okay here's the situation - I've been so busy lately with 4 strokes that I may be hearing a problem with my blaster when there is none. haven't had it out for a few weeks and can't remember if I had any noise then. When it's running there seems to be a lot of noise coming from the head that sounds like a loud tappet in a 4 stroke. Compression is good, plug looks good. Am I hearing things? The bike runs fine

 

Same thing for me. I went ahead and checked the piston and cylinder. A local engine builder checked the piston to cylinder clearance and said it was fine. The rod seemed to be tight on the crank. I put a new set of rings in (the end gap showed mine to be worn) and it still seems to make the noise you talk of. It runs out really well though. Maybe they do have what sounds like piston slap at idle. I don't another bike to compare it to.

 

To you have your oil injection still on? I had the same thing happed to my 97 blaster. I took off the oil injection and it went away. You you haven't removed it yet it would be a good to do it any way. My pump went out after 60 hours of riding. I was lucky I cought it in time and saved the bike.
It only takes a grain of sand to make the pump from woking.

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After 60 hours? Wierd. Mine has been reliable so far, and has well over 300 hours on it.

How could the oil injection cause a top end noise?

 

thanks mahan - everything you described is what went through my mind - a lot of work chasing gremlins that aren't there

 

The Blaster top end is noisy from the factory. Nothing to worry about.

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#24 Hetrick Racing 1997 Yamaha Blaster <a HREF = http://members.aol.com/atvracerx2/blaster/quadpics.html>Blaster97's Quad Pics</a>

 

Is the sound worse at startup, or after the engine is warmed up?

Is it worse at idle, or at higher rpms? How 'bout under load.

Does the noise go away when you pull in the clutch?

Play around with it a little, it'll help pinpoint the problem before teardown.

Another trick, grab a big screwdriver, and stick the business end against the cylinder, then hold the handle up to your ear (do this AWAY from friends and neighbors, they'll think you've lost it!) -- listen to the engine through this "stethyscope" in different places. Check right at the head, then down midway on the cylinder, then down by the crank. pinpointing the location of the sound can help lots in determining it's cause.

Pam