A few years ago bought a used 2000 Grizzly 4 wheeler. About 800 miles on it. I do not know anything about engines or fixing them, have tools but no specific mechanic tools.

Was leaking gas from carb, bought a rebuild kit, took it to a guy. I do not know if I bought a rebuild kit and gave it to him, but I think so. PAid him some $, wheeler came back running with no leak.

Used it for hunting season died in woods, took back to guy, some more $, stuff in carb.

Died again this Spring, would not start, I had the service manual and diagnosed it as not having spark, bought stator/ coil, a gasket, some oil, gave it to guy and $200 later I am fixed.

Rode in woods, died (was going slow, fairly hot out.) Able to start next day with lots of throttle, got back to garage. Got it to start in garage a week later, then dies after idling about 3-5 minutes. Pull plug, does not seem to have spark. Checked spark again today (since I had new plug to put in (which did not fit) seems to have spark.

Almost got it to start, with lots of throttle. Tonight, removed carb. Have not disassembled yet. But did find "a lot" of gas on the rubber gasket between carb and engine. (See pic).

What the hell am I doing? I have a carb kit on the way, and have watched some youtube videos. Other than seeing a rip in the diaphram (unlikely?) or some actual plugged jets (I should be able to see that, right), or just crap and dirt, what am I looking for?

I do plan to drain the gas tank in the next day or 2, and check it for dirt and stuff, and maybe put an inline fuel filter in?

I would rather not take it back to the guy (unless I have to), and could take it to the yamaha dealer about 20 minutes away, but I am cheap (which is how I got into a mess with an old four wheeler and a guy). What are the chances of me fixing this myself with arfcom guidance?
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I think the biggest clue is it "almost" catches with lots of throttle, and dies after idling for a bit.
(It also needs a new battery, I have been getting it to turn over with battery and a jump pack.)

Adjust the valves.

Grizzly ATVs are great machines.

Almost certainly in the carb. Lots of possibilities. Float could have a hole in it. Float needle could be leaking. The choke isn’t a true choke…it’s a fuel enrichment needle valve…works by adding extra fuel when engaged.

First thing before you do anything….check the oil. Give it a good sniff. Does it smell like gas? Does it appear watered down?

I can figure that out I guess, and already bought feeler gauges...

I've got an 05 660 Grizzly.

I had carb issues, replaced needle and gaskets.  New battery and it ran great.  The drive trains are stupid reliable, older tech.  This is why I bought it.


Currently, mine is in the barn.  The center dif won't unlock.  20 year old electronics.



Looks like I'm going to be chasing electrical gremlins now.



I'm no expert at all.  With that much fuel in the carb, I'd be looking at the carb again.  Float needle first.  Then I'd look at a valve adjustment (may explain poor operation when running).


On a positive note, once you/we get them sorted out, the damn things should go another 10-20 years.

Those older machines almost never have valve issues. I would get a completely new carb and put it on. I'm betting previous owner ran cheap gas and the lack of use has lead to the carb being gummed up from the ethanol.

Watch several videos on carburetors. Find one that shows the flows through the different circuits.
That looks like a constant velocity carb.

Once you understand the flow circuits and functions it gets easier. Use a clean area and patience.

I cannot stress this enough:
Buy the factory service manual for your machine. An actual manual. You can download one, but for me having it in my hand works better than a download or trying to print out pages.
They seem expensive, but it will save lots of time and money.

Our hunting camp has a variety of quads in the barn, mostly older to very old machines. They all have issues, some more than others. One guy used to have a grizzly, he traded it on a Polaris. Another guy had a different Yamaha, I remember 3 of us taking a few hours to change the carb on that thing.

I have no experience with your model, but most quads seem to have the same issues. In particular, every used quad seems to have a teething period where you need to sort issues to make it reliable.

From a distance and what you posted - clean out the old fuel. Rebuild or replace the carb and be sure the boot between the carb and cylinder is leak free. Only use ethanol free gas and put Stabil in all the gas. When you put it away, close the fuel petcock and let it burn off all the fuel in the carb.

The above process has mostly ended fuel and carb problems for us. Modern gas is garbage, but ethanol free seems to be better.

Checking the valve clearance won't hurt, but I've only seen valves need adjustment on a Kawasaki. If you don't know what you're doing, I'd leave that alone.

