Let's start by all pointing and laughing at me- never has one motorbike caused me so much stress and made me so mechanically inept*

My 2013 ST 300 Sherco (yes, it's me again) was getting a stuck carb float every single ride.  Free it with a tap, then carry on for an hour.  Deciding to try and cure this issue I did some research, I spoke to Splatshop and this was the agreed plan:

Change the inline fuel filter, disassemble the fuel pump to clean it, clean out the tank, clean out the carb, replace the float valve, check the bore where the float valve sits and ensure the floats aren't catching.

• So tank checked.  No dirt. 
• Fiddly fuel pump checked and reassembled (badly).  No dirt. 
• Float valve seems fine, no signs of gummyness or crud, but replaced with new one.
• Floats appear to move freely, float height not knowingly changed/buggered up.

Try to start it, plenty of kicks and nothing.  Only thing I notice is I think it sounds different when I kick it, like more induction noise.

Decide it must be the fuel pump and it's not getting petrol, but check the plug and it's wet (and a little oily).  Clean the plug, put it back, kick some more.

On about kick 10 it suddenly fires and REVS TO THE MOON.  I hit the kill button and go indoors to get clean pants.

So what have I buggered up this time?  Carb is sitting sweetly in the inlet manifold, throttle is returning nicely and the slide looked fine.

*I don't pretend to be a good or experienced mechanic but I've half an idea.  I managed to remove the engine from my R1, take it for a rebuild and put it back myself so surely removing a carb to replace a float valve shouldn't be too much for me?  Based on how it's going with this Sherco I don't think I'm fit to build a Lego set...

You've most likely got tension on the throttle cable, one end not seated right or cable not routed right.

 

Easily done. Best to check that the slide taps on the Idle screw before you start a bike. Just apply a small amount of throttle and let go, and listen for the familiar tap sound.

Edited October 29, 20214 yr by totty79

1 hour ago, totty79 said:

You've most likely got tension on the throttle cable, one end not seated right or cable not routed right.

 

Easily done. Best to check that the slide taps on the Idle screw before you start a bike. Just apply a small amount of throttle and let go, and listen for the familiar tap sound.

Totty, you've saved me stripping the bike back to pieces again.

Throttle cable wasn't quite seated correctly; wasn't out by much but I guess the choke/enrichment plus a little bit of slide height caused BIG revs.

Than you.  If I can edit the thread title I will do in case it helps anybody else.

On the Sherco rear-tankers, there is a long plastic fuel line, perhaps 60-70cm which runs from fuel tap, up to the top of the fuel tank, then back again, with various bits and pieces attached, including one-way-valve, breather, tee piece and fuel pump.  This fuel line will develop small holes and cracks which cause erratic running, fuel leaks (apparently coming from the carb or pump, but not) and other weird and wonderful issues, which you will attribute to the carb, fuel pump or Brexit.  ALL of this fuel line needs to be replaced every couple of years if you want your bike to run properly.  It will only cost you a few quid.  Just make sure you put everything back together correctly, especially the one-way-valve.

Thank you.

I'll replace these over winter as a preventative measure.

This happened to me when the float needle wasn't located on the float arm correctly. i.e. not in the groove on the needle.