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Steve Morris

Well Known and Active Website User
VOC Member
Hi all.

I did some work to my Comet a month or so ago, now the weather is better i went out on it last week, and was really disappointed!

Ive renewed the ATD, fitted a new cam spindle and exhaust rocker spindle, cleaned out the carb, cleaned and set points etc.

It starts well, 2nd kick, and revs OK but its backfiring through the exhaust (real flames!) and on medium throttle it hesitates/hunts, but its actually quicker than its ever been, plus the fuel consumption is terrible...

Ive re-checked the carburettor this morning as i thought it was fuel related, and removed the plug. The plug is black and looks really coked up. I set the timing static at TDC, points just beginning to open (full retard/starting position).

Any ideas????

Yours hopefully,


Steve Morris

Well Known and Active Website User
VOC Member
Hi Bill, I have changed the plug as i suspected that could be the issue, no joy. I use NGK B6ES and have had no issues. The ignition is standard magneto, I set the ignition timing to TDC points just at the heel, on full retard, feel like I've done something wrong in the timing chest, you know the feeling, it was OK before so it must be something I've done...

It starts well, idles OK, so it can't be that far out in a settings sense can it?

Steve Morris

Well Known and Active Website User
VOC Member
I did think that, but checked this morning, TDC both valves closed, turn through 360 degrees, both valves rocking, plus i checked and double checked when i put it together, TDC-all dots line up.

Bill Thomas

Well Known and Active Website User
VOC Member
What carb', Did you put the needle clip back in the same spot ?.
These things run Ok even if a long way out on settings,
Air leak on Exhaust ?.
If you say it's running better , Your going too fast :D .
I am getting about 80 to the gallon on my Flash spec' Comet, I must be going Too Slow ??.

Martyn Goodwin

Well Known and Active Website User
VOC Member
I have found the following to be very reliable settings for use with modern fuel, magneto, Mk 1 cam and 30mm concentric in my comet.

Valves at equal lift at 4 BTDC
ATD 'tuned' to give 4 BTDC for starting and 32 BTDC at full advance
Mag points 0.012"
210 main jet
Needle in middle groove

stu spalding

Well Known and Active Website User
VOC Member
Could just be a bad plug ?, I prefer Champion N5c Or N9y,
I recently replaced the N9Ys with same for no better reason than they'd been in for a long while. The new ones didn't run as well and examination revealed that the printing on the porcelain wasn't as crisp as the old ones, fake plugs, I thought, so I put the old ones back in and they're fine. From now one I'm only buying online from reputable dealers. Cheers, Stu.

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