Comet tick over

R

revderek

Forum User
VOC Member
My Series C Comet can tick over beautifully, but ...

sometimes, for no apparent reason, it speeds up. For some time, each time I slow down again, the tick over is at the higher speed then, for no apparent reason, it reverts to the slower tick over.

If I set tick over from the fast "version", then, when it slows it slows too far and the engine stalls. Of course, for safety and to allow me to stop at traffic lights without sounding like something from the airport, I set it to tick over when "fast".

I'm guessing this may be to do with the fuel level in the float chamber (new jets, needle, slide etc.). Sometimes when closing the throttle a little the engine picks up which usually suggests a slight richness.

Ideas?

Derek
 
Pete Appleton

Pete Appleton

VOC Hon. Editor
Staff member
VOC Member
VOC Forum Administrator
VOC Forum Moderator
Fast tickover

Are you using an ATD ? and what are the springs like? It sounds to me as though you could be getting stuck at full advance sometimes.

Pete
 
Simon Dinsdale

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
Tickover

My suggestion would be to look at your ignition. Especially if you are using an ATD. The condition of the springs are just one part. The way the ATD returns to fully retarded position off the bike tells a lot as worn / sticking pins, weights rubbing against backplate etc all upset the operation.

After suffering a similar slightly irratic tickover on my Rapide I have just changed over to one of the new BTH magneto's and I noticed straight away the tickover is rock steady. Also when you blip the throttle the tickover instantly returns where when I was using a twin point coil ignition and ATD the tickover would not settle as quickly. I can only assume the ignition timing is advancing and retarding correctly now, as I have not adjusted the carbs at all yet. Also the starting has greatly improved even though it was not really a problem with the coil ignition.

Cheers,
Simon.
 
R

revderek

Forum User
VOC Member
Thanks Pete and Simon.

I'd wondered about the ATD, too. I've just had the mag rebuilt and took the opportunity to refurbish an ATD and replace the previously fitted one. Sadly these symptoms existed before the rebuild so I thought I had ruled out ignition. Blipping the throttle doesn't settle the tickover.

I will take another look to be sure I don't have two sticky ATDs. The springs fitted are brand new and the mechanism moved nicely before fitting.

Mystified :-(

Derek
 
Last edited:
V

Vic Youel

Well Known and Active Forum User
Non-VOC Member
Sticking Carburetter

What sort of Carb are you using? I have found that a monobloc type can frequently stick; caused by distortion as a bike warms up. The original 289/229 should be ok especially if it is a brass one.

Does the throttle cable have a nice easy run and is it well greased.....all this can contibute to the same symptoms.

Vic
 
T

Tom Gaynor

Well Known and Active Forum User
VOC Member
Sticking carbs

I cured an erratic tick-over by changing the cable inners from 0.060 to 0.045. It was the inner that was sticking in the outer. The breaking strain of 0.045 is high enough to lift a slide and compress a small spring.......
 
R

revderek

Forum User
VOC Member
Hi guys,

Well, I have an original carb and a new cable but it has a thicker inner so I'll try easing it and see where we get to.

I'm going to strip it all out over the weekend so watch this space.

Continuing comments still welcome.

Derek
 
Top