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[Westyboy]

Greetings one & all, can I pick your brains please?
I have a 1960 Super Meteor (700cc twin) and from day one it has had a misfire when it gets warm, this usually shows itself after 25-30 miles when I slow down for a road junction and notice that the engine won't tick over cleanly, i.e. missing on the lh cylinder.
I started by checking & replacing the plugs, caps, leads, points, condenser, checked the points gap, checked the ignition timing, advance bob weights, did a compression check and the valve clearances! After all this it was still there, just when I thought I had nailed it, back it would come.
So I ditched the dizzie, coil set up and fitted an SR2 magneto (as fitted to earlier models) ticks over beautiful, looks like I've sorted it............nope, it's back, so it can't be ignition, right?
Carb has replaced too! New monobloc with recommended jets etc, also made sure there were no air leaks on the carb mating surfaces & manifold.
So over to you, I'm going to the Manx in August (hopefully) what am I missing?
Thanks for all your inputs (and sympathy), based in Gloucestershire if that helps!

[simon]

Assuming that you've also replaced the HT leads the most obvious suggestion is that you have a crack either in the head or in the inlet track somewhere. I heard someone suggest a spray of paraffin or perhaps in was WD40 or some such around the carb when the fault is occurring. If this results in a change then you know you have an air leak. Failing that I think it's reasonably easy to get hold of a die pen test kit where you spray on a coat of die that you then wipe off thoroughly the you spray on a talc that reveals the cracks into which the die has penetrated. Good luck S.

[Mark M]

I find that the 1 into 2 carb manifold is difficult to seal because the faces on the cylinder head are never exactly in the same plane when the heads are torqued down. On advice from a friend who had the same problem, I use a steel rule across the ports to see which is "lower" as it were, and then use one (or more) extra gasket to pack out the gap. If you can get the thick original style thick gaskets even better as they compress well.
Worth a try..
REgards, Mark

[Westyboy]

Many thanks Simon & Mark for the replies, will take a look at the weekend and let you know how I get on, regards
Brian

[Old Enfield]

Would it not be a little odd for a crack or gap, that it only happens on the overrun?

[Westyboy]

Hi Old Enfield, it's not the overun it happens on it's at tickover/idle, regards Westyboy

[Bullet Whisperer]

I am currently working on a 700 Meteor which has been misfiring on the left pot. I changed all the ignition parts, carb is good, compression was good, would run fine for 15 or 20 miles then begin to miss at steady throttle openings. Opening up it would run fine, but idling or at steady cruising speeds, it would miss.
On a longer run, I noticed some smoke [not much] from the left exhaust and it used some oil by the time I got home and checked it [after about 35 miles] and the left plug was coated in baked on oil and carbon. Both tail pipes were a dry black colour inside, not wet and oily.
I decided I'd better take the head off and found the oil ring had too large a gap, due to wear and all three ring gaps had come round to line up with each other. Lifting the right pot revealed simillar wear [pistons and bores were ok], worn valves and guides on both cylinders and, sadly, some play in the right hand big end, signalling an engine out and full stripdown job.
This engine is to be fully rebuilt and I am sure it will be ok when done. Your engine might not be so bad in the bottom end department [this one sounded ok], but it might be oil related, like the one I am currently working on.
Paul.

[meteur]

hi westyboy.i have a 1961 super meteor with k2f magneto and had the same problem left hand pot misfiring it turned out to be plug cap metal securing clip moving around and shorting on the cylinder head fins i tightened the cap as it was slack on the plug and its been fine since.

[Westyboy]

Hi Paul, thanks for taking the trouble to reply. It was interesting to read the engine problems that you discovered inside the engine, I'm trying a few last things but reckon I may need to remove a cylinder head to get to the bottom of the problem. I did another compression check this afternoon & it was fine, I also made sure there was enough tappet clearance, Ive never had a bike where the clearances quoted in the manual are NIL for both inlet & exhaust, even racing recommendations are NIL for inlet & 0.005" for exhaust.
My plugs have been clean when inspected, no oil contamination but will see what I find if I remove the head.

Meteur, thanks for the reply, good spot you made with the HT plug cap shorting to the cylinder head, my plug caps are clean plastic with no metal parts but someone suggested I run the bike in a darkened garage to see if I could see any tracking/arcing to earth that might cause the misfire, haven't done that yet.

[meteur]

hi again westyboy you say you have plastic plug caps.are they the suppressed type if you have a magneto as you say you have you need the older unsuppressed type of cap.