[TJP]

Hi Guys,

I have an 08 250 sherco which I love. It starts easily, idles great, it pulls smoothly from low revs through into a nice usable mid range and then it all goes wrong!. The bike absolutely refuses to rev out, its as though it hits a rev limiter!. I have made sure jetting and fuel/oil ratios are correct, fitted a new plug and ensured all electrical connections are clean and tight.

Has anyone got any ideas as to what I can try next?, I feel its going to be an electrical issue but was hoping it isn't the stator!

Thanks in advance for any advice/ideas

[mcman56]

What does it sound like and run like when it hits that limit?

[TJP]

It sounds like the revs are bouncing, a bit like when someone is revving a cold bike that hasn't warmed up properly and I guess it feels a little like that too. It stops pulling and as a result I need to carefully evaluate any climbs and pick taller gears that I wouldn't normally

[t-shock 250]

Sounds like a carburation issue.

[TJP]

t-shock 250, on May 13 2010, 08:52 PM, said:

Sounds like a carburation issue.

Thats what I thought but I've stripped and cleaned the carb and used the jetting recommended by Rathmells with little/no improvement. I have also tried larger main jets as I thought it could have been fuel starvation but had no change in the characteristic of the bike

[Stork955]

Gday - is the air inlet restricted in some way? - over oiled filter for example? Your exhaust should be reasonable at this age but it might pay to have a look in there as well. Maybe repack the muffler at least.

Cheers,

Stork

[TJP]

Stork955, on May 13 2010, 09:07 PM, said:

Gday - is the air inlet restricted in some way? - over oiled filter for example? Your exhaust should be reasonable at this age but it might pay to have a look in there as well. Maybe repack the muffler at least.

Cheers,

Stork

Cheers Stork, I'll check these out

[thespikeyone]

when does it do it, from cold or when hot????

have you checked fuel breather on tank.

I had similar problem but it only happened when fan came on, it was the little black fan voltage reg, only a couple of quid.

[copemech]

What size main jet is in it? Does it have stock reeds?


Do you cary a spare coil in your backpack?

This post has been edited by copemech: 14 May 2010 - 01:30 AM

[ZIPPY]

copemech, on May 13 2010, 07:27 PM, said:

Do you cary a spare coil in your backpack?

Never leave home without one, I carry a spare coil for everything I own.
Coil of electrical wire.
coil of tape
coil of rubber bands
coil of film (old school not that fancy digital HD stuff)
coil of mechanics wire



Just gotta be prepared

[TJP]

Hey guys, I'VE FIXED IT!!!!!, thanks for the advice,

Just thought you'd like to know what was causing this mysterious issue. As I said before the bike started and ran fine except at high rpm, where it wouldn't rev out. Well after going through the jetting, checking timing, rebuilding the engine and checking ALMOST every terminal for cleanliness and corrosion, I thought I’d disconnect the stop switch. The bike now revs to the moon!!, couldn't believe it. There was a reasonable amount of corrosion in the switch closing the gap to the contact and I guess at higher revs, the more intense vibration caused the contact to touch!

Oh well, thanks again, I'm off to enjoy my new revvvvy toy

[copemech]

TJP, on May 16 2010, 04:23 AM, said:

Hey guys, I'VE FIXED IT!!!!!, thanks for the advice,

Just thought you'd like to know what was causing this mysterious issue. As I said before the bike started and ran fine except at high rpm, where it wouldn't rev out. Well after going through the jetting, checking timing, rebuilding the engine and checking ALMOST every terminal for cleanliness and corrosion, I thought I’d disconnect the stop switch. The bike now revs to the moon!!, couldn't believe it. There was a reasonable amount of corrosion in the switch closing the gap to the contact and I guess at higher revs, the more intense vibration caused the contact to touch!

Oh well, thanks again, I'm off to enjoy my new revvvvy toy

Well, that is indeed of interist! And yes, I suppose if one was gunkey it could indeed cause problems.