Two Stroke Motocross
Two Stroke Motocross Forum => Technical => Topic started by: YZ250 on December 03, 2009, 06:22:05 PM
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I just recently got a 2007 yz 250 (used), and i was wondering which is the best way to check the life of the motor, or see how much time i have left on the engine before i have to replace it. I don't have the knowledge of how to test for this kinda stuff, so some advice would be nice.
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A compression test will give you an idea as to how well the ring and piston are doing. To check the seals is more difficult. You need to remove the carb and pipe, seal off all vents etc, plug the exhaust port AIR TIGHT, and fab a piece that you can put in the carb boot with nipple intalled in it (like a soft plug). Then, you use a pressure AND a vaccuum gauge to see how long it will hold pressure AND vaccuum. You'd be surprised how many little leaks you can find and this will tell how good the seals and center case gasket is. As for the bearings...that's just an eyeball inspection. Disassembly required.
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Hi YZ250,
Welcome to the board!
First step, buy a service manual for your bike, then read through it. All the information that you seek is right there.
You'll have to open up the engine to see how much life is left on your engine. Lucky for you the two stroke is a very simple engine to fix, even for beginners.
Before you take it apart you could do a compression test, that will give you an idea of how well the engine is doing.
Did you buy the bike used? New? Have you done any work to the bike yet?
Have you cleaned, oiled and greased the air filter? This one habit done after each time you ride will help your engine to last a very long time! The folks that have problems with their bikes forget this one thing. Dirt is the enemy of your engines internals.
Write back and let us know how far along you are and a bit about the history of the bike. Then we'll try to help as much as possible.
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i bought my bike used and i checked the filter and it was clean and new. my friend has access to a compression tester so i think i'll use that. i haven't made any mods to the engine yet but it came with an fmf fatty pipe and shorty silencer so if that makes a difference....i do know it increases torque, horsepower, and powerband range, but if it effects the life of my engine i wouldn't know anything about that. anyways, thanks for the advice you guys!
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Hey YZ250
That sounds good! The pipe and silencer will change the power delivery, but should not affect the life of the engine as far as I know.
I realize that you may have mis-understood one of my questions, which is have you done any work to the bike yet. What I meant was did you take the cylinder and head off? Did you check the piston and ring clearances?
This information will let you know whether you'll need any thing for you engine.
Generally if I don't know the history of a used bike, I'll automatically do a top end (Piston, Rings, etc) and check the lower end for wear. Usually before I put much time on the bike. I do this as insurance against something bad happening.
It's always better to do simple maintenance then to deal with a catastrophic failure. That will cost significantly more! LOL Besides it gives me confidence in my machine, knowing that everything is up to snuff.
Please keep us up to date on your findings.