AJS & Matchless Owners Club

I had exactly the same experience of poor running when I first started my Model 8. After checking all the above it turned out to be the condenser for the points.

Steve S.

vigo wrote:Copper gasket. Timing, seems to start and run well. But if that could cause the problem I should check it. Sounds a bit elemetry but how do I check the timing. My strobe was binned at the airport security.

Don't need a strobe. The timing is 1/4" BTDC. Get a bit of stiff wire and bend over the top a bit to stop it falling into the bore, get the piston at TDC on the compression stroke (both valves closed) and mark the wire say in line with the top of the head where the plug screws in. remove the wire and make another mark 1/4" HIGHER than the first mark. Go through the process again and bring the piston up so the TOP mark now lines up instead of the original one. This will be 1/4" BTDC. you need to have the ADRTD UNIT FULLY OPEN (wedge it with something) and at this point the points should JUST be stating to open (I use a multimeter on continuity setting with a buzzer to get the exact point, better than a fag paper!!)

So do I understand this correct Oz, 1/4" BTDC is the full advance timing. That's the case isn't it if the ARetard weights are open? Which means before the engine spins up and weights open the engine is getting less that 1/4" advance infact probably no advance.

Well I've answered my own question and read the detail in the manual. That means the timing was out by a about 1.5 mm at the periphery of the plate.

Just finding my round a G5 myself but on this one I would support Steve's post above about the condenser. They often start to break down when they get warm and cause a misfire which might explain the sooty plug. Should be a cheap fix and at least rules that problem out if the issue persists

Andy

I have heard of some people actually moving the condensor away from the engine completely to help this problem after all it can go where you like as it is only connected by one wire.. Interestingly, my Yamaha RD 350 which is still on points as standard has no advance at all which surprises me especially considering the amount they rev and for their prevalence for holing pistons.

Thanks lads for the tips. Set timing properly, started and ran much better but by no means perfect. The plug was still sooty but not wet, I decided to drop the needle a ring. Was set to middle of 5 now 2 from top. Started great, ran till I opened the gate then OUT. Don't have a spark any more. Switch ign on and ameter goes to minus when cranked near tdc. I think that means power from new battery is reaching coil, correct?
Anyway, I will change condensor and could pop in one of my spare 6v commando coils....if I were in UK.
Q does anyone have the condensor rating/spec so I can source one here in Germany, orherwise I'll order from club spares and pay foreign post.


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You can use pretty much any condenser. If you open the points and see a big, splattery spark across the points then the condenser probably isn't working. You should only see a small spark.

The correct condenser looks like this and measures at 0.2µF.

clanger9 wrote:You can use pretty much any condenser. If you open the points and see a big, splattery spark across the points then the condenser probably isn't working. You should only see a small spark.

The correct condenser looks like this and measures at 0.2µF.

I second that, my old school bike shop, John Parker Motorcycles who has been in Southend for ever and is now run by his son Steve, told me the same

Well I don't have a lot of experience with spark types but I think I have an intermittent large splattery spark , new condensor.