E: Engine Comet will not start when hot

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Roslyn

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Not likely anything to do with the carb.
This is classic capacitor failure of an old magneto. Two solutions.
1) take the mag off and have it rebuilt
2) replace the mag with something modern

If you are not running a magneto what ignition do you have

Robert

PM me if you want and we can make contact. I am in Vancouver. I won't put contact details on the public forum.
My way of doing things is to alter one thing at a time even takes notes and photos along the way and taking time out before it starts to get to you I was on the edge of scraping a 1951 black shadow some time ago even a to the stage of putting a hammer though the case and getting the grinder out and cutting into little bits but found having breaks even taking a day off the problem helps an awful you will get there in the end but do it in little baby steps.
before rushing off to throw money away take a long look at the problem and write a check list then do one thing a day at the time you have a lot of support on this web site
 

Chris Launders

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As it now won't start after you're seating of the float needle it points to a carb problem surely, the fuel level I understand wants to be just below the hole where the pilot air screw is.
 

bmetcalf

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I don’t have one, but could someone post a pic of one of those adapters with tubing to check level with a 229?
 

Magnetoman

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I don’t have one, but could someone post a pic of one of those adapters with tubing to check level with a 229?
I hope these photos help with the general principle, as well as with the specific fuel level. These are from the carburetor on my 1928 Ariel. Burnishing the needle stopped it from overfilling (I believe it is the very narrow bright band that does the sealing), and with the level set where shown and it was a one-kick starter, happy runner, and non-fuel leaker, all the way across the U.S. in 2018.

PolishedNeedle.jpg
Ariel_carbfuellevel01.jpg
Ariel_carbfuellevel02.jpg


Amal_preMonoblocFuelLevel.jpg
 

Martyn Goodwin

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Observation - Banging in the exhaust when trying to start suggest the ignition timing is possibly way out.

First Principles to be attended to in order for a Comet:

1. Valve Timing - set the camshaft position so you have EQUAL lift of the exhaust and inlet valves between 5 BTDC and 3 BTDC. 4 BTDC is ideal. Ignore marks on the timing gears - use a degree wheel and measure everything
2. If you are using the timed breather, it should close between 5 ABDC and 10 ABDC
3. Valve clearance is zero when stone cold BUT you must be able to rotate the pushrods
4. Magneto points between 0.012" and 0.015"
5. Spark Plug gap 0.018" with a Lucas magneto
6. Ignition Timing for easy first kick starting 4 BTDC fully retarded and for reliable running without the risk of modern crap fuel killing the motor no more than 34 BTDC fully advanced.
6. Carb adjustments - see attached guide and note that the pilot jet needle should be approx 1 1/4 turns out from fully closed.
7. If the carb is worn (most likely) have it professional rebuilt or replace it.

If you need more info on how to do any of these things - just ask.
 

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gregg-k

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Non-VOC Member
Everiman, I am located in Ottawa and am intimately familiar with the Lucas K-series mags. Full disclosure: I restore Lucas mags and dynamos as my business.
Why not ship your mag over and I'll inspect it for you?
.. Gregg
 

LoneStar

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VOC Member
On a somewhat related note - is there any reason one couldn't fit a (common, inexpensive) K2F magneto to a Comet, using one output and ignoring the other, rather than the scarce standard K1F?
 

Bazlerker

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Non-VOC Member
Full Disclosure..Gregg K rebuilt my twin magneto a few years ago. He carefully examines the mag upon arrival, photographing and measuring everything. He issues a complete report with recommendations. The process includes running it on his test bench for 8 hrs prior to packing & shipping. Impressive & thorough.
 

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
Observation - Banging in the exhaust when trying to start suggest the ignition timing is possibly way out.

First Principles to be attended to in order for a Comet:

1. Valve Timing - set the camshaft position so you have EQUAL lift of the exhaust and inlet valves between 5 BTDC and 3 BTDC. 4 BTDC is ideal. Ignore marks on the timing gears - use a degree wheel and measure everything
2. If you are using the timed breather, it should close between 5 ABDC and 10 ABDC
3. Valve clearance is zero when stone cold BUT you must be able to rotate the pushrods
4. Magneto points between 0.012" and 0.015"
5. Spark Plug gap 0.018" with a Lucas magneto
6. Ignition Timing for easy first kick starting 4 BTDC fully retarded and for reliable running without the risk of modern crap fuel killing the motor no more than 34 BTDC fully advanced.
6. Carb adjustments - see attached guide and note that the pilot jet needle should be approx 1 1/4 turns out from fully closed.
7. If the carb is worn (most likely) have it professional rebuilt or replace it.

If you need more info on how to do any of these things - just ask.

From MPH 737 "The correct 276 float level is just below the hole that exits at the top of the base cap so that fuel does not flow out of it continually "

In MPH 740 we are told that if you use a sight pipe (clear tube) the level must be just below the upper edge of the nut that screws onto the base of the mixing chamber to retain the jet block.
 
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