New FMF Gnarly Woods

[mwm6]

OK - I installed an FMF gnarly woods pipe and Pro silencer and opened up the air box(removed snorkle and drilled some additional holes on cover) on my 98KDX200 last week. The first day was absolutely awesome bottom-mid power increase. I couldn't keep the front end down which was never a problem. I bought the bike used about a month ago and I know it has some miles on it.

The bottom end increase has gone away after that first day and it seems as though the mid increase is still noticable. Does this sound strange ???? Is there something I'm missing - or possibly something I should check (reeds, etc)

Your help is appreciated - I want that bottom end increase back....

 

[Racer#213]

Try Rejetting, if you didn't do so. Because a new pipe will alter jetiting specs, plus opening up the air box will let more air flow causing the bike to run richer which will ruin the power flow (i.e. loss of bottom).

 

[Racer#213]

O, and also try putting in a new plug bc if it's running rich your plug could be a little fouled, which will allow it to spark and ignite your engine, but will not allow the power to be no were near were it should be.

 

[mwm6]

I didn't re-jet. I did replace the plug after I noticed initial bottom end increase went away - didn't make the bottom end increase come back (I'll check plug to see if it looks rich).

Would the bike react in such a way because of jetting???? Run like hell (bottom end) for a short period right after installing pipe - then loose the bottom end increase? I guess it would, wouldn't it as the engine warms up??? Except now it's not even there when the engine is "cold". I do notice a drop in idle RPMs and sluggish initial throttle response when engine warms up. I have air screw 1-1/2 turns as FMF recommends. I'll have to re-jet.


Thanks!!!!!!!!

Thanks

 

[Racer#213]

Yup, no problem.

That should pretty much take care of it. Your lucky that's all the pipe did to your bike. Heck when i put my fatty on my kx100, i had to go richer like 3 mains and 1 on the pilot. My bike was SO lean it wasn't funny. it would just bog down in the whoops. And we had to raise the float level to get more fuel into it's system. I'd just try a leaner pilot and adjust the air screw and that should help.

 

[23jayhawk]

Two things come to mind. One is air screw adjustment and ambient temps. Was the temp the same both days?

The other is age of your gas. I've found that if I don't use a full batch of premix in 2 weeks, I'll notice a loss of bottom end snap by the third week. I'm sure it affects top end HP as well, but the low end throttle response is where it's most noticeable to me. During the hottest 100 days of summer, I need to use it up each week or the response is very flat. :|

I think it has to do with the light ends boiling off in storage, even in a relatively cool garage.

 

[chris kuba]

What you need to do is go higher in number with your pilot and main jets at least one step. Read the carb tuning tips in the tech section. Words of wisdom there. You are probably running too lean, not too rich. Did you have any problem with putting on your pipe? I just got one for my '99 KDX 200 and it wouldn't fit. FMF was a real pain in the @#$ with trying to get it right. It turned out that the cut-out on the pipe was too small so it wouldn't fit.

 

[rethnal]

Originally posted by Racer#213
........, plus opening up the air box will let more air flow causing the bike to run richer which will ruin the power flow (i.e. loss of bottom).

I think the opposite is true.......

Originally posted by canyncarvr
Any other issue notwithstanding, removing the airbox lid will reduce the pressure differential that the carb runs on which will effectively result in a more lean A/F (air/fuel) mixture.

 

[Mac]

Did you use RTV silicon when installing your new pipe? You may have developed an exhaust leak which will hurt performance.