Jetting question for you RB'd guys

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computerguy50
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Jetting question for you RB'd guys

Post by computerguy50 »

Having trouble fine tuning my 03 220(FMF Rev, vforce reeds, RB'd head and carb, fresh rings, clean air filter, repaired KIPS over the summer). Main problem is bog at low RPM. Just rolling throttle 3rd gear off idle pretty big bog, not like the bike was turned off, but slow to respond. Same 3rd gear from about 3500 RPM, hits pretty good sometimes lifting the front wheel. I know there is more there.

Current jetting is 40/150, 3rd clip. Elevation 1250ft. Temps in the 40's, 40:1 mix. Air screw out about 1 1/4 to 1 3/8 is best, tried out to 2 1/2 but not much difference.

Please post your jet setups or ideas for 220 RB'd bikes.

Thanks.
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canyncarvr
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Post by canyncarvr »

Mine FWIW (a 200..not what you asked for):

38/148/DEK-4. El. 15-3500' I'd guess...mostly. Temps in the 40's, 40:1 but with 5% toluene (32oz.), 2 1/2% Trick 114 (16oz.). V-Force III reeds. Not real picky about the 40:1 'cuz of the other additives. Generally put in about 4.7gal. of fuel, would need 4.67gal to make it 40:1. Not enough to matter...I'm just sayin' the way it is.

Gearing: 12/47

Re: 'Air screw out about 1 1/4 to 1 3/8 is best..'

Probably not.

My AS generally sits @ 2.6-2.75.

You're familiar with the SSS? Won't repeat here 'cuz info is all over the place. Will if you wish. Find it. That is your problem...the AS I mean.

Give the CEK (I presume?) on clip 4, too. The clip numbers start from the blunt end...right?

BTW...my bike runs very well. Some days it feels like 250s I've ridden (YZs, CRFs, KTMs). The best it's run is just over the past month or so. There's been a high pressure ridge stuck over the area..and what a difference that makes!!


Although....re: 'Same 3rd gear from about 3500 RPM'

I do wonder about that part. If you have ANYthing in the way of hesitation or poor throttle response from 3500RPM in 3rd gear (as you did say you do)...that's a pretty big 'failure'...and shouldn't be happening AT all..not even a teensy bit. That situation on my bike will either get gravel spit 50 yards out the backside of the tire, OR will dump me on my arse.

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Post by KarlP »

You did not mention your silencer. Probably FMF, though?
I had my stock silencer plug up, my bike was similarly equiped but just would not rev out at all.

That fella who did your carb and head is usually pretty helpful.
He helped me with my plugged silencer situation in a Sunday afternoon phone call.

Try a fresh plug?
Your jetting doesn't sound unreasonable. All kinds of other stuff to check out.

How about some history?
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Post by canyncarvr »

>|<>QBB<
KarlP wrote:

How about some history?


'Four score and seven years ago our fathers brought forth, upon this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal.'


Back when men were men....and women weren't!

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Post by computerguy50 »

Thanks for the responses guys.

Canyncarvr: Wow that seems to me a little lean on a 200. Your modded carb the stocker?
I am familiar with SSS but never experienced it of course. Does that apply more to the 2nd barrel (high revs)? It just seems moving my AS out past 1 1/2 I do not notice much change, especially regarding my bog.
Regarding "same 3rd gear from about 3500 RPM" I should have said same 3rd gear test from about 3500, it pulls decent, sometimes lifting the wheel, but I think there is more to be had and it is not consistant.

KarlP: Yes, FMF turbine core II silencer. I do plan on repacking it soon. Not sure on the history I have fresh rings from summer in it. Wiseco was done before. Bought it 2 years back from a Guy I have seen on this site, so you may know more history than I if I give his name. Are you a 220 BTW and what jetting and elevation or you.

Just not sure which may to start here smaller jet or bigger? Could both of you please describe the symptoms of a lean and rich condition right off idle.
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Post by canyncarvr »

Ooops. I did leave that out. Sorry.

