Hi i have just bought off ebay a keihin carb that has come off a sherco 290, i have ordered the correct jets for my bike, an 04 250 pro which i have been told are;

main 122

pilot 45

with a jjh needle

is this correct?

also does anyone have any good starting point settings for the air screw?

thanks, Tom

Those are the ones I use too, Tom. With regards to the air screw, mine is 1.75 turns out, which is probably a good starting point for you, but you'll have to 'play it by ear'.

Just out of interest, what jets and needle were in the carb when you got it?

Hi Tom,

I prefer to use a GJH needle, gives a better response than the JJH for me. 122 main may well be ok for the 04 bike, for 06 onward a 126 or 128 is a better size as the motor runs lean with the (std) 122. 45 pilot is a bit rich, better with a 40 or 35. With a 45 pilot, the air screw needs to be out approx 2 turns. You must run these carbs with an in-line fuel filter as there is no filter on the carb, like the DellOrto. The Keihin has a larger diameter inlet stub but you can squeeze it into the existing rubber manifold, don't push it in all the way as the Keihin is shorter than the DellOrto and you'll find the airbox hose doesn't reach the carb properly. You can get jets and needles from Allen's in the UK - google it.

You need a longer inner throttle cable with the Keihin, order one that fits the 370 model - can't remember the P/N but I think it ends with ...0003

Bye, PeterB.

thanks for this. fyi, i dont know which jets it has in as it hasnt arrived yet but i thought for how much they cost i'd ring gas gas and get some new ones anyway and they recommended the ones i've stated. after reading around i rang them again to see if there were any adaptors i might need for the reed block but he said you dont always need one so try it on the bike first. he was saying the carb might sit on the crank case in which case i'd need a tapered plate i imagine. the carb should arrive tomorrow, if it does i'll have a fiddle tomorrow night and let you know how i get on.

Cheers.

thanks for this. fyi, i dont know which jets it has in as it hasnt arrived yet but i thought for how much they cost i'd ring gas gas and get some new ones anyway and they recommended the ones i've stated. after reading around i rang them again to see if there were any adaptors i might need for the reed block but he said you dont always need one so try it on the bike first. he was saying the carb might sit on the crank case in which case i'd need a tapered plate i imagine. the carb should arrive tomorrow, if it does i'll have a fiddle tomorrow night and let you know how i get on.

Cheers.

The larger outside diameter spigot of the Keihin may put a little too much stress on the smaller inside diameter PHBL type manifold and it may possibly develop cracks, so you'll really want to keep an eye on it.

You can also use the manifold off the 96' JTR370 which was for the larger spigot PHBH Dellorto (#M01615006) or the aluminum manifold and 34mm rubber boot (manifold-#MT300616131, boot-#MT300616133) designed for the Keihin.

The spacers are #MT280216221 for the wedge spacer to tilt the carb up a little to clear the top of the case and the standard spacer block is #M01614005.

The carb should fit fine as the airbox boot is designed, from what I can guess, for the Keihin/Dellorto flatslide, which is why the standard Dellorto needs the rubber donut adapter. This may also be why the length of the airbox boot seems a little short for the Dellorto PHBL but the PWK Keihin, with the slightly longer body, fits right up with no problem.

My 2002 280 Pro has the stock airbox boot designed to fit only the PHBL (the only carb available that year) so I don't have the donut adapter and the airbox boot fits completely over the carb bell with no short-length problem. The boot was re-designed for 2003 for the Dellorto VHST26BS flatslide and Keihin larger diameter bell/longer body carbs.

Jon

cheers for that jse, are they numbers i can quote to gas gas and they'll know what i'm after if i need them?

it seems to be a bit of a fanny around, why cant they tell you in no uncertain terms what you need?! i'm not trying to save pennies by bodging it together i just havent got a solid answer from them as to what i will need to fit it so i'm kind of waiting for the carb, then i'll have to strip the bike half down just to see if it will fit ok, i might end up putting it back together for the weekend only to take it back apart again next week when the bits arrive (if i need any).

i asked them if i need a wedge spacer and he said "sometimes you do, sometimes you don't" - helpful!

thanks for all your info, i'll let you know how it goes together.

Cheers

cheers for that jse, are they numbers i can quote to gas gas and they'll know what i'm after if i need them?

it seems to be a bit of a fanny around, why cant they tell you in no uncertain terms what you need?! i'm not trying to save pennies by bodging it together i just havent got a solid answer from them as to what i will need to fit it so i'm kind of waiting for the carb, then i'll have to strip the bike half down just to see if it will fit ok, i might end up putting it back together for the weekend only to take it back apart again next week when the bits arrive (if i need any).

i asked them if i need a wedge spacer and he said "sometimes you do, sometimes you don't" - helpful!

thanks for all your info, i'll let you know how it goes together.

Cheers

I would think that those numbers are what you may need but have the dealer check them out just to be sure.

I would probably use the wedge spacer, it will kick the manifold angle up 3 degrees. You don't want the bowl to rest on the engine case as it will often cause frothing of the fuel in the bowl and that will affect the air/fuel mixture ratio and performance. It's true that sometimes you can get away with not using it but that's because the clearances are so tight and I would just as soon have a little more clearance than "just enough" to get by.

I like the aluminum manifold and hose connector (I think it's used on the Raga) as it seals better. The one-piece rubber manifolds (JTR370 type) will often bow between the bolt holes when overtightened (which is a little easier to do with several spacers stacked) and cause an air leak. If you use the JTR manifold and the spacers, you will probably need slightly longer capscrews to attach it.

You'll also need the #E16003 throttle cable that has the 16.6cm free length (the Dellorto cable has a shorter "free length", which is the length of exposed wire cable when it's pulled at one end of the uninstalled cable, due to the reduced travel the slide takes).

Jon

My carb has arrived. I have been to my local gasgas place and they have their own way of fitting them. They put the carb on a mandrel and skim the reed block side so that its round, then they fit a custom made aluminium bush that pushes on to the new diameter and into the reed block. this extends the carb to the right length and brings it away from the slope of the crankcase so no need for a wedge plate. unfortunately they dont have any of this stuff in so i'm doing it at work myself. their bushes choke the carb down to 26mm which he says he prefers but i think i'll make it 28 and see how it goes.

hi, i got the carb on a couple of weeks ago, i did it by skimming the carb so that the piece that fits the manifold was round, i then made an aluminium adaptor which lengthens the carb and makes a nice seal on the original manifold, tried to get it set up and it was running like ****e, it wouldnt start, then when i got it started it would only run with the throttle half open and was chucking loads of smoke out. turns out the piece that the needle locates in at the bottom of the venturi was missing (ebay), so i got that and now it runs a treat. i need to ride for a bit longer to form any more of an opinion and have a play with it but it is smoother. i think i need to tweak it to get maximum response at lower revs. it still feels like i have to rev it to much, if say unexpectedly stopped in a section and want to pull away cleanly and slowly, this should be possible with hardly any throttle, i still feel it needs too much so maybe its too rich?

it has in it 48, 122, jjh.

fyi the set up it had before for the sherco 290 was 42, 122, jjh.

cheers for the advice.

Tom

I run 45 pilot, 122 main and JJH on midle clip on a 250

I run 45 pilot, 122 main and JJH on midle clip on a 250

Any one used one of these on a pro 200? What main did you run with?