where to go from here. jetting q.

[Jim Cook]

I fear that you may be confusing the pilot jet circuit with the jet needle/needle jet circuit, in where it is too rich. If you have the throttle stop screw screwed in too far, the raised slide (and resulting raised jet needle) can effectively bypass much of the pilot jet circuit.

(IMO... The pilot jet controls from 0 to 1/8 throttle. The jet needle/needle jet circuit controls from 1/8 to 3/8 throttle; with the slide affecting everything; and the main jet influencing things more as the throttle opens more, and controlling the jetting from 1/2 to WFO.)

Regardless, the #7 slide will definitely lean things out a bit.

Good Riding and Jetting!

Jim
Good Riding!

 

[iancp5]

Jim,

What's driving me crazy is that I jet it, it runs well, then it changes on its own! I can't decide if it's my imagination or there is something else going on. How much does the weather effect it? The temp has only dropped 5-10 deg but it's gone from dry air to very wet and damp.

 

[Jim Cook]

Jim,

What's driving me crazy is that I jet it, it runs well, then it changes on its own! I can't decide if it's my imagination or there is something else going on. How much does the weather effect it? The temp has only dropped 5-10 deg but it's gone from dry air to very wet and damp.

10 degrees won't affect the jetting as much as the drastic change in humidity. Humid air has less burnable oxygen than dry air.

It's a compromise, but you should be able to come up with a compromise which will work in a variety of situations is a fairly usable range of temperatures and humidity.

One more thing.... I never try to experiment with jetting unless I have fresh packing in the silencer. Dirty silencer packing
throws the formula way off.

Good Riding!

Jim

 

[dank]

throwin a thought out there, could ur needle seat be worn? from what ive read a worn needle seat will make ur jetting next to impossible.

 

[iancp5]

throwin a thought out there, could ur needle seat be worn? from what ive read a worn needle seat will make ur jetting next to impossible.

Could be. Maybe I should bite the bullet and get a new carb. It's almost as cheap as sending it to RB from the here. Although didn't I hear that some of the older Keihin allowed replacement of the seat? Bet no-one in the UK stocks them though. I'm waiting for the #7 slide at the moment. I think the fact I'm using a 35mm doesn't help, not sure what other bikes it's used on. I can get a new 36mm for £110 though.

 

[stainlesscycle]

i have been completely happy with the 36mm carb. my jetting has been pretty stable 50-90 degree weather. i've felt no need to tinker with it once i got it close. it runs way better than it ever did with the 38mm carb. and it truly idles, without cranking the idle screw in/throttle adjuster... and it's way snappier off the bottom.

 

[Skidad]

Any of you guys with the 200's tried adding the 10mm spacer to the exhaust flange like Go Fasters recommended to help low end power?

Maybe Go Fasters (or Scotties) could fab up a kit if it works so good?

 

[stainlesscycle]

i run the ltr style pv cover, which i believe achieves the exact same thing as the 10mm spacer. i also have a 9 oz flywheel weight on it.

 

[iancp5]

i run the ltr style pv cover, which i believe achieves the exact same thing as the 10mm spacer. i also have a 9 oz flywheel weight on it.

+1 Same here

 

[GMP]

Maybe try and get ahold of a newer 200 specific pipe. If someone has one it would be interesting to see the dimmensional differences.

 

[stainlesscycle]

i'm running a doma from a 300 which did not fit 100% - but it was an easy mod (cut 30mm or so off the stinger end..) i'm not sure if this is an issue from having a later subframe on an earlier bike...and the lower frame mount for the doma does not even come close to fitting. but the pipe works signitficantly better than the early gnarly i had. i haven't tried putting the messico on it yet.

 

[iancp5]

i'm running a doma from a 300 which did not fit 100% - but it was an easy mod (cut 30mm or so off the stinger end..) i'm not sure if this is an issue from having a later subframe on an earlier bike...and the lower frame mount for the doma does not even come close to fitting. but the pipe works signitficantly better than the early gnarly i had. i haven't tried putting the messico on it yet.

The pipes for 250/300 used to be the same part number but different for the 200. I don't know if that was because of a different fitting dimension or only because the pipe was differently tuned.

 

[Jim Cook]

The pipes for 250/300 used to be the same part number but different for the 200. I don't know if that was because of a different fitting dimension or only because the pipe was differently tuned.

I'll share a bit of information regarding the '97-2002 FMF Gnarly pipes, which had a different pipe and number for the 200 vs the 250/300.

