Hi All, Sherco 2004 250 Dellorto carb

Bikes been running like a dream, until recently, after a fast 5 gear run it started to bog down and then cut out. Tried to start it again and it wouldn't start. Tried it with choke and it started, just wouldn't tick over as if the pilot jet was choked. Gave it a few revs and it cleared up ok. Anyway stripped the carb out of interest to empty the float bowl and found nothing, all jets clear.

Next outing it seems to have got worse. It will start ok first time, run for 30 seconds then bogs and dies, leave it 30 seconds and its starts again and does the same. As if its a fuel restriction that is starving the bowl from filling up fast enough.

Checked fuel pipe, inlet carb fuel filter, flow from fuel tank, pilot jet, main jet, fuel air mixture, idle screw, floats for getting stuck, inlet needle all free and good seal and not sticking.

After re-assembly it now wont start or run on anything other than choke. So in my mind the only thing left is a big air leak somewhere (replaced big end seals months ago and run fine, used viton) but everything looks fine.

Anyone else had this issue? Scratching the noggin for sure, bloody bikes..

Try starting it will the fuel cap off to eliminate that

A failing stator can give the symptoms of your original stoppage but generally will start & run fine when cold

So you did check the banjo screen on the side of carb?

All jets clear, really? How did you verify?

Remove carb when this is occurring and break the bowl seal over a clear vessel. Look at volume of fuel, ck for water settling and dirt in your sample catch.

Edited May 25, 20188 yr by copemech

Hi, yep banjo is clear. Stripped carb down and blown all jets through with compressed air and passed wire through them. Put a full new seal kit on the carb and tried again and its all the same. Will start on choke but soon as you turn choke off it wont run on 1/4 throttle or full. Just bogs and dies off.

HI!

I have the same problem with my 2001 sherco 2.9. When i go fast in th 4th or 5th gear, it starts to choke and sonetimes stops, like i didnt give enough petrol. When it chokes, i hardly can start it again. It goes right in the 1st, 2nd and 3rd gear

 Make sure the choke jet (the one with the oring) is clear and that whole choke circuit is clear including the one in the float bowl.

Hi, I cleaned it his every single part for the carb. Did not solve the problem...

Try a brand new spark plug, a failing plug can cause weird running issues.....if that does not solve problems, might want to investigate crank seals condition...pressure test?

breather pipe from carb too long and clogs up, common problem on Sherco, creates vacuum in float bowl  causing fuel starvation, gear box breather can also get blocked & cause oil leak, breather pipes need trimming back & problem solved.

Hi did you ever solve this I have a similar problem bike will run fine for an hour then sounds like its running out of fuel suddenl, next day starts fine I've had the carb off so many times never found anything 

Wild guess - sticking float valve...?