07 sherco 290 strange knocking noise

[youthy]

Hi my friends 07 sherco 290 has started to make a strange knock on throttle off. From tick over if the throttle is blipped and realesed quickly there is one sharp knock and back to normal does anyone now what this maybe? the engine itself seems to be mechanically sound no other knocks or rattles. we first thought that it was a pink of some sort as it has also been kicking the kickstart back up ( rattling his knee off the bars) so we retarted the timing a little from its origional setting and everything seemed to stay the same so we put it back to its origional setting.

The bikes running nice and clean and the plug is a nice choclate brown but can be a bitch to start, sometimes firing and running backwards

If anybody has this problem or no what it may be we would appreciate your help. his father owns a very similar 06 290 and his has been great starting and no knock

[gotdirt]

If it runs backwards that would normally be having the timing advanced way to far. If this just started happening after you reset it the keyway may have fallen off during installation of the flywheel and it positioned itself even farther advanced or you moved the plate in the wrong direction.

If all checks out OK with the timing the problem is most likely in the CDI box or stator.

Too much advance will also make it very hard to kick start.

Good luck,

Bill

[youthy]

hi woodruff key was definately in the key way, we moved stator in the same direction as rotatiuon of the engine which if im correct would retard not advance? Always been bad to start and always knocked cant seem to get it to run rich either all 3 jets clean and needle lifted right up still runs clean

[lineaway]

I would go with a larger pilot jet. A lean pilot would cause both the hard starting and the knock.

[copemech]

I would go with a larger pilot jet. A lean pilot would cause both the hard starting and the knock.

I tend to agree. I have had several over the years and they all did it. It was fairly noticable on the '07, and I messed with the thing on and off for quite some time.

It was not untill I went to the #38 pilot jet that it went away for the most. There are reasons for all this, but you are also causing a momentary lean condition by chopping the throttle.

Seems recent reports reveal many still running 33 range using UK fuel, but this would not suffice here. You will have to run the mix screw in a bit with the richer pilot. Mine was in 1.5-1.75 range on the 38.

On hard starts in cold weather, current recco is to take the choke jet(one with o-ring in bottom of bowl)out from 60-70 range to #80. This requires a new jat or a 0.8mm(1/32in)drill.

Kickback on starts, find the tickmark on the stator, it should normally be alighned with the right edge of the top casting web. Take it counter clockwise 2-3mm to help, a bit more to soften the motor, yet not beyond 6mm slow of original.

[youthy]

ok thanks will try re-jetting runh the bike warm today and tried running with choke on once warmed up and i expected it to run realy rich with choke on however it was still relatively clean so im guessing must need larger jet currently a #30 fitted so will try a #35 my friends speaking to our local sherco dealer to try some different jets tommorow

[mcman56]

I have an 02 and sometimes get the same knock when chopping the throttle off at sea level. The timing is retarded and I think the pilot is a 34 or 35. It is a little lean at sea level but starts and runs fine so I don't see it as a problem. This jetting allows it to run clean from sea level to 7500 feet.