This always happens to me...

[Derrick Adams]

I've been trying to get my Z to run with the big carb for over a month now. I've been trying everything I can think of.

Well, I checked the compression a couple weeks ago and it was around 150lb. Not the highest, but the engine was cold so I figured it was ok. Then I learned last week, to check it with the throttle open. So I did that Saturday and found it to be 125lb. NOT GOOD.

I tore the top-end off and took it to get checked out. Turns out the top-end I put on in Feb. (that had about 6hrs on it) is shot. Not only are the rings wore down, but the piston was cracked and getting ready to seperate! No doubt to to the severe conditions of the last hare scramble. That was a very close call!

So I suppose I've learned my lesson for running an old stock Yamaha piston kit. The cylinder is getting bored today and a Wiseco kit is on the way. I also took the oppurtunity to add the intake spacer and might even do a little porting on that cylinder while i'm at it.

Now my bike didn't run near what I felt it should before. But it did run pretty well. So, i'm really excited to see how it runs with a GOOD top-end in it.

[Blown 331]

Lucky you caught it. Same thing happened to my 250R with a stock piston, unfortunatly the piston broke.

[max]

Check The Muffler Bearing Grease. It Could Be Melting And Draining Back Into Your Carb, Clogging The Needle Position.!!!!!!!!!!!let Me Know If I Can Be Of Some Assistance. Ill Role Out And Help Ya Tackle It. I Got Some Tuning Of My Own. We Can Be Tuning Buddys? Seriously. I Might Be Bring My New R Out.
Max

[Derrick Adams]

It'll be back together by this weekend. Come on down!

[TimSr]

I think you need to seriously look at who is boring your cylinders. There is no reason a stock piston should be toast that soon. It should handle a lot more extreme conditions than that. Did you have it bored the same place that did your 250R?

You should really consider having Wiseco do your boring, especially since you are in Ohio. I shipped one out on a Monday and got it back on a Friday. There is a lot more to quality boring than drilling it out, and your not saving any money when you do each cylinder twice.

[cool_racer]

i agree, i blew top end on my blaster all the time when one guy did them. but when a perf shop did them (hetrick, a local guy that does some of my stuff) they hold together alot better.