Shwine617

I have been trying to get two of these for a while now and finally got a set. I can wait to bring them upstate. I got them both up and running but one sounds sluggish compared to the other. Cleaned both carbs, drained tanks, new plugs. One is an 88 kickstart. other is an 89 electric start.

the 88 is sluggish (150psi compression)
89 runs great (160psi compression)

Shwine617

Here is a video, so you can hear what I am explaining.

1988 and 1989 Yamaha Sno Scoots Snowmobile - YouTube

yamadad4

if the carb is clean, it sounds on the rich side. try checking the choke cable and make sure its not stuck and adjusted properly.

from there, check the air adjustment screw. most of those started at about 7/8 to 1 full turn out. compare with the one that sounds better and set it accordingly.

last thing i would look at would be confirming jetting and float height.

Shwine617

Thanks!
I am going to soak the carb overnight just in case. Pine Sol has been my favorite carb cleaner now, I have tried a lot of stuff and it works really well for the price. The mixture screw on the good one is about 2 turns out. it was 3 turns on the rough one. I tried adjusting it all over but no difference. I am going to pull the choke assembly out this time and clean that as well. Jet are clean and identical. I will check the float height while I'm in there.

Someone else told me that the exhaust might be plugged up some. I will do the carb one more time and report back.

I really appreciate the reply, now all I need is some snow! should be going to Vermont with these at the end of January, I just want to make sure they are up to par before I go.

yamadad4

plugged pipe will usually stall the engine after a certain amount of run time, but not out of the equation. not much pipe diameter on those.

fine tuning the air mixture on those is similar to any 2 stroke engine from the day. rotate the air screw in small increments either in or out until the idle starts to rise. from there you can reset the throttle cable or the idle adjustment screw until things are right. takes a bit of playing.

i would guess the spark plug to be quite dark on the scoot in question.