Ignition and electronic issues seem to mostly afflict the newer quads. Electronic ignition issues can give you big headaches trying to figure them out.

First of all I’d stop taking it to the guy you’ve been using. Next if it was mine, I’d suck it up and put a new carb after throughly cleaning out the fuel tank and lines. May even replace the lines entirely. With the new carb, start with the mixture screws between 1&1/4-1&1/2 turns open from fully (gently) seated.  That should get you starting, maybe not running smooth, but it should start.

That much gas suggests to me there’s definitely a carb issue. Maybe not the only problem but for sure needs a carb.

While checking the valve clearance is considered to be part of maintenance, it’s actually very rare that they actually need to be adjusted. Definitely not causing your issues in this case.

Some people will recommend an aftermarket carb. That should only be a last resort. Always try to fix the OE carb before trying a Chinese carb. The Chinese carbs are typical Chinese quality….some work great….some don’t work at all. If the inside of the carb appears clean, then usually most issues can be repaired.

Thanks for the collective words of wisdom -
- going to sniff the oil tonight to check for gas;
- going to disassemble the carb tomorrow - thinking of buying an ultrasonic cleaner depending on how it looks. Do not think I know of anyone who has one to use;
- have a service manual - it was pretty helpful with past electrical issues and diagnosing
- will check valves tomorrow against spec
- it spends a lot of time parked, so I should treat it to ethanol free (bet it would easily be less than 10 gallons a year), and let it run the carb out like I do with snowblower and generator and mower at end of season;
- trying to avoid new China carb - have heard lots of bad things - if not needed not touching it;

Will report back on findings!

As far as videos - there are a lot of Grizzly specific ones, including of this vintage, they have been helpful. I also watch A LOT of a channel called 2vintage, where he fixes lots of bikes and quads - his process is boring and the same every time - its actually helpful to see issues tracked down like that!

If you smell gas in the oil then you have a leaking float seat and would also cause your running issues due to excess fuel.

Do you have the plug it was running on? If so, what color is the center electrode?

Will take a pic of plug tomorrow - it was new, maybe has 10 minutes run time, so not sure it shows anything.

Hard to tell if oil smells of gas - the whole quad and garage do since taking the carb off spilled plenty.

<------------  efi Grizzly gang  ('09 550)


Is it possible to upgrade carb to efi?

Need to look at the old plug not the nee one. New one might hold some clues but not likely.

Here’s a link to what you are looking for.

https://www.tuningmatters.com/how-tos/beginners-guides/check-spark-plug-correct-carburetor-setting/?amp=1

How much money you got??  Anything is possible with enough money!!!  But, it’s not really feasible for most equipment.

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Not much of an update: carb is off. I can only get 1 screw off the diaphragm, going to get a manual impact and screw remover tomorrow.

Rest of carb apart as far as I can, nothing seems dirty, gummed up, or plugged.
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I would definitely try to get that carb running since it looks good on the inside. You need to pull all the jets out and give them a good cleaning.  Spray carb cleaner in the jet and when you see where it comes out, spray it the other way. Then, blow compressed air the opposite direction. Then, do it again.

Hold the float closed and try to blow air with your mouth into the fuel input. See if it’s leaking. Then, take the float off and look inside the seat. Is there a wear ring inside the needle seat?

Also, pull the fuel petcock off the tank and take a look at the screens inside. Clean the tank while you have it off. If the screens are damaged, that’s your fuel filter. Either replace the petcock or install an inline filter.

This is sound advise. I worked on my cousins Grizzly that had a lot of garbage in the fuel tank.  I also added an in-line fuel filter to help prevent garbage from making its way in to the carb.

I did the same for a Suzuki I used to have. The Suzuki had some running issues….excess fuel. Turns out, the particular Suzuki used a vacuum activated petcock. There was a diagram in the petcock and it had a pin hole in it. Vacuum would pull the fuel out and directly into the intake. Replacing the petcock solved the issue. I did check the OPs unit (parts diagram) and it doesn’t appear it uses a vacuum activated petcock so that’s not his problem.

Had to cut a slot with the dremel in the remaining bolt head. The diaphragm is now off - that end of the carb seems just as clean as the other. Very clean. I have sprayed carb cleaner into every orifice I can find. Then air. 2x. Tomorrow I will use some feeler gauge/ wires to run through anything I can fit them through.

