1981 250R resto-mod

[350for350]

That almost makes me jealous. Mine's been sitting in the shed since December. I want to work on it SOOO bad, but I have too many other things to do.

[81300R]

[ATC King]

Sounds like a rev limiter past 1/4 or so throttle.

It could be an electrical issue, especially at certain vibration frequencies, which I've dealt with myself. Those are some head scratchers. Loose connections can behave like that, fine at some RPMs but act up at others.

I'd be more inclined to look at fueling though. Two cycle engines will burble if too rich, it's something like a rudimentary rev limiter.

Small, two cycle power equipment is tuned from the factory to limit RPM by having the high side of the carb rich past a certain RPM. That keeps inexperienced operators from yelling at retail store employees because they didn't have a clue how to operate something because most everything nowadays is made to be idiot proof and that's what they're used to.

I've worked in a chainsaw factory and adjusted the carbs on thousands of saws.

If it's hitting a wall, check the carb over. When the company I worked for changed carb suppliers, we had a week of total hell. The first carb shipment was all over the place. Probably less than half of the new saws ran right off the assembly line. The repair techs at the end of testing were jumping through their arses replacing carbs and sending back through testing.

If that checks out, then attack the electrical gremlins.

[81300R]

It could be an electrical issue, especially at certain vibration frequencies, which I've dealt with myself. Those are some head scratchers. Loose connections can behave like that, fine at some RPMs but act up at others.

I'd be more inclined to look at fueling though. Two cycle engines will burble if too rich, it's something like a rudimentary rev limiter.

Small, two cycle power equipment is tuned from the factory to limit RPM by having the high side of the carb rich past a certain RPM. That keeps inexperienced operators from yelling at retail store employees because they didn't have a clue how to operate something because most everything nowadays is made to be idiot proof and that's what they're used to.

I've worked in a chainsaw factory and adjusted the carbs on thousands of saws.

If it's hitting a wall, check the carb over. When the company I worked for changed carb suppliers, we had a week of total hell. The first carb shipment was all over the place. Probably less than half of the new saws ran right off the assembly line. The repair techs at the end of testing were jumping through their arses replacing carbs and sending back through testing.

If that checks out, then attack the electrical gremlins.

When i first brought it home, i thought for sure the problem was the strange Blue Magnum carb it had on it. Played with that for a bit with no change. OK, ordered a PWK. Exactly the same issue. Doesnt quite sound right at idle and doesn’t rev up hardly at all/misses/holds back. Check coil grounds. Compression didn’t seem great so i pull the top end to find a polaris piston that comes up at least 1/4” shy of the cylinder deck. Bingo. Apparently that wasn’t it either

Definitely seems like an electrical issue. Going through stator and wiring before i order a cdi.

[atc300r]

Try another coil.I had an issue like this with my 85 250r back in 09.The trike would start and idle fine but over 1/4 throttle it would run like the choke was on.I tried different cdi,carbs,plugs,fuel that didn't work.I changed crank bearings and seals and new carb kit that wasn't it.When I tried a different coil it started running correctly. Just my 2 cents.

[81300R]

Try another coil.I had an issue like this with my 85 250r back in 09.The trike would start and idle fine but over 1/4 throttle it would run like the choke was on.I tried different cdi,carbs,plugs,fuel that didn't work.I changed crank bearings and seals and new carb kit that wasn't it.When I tried a different coil it started running correctly. Just my 2 cents.

I will do that. Thanks for the suggestion!

[ATC King]

When i first brought it home, i thought for sure the problem was the strange Blue Magnum carb it had on it. Played with that for a bit with no change. OK, ordered a PWK. Exactly the same issue. Doesnt quite sound right at idle and doesn’t rev up hardly at all/misses/holds back. Check coil grounds. Compression didn’t seem great so i pull the top end to find a polaris piston that comes up at least 1/4” shy of the cylinder deck. Bingo. Apparently that wasn’t it either

Definitely seems like an electrical issue. Going through stator and wiring before i order a cdi.

Good luck. Hopefully you'll find the issue without much hair loss.

I stopped testing any type of coils, be it a stator, pulse, ingnition, or anything that's wound with magnet wire, by the manual's resistance spec, years ago. A bit of bad insulation on the magnet wire may pass resistance specs, but with a load, they won't produce the voltage. That's why I test any of them by voltage anymore.

I've also not had the longevity out of any aftermarket stator compared to OEM. Rewinds of the stock stator seem to be more reliable. My experience is Chineseium doesn't last.

[81300R]

Stator tested good. Tried known good coil with same issue. Cdi is on the way.

Got it about buttoned up!

[shortline10]

Turned out great

[81300R]

Should of put these in the intro but this was when i crammed it in the back of my tahoe to take it home

[81300R]

Good luck. Hopefully you'll find the issue without much hair loss.

I stopped testing any type of coils, be it a stator, pulse, ingnition, or anything that's wound with magnet wire, by the manual's resistance spec, years ago. A bit of bad insulation on the magnet wire may pass resistance specs, but with a load, they won't produce the voltage. That's why I test any of them by voltage anymore.

I've also not had the longevity out of any aftermarket stator compared to OEM. Rewinds of the stock stator seem to be more reliable. My experience is Chineseium doesn't last.

New used CDI did not cure it either.


Are there any specs available for what the stator should be putting out for voltage?

[81300R]

You guys will get a kick out of this…

I swapped stators with a spare. Same issue. Well its either in the harness or that damn supertrapp muffler.

Pull the muffler and it revs

So, even though i gutted the muffler, the disc baffles must be just restrictive enough. Funny because i have used one of these style mufflers on a 490 Yamaha in the past.

[81300R]

Modified a DG silencer.

Pretty much done except a kill switch and some jetting.

[Footy]

Dang! Guess I jinxed you when I mentioned the supertrapp being for a 4 stroke.

[ATC King]

Dang! Guess I jinxed you when I mentioned the supertrapp being for a 4 stroke.

It wasn't the Supertrapp, it's that it was gutted. A muffler is a muffler, unless it's a large, empty shell, with an endcap, then the exhaust gasses dump into it from the mid pipe and velocity stalls, causing everything from there to pile up in the system. If it's just a core with no packing, there's increased turbulence, and performance suffers.


Supertrapps are sold for two and four cycle engines. I think the two cycle versions come with six discs and and twelve discs for the four cycle.



Regardless, trying to guess someone's issue on a trike that isn't stock anymore or has been monkeyed with is a left field guess. May as well suggest to check the fux capacitor.