Yamaha 115 two stroke. Bad stutter and Bog on Acceleration. Need some help.

[big_builder]

Hello All,

I wasnt sure how to describe this in the title.

Have a late ninties 115 yamaha two stroke.

We have removed the oil injection and installed a tiller on this motor.

Ran beautiful until the last run of last year.

Again now on first run of this year.

Starts up, idles.

If you rev it up in neutral it stutters just like it is hitting a rev limited. nah nah nah nah you know the sound.

Will do the same once in gear and you try to accelerate. The more throttle the more it shakes. Not possible to plane out.

Mechanic came to look. Did spark test, changed plugs. He thinks it might be the ignition pack ( located between cylinder heads at back of motor)
Has any one ever heard of this problem before? Before I go buy this part.

Thank you for all help

So far we have tried.

New plugs. Spark test.

Check wiring harness for shorts.

Disconnect tach.

Install used working ignition pack from working motor. No difference.

Reinstalled oil injection tank and sensor to see if that was doing it. No change.

Any thoughts are appreciated. Sounds like it is stuck in limp mode or something.

 

[robert graham]

Have the carbs ever been removed, disassembled and cleaned?....could be some plugged carb jets...

 

[big_builder]

I asked mechanic. He is sure this is electrical. Just the exact timing of it. Will happen in neutral or when trying to accelerate.