Then I plan to drain the gas tank, and see what's in there, and check screen if I can, or at least blast some air backwards through the petcock.

Then I will will check the valves.

Seeing nothing obviously wrong, should I use the parts kit and rebuild the carb, or leave the "original" pieces in there?

I do now recall having my guy adjust the float when I first bought this, as it would leak gas when parked if the petcock was not shut off. But he did not rebuild (but did fix this issue). I do have the service manual, and will use that to set the float when I put it back together.

Yes replace the parts in the rebuild kit. There is no point taking it apart and reassembling it with old parts when you actually have the correct parts on hand.

When you’re buying parts, are you buying Yamaha OEM stuff or China stuff?  I remember way back when I had a Grizzly that parts from Yamaha were not cheap, but they worked.  I did the brakes and it cost me 3X the cost of my car brake parts.

That old of machine I hope you drained the gas tank, rinsed it out, and changed the fuel filter first thing. Buy new battery. Then take it to Yamaha mechanic.  

Haven’t read all the threads.

Unless someone added an aftermarket fuel filter, the fuel filter is in the tank on the petcock.

Somebody should have told you to buy JIS screwdrivers before you start tearing in to the carb. See that little dot on the screws? That tells you they are not Phillips and your American screwdriver is going to do nothing but strip em out.


Link to one of my IG reels showing the difference.

Yes, those are not Phillips I now know. But now they are allen head!

Its not the gas, no water in it. The black specks in pic were in the container to begin with.
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Screens in tank were clean.

I gave up on measuring valves for now, rebuilt the carb and have 2 pieces leftover. The needle in the kit was too small for the parts that needed to go on it, and I do not think the air pilot jet goes in my carb?

I ran out of time for reassembly and test, and going out of town for weekend...

The aftermarket parts kits usually have extra parts since the kits are usually for several different models. But, you still need all the right parts in the carb in the right places for it to work properly.

The idle mixture screw needs to be preset. I usually do 1.5-2 turns out from bottom for starters and that usually works. However, sometimes you have to make small adjustments after it’s on the bike. It might be possible to adjust the mixture screw without a special tool but the special tool makes it MUCH easier….and in the case of some bikes, it’s mandatory.

https://www.amazon.com/Motion-Pro-Pilot-Screw-Adjusting/dp/B07PRYRCW1

The valves are unlikely to be out of adjustment and even if they were, they would not be causing your problems. They would cause other problems.

After you get the carb assembled, turn it upside down and try blowing in the fuel input with your mouth. No air should go in. If it does, there is an issue with your needle valve. You can also connect it to a fuel source before you install it and see if any fuel is leaking out. Also, another good check is to take the float bowl off, connect it to a fuel source, then hold the float up with a finger (should close off the fuel flow). Allow the float to drop and it should start flowing fuel. Raise the float up again with your finger and verify the flow stops.

I reset to 2.5 turns, as that is where it was when I took it apart.
It passed the blow test.
I replaced the battery (I think it was more than the battery I put in my car).

Still will not start.
Spark still good.
Caught for a second on starting fluid in the spark plug hole.
Opened carb drain screw, gas did come out.

Stumped and about to ship it to the guy who fixes my snowblower, or a small repair shop that seems to do a lot of business on mowers, wheelers, etc, or possibly the dealership. Trying to avoid the cost, but do not know why.

Spray carb cleaner into the intake while cranking it over. Can you get it to run….even a little and rough…..while spraying carb cleaner in?

Do you have a compression tester? Be worth running a compression test on it to see if there is enough compression to start and run. If you don’t, hold your hand over the carb air intake and crank it over. Does it suck your hand against the intake? Should be pretty strong suction.

Remember you need spark under compression, compression, and proper fuel/air mixture for any gasoline powered engine to run.

FYI the normal starting point for mixture screws is 1&1/2 turns open from lightly bottomed out. Or so I was told by an ex mechanic. That’s always gotten me in the ballpark  where the motor would crank. Maybe not run worth a crap but it’d start.  May I suggest you ignore the original setting and try that?

The idle mixture screw on those carbs isn’t very precise. It may be fine tuned after getting it running but I’d rather start a little farther out than too far in when diagnosing a failure to start issue.  I always fine tune it later anyway

Easiest fix is upgrade carb to a efi Honda

Did you remove the pilot jet from the cab and look through it? That is the issue with 98% of carb issues.

