Hi everyone, I just picked up an 89 moto 4 yfm 250 the other day and can't get the thing to start... it is getting good spark and fuel. I've tried starting it with just gas and also starting fluid and can't get it to do much more than backfire and blow flames out of the air box. I took the carb off and took it apart and it is spotless (the guy I bought it from said he cleaned it). one thing I did notice that was that the cover over the timing gear was loose and I'm wondering if someone messed with the timing? I know how to set timing on a car, but how do I set and verify on an atv? Any help/pointers will be greatly appreciated. Thank you in advance.
Update.... I figured out how to check the timing and it appears that the timing is retarded by about two teeth on the cam gear when I line up the crank gear properly... which brings me to my next question, how do I get to the tensioner to adjust this? I was going to remove the left crank case cover to see but didn't wanna dump all my oil if I didn't have to... thanks again in advance for any help.
thanks Mike. Sorry to just jump on the forum and not introduce myself before asking questions.... now onto the quad... I pulled the head yesterday and found out my intake valve isn't seating properly. After I removed the head and pulled the cam, I poured a little bit of gas into the exhaust port, and not a single drip came out of the exhaust valve... poured it into the intake port on the head, and it poured out around the intake valve just as fast as I was pouring it in. (mind you with the cam out, the valves are seated). so, it's off to the shop I go this a.m. to get a spring compressor and some gunning compound to try and reseat the valve.
Heres what you need to do to get the timeing right, first rotate the motor over and bring it up to the "T" on your crank then remove the tensioner from the cyl.Now, pull the cam drive sprocket off the cam and adjust it right or left so when you put it back on it alines with the pointer above the top of the sprocket. If everything alines then remove the spring from your tensioner and bolt it to the cyl, after that install the spring and replace the covers. What I just discribed is the mechanical timeing of your motor, simaler to setting the timeing gears on a v8. BEFORE YOU ATTEMPT THIS BUY A MANUAL, EVERYTHING YOU WILL EVER NEED YOU'LL FIND THERE. GOOD LUCK....GREASY.:hey:
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