1999 Yamaha 115 two stroke- Bad stutter, sounds like rev limited,

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 fro 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.

big_builder said:

...

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

Click to expand...

Do you happen to live in an area where Stink Bugs exist? End of season is when they start finding places to hide out for the winter. They hosed me up last year badly.

Your symptoms are very similar to what I went through. After paying for and waiting for a new neutral,safety switch and new shift cables, and again experiencing the exact same symptoms as before all that work, we found the problem to be Stink Bugs. No joke. My story even made a SeaTow advertisement.

https://www.google.com/url?sa=t&sou...49_FnRDMwyslYc8Yw&sig2=R1QesJjthJ9vkOeWjTMNew

Page 26.

So, if it isn't stink bugs, check your neutral switch. Its adjustable to a point. Mine was beyond that point.


Hopefully, this helps.

what did the spark test that the tech did look like..did he say good or bad spark?..did he check compression?....