RPM goes up as it idles

[shok47]

Fresh rebuilt top end with weisco piston. All stock engine with one size over bored. Just got new reeds for it and it starts and idles nice now. Been doing the break in, but at the slow, less than 1/2 throttle runs, I engine would sometimes rev on itself and it goes pretty high. I would feather the clutch to lower it but comes back again.

What is this problem?

 

[blasterfreek30]

key symptom of an airleak somewhere...check all ur bolts again to makes sure they are tight

 

[brandoz28]

what he said^^^^^

 

[motoman9911]

What they said ^^^

 

[DirtDiggler]

yeah , air leak check bolts , also check the carb cap , and check where the throttle cable comes through the top of the carb. Air leaks are bad because it can lead to a fried motor

 

[shok47]

I have checked the cylinder bolts 25ft lb, and the 4 under it. The boots are on tight, reed valve bolts on there tight. I double checked the top of the carb where it screws off and have tightened it with channel locks to make sure, then tightened the screw to hold it in place. I sprayed some carb cleaner around the gaskets, and carb but nothing happened. Though eventually after it warms up for 1-2 minutes it started to rev up.

 

[brandoz28]

bet its the stator side crank seal

 

[brandoz28]

or you have a leak between the cases, if you're positive that it's not leaking from any of those areas

 

[shok47]

well first, how many screws out for the idle? I had about 1.5 turns out. I made it to 1 turn and its doing fine! could that have been it? I hope so. The engine was running fine before the rebuild and I never touched any other gaskets. Lets just hope you guys will clarify the idle screw!

also, my spark plug was a light grey color, no residue, all dry and light grey

 

[brandoz28]

you mean the air screw on the side of the carb? may have some junk in the pilot in the carb.

 

[shok47]

yea, on the choke side. I cleaned the carb as well, forgot to mention.

what about the light dry grey color of the spark plug? (added it after postng)

 

[brandoz28]

that means its running lean!

 

[shok47]

new jet then???

 

[Troyaughenbaugh]

or his plug color could just be from the air leak. Was this a new plug that you put in after rebuild, or was this plug one that you used before the build?

 

[shok47]

It was a new plug. Took it out for another run and it's feeling pretty good, snappy throttle and picks up real quick, and idles fine with the screw 1 turn out. (though no experience with previous 2 strokes)

 

[Troyaughenbaugh]

what carb do you have on it. any mods? what size jet is in it. I'd keep a close eye on that plug!

 

[Ranger87]

Not to thread jack but i got the exact same problem. Revs on its own. i also feather the clutch to idle it down. Im running stock carb with FMF fatty and Moded airbox lid. Jetted to 260.

 

[brandoz28]

check for air leaks.

 

[little3mil]

hey man i have leak testers in the for sale thread for 30 bucks shipped and complete, you would be able to find the leak in minutes with it... LMK

 

[little3mil]

Not to thread jack but i got the exact same problem. Revs on its own. i also feather the clutch to idle it down. Im running stock carb with FMF fatty and Moded airbox lid. Jetted to 260.

same thing dude when i first got my blasty it pissed me off for 3 months till i leak tested it, when you find your leak with my tester and fix it, it will run cherry I:I