E.W. Motocross Schools Northwest Motocross Forum Northwest Motocross Forums General Discussion **PIT**TALK** Two stroke compression
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Anybody know how much compression a 09 yz125 should have? I am finding a lot of varied answers online and my manuel doesn't say.. I was told that you need to hold the throttle wide open when kicking/checking compression but I don't understand why | ||
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I never checked compression on my 2-stroke. Removed pipe and looked up exhaust port to check piston condition every two or three rides. With a good flash lite I could see piston, rings and most of the cylinder. | |||
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150 to 160 is normal. Below 150 time for at least a ring for most stock 2 strokes. Hold the throttle wide open and kick it untill the gauge stops inching up. Usually about ten kicks and this is what your compression reading is. | ||||
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Thank you | |||
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Gage read 85-90lb..I thought it felt alitttle slow coming out of corners generaly its a rocket---> I pulled the pipe looked up in there looks brand new, I was expecting it to be all brown black burnt on the front side of piston, so I'm thinkin just needs rings? Proly should do the piston/pin while I'm in there and go oem kit- I was told go up one size on main since its colder out | |||
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FYI on a side note; Prior to needing a new top end I ran some high octane VP mixed 50/50 with 91 pump gas and the bike didn't run any better it ran worse, then I read on VP site you need to go up 2 size main jets on two strokes when runing race gas, I drained it went back to straight pump but I think it was to late I lost a lot of power...awesome so pumped now I need new top end! lol | |||
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I ordered complete new topend kit including piston, rings, gaskets, wrist pin an bearing.. With sales tax and shipping my cost $77!!! | |||
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I wouldn't go up any on the jetting until it starts to knock, then change it. Running high octane fuel in a 2 stroke wont buy you anything unless you are pinging. The good gas only makes jetting more even but if the jetting is already right and doesn't seem to vary from tank to tank, save your money. If you really want to have some fun, do a google search on wetline jetting. It takes a while to do but once you get it right you will really be impressed with the performance. ------------------------------------ If you wanna live life on your own terms you Gotta be willing to - CRASH AND BURN! ... | |||
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We have been mixing 1 gal of race gas to 3gal of regular for a year two.It eliminates ping and keeps the cylinder from getting pitted.Never did re-jet for it #329 40+ class | |||
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Idk maybe it wasn't the race gas, probaly just time for new topend. I was just surprised on VP site it read if your runnin race gas in two stroke need to go up two on the main, I've never heard that before and have ran 50/50 on many two strokes with no problems. Paul I looked up that wetline jetting, I've never heard of it, thats was very interesting to read, I might try that once I get the fresh topend. | |||
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I went to a motor building seminar with Rod Falkner, the owner of Dumonde Tech. It was a very interesting evening. He explained wetline jetting and the theory of jetting over and above above the stoichiometry parts. I did the process when I had my KX250. Took me about 2 hours and I got really good at pulling the springs off the pipe. It made a huge difference and really helped me understand and feel jetting changes. ------------------------------------ If you wanna live life on your own terms you Gotta be willing to - CRASH AND BURN! ... | |||
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On my YZ125 I run half C12 and half ethanol free unleaded premium fuel. Its a stock 2005 with a Pro Circuit pipe, silencer and V-Force 3. I don't have the jetting specs in front of me, but I called Pro Circuit and they gave me there recommendation. And of course EVO did the suspension. It is the best bike I have have owned. Ride 2 strokes be happy. | ||||
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Good idea..the bike came with FMF so I will call them for jet specs and might even call PC for second opinion. Yes I agree the best bike I have ever owned and I have owned a lot of them, so much fun it could be illegal ! | |||
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pro circuit has all jetting on there web sight under support and jetting its a good start | |||
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Nothing is more fun than a 125. AS I got older the more fun they got. | |||
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I put the new 125 topend in. The old piston was severely eroded around the top edge all the way around the most severe part was the back half. Something I've never seen before. The bike is stock so I would think 91 pump gas with 927 mixd 32:1 should be good but people are tellin me I need race gas..? I would rather not$-- I went up one on the main from 410 to 420 haven't started yet thinkin about up one more to 430.. ugliest piston I have ever seen- I had 80psi now have over 160 | |||
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TRA, you have to run 95 or higher octane fuel in a stock YZ125 (On page 1-12 of the manual). They will detinate and ruin the cylinder. 2 gallons of race gas to 3 gallons of premium pump gas is what I run.
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I bought some VP 110 ran the mix ran waaay better! Thanks EW! | |||
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I run C12 1/2 and 1/2 with Silkolene 32 to 1 in my YZ125 and YZ250. | ||||
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E.W. Motocross Schools Northwest Motocross Forum Northwest Motocross Forums General Discussion **PIT**TALK** Two stroke compression
Northwest Motocross Forum Northwest Motocross Forums General Discussion **PIT**TALK** Two stroke compression© YourCopy 2002