I did a light trail port on our LT80,took about .005 off the head. Can anyone with past experiance recomend a main jet size? The bike is 1997,using stock exhaust,stock carb,etc. I bored it .020 over for a rebuild(had a lot of use in past 6 yrs),and used a wiesco piston(not my first choice but available quick).
It surprised me to see 150 lb compression after the engine was back together? Thanks in advance for any replies. ...Oh,my 8 yr old will be doing some 300 ft drags,any rec. sprockets with 19'' tires?

 

You can take .025 more off the head, but 150 is fine.Maybe a 2nd base gasket and more off the head.
Removing 2 front clutch rollers is a good thing. it will holeshot better.
You'll prolly need a 12 and 13 for a front sprocket.
Thats about all I can recommend for a stock motor. If you tell me exactly what you did porting wise (openings from TDC in degree's) I can advise further. [img]i/expressions/face-icon-small-smile.gif[/img]

 

Thanks for the reply LT80. I never did put a degree wheel or indicator on it,I was just cleaning it up because it was off anyway. I raised the exhaust port 1 mm, and widened it a bit,cleaned up the transfers a bit. Thew compression seemed high to me for all that was taken off,I thought maybe from the weisco piston and aftermarket gasgets were not accurate. What jet do you think i should run????

PS I drilled a little out of each roller,they total 54g. (9g each) Thanks for your help,I made some jugements on this thing from reading your posts.

 

jets stock are: 92.5/17.5
I guess that I'd try a 90 or 87.5 main jet and pay close attention to the plug.Whats the plug look like now? (light/dark?)

 

I'll stick a 90 in it and keep an eye on the plug,Thanks. I was wondering how sensitive they are to a little porting and compression,plus the fact that it now runs premix. How high have you gone on these things(compression ratio )on pump gas?