motor revving problems

M

masterx1234

New Member
what would cause my 52cc two stroke motor from monsterscooterparts to rev madly high when started then return to perfect idle? it cant be an air leak, because ive changed every single gasket with brand spankin new ones, and it did the same thing when it had the old gaskets on it, could it be that im running too rich/lean? and also my engine can now barely go 24 mph, when i could normally achieve 34 mph. does anyone have any answers?
 
Spark plug color is a good indication of the air/ fuel ratio.
Too lean can cause a high idle speed.
It still could be an air leak. Did you inspect the crank shaft seals?
 
I concur with Gearnut. I did have a crank seal fool with me once on a motor. It had a temporal personality on that one.
 
Listen to these two guys. What you're describing is consistant with a bad crankshaft seal. The most common one is behind the magneto rotor on the left side but there is another one behind the small gear on the right side. They might look okay or they might be installed wrong. take a close look at your seals. A quick squirt of carburetor cleaner into the hole where the ignition wires exit the engine will confirm if the magneto side seal is bad. Likewise a squirt into the clitch cover on the other side will point to a bad seal behind the small gear. A noticible decrease in idle speed will confirm an air leak at these two places.
Other indications will be oily residue inside the engine side covers.
Tom
 
oh ok thanks guys, yea i am just gonna buy another engine because this one has almost 6000 miles on it as of now, so i dont blame it for being like this, im getting paid next week so ill just get another one, they only cost 119 bucks so i aint complaining
 
His engine is not an HT. Don't worry about "behind the little gear" or "carburetor cleaner in the hole where the ignition wires exit". You don't have any of that on your engine.
One crankshaft seal will be behind the pull start bell that is attached to the end of the crank shaft. You will need to remove the bell before you can access the seal.
The other seal is behind the flywheel. You will need to remove the flywheel from the end of the crankshaft to access that seal. My bet is they are either cheap seals and now are worn out or one of them has drifted out of the bore that it sits down into. Good luck on your repairs, and take things slowly. Don't rush it, and if it is aggravating you, walk away from it and take a breather before you start beating on it with a bigger hammer.
Check the internet for exploded views of the engine as well as some pocket bike sites for helpful info on torques and thread direction. If I am not mistaken, the flywheel has left hand threads (backwards) but double check that before you try to work on it.
 
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You'll also find with a bad crank seal that the bike won't pull hills the way it used to and usually blows black oil all over the place eventually. It is a cheap easy fix for most 2-strokes.
 
holy crap! just found out it wasn't an air-leak after all! it was the carb tuning screw!, ok so i took the carburetor completely apart for a good cleaning and when i removed the carb air/fuel screw it was broken in two peices!, what a surprise, all this time the motor was running at max richness! (that explains the high revs when started), i had a spare carb from my last engine and took the screw outta it, and viola perfect fit, now my babies running at 32 mph again! yay, tthank you guys so much for your support, you wont believe how happy i am, i hope to get another 5,000 miles on this engine.
 
Wow...My Bad, sorry for the wrong info. I read 2 stroke and immediately saw HT instead of researching a little. Thanks for the clarification, GearNut.

Masterx, glad you found the problem. That had to feel good. Have fun, ride safe.

Tom
 
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