YX 150 rebuild with TB piston - now smokey

[Phil67]

First race with it yesterday, sx track, all second gear. Holeshotted 2 races against a 190 and a TB bike, so it has some pull. First 3 motos had some trouble with it stalling, upped the idle a bit and went back to the old faithful main jet and it was fine for the rest of the day. Ended up with 2nd place for the day, so I'm stoked considering it was a new engine combo.

 

[my67xr]

Well Done Phil, Top Effort!

+ reps for all your troubles

 

[Phil67]

Thanks bud, pretty stoked. Number 1 vets too, hahaha

 

[my67xr]

it's good to have someone putting in all the hard hours sorting their engines out.
it has given me a few ideas for my up coming 155 build

 

[Phil67]

Go the 67mm Craig, you won't regret it. Took awhile to get the shimming right, but now I know for next time. If you want to go nuts and get the piston up the bore for better squish etc leave the base gasket out, use honda bond, and even take some meat of the bottom of the barrel. Or, leave the head gasket out. It's funny how the same methods used on the old big block drag race motors is the same stuff on these china engines. That's how I built it anyway. Grinding here and there, oil pump clearancing, piston blue printing etc. wish we could get zero gap rings for better leak down, should email Childs and Albert and see! Cool stuff doing these engines.

 

[zwebx]

Go the 67mm Craig, you won't regret it. Took awhile to get the shimming right, but now I know for next time. If you want to go nuts and get the piston up the bore for better squish etc leave the base gasket out, use honda bond, and even take some meat of the bottom of the barrel. Or, leave the head gasket out. It's funny how the same methods used on the old big block drag race motors is the same stuff on these china engines. That's how I built it anyway. Grinding here and there, oil pump clearancing, piston blue printing etc. wish we could get zero gap rings for better leak down, should email Childs and Albert and see! Cool stuff doing these engines.

on that note i will talk to the bloke at work that converted his bike to gapless rings..
then theres nikacil bores.. coatings on the piston and race gas

 

[Phil67]

Piston was coated already, no need for race gas, 98 is enough. Although I used to run avgas in the 250, whatever was left over went in the whipper snipper and mower, haha. If gap less rings are available, I'm interested for sure. Was almost gonna linish the rod too, maybe next time. Apparently I have a trick rod already. Hpc coat the pipe? Where does it stop! Ti valves? 3 angle valve grind? Hardened seats? This could get serious!
People still laugh at my engine build, that 2nd place medal mustn't be enough, in fact I would be number one in vets too. All that with a 22 mm carby, hahahah

 

[zwebx]

Dont forget boost

 

[timeeh]

Thanks bud, pretty stoked. Number 1 vets too, hahaha

So who gets to ride in Vets? 35+ or 40+?

 

[Phil67]

I'm super vets, +45, hahaha. There no vets class yet Tim, waiting on more guys to get involved.

 

[timeeh]

I'm super vets, +45, hahaha. There no vets class yet Tim, waiting on more guys to get involved.

Jesus! how do you fit your walking fame in the with the bike? :hidesbehindsofa:

 

[motorman]

Piston was coated already, no need for race gas, 98 is enough. Although I used to run avgas in the 250, whatever was left over went in the whipper snipper and mower, haha. If gap less rings are available, I'm interested for sure. Was almost gonna linish the rod too, maybe next time. Apparently I have a trick rod already. Hpc coat the pipe? Where does it stop! Ti valves? 3 angle valve grind? Hardened seats? This could get serious!
People still laugh at my engine build, that 2nd place medal mustn't be enough, in fact I would be number one in vets too. All that with a 22 mm carby, hahahah

The TI valves, better springs and TI retainers is a worthy investment. But if you go down that path you better off just getting a decked out V2 head.

 

[Phil67]

Walking frame is collapsible Tim, fits in the back seat

Yeah I hear ya Nick, I'll see what happens head wise later.