E: Engine Series 'C' Comet Idle Hanging Up

Steve Morris

Well Known and Active Forum User
VOC Member
OK, I have an issue with the Comet. The idle hangs up when warm, i posted about this a while ago, and the general consensus was that as i am running the original 229 carb, the carb slide is potentially worn which would cause the hang up. I met with the previous owner at the weekend, and he had found the carb that was on the bike when he used it, an AMAL Concentric. He said the bike was fine on this carb, so yesterday i set about fitting it. No real issues apart from i had to modify the throttle cable slightly but it went on and started pretty well. I have to say at this point i did strip the concentric down before i fitted it and gave it a thorough check over and clean out.

Went for a short test ride, and the difference between the concentric and the 229 was minimal, the concentric revs slightly cleaner, but performance is almost identical.

But, the idle is still hanging up! i sat and played with the adjustments for about 10 minutes but to no avail. So, do i have another faulty/worn carb? The concentric looks in very good condition, so i am not really suspecting this.

This turned my attention to the 229. I sat at the bench and stripped it (again).. to see if i could work out the issue, if any, with it. I have to be honest, i could not find an awful lot wrong with it? so i set it up on the bench and sprayed some WD40 (its all i had to hand), into the engine side of the slide with the slide fully closed. it actually stayed in the mouth of the carb and did not leak past as i expected a worn carb to do? My initial thoughts are there isn't a lot wrong with the 229, so its going back on, the question is how everyone else sets up the 229 on the bench. A couple of questions;

1. Initial set up. The way i see the operation of both carbs is, idle should be achieved with a closed throttle, via the by pass. the throttle slide is set up just off closed, so as long as the needle is set correctly, good, smooth acceleration is achieved. Am i doing this correctly?

2. Set up when warm. Initial set up for the idle enrichment screw is 1.5 turns out, then trimmed to achieve the best idle when the engine is warm (best idle for me is highest rpm/smoothest running).

Am i doing it wrong?

Thanks in advance,

Best regards,

Steve.
 

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
I had this a few years ago on my Rapide and in the end I cured it by fitting a new ignition ATD. The old one was worn and the weights were flopping around and sticking sometimes on the ATD backplate and so not returning to the correct fully retarded ignition timing which is where it operates at tickover.

I see Martyn has just posted the same answer.

Simon
 

Steve Morris

Well Known and Active Forum User
VOC Member
Thanks chaps,

I have taken the cover off to expose the ATD and it is not returning when i twist it, although i know that this is not the best test in the world as i am fighting the resistance caused by the magneto itself. I have ordered a pair of springs, as Martyn said they are cheap enough and by the look of them they have been on a few years, infact i spoke to the previous owner of some 25 years and he never replaced them?

I'll keep everyone posted. 1 question though, do you need to remove the ATD to replace these? it looks like not but i may drop it out anyway and give it a bit of a clean up..

Best regards,

Steve.
 

Steve Morris

Well Known and Active Forum User
VOC Member
Hi Martyn,

Thanks for this, great advice! I have ordered a wave washer from the spares shop and will trace a nyloc nut.

All the best,

Steve.
 

bmetcalf

Well Known and Active Forum User
VOC Member
I was concerned about changing the springs with the timing cover on and dropping one in and having to do the work anyway. I tied some string to the springs to control them before trying to unhook/hook them. It was 20+ years ago , but I think it was able to do it. On the other hand, having the cover off and inspecting things isn't a bad idea.
 

erik

Well Known and Active Forum User
VOC Member
For me as a dentist it was possible to change the springs without dismantling the timing cover.It is best done with fine instruments.Sometimes one end of a double sided instrument breaks and it is normally for the bin.I use this dental instrument then in my workshop.Ask your dentist for broken instruments and used and scratched mirrors! Erik
 

Robert Watson

Well Known and Active Forum User
VOC Member
I have changed them in situ, and as suggested thread a small bit of string through the spring just in case. It has been a while but I think I used a small pair of needle nosed pliers to do the job, but ---- It could be other things.

I had a a mag that acted like this and the back side of the ATD was rubbing on the end of the magneto, and on another a new fibre gear was about .030 oversize and when engaged with the breather pinion was putting a large side load on the magneto. I checked the gear with thread wires and the pitch dia was good. I first spotted the real issue when I noticed that the face of the tips of the teeth were quite shiny. I chucked it in the lathe and took about .040 off the diameter and all was well.
 

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
I was concerned about changing the springs with the timing cover on and dropping one in and having to do the work anyway. I tied some string to the springs to control them before trying to unhook/hook them. It was 20+ years ago , but I think it was able to do it. On the other hand, having the cover off and inspecting things isn't a bad idea.
just remove the timing side cover. Its not that hard
 
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