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[Westyboy]

Well after giving more clearance to the tappets (0.002 inlet & 0.005 exhaust) I took it for a long ish run approx 40 miles and it behaved itself, feeling smug I took it out again today for abt 35 miles and it was missing on the LH pot @ tick over, aagh, dammit.
Did a compression check whilst hot and 8-10 bar on the lh pot (same as cold), checked the points gap, 0.010" all ok there, the spark plugs are plastic but they are the non-suppressed type that are ok for magneto's (thx for the advice tho).
I really don't want to lift that cal head but ..........

[m1ks]

If you suspect a plug cap try swapping the caps or the whole leads to the opposite cylinder, if the daily switches to the rh you know it's a cap/lead problem, is each cylinder fitted from a separate coil? Swap these first if so, ht and lt, it could be a coil breaking down under load, impossible to check other than substitution, again, if prob transfers to opposite cylinder, there you go.

[m1ks]

Daily = problem, fitted= fired.
I swear, this autocorrect feature puts the dumb in smartphones!

[Westyboy]

Hi M1ks, the bike is magneto ignition, so no coils I'm afraid, the problem has persisted with every plug, plug cap & ignition lead combo I've ever had fitted, head coming off next

[meteur]

hello again westyboy try opening the mag points to 15 thou i run mine at that.

[Westyboy]

Had the chance to do a hour or so on the S Meteor so prepped the bike to remove the head, as I needed to remove the carb & inlet manifold first I thought I'd check Mark's suggestion and check the faces of the two cylinder head inlet ports to see if they were even, no they weren't! The LH head face was approx 0.025" (at the top) to 0.015" (at the bottom) lower than the RH head, (which is the side that misfires co-incidentally) so before I rip the heads off I've ordered some more inlet manifold gaskets to build up the LH side, worth a try. Meteur I've also opened the mag points gap to 0.015" as you suggested, thanks all glad of the advice you willing to impart to me. Regards Westyboy

[Westyboy]

Ok, here's an update for those interested, tried the inlet manifold packed with the extra gasket on the LH side but didn't seem to do anything that I could notice, did note that the manual says when refitting the heads to nip them both up then fit the manifold before finally torquing the heads down, maybe for this reason? Anyway tonight I removed the LH cylinder head, at first glance there is a bit of carbon deposited in the head & piston crown but not a great deal, valves seem ok and guides too but these still need inspecting tomorrow, the pistons are showing the STD mark on the head, engine done 35,000 so will check the barrel bores & measure the ring gaps before I re-assemble.
Regards
WESTYBOY

[Westyboy]

Hello all, an update about the S Meteor misfire when warm. When I last posted I had removed the cylinder heads & found all well (apart from a little carbon), I took the opportunity to de-coke & lap in the valves and fit new springs. Also removed the barrels to check piston ring wear etc, all good & bottom end felt solid on the con rods (good to know)
All re-assembled I gave thought to the fact I had dismissed the SR2 mag as faultless, which was wrong, it was bought from our host's used stock, and although sparking well I was'nt to know wether any internal components where breaking down once hot, so it was removed and the 18D2 dizzie refitted.
It was while I was re-timing the dizzie that I noticed between removing & re-fitting the cap that the misfire swapped sides!! Ok, now we're getting somewhere, I tried another cap & rotor arm and things were much better, I can only assume that the rotor arm could have been earthing to the points cam occasionally thus robbing one of the cyclinders it's spark.
As this could all happen again one day I elected to fit a twin output solid state coil, still operated by the points set, the rotor arm having been removed and the dizzie tidied up by fitting an 18D1 cap, which looks much neater. I can now report that after several longish (75-100 mile) runs, it has been performing well & not a hint of a misfire, either hot or cold, ticking over lovely.
Hope this info will be of use to someone one day, and thank's again forum for all your interest & help,
Safe riding
Westyboy

[Mark M]

Westyboy, thanks for coming back with that, very interesting! In the meantime since you posted I was working on a different problem and a mate in the dynamo trade directed me to the site for the Distributor Doctor who mostly does car stuff but he has some interesting things to say about pattern distributor rotors and has a range made to his own spec to eliminate problems just like this! Thanks again,
REgards, Mark