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I have a 1985 YZ490 and they carb started leaking gas so i figured it wasn’t a big problem just the floats, took the carb off and cleaned the floats and it still leaked. woke up the next morning and it was fine, well then it started running very badly the next morning and i had no idea why, when i would give it gas if would pop and wouldn’t ride well. i took the carb off, cleaned everything and put it all back like it should be and i even put a new spark plug in it. the carb took a crap so i bought a new one, now it won’t start at all and pops when i try to kick it about every 10-15 times. HELP PLEASE
First post to the forum, I have no idea if I’m putting this in the right spot, if not I apologize. Anyways, I have a yamaha Blaster frame with a yz490 84-86? Motor in it. when I picked it up I knew I was getting into trouble but not nearly this bad. Motor would NEVER kick start, so off I went. Had a smeared piston from a base gasket leak, no big deal. Replace the entire top end, have the head mod done to prevent the dreaded pinging issue, reassemble it. starts first kick! Shut it off, won’t start. Kick it a million times, won’t start. Would pop start fairly easy and run like a MF but idle would fluctuate like crazy so I figured I had a vacuum leak. was out riding and it ran away on me, had to pull the choke to kill it. Since then it has refused to start at all again except for the occasional major backfire and now the clutch slips when I try to pop start it. New tm38 mikuni flatslide carb, New CDI, new coil, Brand new reeds, compression is 150, timing was verified to be correct, plug is new. Cannot get it to start. only thing I have not done is a leak down test and replaced crank seals. At this point I am grasping at straws. The ONLY other thing I can think of is that the ends of the reed cage have slight pitting to them and have a minuscule gap on them when held to light but slight pressure closes them up, so I would figure case pressure would shut them easy. This is my first 2-stroke bike project as I have always built jetski for the last decade. Carb is jetted to factory spec. Still won’t start with OEM carb. I have way to much money into this thing to sell it now. Any insight would be appreciated.