Good shout Bill, I would say the earth screw and brush are OK as the Mag was overhauled in 2019 and I really haven’t used the bike much since. I’ll play with the float height, although I never did change that initially
E: Engine Comet Problems
- Thread starter Steve Morris
- Start date
All ways willing to learn !,
Just found this in Vincent.com.
Trying to find the length or ID of the needle, =Nothing !!.
Anyway, Pull up a chair,
"Banging in the Exhaust, May be caused by too weak a pilot mixture,
When the throttle is closed or nearly closed,
Also may be caused by too rich a pilot mixture and an air leak in the exhaust,
The reason in either is the mixture has not fired in the cylinder and has fired in the
hot silencer.
If the banging happens when the throttle is fairly wide open,
The trouble will be Ignition not Carburation ".
I need a cup of Tea !.
Just found this in Vincent.com.
Trying to find the length or ID of the needle, =Nothing !!.
Anyway, Pull up a chair,
"Banging in the Exhaust, May be caused by too weak a pilot mixture,
When the throttle is closed or nearly closed,
Also may be caused by too rich a pilot mixture and an air leak in the exhaust,
The reason in either is the mixture has not fired in the cylinder and has fired in the
hot silencer.
If the banging happens when the throttle is fairly wide open,
The trouble will be Ignition not Carburation ".
I need a cup of Tea !.
Well, as it rained all day, i decided to have a go at the Comet...
I took the bike out last Tuesday evening for a local spin. It was almost un-rideable. Hesitation/spitting/stalling/really playing up, couldn't hold it at a steady speed, awful, something had to be done...
Methodical is always best i think, so i started the engine with the bike on the ramp, sure enough it started spitting and farting, hesitating, backfiring through the exhaustion the overrun etc..
So, off with the timing gear cover, let's check the valve timing first. The valve timing was absolutely spot on, as was the breather timing. I did a check on the ignition timing and at full retard (static) the points were just opening at c. 4-6° BTDC. It all looked absolutely fine to me?
So, what did i do last time, well i replaced the cam spigot and the exhaust valve lifter spigot. Checked them for correct end float etc, all good.
I then turned my attention to the ATD. I bought one off Tony Cooper, it looked identical to the old one, i do remember i had a bit of an issue with the bolt thread on the new one, it went on but it was tight, i had to remove the magneto and do it on the bench, but it went on and tightened up OK in the end. I removed the new one again making sure it wasn't loose on the taper, and it wasn't. Took it off and did some measuring/tooth counting on the bench, identical..
Was scratching my head at this point to be honest, so i decided o re-fit the old ATD. Set the timing as before and put the cover back on.
It started more or less second kick, and sounded good. Revved cleanly, idle was a bit low so I set up the carb, and it appears to be running OK now! I am back to the old problem of the idle hanging up but from idle it now revs cleanly, appears to have lost its stuttering and subject to getting it on the road for the acid test i would say its OK now?
My 'problem' is this though, how on earth can an ATD make the bike run rough like this? I mean it was unrideable, literally, and all I've done is re fit the old ATD and it seems OK? I know they are a very simple device, and the new one was opening/closing etc OK?
Any thoughts??
I took the bike out last Tuesday evening for a local spin. It was almost un-rideable. Hesitation/spitting/stalling/really playing up, couldn't hold it at a steady speed, awful, something had to be done...
Methodical is always best i think, so i started the engine with the bike on the ramp, sure enough it started spitting and farting, hesitating, backfiring through the exhaustion the overrun etc..
So, off with the timing gear cover, let's check the valve timing first. The valve timing was absolutely spot on, as was the breather timing. I did a check on the ignition timing and at full retard (static) the points were just opening at c. 4-6° BTDC. It all looked absolutely fine to me?
So, what did i do last time, well i replaced the cam spigot and the exhaust valve lifter spigot. Checked them for correct end float etc, all good.
I then turned my attention to the ATD. I bought one off Tony Cooper, it looked identical to the old one, i do remember i had a bit of an issue with the bolt thread on the new one, it went on but it was tight, i had to remove the magneto and do it on the bench, but it went on and tightened up OK in the end. I removed the new one again making sure it wasn't loose on the taper, and it wasn't. Took it off and did some measuring/tooth counting on the bench, identical..
Was scratching my head at this point to be honest, so i decided o re-fit the old ATD. Set the timing as before and put the cover back on.
It started more or less second kick, and sounded good. Revved cleanly, idle was a bit low so I set up the carb, and it appears to be running OK now! I am back to the old problem of the idle hanging up but from idle it now revs cleanly, appears to have lost its stuttering and subject to getting it on the road for the acid test i would say its OK now?
My 'problem' is this though, how on earth can an ATD make the bike run rough like this? I mean it was unrideable, literally, and all I've done is re fit the old ATD and it seems OK? I know they are a very simple device, and the new one was opening/closing etc OK?
Any thoughts??
Is the new ATD going the right way.
Bill, that's a great shout..... I'll check tomorrow and let you know...Infact, i'll go and check now!
OK checked and it appears to be same as the old one so yes…
We did a Comet for a friend.
That had a new type of points to what I am used to.
There were 2 sets of points.
You could use them. Clock wise and anti.
But one was not proper point.
It ran for a short while. Then dead.
The points were badly burnt.
Wrong metal.
It was a Velo mag. But we. Changed it..
Lucky I had an old set of points with me.
That had a new type of points to what I am used to.
There were 2 sets of points.
You could use them. Clock wise and anti.
But one was not proper point.
It ran for a short while. Then dead.
The points were badly burnt.
Wrong metal.
It was a Velo mag. But we. Changed it..
Lucky I had an old set of points with me.
Hi Steve,
A couple of things to check on the 'new' ATD. Have you actually measured the advance it provides? Also check the springs, they need to have some preload - i.e. stretched a bit, when at rest. Does everything move easily - all the pivots etc.
The Lucas ATD has been covered extensively in OVR. check out editions 82, 84, 88 and 89 in the archives here https://ovr270.wixsite.com/ozvincentreview
Martyn
recently noticed one of the contact pads on the points was 'loose', re peened points pad fixing which made acceleration and cruising much more responsive, although it wasn't exactly missing, spitting and stalling beforehand.
Replacement points are getting very hard to source. Here is where I obtained my last set.
