FMF pipe and Jetting

[Matt]

In article <33FB4F...@pacbell.net>, a91...@pacbell.net says...
> Hey.
>
> Recently added a FMF Fatty pipe on my 86 YZ490 (like I need more
> power). The bike seems to run great at low and mid RPM's....in fact the
> mid is considerably stronger than with the stock pipe. At the top end,
> the bike bogs and cuts out like it has a fouled plug. Checked the plug
> and it looks the ususual white/tan color on the insulator with a little
> black soot around the rest of it. New plug....no improvement!?
>
> I'm thinking with the addition of the pipe, the bike (which has stock
> jetting settings except a one step richer main jet) is now too lean at
> the top end. Comments...Suggestions...experiences... Help all mighty
> RMD'rs
>
> Thanks
>
> a914nut
>

I agree to see if FMF tech support can help you. If you don't want to
try that, I dont' think it would hurt at all to try a richer main,
especially if the plug is white. I read the reply suggesting going 3
leaner on the main and I duuno. I would be VERY careful going leaner on
a 2stroke, especially if the plug is already comming out white. If you
can't get ahold of FMF, ask a certified mechanic/tuner at your nearest
dealer, they should be able to point you in the right direction.
--
Matt

[Rex Mckinney]

FWIW. I just put an FMF pipe on my YZ and had to go one jet richer,
plug was white after running my standered jetting.

Rex Mckinney
97 YZ250
95 KDX200 fs