Sherco st290 2012

[Biffda85]

I have a problem with my bike and wondered if any one might know what it could be. Basically from cold it will always start but once you ride it for a while it starts to run strange and then cuts out. and then you got no chance in getting it started again. It needs to be left for ages and then it will start again. Some times it chucks quite a bit of fuel out of the overflow pipes and I do notice fuel on the trailer too & from the woods. Could it be  something to do with the carb or could it be something completely different ??? My dad thinks it’s because the exhaust is clogged up which it could be but I’m not sure if it should be throwing fuel out ? Has anyone had anything like this before?

[mink_man]

Have you had the carb off and cleaned it recently?

Sounds as though the fuel valve is staying open too long or not completley closing. 

Take the carb off and clean it out properly, inspect the fuel valve and the floats. 

[stpauls]

I can always do a trial on one tank of fuel.  Then once I had to use reserve at the start of the 4th lap.  The next week I ran out of fuel and had to walk back for the fuel can.  Additionally, my 2014 Sherco ST rear tanker was having starting issues and then when running, fuel APPEARED to be running out of the carb and down beneath the overflow pipes.

If it is a rear petrol tank model (which I think yours is) then you need to take the carb off, dismantle it and clean everything, to make sure that dirt is not interfering with the float mechanism.  When you reassemble the airbox onto the mouth of the carb, be sure to lightly oil the outside of the carb mouth and the inside of the airbox "trumpet" with a finger of two stroke oil so that it slips back on EASILY.  It may be fixed.  Mine wasn't.

If not, then (and this was my bike's problem) check very carefully that the rubber fuel breather pipe/pump bypass loop that runs up the OUTSIDE of the fuel tank (underneath the rear mudguard) is not holed or split.  It turned out that mine was and was causing fuel to leak out.  (These bikes have a small, separate fuel pump, which I assume kept pumping fuel and probably air into the float chamber).

Anyway, after disassembling the carb a couple of times, I spotted the leak in the fuel loop.  The fuel pipe had hardened after only 2 - 2.5 years.  I replaced all the rubber fuel lines and the problem was solved.

 

Edited December 28, 2017 by stpauls

[Biffda85]

Year I’ve had the carb off a couple of times and cleaned it with carb cleaner. I haven’t really looked at the fuel valve though to be fair. I’ll strip it all down again and have another look. Do you think it’s the carb that’s causing my problem ? 

[Biffda85]

7 minutes ago, stpauls said:

I can always do a trial on one tank of fuel.  Then once I had to use reserve at the start of the 4th lap.  The next week I ran out of fuel and had to walk back for the fuel can.  Additionally, My 2014 Sherco ST rear tanker was having starting issues and then when running, fuel APPEARED to be running out of the carb and down beneath the overflow pipes.

If it is a rear petrol tank model, then you need to take the carb off, dismantle it and clean everything, to make sure that dirt is not interfering with the float mechanism.  When you reassemble the airbox onto the mouth of the carb, be sure to lightly oil the outside of the carb mouth and the inside of the airbox "trumpet" with a finger of two stroke oil so that it slips back on EASILY.  It may be fixed.

If not, then (and this was my bike's problem) check very carefully that the rubber fuel breather pipe loop that runs up the OUTSIDE of the fuel tank (underneath the rear mudguard) is not holed or split.  It turned out that mine was and was causing fuel to leak out.  (These bikes have a small, separate fuel pump, which I assume kept pumping fuel and probably air into the float chamber).

Anyway, after disassembling the carb a couple of times, I spotted the leak in the fuel loop.  The fuel pipe had hardened after only 2 - 2.5 years.  I replaced all the rubber fuel lines and the problem was solved.

 

Sounds like you’ve had a nightmare to then ! It is the rear petrol tank model,that’s something I haven’t checked ( the fuel lines ) but could this be the problem for why it’s cutting out or would the bike still run ? Thanks 

[stpauls]

If I remember correctly, it would refuse to run on tickover and was reluctant to start.  It would also just die.  I forgot to say that at the 3rd meeting it appeared that fuel poured out of the carb continuously when it was started.  I had signed on, but not even ridden the first section.  I just went home and started to investigate.

