first build

[Yamaha#13]

okey i dont have a lot of carb experience, this is my first build I have a 30 mm kiehn carb bran new, it came with extra jeting, my set up is going to be FMF Fatty pipe and matching power core, uni clamp on foam filter no air box, stock read valves, with over size piston, but i dont know the size. The guy i got the engine from said it was freshly rebuilt but didnt know what size was put into it just that it was over sized. Can i get some one to recomend an initial jetting set up.

 

[brandoz28]

I would start with a 55 pilot and a 155 main jet and see what the plug chop looks like.

 

[blasterdemon7]

Welcome to the forum. Above post sounds right on with the jet size.

 

[DirtDiggler]

I Suggest doing a compression test , that will tell you the true condition of the top end .
A leak down test should also be performed , one little air leak can ruin your motor .

 

[wwholden]

Dont you loose a little power by using a direct clamp on filter? Because the air doesn't have a long tube to travel through to get velocity before entering the engine.

 

[brandoz28]

Most end up with a dead spot down low, adding a short piece of tubing between the filter And the carb helps this dramatically.

I also recommend a uni filter over a k&n. Better protection without sacrificing power

 

[wwholden]

Most end up with a dead spot down low, adding a short piece of tubing between the filter And the carb helps this dramatically.

I also recommend a uni filter over a k&n. Better protection without sacrificing power

I agree on the K&N but a Uni over No Toil or Twin Air? I thought maybe people just got Uni because it was what their local shop carries. But if there was a better filter then it would be No Toil or Twin Air?

 

[Yamaha#13]

not to worried about the leak down, or compression, the engine has just been rebuilt by local machine shop. Thanks for the tips. I would still use the air box but tube leading into the carb does not fit my new carb.

 

[Yamaha#13]

how important is it to know the new piston size for jetting?

 

[brandoz28]

not very. the bore size won't affect jetting much at all, unless you make a VERY large change (like going to a BBK)

 

[Larry's Shee]

Well, unless you know for sure that the shop performed a leakdown, it's the only way to be sure it's ready to go. NOBODY's perfect.

Peace of mind= PRICELESS I:I

 

[slickerthanyou]

Well, unless you know for sure that the shop performed a leakdown, it's the only way to be sure it's ready to go. NOBODY's perfect.

Peace of mind= PRICELESS I:I

Correct! I actually asked three local yami shops if they leak test there motors--- answer NOPE! Only used for troubleshooting purposes! They prefer to take your money again!

I would have it leak tested or do it myself, before you fire it up! If it leaks, won't last very long!I:I