Backfire (afterfire?), shifting, and brake light issues

[Orphanclone]

After going over the thread from my last post a couple months ago, I was unsure of the future of my GZ250. I completed some easy repairs and took the bike to a reputable mechanic and have been riding around ever since. I've accumulated nearly 900 miles with no issues whatsoever (except for bugs smearing across my jacket & visor).

Until today.

I was out riding with a friend and he told me my brake light wasn't working. We stopped for gas and I figured that light not functioning from engaging the rear brake is an easy fix (tighten cable/shorten the connecting spring), but I am at a loss for what might be causing the same malfunction with the front brake. (Yes, the brake light still works. I can get it to turn on/off manually by moving the brake light switch.) Any thoughts?

We continued our ride, but I had my friend stay behind since he knew our route and had functioning brake lights on his GS500. Shortly after maintaining 50/55 for a few minutes, I noticed shifting seemed a little delayed, but chalked this up to possibly not disengaging the clutch entirely. (I have a tendency to cover the clutch, especially on roads I'm not familiar with.) I began to engine brake as we approached a stop, and heard a loud pop. I thought it was a backfire, but after reading the forums, I'm not so sure. After getting back up to speed with no issue, I noticed some hesitant shifting again when I downshifted for a turn, and this time I made sure that the clutch had been smoothly and fully disengaged. The backfire/afterfire occured twice more, both times when engine braking above 40 mph. At slower speeds, the engine seemed to run perfectly fine, though I did have a couple more shifting incidents.

A post-ride inspection revealed nothing. Fluid levels were where they should be, no detectable leaking, and nothing seemed mechanically out of place, so I'm stuck. I would really appreciate any input you might have.

[Orphanclone]

Before I forget, there were also no issues (backfiring, etc.) when starting or shutting off the engine.

[Easy Rider]

Originally Posted by Orphanclone

but I am at a loss for what might be causing the same malfunction with the front brake.

The backfire/afterfire occured twice more, both times when engine braking above 40 mph.

Brake light, front. Bad switch or broken wire or loose connector; that's about it......maybe blown or loose fuse but other things would probably be out too.

Backfire: Lean mixture. Loose carb boot, crack or hole in air box, loose air filter, plug off air box drain hose........exhaust leak (but that probably would be obvious).
Also could be bad gas.

If nothing else shows up on inspection, I think I'd drain the gas from tank and float bowl and put in fresh with some carb. cleaner.

[Water Warrior 2]

Originally Posted by Orphanclone

After going over the thread from my last post a couple months ago, I was unsure of the future of my GZ250. I completed some easy repairs and took the bike to a reputable mechanic and have been riding around ever since. I've accumulated nearly 900 miles with no issues whatsoever (except for bugs smearing across my jacket & visor).

Until today.

I was out riding with a friend and he told me my brake light wasn't working. We stopped for gas and I figured that light not functioning from engaging the rear brake is an easy fix (tighten cable/shorten the connecting spring), but I am at a loss for what might be causing the same malfunction with the front brake. (Yes, the brake light still works. I can get it to turn on/off manually by moving the brake light switch.) Any thoughts?

We continued our ride, but I had my friend stay behind since he knew our route and had functioning brake lights on his GS500. Shortly after maintaining 50/55 for a few minutes, I noticed shifting seemed a little delayed, but chalked this up to possibly not disengaging the clutch entirely. (I have a tendency to cover the clutch, especially on roads I'm not familiar with.) I began to engine brake as we approached a stop, and heard a loud pop. I thought it was a backfire, but after reading the forums, I'm not so sure. After getting back up to speed with no issue, I noticed some hesitant shifting again when I downshifted for a turn, and this time I made sure that the clutch had been smoothly and fully disengaged. The backfire/afterfire occured twice more, both times when engine braking above 40 mph. At slower speeds, the engine seemed to run perfectly fine, though I did have a couple more shifting incidents.

A post-ride inspection revealed nothing. Fluid levels were where they should be, no detectable leaking, and nothing seemed mechanically out of place, so I'm stuck. I would really appreciate any input you might have.

Sounds like the rear brake light switch needs adjusting. It needs to be turned to move it further forward or back when adjusting. You will probably need to turn it to move it forward to the front of the bike. Just be a little gentle as it is only a plastic threaded switch. Thr front brake lever probably has corrosion on the contacts for it's switch. Now for the next problem. It was running great till you got gas. Have to agree with Easy, dump the gas.

[Orphanclone]

Thanks for the tips. I'll let you know what I find. Hopefully, I'll get the chance to work on it this afternoon...

[Orphanclone]

Good news and "eh" news:

I've got both the front and rear brake light switches working again. For the front, it turned out to be quite a bit of corrosion on the contacts, so some cleaner and a wire brush took care of that. As for the rear brake, I had forgotten that the prior owner was a midget. Not literally, but short enough that he had to move the position of the brake pedal extremely high. When I readjusted this, I neglected the rear brake light switch. It ended up being positioned so that the pedal itself couldn't physically engage the wire/switch, but when placed in proper position, the spring wasn't long enough to allow the switch to disengage. I'm guessing when the previous owner adjusted the pedal, he also put in a shorter spring because the necessary adjustment would have maxed out that of which the plastic threads on the switch are capable. One new (appropriately-sized) spring later and a few fine-tuning adjustments later, and it works like a champ.

And for the bad: before I started working on the brakes, I started the bike up, just to see how it would run. I'm not sure how to describe the sound, but had it been on a larger engine, I would say that one of the cylinders wasn't firing (or was misfiring). This would also reinforce the "bad gas" theory, but since I played around with the electrical so extensively, I drained the battery enough so it wouldn't start. As soon as I get charged up enough, I'd like to run the engine for a bit, just to listen to it, but I'm still probably going to have to drain the tank and put in some fresh gas at bare minimum.

Thanks for the advice so far!

[Water Warrior 2]

Considering the environment the electrics have to live in it is a wonder they work at all.

[Orphanclone]

Originally Posted by Water Warrior

Considering the environment the electrics have to live in it is a wonder they work at all.

True story.

On a separate note, the winning answer of what was causing the backfire: (drumroll, please!) ...exhaust leak.

Kind of. When I replaced one of the header bolts that had been sheared off, I had to go with a slightly shorter bolt because the threading inside the engine block had been damaged and I didn't want to damage it further. It would seem that the shorter bolt was not sufficient and is now gone, allowing the header to slip out slightly and cause an exhaust leak of sorts. Exciting stuff.

Once again, thanks for all of your help.

[Water Warrior 2]

Good job tracking done the header leak. Now that everything is working properly you can get out there and ride.


Please develop this safety procedure : at the beginning of every day you ride check "every light" on the bike. It only takes a minute and can save you from a disaster. Who knows how long your brake light was out and how many potential rear enders you luckily avoided. New and old bikes alike have bulbs go out at the drop of a hat. Ride Safe, don't give the cagers anymore advantage to run over you.