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matchless g3l -spark plug problems?

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ive fitted champion l82c spark plug to my g3l,she runs fine apart from occasionally stalling at idle and then i have to clean the plug or even fit a new one to get her started again,ive removed and cleaned the carb,played around with needle positions,and she idles lovely when warm with no ignition advance.the plug is sooty but not wet.if i stop engine by turning fuel off and let her go lean and die she will start up fine.any ideas,is the L82c the best plug to use,i did write a long post about everything ive done but the bloody site keeps crashing,so this is the abreviated version

cheers

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Are you sure the plug is a suitable grade / heat range, for the G3L? The original spec was a Champion L10, and as far as I know, the L82C, which is a more modern type of plug, is a replacement for the L5 or L7.

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I am using Champion L82C in my OHV's and L86C in my SV's. I don't know of a better modern equivalent......But willing to learn.

 

Ron

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I am using Champion L82C in my OHV's and L86C in my SV's. I don't know of a better modern equivalent......But willing to learn.

 

Ron

 

Ron,

The Green Spark Plug Co. recommend a L86C as an alternative to the L10 (which is the recommended grade in the Matchless G3L handbook). Our friend is using a L82C. There is a science in these plug grades, going up or down a grade to stop fouling or overheating, remember doing all that on my bikes.

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I seem to recall that some 1940 G3's were specified as having Lodge H52 / 53s...? (listed in the riders instruction manual)...

 

Personally, I've always run my M20's and G3s/G3L's on NGK B6HS.......they have performed, and lasted, very well in comparison to Champions......but there again, I know others who have always used Champions with no problems at all.....my W/NG also runs on a B6HS faultlessly......

 

The old saying used to be soft plugs in oily sidevalves and harder plugs in higher compression OHVs........I have on occasions used NGK B5HS in the M20 but never really noticed any difference when later fitting a harder B6HS......

 

I still use NGK's in the 16H, but 18mm size peculiar to the model.......

 

Somewhere in my store I have a couple of NOS wartime Champion L10s in the boxes.......from memory, the plugs are actually WD-marked complete with the arrow mark.......haven't tried 'em out but I'm sure they would still function perfectly......

Edited by wdbikemad

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fitted an l86c spark plug and this seemed to sort the problem out the bike now starts easier when hot,still hasnt sorted the misfire at high loads ,im going to recheck the ignition timing next.

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just a quick heads up on what ive found,after changing plugs to l86c i did have some improvement,it seemed as if i was chasing my tail as soon as i sorted one problem out another would crop up,so i decided to send the mag to tony cooper who reconditioned it and apparently it hadnt bee touched for many years,i wish he had checked it on the dyno before he stripped it but as usual he did a cracking job at rebuilding it and getting it back to me within a few days.while the mag was away i decided to have a look inside,firstly i found that the inlet pushrod had been repaired poorly at some time so as the pushrod span round the repair was not concentric so it changed the valve clearance,quick call to steve at amc spares and a new pushrod was sent.then to my surprise the the inlet valve was in the exhaust and you guessed it the exhaust valve was fitted to the inlet,also only had one valve spring was fitted to both valves and the springs were very weak and 0.080" (2mm) shorter free length than spec.the valve seats were both pitted and in need of a cut.luckily ive got access to a mira seat cutter,so after making a new mandrel to fit the guides i cut the seats and while i had the machine put a 60degree cut into the throat and bored out and gave the ports a tickle to improve flow.i then rebuilt the top end and stripped and cleaned the carb,i also fitted an insulating block between carb and inlet port(original one was ally which was transferring heat to the carb).fitted everything and she ran up within a few kicks,i have used the bike to go to the victory show and after many stops and starts she hasnt fouled a plug and she starts hot or cold with a couple of kicks.now that ive got the engine running ok the clutch is dragging and slipping and finding gears is becoming a problem and the carb is still running rich (needle position does not help) I need to re-sleeve the carb for (anyone know of a good place to get my carb sleeved) so thats my next job,and then hopefully i can get the ariel w/ng finished and start on the indian,thanks for everyones suggestions and help

gruff

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My G3L has also always run rich; like you, I suspect a worn body, but its not a problem really as I just keep a spare spark plug ready if it won't start - its fine on long runs. I use NGKs. Try adjusting the clutch springs (in the manual); mine has replacement clutch plates - maybe yours is still on cork plates? I don't get clutch slip, but it can drag at times - improved by using a lighter grade oil in the chaincase - engine oil tends to make the plates stick together. Anyway, sounds like you have sorted out the engine properly and you are now on to the more minor stuff. Good luck with it.

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The only person I know who does carb rebores and re sleeve the slide, is good old Marty Bratby on 01543572583.

 

Ron

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