him to take it to a shop. Yeah, ok. Take your 1980's mini bike that blew up once to a shop and see what they say. That's probably the same guy that takes his 40 year old craftsman chainsaw to a small engine shop and gets pissed when they say they wont touch it. I expected to have to wade thru clueless posts, it's no different then when somebody stops by when I'm wrenching and feels the need to offer me their .02, which more often than not is a confusing conglomeration of elementary troubleshooting (when I'm already far beyond that point), retardedly misinterpreted whiskeytalk from barstool conversations, and just plain stupidity that makes absolutely no sense. It can be entertaining and frustrating at the same time.
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Posted: 6/12/2024 12:02:26 PM EDT
[#50]
Quote HistoryQuoted: Most of the time "smoke" coming out of the exhaust port connection with a pipe is no big deal. Any spooge coming out with the smoke? Is it dripping premix? Did you replace the exhaust gasket? GASKET, EXSTPIPE 3MT-14613-00-00 In Stock Partzilla Did you seal off the exhaust port (pipe to gasket to port connection) with red hi-temp RTV? This is where I would start. Small amount of spooge coming out with the smoke that looks like raw 2-stroke oil, but I attribute this to the fact that the seals had gone bad in the oil pump and filled the crankcase with raw oil while it sat for awhile after I had reassembled the engine, hence the reason the oil pump was eliminated. A new factory oil pump is unobtainium. I want to run the engine a little more to be sure the crankcase is cleared out. At this point the engine hasn't been run very long and only at idle, maybe a minute or two if that. When I saw the leaky exhaust I shut it down. I Replaced the exhaust gasket, I didn't see anything in the manual about using RTV (I'll recheck the manual later this week), and there was none when I tore the bike down, which doesn't really mean anything. There was virtually no compression on the exhaust gasket, less than a 1mm, the one I installed is the same thickness as a new one. It's a "softer" style gasket, not like some of the harder ceramic looking ones. Seems to me it should be compressed at least a little bit, maybe I'm wrong. |
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