KDXRIDER.NET

What is the general jetting recommendation for a RB mod head with a
stock carb? needle, MJ PJ clip?



92 KDX 200
FMF pipe
Boyesen reeds
92 pump gas
no air lid

Thanks

There are so many starting points it's hard to name all of them. Normally start with what you have at hand. You have to get to a point.

What jets are in it now? Needle? Clip position?

45PJ, 155 MJ, 1172 needle, 4th clip

Wow... a perfect generic setup! That's rare and a great starting point.

If you read the jetting guide in the jetting section, then it will guide you through dialing in your new setup. The air screw will tell you allot and help dial in your new setup too, so don't overlook it.

http://kdxrider.net/forums/viewtopic.php?t=1156

If you don't have any spare brass right now... buy smaller than what you have in there right now. A CEL or DEL needle should work better in your carb too...

Play around with it... just don't go too extreme on changes without exploring the differences in between.

I keep getting conflicting advise

"skip the CEL needle and use CGK instead for your 92.

Probably around 38-42 pilot and 150mj. "

CEL vs CGK???

according to the chart the CGK appears to have a bigger low end 'hit'?
if moved to the 5th clip the top end is nearly identical to the CEL.

Any thoughts on CEL vs CGK needle with the RB head mod?

OK, the head is headed back.

I'll try he CEL needle.

any recommendtion on MJ , PJ #s?

92 KDX 200
FMF pipe
Boyesen reeds
92 pump gas
no air lid

I would say around a 42-150 setup....

Which clip setting?

what about the 1172 needle settings?

Always start in the middle position.

Does this sound right?

I was not able to get the air screw to make the bike rev higher, so I went
down on the pilot jet (45 to 40) but I got a bog when I crack the throttle hard so I lowered the clip on the needle ( from 3rd to 4th). It cleaned up a bit but not completely.

Any other suggestions?

92 KDX
Fatty Pipe
No air box cover
1172 needle
155 MJ
140 pilot
RB head

45 to 40 may have taken it too far. Try a 42, or run the airscrew in until the bog stops.

You want to set the airscrew for throttle response, not fastest idle. The fastest idle check is just to verify whether you have the correct pilot installed or not. Stock needle should have been r1173n as far as I know. I will reiterate, the CGK needle is recommended for 89-94 carbs. The needle jet is positioned differently in these carbs than the H series carbs.

CEL should work fine though.

Thanks / the stock needle is 1172, I'll try the CEL and go up to 42 on the pilot.'

Is 155 ok on the main or should it be 152 or 150.

I'm at 900 ft elevation.

Gotcha. Stock needle for my 89/90 were both 1173. I know they made some changes with factory jetting later on, so I guess that's what happened here.

I think you'll be much happier with the cel/del/cgk needles than that 1172. Make sure and let us know though, as I'm quite curious!

Will do, Thanks!

how does the head mod effect jetting? just curious... if you take compression, or add compression by reworking the head, how would the engine know any difference? just asking.

Simply put; more or less air flow will require more or less fuel to match. Any change in compression is going to alter airflow characteristics.

Looks like I have ended up with 40 / 150 / CGK pos 3. I like it, a LOT.

juliend wrote:Simply put; more or less air flow will require more or less fuel to match. Any change in compression is going to alter airflow characteristics.

Looks like I have ended up with 40 / 150 / CGK pos 3. I like it, a LOT.

uh, are you not compressing the air and fuel you have more? the head chamber size doesnt PULL more air in, that would come from porting you cylinder...... right??

Yes, to a point. The head mod alone will not affect jetting too much as far as I know. Mostly you are getting a more efficient burn, so jetting may need to be altered to suit. In any case, it won't be a huge difference from a jetting standpoint.

there you go! you got it! compression has nothing to do with jeting! you are just compressing more of what you have... you may have to set your air screw, but that it. compression only adds bottom to mid......and trottle response, not a lick of topend.