Guys I have a 2010 sherco 290. It ticks over fine when cold but as it gets hot, say after an hours running the tickover gets slower and slower so I have to turn the idle screw a bit. Then it ticks over too fast so I turn it down and it's ok for a bit then slows down as if it's going to cut out so I have to keep blipping the throttle. Any ideas welcome. All I have done is clean the carb, I don't know what jets are in it or where the needle clip is..

Carl

give it another clean something is in there

hOW DOES IT DO IN NEUTRAL? typically a dirty carb or developing crank seal issue will give a floaty or inconsistent idle, yet not lower it.

Dirty carb guarentee it. When your cleaning the carb have x2 tubs to hand .... one for the carb and the other for the cleaned jets and components. Take your time doing the carb its something that shouldnt be rushed

assuming that you have stripped the carb to clean it, after first cleaning the outside body of the carb.

You removed the jets including the choke jet. Cleaned them.

Have you then set the fuel mixture screw to give a nice clean throttle response? Before setting the tick over

screw to where you want it. (best done in gear with clutch in)

Make sure Air filter is cleaned and oiled too.

TLTEL

Thanks guys. Looks like I'm cleaning the carb again

Carl

Find a strand of fine wire to pass through the pilot jet opening, copper is best, as they are difficult to see through.

Right I have cleaned all parts of the carb and checked all jets with a piece of copper wire and all holes are clear. It still has a "floaty" inconsistent tickover which I can't get right. It has a 122 main and 30 pilot and the needle is 3rd clip down. I have a sound recording but can't work out how to upload it, I this will help I'll try again

Many thanks

Carl

Hi, Could be a possible air leak, Check the intake manifold. The connection for the fuel pump vacum tube can leak around the rubber, Superglue will seal it from the inside where it meets the alloy nipple.

could be a crank seal, they are less noticable from cold, It could be slightly burning gear oil when it heats up and thins the oil and that will affect idle by leaning the fuel ratio with too much oil. They don't always smoke excessive when the seal 1st starts to go. Ignition side crank seal will cause problems too. Plugs will also foul when riding around at low revs also.

When you blip the throttle does it return to idle quickly or take a while to die down. If it seems to hang then it is very likely you have an air leak on the manifold or the flywheel side.

I dont want to scare you but a stator starting to fail will give similar symptoms The triggers go down and give a intermitent signal at low revs, I had to fix mine about 6 months ago, Costs about 2 quid for the hall sensors if you are good with a soldering iron.

Do a search for air leak on the forum, Sherco's around that year are prone for it, best to check this as a first point of call.

I'm local if you get stuck give me a shout if you need help.

One more thing, check it's not overheating, Sherco's hate being hot at the best of times and a failing waterpump or bad impellor will make it run hot. It can get hot quite quickly and that will affect idle and make it seem to run lean, been down that road myself!

Hi Steve. Thanks for the comprehensive reply. As far as I know it doesn't overheat and the fan comes on as it should. The revs don't hang as I remember, it seems to run well apart from the tickover. I'll check the vacuum connection next and let you know how it goes. Thanks for the offer of help I may take you up on it

Carl

Sherco 250 2011 rider.. Yep, my fan failed during a trail last week, caused scorching to cylinder head, the revs to build when idling, also revs would not drop straight away after releasing throttle, I've changed crank/ fly seals about 6 months ago, maybe due again?! How can I tell if the stator requires work?

Already been through the carb saga on this bike,

Right I have cleaned all parts of the carb and checked all jets with a piece of copper wire and all holes are clear. It still has a "floaty" inconsistent tickover which I can't get right. It has a 122 main and 30 pilot and the needle is 3rd clip down. I have a sound recording but can't work out how to upload it, I this will help I'll try again

Many thanks

Carl

Prolly needs the seals, I give them 2-3 years on average unless you use the Viton ones from Splatshop. Factory seals do not seem to like the alcohol induced fuels.

Edited January 25, 201412 yr by copemech

Sherco 250 2011 rider.. Yep, my fan failed during a trail last week, caused scorching to cylinder head, the revs to build when idling, also revs would not drop straight away after releasing throttle, I've changed crank/ fly seals about 6 months ago, maybe due again?! How can I tell if the stator requires work?

Already been through the carb saga on this bike,

Address known issues(fan) and whatever else, then ride for testing. The seals would not normally be toasted by a top end overheat.

Ok so I've ordered viton seals and a flywheel puller from splatshop. Has anyone posted any instructions on how to do this? I'm not a mechanical numpty and can tackle most things but instructions would help. Also do I need any other special tools? Which side is the easiest?

Thanks in advance

Carl