Carb seemed very clean, including being able to see through jets.
I think I messed up by not just cleaning it and trying to restart - I suspect the parts from the rebuild kit sucked, but have no way to know, I just do not trust them.

But I TAPPED OUT - there is another small engine guy I have use in the past for my snowblower, he picked it up Friday afternoon to look at it. Hope to hear back early in the week.

When re assembling I had a hose I could not figure out where it went, and some kind of air intake that I never saw a place to install, and no picture of it in the service manual.

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#1. Don't buy carb kits. These days you are probably replacing high quality Japanese parts with cheap Chinese counterfeit trash. I've literally cleaned thousands of carbs for a living and I've never once bought, needed, or used, a carb kit on a Japanese motorcycle carb. American car carbs, different story.

#2. Stop ramming everything you can in every orifice you find. you're not in your Camaro after the prom, and most of the orifices you're ramming steel wire into are precision-drilled aluminum or brass holes that really need to be a certain size. Nylon bristles WILL get the job done and you'll stop fouling plugs if the jets and air bleeds aren't gaping like some Pornhub feature.

$3. Carburetor cleaner in a spray can will get you 99% of the way there.

If you can take it apart, and put it together EXACTLY the same way it came apart, and dissolve all the crap will be a big part of it.

If it keeps overflowing, you'll likely find trash in the fuel bowl, then you don't need an inline filter; either some jackwad has messed up the strainer on the fuel valve, or it's come loose in the tank. Pop the fuel valve out and make sure both the main and reserve stainers are in place. Yes, these are sold a service parts.

Once you get the jets clean, you should be able to look at a light through the hole, and the hole should appear circular and clear (blow though it to make sure it's dry).

Every passage in the carb should be clear, spray only, no wire halfassery required.

If you stabilize your fuel before you park it for the season, shut off the fuel valve, and run it until the carb runs out of gas, you will NOT need to clean it next year. If you don't do this, fuel evaporates out of the bowl, leaving varnish. The fuel being on means a constant supply of fuel, and there for a constant supply of varnish. Shut the valve off but don't drain the carb, you'll get varnish but it'll build up over time.

Non ethanol fuel helps but the Japanese quads are fine on e10 IF you drain the bowl when it's going to be parked for more than thirty days.

Further, if an NGK spark plug gets fuel fouled, toss it. Small ATV single cylinder engines can't accept compromised spark and it can never be cleaned, the fuel soaks into the porcelain and they short out internally over time.

It won't hurt to adjust the valves, but at the mileage you're talking about, it's likely a waste of time.

This is absolute and utter bullshit. I've used nothing but #2 Snap On Phillips for all of my carbs and I have yet to strip out or even mar a screw

Sure thing. I haven't used my snap on screw drivers since I bought the Japanese Vessel ones.  They work better on regular phillips screws also.

I can grab more some more JIS screws, and Phillips screws and both screw drivers and make more videos. They fit tighter and can apply way more torque before they cam out.  I did break one but I wrote them on Instagram and had a new one inside of a week straight from Japan.

Almost every carb and brake master on used bikes I've bought or bikes I work on have ruined screws, or screws replaced by hex heads.

Its coming back home soon.

My carb rebuild was not the issue
And possibly the carb was never the problem.

New guy found disintegrating air filter material in the gas tank, and water in the gas.
Pics to follow.


(Not sure it really makes sense to me, since I drained the gas and did not find any of that. But he says its running fine now.)

Yea no of that makes sense at all! Maybe he just has the magic touch.

I’m having trouble to understand how air filter material can get into the gas tank.

Fingers crossed that it is running OK for you now.

I may have misunderstood the debris in the gas tank and where it came from - its all over text for now, and I do not have the wheeler back yet - he was waiting for a new air filter to come in, and I am having him add an (another) inline fuel filter I can see.
His pictures of filter box and filter:
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I knew the filter was in bad shape and crumbling, unsure on how much that would have impacted the machine running (unless debris got sucked into the carb, which I do not think it did.)

Picture of what he drained from the fuel tank:
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Picture of what I had previously drained from the tank (note no water, so it still does not make sense for me why it wasn't running).
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Those black spots on the bottom in
my pic are part of the jug, not something in the gas.

Hoping to have it back for the weekend, and I will have time to run it around the property for a bit, haul some firewood, etc.