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Cr125 help!

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Thanks in advance for any help. Bought a 93 cr125 this summer and have had nothing but problem! The bike ran fine for the first couple of rides a little bit boggy coming out of corners but hitting the power band no problem. It then started to stutter, almost coming on and off the power when the throttle is wide open! So pulled the engine and found lots of oil in the flywheel side cover. Read here that the seals were bad so changed them( without splitting the cases) and the bike ran the same! So pulled the top end and the piston and rings were gone( the piston being quite heavily scored but the barrel in good shape) so put a new piston in it and still it runs the same( stuttering and not wanting to hit the power band! Any ideas?

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Did you richen the mix by adjusting the air screw? If the air screw doesn't solve your problems you need to re jet, sounds like your main jet is lean. Temperature will affect how a 2 stroke runs.

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Did you richen the mix by adjusting the air screw? If the air screw doesn't solve your problems you need to re jet, sounds like your main jet is lean. Temperature will affect how a 2 stroke runs.

the cylinder looked fine no scratches or marks. I cleaned the carb before I put the new piston in. When it's running at its best(still very badly!) I have the air screw about a 1/2 turn out.im on the verge of scraping this thing!

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the cylinder looked fine no scratches or marks. I cleaned the carb before I put the new piston in. When it's running at its best(still very badly!) I have the air screw about a 1/2 turn out.im on the verge of scraping this thing!

 

You need to re jet your carb. Pick up a jet kit for your bike or some pilot and main jets of sizes up and down from what you have. I think you need to go bigger on your main jet if that gives you a sense of direction. Your bike isn't getting enough fuel, which is why its sputtering out like that and not getting good power. You can clean the carb as much as you want but you have to put in bigger jets to get the right flow into the engine. Also did you take a look at your reeds when you changed the piston?

Edited by dan2581

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You need to re jet your carb. Pick up a jet kit for your bike or some pilot and main jets of sizes up and down from what you have. I think you need to go bigger on your main jet if that gives you a sense of direction. Your bike isn't getting enough fuel, which is why its sputtering out like that and not getting good power. You can clean the carb as much as you want but you have to put in bigger jets to get the right flow into the engine. Also did you take a look at your reeds when you changed the piston?

Actually, you need to make sure you dont have partially clogged jets, causing a lean condition. Just changing jets randomly is a good way to waste an engine. Fresh plug, proper float level, clean filter, no leaks and clean jets are a must to properly diagnose. Best of all, it's free (other than plug)! Dropping in smaller jets is something best done by experienced tuners who can read a spark plug and understand throttle openings/which jet is feeding @ that rpm. Edited by ickfinger

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