290cc Sherco Keihn Carb Set Up

[sherco250cc]

Hi i have recently purchased a Keihn Carb for my 2008 290cc sherco with Boysen Reeds in, but i cannot get it to run properly with this carb on, what i would like to know is:

The Needle Height

Mixture screw (Number of Turns)

Float Height in mm

Also on the float height where do i measure from, the heighest part of the carb ar the flattest point where it joins?

and any help that you will think is neccesary would be great many thanks Tom

Edited June 18, 2008 by Sherco250cc

[pandelboy]

they are not measured when tipped upside down. the carb has to be at an angle with the float needle not depressed. visit kehin website.

http://www.keihin-us.com/tune.htm

Edited June 9, 2008 by pandelboy

[copemech]

19mm with the carb held at a 45 degree angle

[sherco250cc]

HELP!!!!

[worldtrialchamp]

Depends on what set-up you have used.

Did you fit the carb to the existing manifold?

What jets are installed?

What size needle jet?

What altitude do you ride at?

[clav3]

Some variations - 2008 290 Sea level Boysens and Kiehin PWK 28 existing manifold

35 pilot 1/2 turn out, LJJ needle 2nd clip groove from bottom, 3.5 slide, 112 main too much power for begginers try and you'll see. Can use a 3 slide with pilot 1and 3/4 turns

out gives richer off the bottom.

35 pilot 1/2 turn out, LJH needle middle clip, same slide and main. easier to handle still very fast power when opening the throttle due to L needle tapper

35 pilot 3/4 to 7/8 turn out, JJH needle 2nd clip groove from bottom, 3.5 slide, 112 main very smooth.

115 main also works with all these settings

JJJ needle too lean midrange with pinging. some will still use.

38 pilot also works but turn out to 1 and 1/4 to 2 turns .

Float height - Carb upsidedown - tilt 45 degrees - the float should be resting, but not depressing, the spring-loaded float valve pin - measure from flat point where it joins the float bowl to top of float 19mm.

Does anyone know what settup Pat Smage uses on his 08?

Edited June 19, 2008 by clav3

[borus]

Some variations - 2008 290 Sea level Boysens and Kiehin PWK 28 existing manifold

35 pilot 1/2 turn out, LJJ needle 2nd clip groove from bottom, 3.5 slide, 112 main too much power for begginers try and you'll see. Can use a 3 slide with pilot 1and 3/4 turns

out gives richer off the bottom.

35 pilot 1/2 turn out, LJH needle middle clip, same slide and main. easier to handle still very fast power when opening the throttle due to L needle tapper

35 pilot 3/4 to 7/8 turn out, JJH needle 2nd clip groove from bottom, 3.5 slide, 112 main very smooth.

115 main also works with all these settings

JJJ needle too lean midrange with pinging. some will still use.

38 pilot also works but turn out to 1 and 1/4 to 2 turns .

Float height - Carb upsidedown - tilt 45 degrees - the float should be resting, but not depressing, the spring-loaded float valve pin - measure from flat point where it joins the float bowl to top of float 19mm.

Does anyone know what settup Pat Smage uses on his 08?

my 07 caby factory kiehin setup is:

(i was told they are pauxa tuned???)

existing manifold

122 main

45 pilot

JFH needle on second clip from top

5/8 turn out air screw

slide measures 3.5 mm (stamped #4 on bottom)

i think the only difference from a 08 is the 07 caby has a different head

i tried boysens but is didn't run right and i wasn't interested in changing jets at that time.

cheers

[copemech]

A wealth of info there! Good to see! Clav should probably state" for old and slow, stick with your dellorto"! possibly add muddy events and slick conditions!

Go for it Clav! My opinions only!

[clav3]

Great info borus. Wouldn't mind trying that setup. Richer pilot but leaner slide to compensate and a richer needle dropped lower to compensate.

Can't get the JFH needle. Isn't even on the Keihin chart. I'll try through the factory. Might be a special.

[borus]

Great info borus. Wouldn't mind trying that setup. Richer pilot but leaner slide to compensate and a richer needle dropped lower to compensate.

Can't get the JFH needle. Isn't even on the Keihin chart. I'll try through the factory. Might be a special.

well, after reading your post i thought you might like to know what the factory caby setup is. you've done some real nice testing there, i'm glad it might give you and sherco250 an alternative to test out. i can't imagine my bike running any better, i have no need to touch anything in the carb. if you ever get to testing the caby setup out i'd be interested to hear your thoughts. it's interesting that sherco has set up both the 2t and 4t keihins where the air screw is turned out to around 3/4. i've read where the norm is around 11/2??? regardless, both bikes run well from the factory.

cheers

[clav3]

well, after reading your post i thought you might like to know what the factory caby setup is. you've done some real nice testing there, i'm glad it might give you and sherco250 an alternative to test out. i can't imagine my bike running any better, i have no need to touch anything in the carb. if you ever get to testing the caby setup out i'd be interested to hear your thoughts. it's interesting that sherco has set up both the 2t and 4t keihins where the air screw is turned out to around 3/4. i've read where the norm is around 11/2??? regardless, both bikes run well from the factory

No problem! Might take a month or two though.

[copemech]

A couple of things here:

Getting back to the original post, running the Boyesens you may find you need to lean the main jet quite a bit in order to rev out cleanly. As an example on my '07 I had to drop from a 118 to a 110 with the dellorto. This is with the timing set back a bit for smoothness, but it would clean out and rev to scarey highs! So much so that I actually went back to a 115 to limit the revs.

