I Have a problem with my Wm20 as much as to say when the old girl gets up to 45mph she starts to hold back had a look at the points checked the cap 0.12 thats ok checked the fuel bowl taps ect even the flow of petrol no problems their , then i remembered when i rebuilt my M22 racer the spark plug is a K.L.G L777 n.o.s with the three prongs thee type you can't adjust . I think i may have a lodge c14 about the place some where . when its cold down a bit ill set plug to 0.18 and fit said plug and hopefully that will solve the problem of holding Back at 45 pmh

email (option): garypitt@talktalk.net

Hi gary had a similar problem with my wm20 , kept on killing plugs , three in a week last year in Normandy then found some of the said plugs KLG 777 fitted one plug and sweet as no more running issues and a year later still the same plug

I replace my Champion L86C plugs when the outside gets really rusty... ..I've never had one fail.

Gap to .018" before fitting and run a non supressed plug cap...Ian

email (option): ian@wright52.plus.com

Been out today on my WM20 bike going well sitting at a nice cruising speed of 60 mph blatting past all the cues of holiday traffic then a hell of a backfire with a cloud of black smoke bike starts to slow and misfires and pops & bangs I keep the engine running to get me around the roundabout so I can pull over onto a minor road to have a look.I keep the engine running and decide to get home as I dont want to pull apart a hot engine on the side of the road as I think it will make it home, the symptoms are similar to garys at the beginning of this thread .Once there I let it cool down then remove the float bowl to blow them out with a airline remove points clean them up check the plug & lead and pickup but the bike is still popping and banging beginning to think my recently recon mag has gone tits up! go for a test ride still not good so think I will remove complete carb to have a look before I tackle magneto remove petrol pipe then unscrew carb top as I pull the slide out I notice the needle has dropped to the top notch!!! never had this happen before and cant really see why it dropped as the clip is still nice and tight on needle, but glad it was a easy cure as I intend to take her for a long ride tomorrow..Dave

I keep a timing stick in my tool box.
First thing I check is the timing as the thing that go bad most often is the timing pinion slippng on the shaft, particularly with/ during a healthy back fire.

email (option): wariron@tpg,com,au

I've never experienced a mag pinion slipping yet! I did however have a pinion on an Enfield come out of mesh becuase the shimming under the mag was wrong.

Ron

email (option): ronpier@talk21.com

Likewise..I've never had the timing slip in 40 years...

If it moves regularly I would suspect a problem with the taper in either the gear and/or on the armature..

A hairline crack in the gear (this happens occasionally)...

A lack of clearance between the back of the drive gear and the front face of the clutch spring retaining nut where it protrudes through the drive end cover...Ian

email (option): ian@wright52.plus.com

I changed me plug symptoms were still the same , then after about 10 miles there was the loudest F@*$in bang . you'd ever heard , sounded like an artillery field gun going off, so when i got back in me skin picked me helmet up and collected a plentiful supply of toilet paper up . The m20 seemed to be running on rocket fuel so dug my spurs in pulled back on the rains , then you guessed it back to square one holding back at 45mph its doing my scone in . Iv even had the mag/dyno re done whats the modern aquiver-lent of the lodge spark plug for an m20 ?? do any one know ?? iv got a plug nos that fits but is only a shallow reach

email (option): garypitt@talktalk.net

If you have an iron head fitted a Champion L86C or an NGK B6HS...
Both are short reach plugs...

If you have an alloy head a Champion N5C or NGK equivalent..All these types are currently available plugs....

I would suggest you check your ignition timing as well....Ian

email (option): ian@wright52.plus.com

Thanks Ian i will have another look ! the pug I'm using at the mo is a nos Lodge can

email (option): garypitt@talktalk.net

Check for a loose points assembly, I had erratic running when the screw retaining the assembly come loose because the previous owner forgot to flip up the tab washer.

email (option): spacemonkeym@gmail.com

Well bike didnt go on my planned ride as I still have the same problem after a few miles it starts popping and banging and holding back, as I had checked everything which I thought it might be I started her up without the points cover on and the points lit up like a catherine wheel, bugger !!! So my recon mag has lasted 2 years and guess what its 3 weeks out of guarantee.Now have armature out and going to fit a easycap once I disable old (new) condensor, at least I can then service and check out condensor without pulling it all apart everytime, and will also carry a set of spare points with a new easycap condensor fitted for roadside repairs.Dave

Now sorted! problem was condensor wire had fractured but the bike still started well even when hot just had a misfire at high revs ,well high for a M20.So not your normal syptoms of a condensor, dont know how it ran. I decided to just solder a longer copper wire to the condenser to remake the connection and cover exposed condensor wires with epoxy resin to dampen the vibration something which should of been done during armature rebuild also found the two screws that hold both end of armature together were loose so guess that helped to fracture wire.Magneto all back together with a cracking spark ready to refit tomorrow..Dave

I Found out the problem with the WM20 .Nothing to do with fuel or spark plug nor timing . It only became apparent when i road with a pudding bowl helmet , As i was going up the rev range i heard a load whistle ????
What the bloody hells that ??? pulled over sounded like Tweetie pie was sat on the engine . put it on the stand my bike that is ( not Tweetie ) took my Helmet off and traced this whistle to the top of the carb were it bolts to the Engine the gasket was acting i guess like a reed in a musical instrument .. anyway took the carb off put a piece of 1200 grit on a flat surface and rubbed away un till completely flat and level again
Problem solved ....... Who would have thought it Ah

email (option): garypitt@talktalk.net