Possible timing issue? With video

[Sp1990]

Got the 86 Suzuki alt125 going again, it had the summer off bc leaky fuel plunger and missing idle screw. Got a new carb on there and starts up 1st pull idles great. So now onto the issue, the trike has had this intermittent problem since I got it, also with the old carb exact symptoms. Has new coil. I can go out and ride a 20 mile ride no problem but then later or even the next day when cold, it still starts and idles fine, but the exhaust note is SLIGHTLY different as is the power level, barely makes it to 5th gear. It will usually go away after a while riding. exhaust starts popping slightly when exhibiting the symptoms. Went on a 5 mile ride today and it started off with the symptoms then went to normal power etc, then back to symptoms. noticed engine gets a lot hotter when exhibiting the symptoms and exhaust will be red hot. (Running lean?) I checked plug and pretty much have the carb dialed in. On the same ride I got the red hot exhaust, it went back to normal and motor and exhaust cooled back to normal temp started driving good again. I’m thinking the timing is jumping around? I’ll have to check that tensioner tomorrow, but it’s not making any excess noise and also valves were adjusted probably 50 miles or so ago, made no difference to symptoms. Anyone had their timing jump around like this? Funny how this alt125 seems to have way more pep than my old alt185 and also the old lt125 I had.

[Sp1990]

Well haven’t messed with the timing chain tensioner yet but like I said it’s intermittent. Anyways here’s a quick video of me ripping around on it, ran great. Rattling is exhaust heat shield. https://youtu.be/U8VZcrXFLyc?si=W5suNcxdxWKu-KZx

[6spdls1z28]

Well haven’t messed with the timing chain tensioner yet but like I said it’s intermittent. Anyways here’s a quick video of me ripping around on it, ran great. Rattling is exhaust heat shield. https://youtu.be/U8VZcrXFLyc?si=W5suNcxdxWKu-KZx

I replied to you on the YouTube video. After you did the quick wheelie it started to die. Check your float level.


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[RIDE-RED 250r]

Watched your vid, pretty touch to know what's going on.

I'm not familiar with the mechanics of the ignition timing system on that particular engine, but I would wager it's a flywheel based trigger coil. If so, the only way timing can move is if the flywheel key is sheared and the flywheel is not holding its proper position on the crank, or the trigger coil (aka pulse generator) is loose/poorly mounted and moving. In either case though, I would not expect it to correct itself when the symptom arises. Cherry red exhaust can be caused by improper ignition timing or a lean condition.

I agree with the above post to check your float height as well as smooth operation of the float. An engine will run with fuel level too low, but it will run lean. Also, it can run with too much fuel in the bowl but it will run rich. At the extreme ends of both conditions the engine won't run at all. It's possible that your float is occasionally sticking and your fuel level is getting low enough in the bowl to cause a lean condition but still run. When the fuel level returns to normal (float frees up) the problem goes away.

Also might be worth checking your exhaust closely for an obstruction of some kind. That little trike is nearing 40 years old, there may be a baffle or some other internal component in the muffler that has broken loose and is intermittently obstructing the exhaust causing this issue.

Good luck and let us know what you find.

[Sp1990]

Thanks for the replies but after that wheelie it died bc I hit the off switch, turned it on again before it died. Float level good it idles great. I’ve already eliminated it being a carb issue as it did the exact same thing with the OE carb. And I have the new one dialed in. Oh and in the video it was running fine wasn’t doing the timing thing during that ride. It’s intermittent

[Sp1990]

Started her up today and right off the bat engine got really hot and I had real low power, popping out of exhaust, sometime I can throttle through it and it will go back to normal and engine temp will almost instantly drop to normal, but it only did that for a little bit then began popping again, and low power, hot engine. I’ll have to start digging into the engine soon as I get some time.

[RIDE-RED 250r]

Man that's puzzling.

Did you have a look at the exhaust??

[Sp1990]

I didn’t get a chance to pull exhaust and check if it’s stopped up yet. Went on a little ride today, no problems at all. Gonna check exhaust and double check there’s no vacuum leak or something causing it to lean out severely sometimes. Just got the service manual for it today so gonna look that over.