I have an '88 that has a .010 stock piston, rad valve, fmf fatty pipe. I run Bel ray oil at 40:1. I haven't finished putting this all together yet and was wondering if anyone could tell me a good main jet to start with. I think the stock main jet is a 158? This motor isn't ported and uses the stock carb. Also, what heat range of plug should I use? NGK 7, 8, 9? I ride in MN so elevation isn't a problem. Thanks in advance.

 

Well on my 86 the stock main was a 150.I am now using a 152.I have a FMF gold series fatty pipe and silencer,A little bit of port work,boyesen reeds,uni filter,a .020 wiseco piston.

IT runs a little rich just a little.lately it has been acting spot on though.I haven't fouled a plug in a long time and it is a little brown like it should be.But during the winter it was acting rich.

I run maxima castrol 927 at 32.1.And I also run a 50/50 blend of race fuel and premium pump gas.

 

does the race gas make it faster?

 

letitsnow: I'd start with a 160 main (probably fat, but better safe than sorry) needle clip in the middle position, and a 50 pilot..when my R was stock, I ran a 158 main, 50 pilot, and needle in the 2nd clip from the bottom, and yes, I'm in Mn too, if you have problems, I make it up that way frequently, so maybe I could swing in and help you out.

 

No it doesn't make it faster.I just run it that way to help and keep the engine clean.My dad and some guys that I used to race with sadi that race fuel burns hotter and cleaner.

Plus it smells cool.

 

Thanks for the advice Dill, i'll try what you said. What range spark plug do you use? Thanks again.

 

I run a 9 right now..I do mostly higher speed riding, so it works fine and doesn't foul out...if you do alot of real slow trail riding and putting around, run an 8.

 

I have an '88 with a FMF silencer,stock pipe,.005"head gasket,cylinder spacer,'86 boostported .010"Pro-X piston,6mm reed spacer,V-Force reed cage,stock carb,and a K&N filter with outerwear.My main is 162,pilot is 40,needle clip in the 2nd groove,airscrew at 2and1/4.Hope I helped.

"88 250R many extras