Hi there, the bike in question is a Sherco 2009 290, great condition and has ran great for months but lately something has gone wrong.

I can start the bike, however it doesnt sound like it used to, the idle is unsteady. The revs pick and drop and sometimes cuts out. I have cleaned and adjusted the carb and it is at the setting that it use to run perfect(I know you have to adjust the idle screw sometimes as it never stays the same but now there IS NOT a setting where it sounds right). It revs up fine, its just that the idle being slightly off (Theres no "Put, Put Put) even when adjust. I Have no idea where the problem lies, can you help?

Thanks!

Crank seals would be suspect.

Thanks For the reply, how much are the crank seals and is it an hard fix?

Lewis

seals are around £5 each. The good news is that they can be replaced without removing the engine and splitting the crankcases.

The bad news is you need a couple of special tools and you could make a make some expensive mistakes if your not experienced at this.

Special tools are:-

• Clutch holding tool £75ish
  
• Flywheel puller £13ish
  
• Seal driver (i just find something that suits)
  

So, if your good with this sort of engine work (bodywork off, drain fluids, brake lever off, clutch cover off, clutch off, crank pinion off etc.) great.

If not, i'm not sure how much a local shop might charge. Probably not much more than the cost of the tools.

Dom

Hi Mate, It does sound like a possible air leak, could be crank seals but rule out everything else 1st before getting involved with changing crank seals. It will most probably be the flywheel side (the easier one to change) If it's an air leak. If it's the other side it will burn gear oil, smoke and oil up the plug.

Could be a leak from around the reedblock or it could be fuel related, check the tank is clean, double check the carb again, Check the filter in the carb if it's a dellorto, Check the spark plug is clean and gapped to 0.6mm. Check you have installed the needle in the slide properly if you have had it apart.

It's normally quite hard to diagnose a fault like this without hearing the bike, People are very kind and want to help, Many know what they are talking about, but don't go diving in on the strength of other people's advice with this sort of problem. If in doubt take it to a mechanic.

I have a slight lean situation on my bike and im gradually ruling things out, It may be a crank seal on mine but it will be less likely as the new bearings are sealed themselves. My bike is a bit different to normal sherco's (factory 300) I will get it running to my liking in the end. Chris at splat shop is a good man who knoes his stuff.

Good luck

Hi Mate, It does sound like a possible air leak, could be crank seals but rule out everything else 1st before getting involved with changing crank seals. It will most probably be the flywheel side (the easier one to change) If it's an air leak. If it's the other side it will burn gear oil, smoke and oil up the plug.

Could be a leak from around the reedblock or it could be fuel related, check the tank is clean, double check the carb again, Check the filter in the carb if it's a dellorto, Check the spark plug is clean and gapped to 0.6mm. Check you have installed the needle in the slide properly if you have had it apart.

It's normally quite hard to diagnose a fault like this without hearing the bike, People are very kind and want to help, Many know what they are talking about, but don't go diving in on the strength of other people's advice with this sort of problem. If in doubt take it to a mechanic.

I have a slight lean situation on my bike and im gradually ruling things out, It may be a crank seal on mine but it will be less likely as the new bearings are sealed themselves. My bike is a bit different to normal sherco's (factory 300) I will get it running to my liking in the end. Chris at splat shop is a good man who knoes his stuff.

Good luck

Steve, I do not dispute your logic here, yet the track record on these things is not good. Based upon my own experience, and the reports of others, I might estimate the lifespan of the stock seals at 2-3 years when using pumpgas(which is mostly alcohol induced nowadays, thanks to our govners).

It appears they will suck air(or oil) right through the bearings as well, which cannot be good for them. Failure modes vary, as they can blow out trans lube as well.

So as far as not overlooking fundamentals goes, this now becomes a fundamental! Not a question of if, but when!

Current recco is the Viton replacements from Splatshop. Get yourself some!

Right i have ordered two viton crank seals from splat shop. I will let you all after they been fitted to let you know if they've worked!

We had similar troubles on a Gas Gas. Eventually traced to a faulty Woodruff key. Might be just worth checking if it's easy access.

Right i have install the new seal on the right side, and need a new gasket. However i cant even get the metal thing off on the left side Can anyone link me to the tool needed?

I take it you mean the flywheel, the puller to remove it fits quite a few different bikes & doesn't cost much. They are listed all over ebay & any of the site sponsors will be able to supply you 1 the same or next day

http://www.splatshop.co.uk/sherco-flywheel-puller.html

I have the same 1 as this in my bag that I take whenever I'm riding

http://www.trialscen...n-what-happens/

Just stumbled upon this post, It's 10 pages so happy reading!!

Hope yours is just the crank seals, Would make sense so fingers crossed for you mate!

Will sort mine eventually but it's so slight and I can ride round it so to speak. Probably just the fact mines running a keihin and there cr@p and i've been riding gassers that run miles better than any sherco i've ever heard.

Edited December 28, 201213 yr by steve_earle

Steve, the Kiehin IS the premimum carb for both brands, and they are sensitive on setup and tuning on the day, yet do run quite well. They will also tell of early onset of such issues as crank seals early on due to their sensivity! Blessing and curse!

They like to be totally clean aS WELL, ANT AN INLINE FILTER IS RECCO~ Proper bowl venting is critical and may cause problems.

If your stuff is right, it should work right for you for the most.

Thanks, changed the seals on both sides and new gaskets. And its fixed my problem, it has a steady "put" again, rev's up super crisp and most importantly doesn't cut out! Should have more grunt now!

Good going! I'll send your invoice for consultation via Paypal!

Good news Lewis

always nice when some hard work pays off

Dom