Posted: 8/23/2006 6:04:59 PM EDT
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If you'd like to just read the problem and not the story, please see the last few lines. Alright, here I am, on a nice but slightly warm day cruising along in 3rd or 4th gear at about 6500rpm (after bump-starting my bike, which is another problem altogether). Out of nowhere, I get some pretty stong engine braking, like I instantly cut off the throttle but even more, and my rpms drop down to roughly 3500. I pull in the clutch and coast her in neutral to the parking lot up ahead. So my bike finally dies, and when the key is in the 'on' position, none of the lights that should come on do. Battery not properly connect? So I bust out the crap-ola tool kit to take a look-see, and everything seems to be in order. I use a zipper cover thingy off of my jacket and tie down the clutch. With my right hand I hold onto the throttle, ready to blip it when I do this next step. That is, hold onto a pair of pliers from the aforementioned crap-ola tool kit with the book I was returning to the library (A Clockwork Orange) and bridge the gap there. I do this, and get sparks, meaning my battery is good to go. Strange, I think to myself. Anyways, it didn't start, and I bump started it (I'm an expert at this, I bet I've done it almost 100 times on this bike). I nurse her home at 3300rpm in first gear (which is 10 mph, by the way), which luckily is only about two miles away. Well, as I near the downhill portion of my journey, I kick her back into neutral and just give enough gas to keep her alive. Here's where it gets interesting. As I'm getting ready to take this downhill turn, I throw on a little rear brake action to slow me down. Right as I step on it, my rpms jump up. An anamoly, I think to myself and head on home. I did some more testing and it turns out that any time I hit my rear (not front) brake, the rpms go anywhere I want them to. I tried unhooking the little actuator thing from the rear brake, and lo and behold, I find myself once again limited to ~3500rpm (even when depressing rear brake). I double checked after replacing these wires, and the rpms jump exactly when the brake light comes on. I am riding a bicycle to work tomorrow. For those who skipped the story: My rpms won't go above roughly 3500rpm, UNLESS I depress the rear brake. I have determined that the action of the rear brake light coming on is allowing things to work as they should. |
| What kinda bike and what year. Sounds to like you may have a shorted wire in you wiring harness. I bet if you take the rear break light switch off and press it the RPMs will be fine. I wouyld trace that wire and see if there are any striped wire in contact with that if not i would say you have a problem in the CDI box. Otherthan that Motorcycle+electrical problem= satan |
'85 Suzuki GS450L I put in the story that I did take off the three wires (one white, one brown, one black with a white stripe, but I don't know what any of that denotes) that go to the rear brake light, and it had the same problem as before, except that when I hit the rear brake my rpms still stayed low. I don't know what a CDI box is and I couldn't find a box with fuses. |
IF you want to keep the bike, and IF you are looking to fix it yourself, you MUST get a service manual, be it a Clymer (I use them), Haynes, or factory Honda. All of your electrical schematics will be in there, along with some basic troubleshooting logic. Electrical problems are a challenge all their own. However, for this problem... I think venom11b is on the right track with the “short” theory. Remember, electricity follows the path of least resistance (I know, we've all heard that). I think rather than a short, you may have an arc somewhere, where the electricity is jumping through the insulation of a wire or maybe the insulation is worn away somewhere, thereby allowing the wire to discharge to the frame, engine, etc. When you activate the brake lever, you might actually be increasing the "uninsulated" wire to frame distance (by the wire moving away from the frame, engine, or other "ground") so the electricity can no longer "jump the gap". First thing I would do is find all of the linkage (levers, etc.) involved in the rear brake from the pedal to the rear drum. Then look for any wires next to the brake components (pedal, linkage, frame, etc.), which might be thin on insulation or missing it entirely. Observe what happens to the wires when you depress the rear brake pedal. If you still can't find anything, put the bike in a really dark room, or try outside if dark enough, and run the bike. Have someone else work the throttle, and you look for electrical arcs. You should see a little "bluish spark" for lack of better description if something is "arcing" (no, you should not see this normally). ALWAYS allow for ventilation if you're inside, as you don't want to "go to sleep" while trying this. If you still can't find anything, check wiring where it tends to wear the most, like around the steering head, the headlight, under the seat sometimes, etc. Good luck. My $ .02 |
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very likely that your problem is a loose or faulty ground... when you activate the brake light, you are allowing a viable ground. I used to have a lot of weird problems when i worked on freighliner trucks, cigarette lighter would increase throttle, truck wouldn't start without headlights on, etc.. EVERY crazy non-sensical problem i have had on any vehicle has been a ground problem. Good Luck!! |