No. My carb is an airstriker. SSS was the same on the OEM 35mm as I recall. Others have noted the modified OEM 35mm PWK to have it, too. Also, it's been noted to have been found on a 220 as well as a 200.

Re: 'I am familiar with SSS but never experienced it of course. Does that apply more to the 2nd barrel (high revs)?'

No. The difference is off-idle pull. That and IDLE pull. When it's right, you will be able to count the ticks of the motor and it will NOT stall. Not exaggerating for effect..the difference is huge. 3rd gear will pull every bit as well as 2nd used to, there will be NO noticeable lazy throttle (not quite a bog) that is common between 3rd-4th ('cuz the ratio spread between the two is pretty big).

Re: 'past 1 1/2 I do not notice much change, especially regarding my bog.'

I can't say your response problem HAS to be the air screw...but I know for sure it CAN be.

You won't notice 'past 1 1/2' if that means moving it to 1 3/4 or two full turns. START at 2 1/2, bracket changes on either side from there, in small increments..like the width of the marker line on one of RB's knurled screws. Take the time it takes to find it. It's there. Once you find it, you will learn quickly what makes it change and will be able to adjust it on-the-fly if you wish as temps/conditions change during your riding day.

IMO, but I would tune what you got before you change stuff. At 40/150, you're close enough to get that AS set to where it will work noticeably the best it can get. That said, I'd change the needle..but that just 'cuz I've found -4 to consistently be the best choice in the C/DEK needles in the modified carb.

Given the above, then, re:

Re: 'Just not sure which may to start here smaller jet or bigger? Could both of you please describe the symptoms of a lean and rich condition right off idle.'

A lean pilot will be harder to start when choke-cold (than a pilot that is NOT lean). A too-lean pilot will exhibit a hi-rev condition on choke-cold start that you can 'regulate' with the kill button. By 'hi-rev' I mean it will rev hi enough to scare you...'She's gonna blow!!!' high...well past the KIPS point. As far as throttle response, a lean pilot will be downright touchy. It will pull quite well in low-speed stuff but with just a tad too quick a twist of the throttle will get you a very non-linear response..as in loop-it hit.

..which is kind'a fun..and what I get with the 38 in current 'conditions'.

A too-lean pilot will rev cleanly off-idle..but it won't have the pull a better choice pilot will have..and if you run the bike there a lot (off-idle), you will likely notice your coolant gurgling when it never used to (things will get hot).

The end result you're after is to have your bike run to suit you. It doesn't take a ton of time to get it sorted out, but it certainly takes some..and you have to pay attention to what's going on response-wise. The benefit is you won't be wondering, 'I think there is more to be had...'

Then THAT idea will get blowed out of the water when you 'find' the next greatest thing. Say....toluene 'fer example........... :grin:

When your bike runs well, your riding experience improves BIGtime. You come to trust your bike to do what you know it WILL do instead of wondering when its shortfalls will bite you in the rear.

Change that clip..move that AS...post-up what you find out!

BTW...you will likely find that the bike WILL start better (talking choke-cold..not every time you start it over the course of a days ride) at a 'reduced' AS setting. If so, then simply take note of where you started from, turn it back out to that spot (to start with for the day) after you get it started. I used to do that..but decided to leave that step out (turning the AS in)..and kick it maybe a couple-three more times than I would otherwise.
Last edited by canyncarvr on 11:46 am Dec 16 2008, edited 2 times in total.

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Post by Mr. Wibbens »

Airstriker??

I thought you had to give that one back?


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Oh I guess maybe it was the other carb you had to send back?
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Post by canyncarvr »

Kept the modified 35mm air striker...the one I've run for years.

Yep..it was the 'other one'...the modified 33mm..that was returned.

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Post by september9 »

Sorry, I am a little lost. I think I know what your talking about KarlP, but I am not sure. When you said that you had a plugged silencer, what did you mean?

Was the stocker just full of old oil? Did you just clean it out?
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