My mechanic finished doing valves, new piston & rings, Carb rebuild. He's got 40+ years of British bikes behind him. The problem; we get a spit and a pop but she won't run. Tried everything, got spark, fuel, timed, good battery .Temp here in Maine is about 50+-. Getting tired of kicking it. Any best guesses on something that we may have missed? Thanks, Bob

email (option): bobdukw@aol.com

If you are confident about the condition of the mag, then sounds like you have got to check the timing again.

Mag pinion could have slipped.

Does the mag cable enter the mag on the left or right hand side?

Regards

Pat

email (option): sacombsashtrees@hotmail.com

Agree, symptoms sound like timing. But another thing to try, if not done already, is to fit a new spark plug.......and not one from the same batch as the one already installed. Never happened to me, but have heard lots of tales of bad plugs that dont spark properly when under compression.

A mistake many people do (including me when I first started) is to open up the throttle to try to start the bike. It will not start unless the throttle is shut to it's adjusted idle speed. You'll wear your leg out otherwise. Incredible, but for me, it was that simple.

Yes, BSAs like to start on a closed throttle I have found...

Don't 'kick and twist'...Kick on a closed throttle and when it fires then 'catch' the engine by opening the throttle..

Also, set the ignition as advanced as it can be without the engine 'kicking back'...

Set it fully advanced, if it kicks back reduce the amount of retard marginally and try again...Don't retard it any more than needed to stop it kicking back (if it does)...

Too much retard and it will get reluctant to start...

Give it a good strong kick when you do try to start it...and make sure you have the piston in the right place just after TDC before attempting it

Finally don't over flood it...Open the tap, hold the tickler down for a couple of seconds and then try starting it....It is not necessary or desirable to have petrol p*****g out everywhere from the carb...

There is some technique to starting every bike and singles are probably the worst...Once you get the hang of it you'll wonder what all the fuss is about...Ian

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

Check that your "mechanic" hasn't timed it on the exhaust stroke instead of the compression stroke. Also if you've had the cams out since it was last run check the valve timing. Don't trust the marks do a rough check with a timing disc. I think that and what everyone else has said just about covers it.

there are some other techniques , if the bike is not starting :-)
get 3 friends and a van

https://www.youtube.com/watch?v=paZXDgWSfqM

Thanks for everyone's input, currently trying to get together three guy's and a van...!

email (option): bobdukw@aol.com

Those French guys seemed to be using the huge decompresser lever to get the engine up to compression instead of past it

Something definitely not right if you have to use a paddock starter like that. Even when it was running he still needed a push

Ron

email (option): ronpier@talk21.com

...and the winner is~ Ferg! Bad plug! Thanks to all for trouble shooting. Bob

email (option): bobdukw@aol.com

I find over here in Australia that if you foul a NGK spark plug, you then have to throw it out as it never sparks good. Regardless of if its fitted to an old 1930's motorbike or a 1971 Honda trail bike. Just as well the plugs are cheap to buy new.was the problem plug NGK?

I have nothing but trouble from NGK plugs. I was trying to start my Manx, so new NGK plug, it sparked holding it on the head and bike started and ran up the road then stopped. We played about with carb etc and couldn't get it going. We're all knackered from bumping it up and down the road. Checked plug on the head again and no spark. Did this 3 times with 3 new NGK plugs. I then found an old Lodge plug in the garage and it had a lovely spark and the bike ran. I think NGK plug don't work well with magnetos.

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

Try Champion..I've always used them and had virtually no problems in 45years...Ian

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

I used to trial (badly) an old twinshock TY250. Routine maintenance meant a new plug each time out and from a box of ten, one or two were duff after the first start.

I've never had a Champion fail in a Norton...

Modern fuel is the culprit.
Old plugs have glazed insulators.
Modern ones do not because they run at higher temperature .
Modern fuel, which is not petrol, is highly conductive at cylinder compression.
Also modern fuels require hotter plugs.
NGK's have a lot narrower heat range than Champions.
If you use one of the plug interchange sites you will see that most Champions cover 4 NGK's.
I run BP5HS in my M20 and have done so for 80,000 miles over 20 years.
The "equivalent" plug heat to the specified Champion was 8,7,6 & 5 in NGK's
being conservative I naturally fitted the 8's which was a disaster.
the 7's were not much better
The 6's ran quite well provided I always stop the bike by running the carb dry.
I ran out of 6's and slipped a 5 in and that plug has now been in there for 5 years, runs fine , short trips ( less than 2 miles) and long trips (400 miles /day )

a plug i always use in my WM20 is an air cooled VW beetle Bosch plug,mine has been in for 10,000 miles+!