I wouldn't describe it as a nightmare.  My brand new 2013 Beta Evo 250 would sometimes jump out of first or second gear. Mid section.  Lost me lots of points. Made me afraid.  It turned out that I was not alone.  It was a manufacturing fault - the selector fork was too thin and springy.  That was a nightmare.

Trials bikes need ongoing maintenance - especially older ones.

Remember that the fuel line on these bikes is pumped - slightly pressurised, not gravity fed like most trials bikes.  Also, from memory, it is perhaps nearly 2 feet long, with several joints, a pump. check valve, auto air vent etc.

Not unreliable, just different.  You have the weight of the fuel where you need it - over the back wheel, not the front wheel!   That's one of the reasons that these rear tankers feel so light and nimble compared to other models and makes.

Edited December 29, 2017 by stpauls

[Biffda85]

8 hours ago, stpauls said:

If I remember correctly, it would refuse to run on tickover and was reluctant to start.  It would also just die.  I forgot to say that at the 3rd meeting it appeared that fuel poured out of the carb continuously when it was started.  I had signed on, but not even ridden the first section.  I just went home and started to investigate.

I wouldn't describe it as a nightmare.  My brand new 2013 Beta Evo 250 would sometimes jump out of first or second gear. Mid section.  Lost me lots of points. Made me afraid.  It turned out that I was not alone.  It was a manufacturing fault - the selector fork was too thin and springy.  That was a nightmare.

Trials bikes need ongoing maintenance - especially older ones.

Remember that the fuel line on these bikes is pumped - slightly pressurised, not gravity fed like many trials bikes.  Also, from memory, it is perhaps nearly 2 feet long, with several joints, a pump. check valve, auto air vent etc.

Not unreliable, just different.  You have the weight of the fuel where you need it - over the back wheel, not the front wheel!   That's one of the reasons that these rear tankers feel so light and nimble compared to other models and makes.

Thanks for your help and advice, I will strip the bike down and investigate. Cheers 

[stpauls]

Here is a picture of the fuel line on a 2013/14.   All mine had hardened and were brittle.  Any leak causes issues.

Edited December 29, 2017 by stpauls

[tony27]

13 hours ago, stpauls said:

Here is a picture of the fuel line on a 2013/14.   All mine had hardened and were brittle.  Any leak causes issues.

Being so close to the heat from the exhaust will have contributed to the short lifespan of the fuel lines

[Biffda85]

17 hours ago, tony27 said:

Being so close to the heat from the exhaust will have contributed to the short lifespan of the fuel lines

Very true. I still haven’t had chance to strip but once I have I’ll post an add. I just want to enjoy riding lol. But this is all part of it I suppose unless I get a brand new bike ! ( dream world ) 

[Biffda85]

On 30/12/2017 at 5:43 PM, Biffda85 said:

Very true. I still haven’t had chance to strip but once I have I’ll post an add. I just want to enjoy riding lol. But this is all part of it I suppose unless I get a brand new bike ! ( dream world ) 

 

On 30/12/2017 at 0:01 AM, tony27 said:

Being so close to the heat from the exhaust will have contributed to the short lifespan of the fuel lines

Just been looking back at pics and realised that there’s no one way fuel valve. Previous owner has taken off original breather pipe and replaced with a short breather pipe. Do I need this valve, could this be part of my problem? I would up load a pic but don’t know how too ? Thanks 

[Biffda85]

Just now, Biffda85 said:

 

Just been looking back at pics and realised that there’s no one way fuel valve. Previous owner has taken off original breather pipe and replaced with a short breather pipe. Do I need this valve, could this be part of my problem? I would up load a pic but don’t know how too ? Thanks 

Also I washed off bike today to get ready to start stripping fuel tank and carb and as I finished it started first kick. Rode around patio for a bit until fan kicked in and bike is fine. It’s just when I’m out and been riding for an hour say it starts to sound funny and I’m fighting with the throttle to keep it running then it just shuts off ! It’s so strange ??