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2008 290cc Sherco Not Reving Out ?

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Hi im having a few problems with my 2008 290cc sherco, it just wont rev out properly, it starts splutering when at maximum revs. ive done every thing i can think of, mixture screw is set to what it says in the guide book i got with the bike, but still fouls plugs up, the tic over is all ok, i have tried the standard filter and two aftermarket filters in the bike. I also clean the airbox and carb out after every time out, also tried some "Boysen Reeds" as i herd they are good, runs abit better but still wont rev out, this is really doin my head in so any help will be much appriciated, i was thinking of trying a Keihn carb but its alot of money to try if it isnt going to make differance many thanks Tom

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From whom did you purchase this bike? I hope that it came from a dealer. I highly recommend that you take it back to him and have him analyze this problem.

What jets are in the bike, what plug are you running, what gas are you using what oil/gas mixture?

Where is the timing set at.

Wayne

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From whom did you purchase this bike? I hope that it came from a dealer. I highly recommend that you take it back to him and have him analyze this problem.

What jets are in the bike, what plug are you running, what gas are you using what oil/gas mixture?

Where is the timing set at.

Wayne

hi i got the bike from the UK yes, i do not know the size of the jets, they are the ones that come standard in the carb, i also use silkolene 2 stroke oil and i put 75ml to a 5 litre can, i am also using the NGK BPR5ES spark plug thanks Tom

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You may need to run a smaller main jet with the Boyesens. Possibly all the way down to a 110-112!

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My 2008 290 ran as blubbery as hell when I opened the throttle with factory reeds or boysens. Jets were 33 pilot 3 turns out and 120 main. I put a 115 main in and it helped a little but since I already had a Keihin I put it on, but this bike doesnt like too much fuel. Jets in the Keihin are 35 pilot 3/4 of a turn out which is JUST not hunting for fuel. Like Cope said in another post this gives nice smooth power roll on the first part of the throttle. JJH needle on second clip groove from the bottom and 112 main. Standard or boysen reeds, this settup still hard to clear at the very very very top. I tried a 108 main but lost power on wide open throttle. My old 2000 had 40 pilot JJG needle first clip groove from bottom and 120 main and still cleared out at the very top. I can use a JJJ, JJH, JJG, LJJ or LJH needle in the Keihin but the bike runs best with all, second from bottom clip groove. Changing the needle gives more subtle changes to fuel delivery than changing the clip position. The Keihin is a tight fit on the 08. I had to heat and bend the throttle cable straw, make a new air box boot and use a thick zip tie around the back of the carb up to the frame under the rear guard to keep the carb up off the case and a little bit of careful filing the float bowl helps as well. Sounds like its all abit too hard but I tried the dellorto out again a couple of weeks ago and put the Keihin straight back on. The Keihin now comes on and off easier than the Dellorto. You can try different mains in the Dellorto but for me personally the Keihin is heaps faster and cleaner revving.

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I know this a long shot but a fella i know had a similar problem on a 2004 290 sherco.

when he bought the bike he was assured no major work had been done to it, he also couldn't get it to run right . Tried everything to do with the carb , ignition timing etc but with no joy. So after about 12 months of head scratching he decided to give the previous owner a call and after much discusion it appeared the previous owner had replaced the main bearings and it had never run right ever since and that was the reason why he had sold it.

So my friend decided to check the said mains and on the strip down he found the piston had been put in the WRONG WAY ROUND. Needless to say this was corrected and it now runs a sweet as a nut .

So it may be worth having a word with your previous owner , he may know what is wrong but is to embarrased to say !

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You can also try this:

Close the fuel tank valve, and keep trying reving the engine (keep blipping the throttlle) until it runs completely out of fuel. If you got a moment when the engine was reving out, then the problem is a too rich mixture. If no, then you need to search elsewhere, because the problem is not with the carb.

Edited by fkrisztian

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well, i know this sounds "too" simple but i've seen this on a number of trials bikes, have you tried just running it wot in 5th for a long stretch to heat up the muffler and blow/burn out all the crap. you've done the air filter and carb but i didn't see if you had cleared it out with a good hard run. it a realitivley new bike so maybe running a "run in" oil mixture has gunked it up???

cheers

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Hi yes, it revs out :wall: put a keihn carb on it from <mention of this company is not permitted on Trials Central> and it rides a dream, didnt think it would make the difference it does, the carbs are deffinately worth the money !!! thanks Tom

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