Hello.

I have rebuild a M20 and the engine starts on first kick when hes cold, but when I drive it like 40 km and stop then (turn off the engine), and after 15 or 30 min I want to continue the drive it wont start, it has a good spark but want start any way. Then I push the bike and in the 2nd gear he starts after few meters.

Someone has any idea what this could be?

BR, Mitja

Here is a picture from my bike in my eyes its a beatiful bike :) even if it doesnT start every time :)

email (option): mitja.peterka77@gmail.com

carby float bowl is too hot and you are getting fuel vaporising in the bowl.

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

What can I do to awoid it or fix it?

BR, M

email (option): mitja.peterka77@gmail.com

Fit a tufnol spacer between carb and barrel. Search forum for piccys and dimensions etc.
Quick fix for a beautiful bike

I have it already it is around 0,5 cm thick.

BR, M

email (option): mitja.peterka77@gmail.com

OK try using 2 see if any improvement
Or give the carb a little tickle just to richen up a touch before starting.

This sounds like the magneto packing in, I've had this trouble with a Triumph, it would eventually start with a bump but you wouldn't start it by kicking.

email (option): horror@blueyonder.co.uk

I agree with Horror, my AJS had the same problem, ended up being the ignition coil in the magneto, when it got hot the windings failed.......had it re wound and problem fixed !
Cheers Stu

email (option): stuartcameron66@hotmail.com

On my rebuild magneto the slip ring failed, after fitting a new one it always starts hot or cold.

An insulator as thin as you are using doesn't help a lot to keep the carburettor cool.

Henk

email (option): ahum@quicknet.nl

Beautiful bike.

I had the same problem some years back. The (modern) spark plug was the wrong heat range.

email (option): jonny.rudge@verizon.net

Which spark plug is the best

Like Henk

I had a problem with my magneto & hot starting was not possible

All symptoms indicated a condenser problem, but in fact it was the slip ring

It was worn & had a hairline crack which when hot would not allow the engine to restart, it was grounding through the armature

Once it was cool, it worked again

At the time of repair, I converted to the brightspark external condenser

Since then, it's perfect

I also use champion L10 plugs ( not so easy to find) and since the magneto has been done, it has stopped eating plugs !

Champion L86c or NGk b6hs also easily available and work reasonably well

Maybe time to consider a specialist repay your magneto

Best regards

Job

email (option): Jonnyob1@googlemail.com

Just carry around a can of Aerostart!

I love the champion sparkplugs.
I think that it works best,
By the way, not only with the M20,
But also with any other bike I had in the past, (14 of them)
Which were mostly 2 stroke high-rev Italians.

I could always get higher revs and "pull" longer gears with Champion.
The L86c are the ones I normally used, but I found a packet of 10 L10s,
So I have a supply for the next many years..

Noam.

email (option): noam10@gmail.com

Like Noam I favour Champion plugs as well and have used them for decades...

Regarding the mag I'd have it rebuilt..they are generally reliable once done.

The bike looks very nice by the way...Ian

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