Throttle not closing properly?

[MalcW]

My 650 twin has a tendency to apparently keep the throttle cracked just slightly open when closing it, resulting in less than expected engine braking, and revving a bit when pulling in the clutch to change gear. The revs do drop, but more slowly than they should. Tickover is fine.

I'm confident that the cable is OK; is has a slight bit of free play, and however gently I close the throttle with the engine off I can hear the slide make contact with the stop screw. I can't feel any obvious play in the slide when I try and rock it via the intake. It's worse when closing the throttle gently from a small opening. Banging it shut, especially from larger openings, is better.

I'm wondering whether suction is causing the slide to stick slightly? If that's the case, would a light polish help, or perhaps stretching the return spring to give a bit more compression? I should mention that it's a fairly new Monobloc via club spares, jetted by them according to the bike model (31 DL,no air filter). It's only recently started doing this, it was fine beforehand. Plug colour is good.

Any other ideas?

Thanks,

Malc

[Mick D]

Hi

You may have just sucked in a little bit of grit - give it a good clean and remove any burrs.

If it's a new carb things will get better as it beds in, I wouldn't be tempted to polish the slide or bore.

Regards Mick

[MalcW]

Thanks Mick

I'll do as you suggest and see how it is then. A good excuse for nice long ride!

Malc

[Chazzyb]

Overtightening the nuts on the carb mounting flange can cause the body to distort and grip the slide.

[MalcW]

Hi Charles

I did have that when I first fitted the new carb quite some while ago, but I slackened it off and all's well, at least when cold. Good point though; I'll check it again when everything is hot.

Malc

[peter ranson]

I had the same issue with my G12CSR about 10 years ago , I tried everything that you have tried but to no avail . My carb had been bored and sleeved some years ago but was still good. A mate who works on modern bikes suggested that it could be carb icing , which is something that some jap bikes with carbs suffered from and suggested that I try running on super unleaded which I did and it worked. I now only run on super in my classics.

[MalcW]

Hi Peter

I need to get some fuel, so that would be an easy thing to try.

Thanks,

Malcolm