In 1999 when GasGas North America was the US distributor, Don Knight was desperately trying to lower the cost of the bikes. The Messico pipes were very very expensive; so one of the first things he did to lower costs was to talk to Don Emler at FMF, to get them to make a Gnarly pipe for us. (He called him Donny Emler in our conversation, so I figured they knew each other pretty well.)

GGNA sent three crated bikes to FMF to use for getting the fit correct; a 200, a 250, & a 300. (With the OEM Messico,, all three bikes took the same pipe.) Soon, GGNA was sending us new bikes with a Gnarly pipe in the crate, instead of the Messico.
With our first shipment of these bikes, during set-up, I immediately observed that the lower pipe mount was positioned incorrectly on the 200cc Gnarly pipe, and the 250/300 pipes were much closer to correct.
Other than that, the pipes were identical.

We (GGNA, and then SMS) found that the EC200 that was sent to FMF had the lower pipe mount welded to the frame incorrectly (placement wise), resulting in the different FMF pipe for the EC/XC200.

When the FMF pipes were reconfigured to accommodate the change in the engine/frame relationship in 2003 (and the Fatty pipes were added to the offerings), this was fairly well rectified; and the 200 pipe was also reconfigured a bit to be more efficient and compatible with the 200 engine. The 2003 and later (at least through the 2006, which was the last year I was a franchised dealer) 200cc FMF pipes have a different confirmation than the 250/300 pipes.

Good Riding!
Jim

 

[iancp5]

Back to the jetting.
I have now fitted an EEL needle on #3 with 35 pilot and it still seems rich low down but probably ok for my riding which needs smooth torque! Was going to use the thumper for the next event but may use the 200 just to see how it goes.

There's something weird going on with this 200 and one day I'll get to the bottom of it. I'm still waiting for my #7 slide to arrive. I did notice the current slide (#5) seems to have some of the surface coating being rubbed off so I'm wondering if this is the cause of the behaviour. What I don't understand is why it gets richer unless the needle seat is being eaten up. Maybe I just need a new carb?

What effect do tired reeds have?

 

[iancp5]

This is getting very weird.

It ran great on the EEL, idled great at the beginning, very slightly too snappy but nothing worth worrying about. By the end of a 3 hour H&H I again had the throttle stop screwed all the way in to get an idle and stop it stalling. Bizzare! Now I'm going to go exactly opposite and try a much bigger pilot and see what happens but I don't understand why it starts off idling fine then after some hard use refuses until I pull the carb apart and change something then it idles!!!!! For a while

 

[dank]

have you talked to anybody like ron at r-b designs, or jd jetting, and get their opinion? they may be able to think of something that we are not.

 

[stainlesscycle]

This is getting very weird.

It ran great on the EEL, idled great at the beginning, very slightly too snappy but nothing worth worrying about. By the end of a 3 hour H&H I again had the throttle stop screwed all the way in to get an idle and stop it stalling. Bizzare! Now I'm going to go exactly opposite and try a much bigger pilot and see what happens but I don't understand why it starts off idling fine then after some hard use refuses until I pull the carb apart and change something then it idles!!!!! For a while

change your float needle/check your float level. perhaps fuel is slipping by..hence rich running...

 

[iancp5]

It's not that it's rich that confuses me it's that it seems to get richer on its own!
Think I'll take the carb off at the weekend and have a good inspection. Hopefully I'll get time.

 

[iancp5]

Well some of the mystery is revealed. I now know why my jetting is so radically different to others running a 36mm carb. I have a 35mm by the way and I seem to have a different design of PWK! I seem to have a special recess in the slide which fits into a protruding specially shaped tang in the carb when the slide is fully closed. As I couldn't seem to get it lean enough from idle to 1/4 throttle I bought a #7 slide to try instead of the #5 and the design is quite different. With the #7 in it just revved its tits off as soon as I started it because I find the new slide doesn't have the recess and can't close completely.

Does anybody know about the carb I seem to have? Has the "tang" been fitted to better locate the slide to reduce wear from vibration?

Inspecting the #5 slide I notice in addition to the recess it has a small slot cut in it ostensibly to allow a bleed airflow?

So I'm back to my 35P, EEL needle on #2, airscrew at 3 turns and it is still too rich at idle. I am sure it is not pulling over because I tried a 42P and it was sick as a dog being so rich. I was considering dropping the needle again but am hesitant because from 1/4 ish upwards it is on the edge of lean until the main takes over. It's just idle to 1/8 that it's rich. Can I get smaller than a 35P I wonder?

 

[dank]

so is it still a keihin pwk model? they list the pwk35, and the pwk air striker.