Point being, you may well find a need to lean the kiehin main as well running the boyesens.

With reguard to Clav, I find it rather interisting your settings. I have not ran my K since the '05 2.5. I did try it briefly on the '07 2.9, but it was just to much power across the range, specially where I live, in the lower revs. And although I do believe the K is a far better mixer, it was just too much for me on the 2.9. Which brings me to my point, as mine was setup with a 45/125 setup, a JJH needle and a 3.5 slide, needle in mid.

Oh, I can set she screw and it runs fine, just too much! Makes me wonder about dropping all the way to the 35 pilot to choke this thing down a bit, a big jump. I can always deal with a main jet later, as I seldom go there at 3/4 and above.

As I have not attempted such wide swings, I have been hesitant, as it is sometimes difficult to turn a racehorse into a jackass, and visavie!

Thoughts?

[clav3]

cope, you've probably read some of my previous posts (not many) about the jetting on my old 2000 being alot richer than my 2008.

Look at borus's FACTORY setup. #4 slide and 45 pilot. The needle has the H diameter, J taper angle, F length before the taper starts but the needle is dropped all the way down another two clip positions from middle. This setup would be quite different from the setup you used on the 07.

As soon as I've changed the slide I have to adjust the air or change the pilot to get nice smooth response just as the throttle opens.

I can easily run a 38 pilot at about 1 3/4 turns out and it gives me the same performance.

Tell me if I'm wrong but all the circuits overlap, so if I want to run a bit richer in the mid I still have some adjustment on the air screw with a 35 pilot at 1/2 turn out.

Alot of people talk about Keihins giving them more power but all it is is a bit more fuel delivered in the right place. You can do the same with a Dellorto but the three levels of adjustment on the needle in the Keihin mean the lower to upper midrange can be tailored to suit.

This is what I love about the Keihin. You can literally have a bike for every day of the week. Some would say why bother,and thats up to them, but I say why not.

I,ve tried the exact setup that you've described except for a 120 main and I found the bottom too rich for slow floating turns, the mids were weak and pinged alot and wot was rich and much stronger with a 115 main. In saying this I'ld also like to add that my 2008 has a cab head (which doesn't make a massive difference) and the engine (going by the parts book only) would be similar to the 07 cabby.

I,ve had nothing to do with any other Sherco's but both the 2000 or 2008 pinged alot when using the middle clip on the needle, exept the LJH on the 08, which still pings just a little. We have a good range and quality of fuel down here, 91, 95 , 98 octane so between the two bikes, pinging can only be put down to carb setup. Even the 08 factory setup pinged in the mids.

I'ld like to know how you setup your air screw.

I set the idle then turn out air until engine just starts to hunt then back in about 1/4 turn to hear a nice even idle.

My setup now is 35 1/2 turn out LJH needle middle clip and 112 main but I could go to a 115.

It's definetly not choked down.

The LJJ second groove up was great power, more than the LJH middle, but the L taper gives such fast power it was a bit scary in tight sections with big drops. The fast power might be better for people like me who don't do the rev and dump much.

I,ve probably mentioned alot of things you already know. Hope I have'nt bored you too much with the length.

It would be good to see you chuck that Keihin back on and try some different settings..... Maybe?

[copemech]

Good stuff there Clav, not boreing at all, nor redundant, as I never really messed with the K carb that much. It runs fine at the stock settings, just too much power(for me). Add the fact that it takes a lot of time and money to start playing with guestimates.

If I knew I could tone the thing down with the K installed, I would consider it, although I still do not like the tight fit, seems no way to keep the thing off the engine case even gringing down the little nub helps little.

I too think the ping at about 1/4 throttle has been an unaddressed issue even with the Dellorto.

Understand, I consider the Dellorto to be the best carb that $15 can buy, but it does work, and as far as I know of last, Smage still runs it on the 2.9 and probably the 1.25 as well. At last check, Paxau only likes the K for the power riders. Thus the Caby setup. I have not ridden the '07 Caby, just a '06. I suppose you could say my bike, a 2.9 runs more like a 2.5, a smooth 2.5.

Smooth floaters important? This thing is dialed in!

Sounds like your airscrew setting style is spot on to me.

I will bet back later for more chat!

[copemech]

As a bit of of a follow up, here is a quote from PeterB re the usage of the K carb on the gasser and his input!

" You need a 28mm flat slide Keihin, 122 main, 35 pilot, GJH (Best) or JJH needle. Also need a longer throttle cable (inner) that was used on the older 370 GG model and you must use an in line fuel filter.

Bye, PeterB. "

I think Peter is a pretty good ratchethead, and offers good suggestions. Point being, when you take in variations in bikes even, the resultant opinions can be very similar. Well, the motors are very similar really, specially when you are focused to the volumetric requirements of a given displacement at a given useful rev range the results are near identicle.

Then comes the rider, and personal prefs, and will the setup be right for them! Is it too aggressive?

In other words, if Peter or Clav threw in a 45 pilot with a JJH needle set in the mid, will the bikes then become overly sensitive for the riders? Who in fact are not Caby or others running this setting. Those guys like it RIGHT NOW! What happens then, in reverse?

In fact, I have noticed the more aggressive the rider, the fewer throttle settings they use, the application is all in the clutch side of things, which totally negates all ! They simply do not seem to care after a point!

Tell me if I am off the nut here!