Magneto problem

[Bill Thomas]

I don't trust "Rita"!!, I am thinking of putting a scope on the unit at tickover, I hate Magic boxes !!, With the TT carbs, It used to start befor the kicker was at the bottom !, It just feels more retarded but once started it goes so well. Cheers Bill.

 

[aluminiumbronze]

Are you sure it is timed on the correct lobe on the magnet, backfire sounds like wrong lobe to me?

 

[Bill Thomas]

I check mine by getting TDC both valves closed, Then take off the brush pick up and look for the brass strip on the slip ring, (Only on twins and the old Mag's !!, ) Funny thing was, I had a Mag' converted to manual, Slack wire advance, And it worked on the other hole !!, Many years later took it to a repairer and he looked at it and said , This is number one and I said no it's the other way round, He was not happy, I thought the mag' would be flying out the door !!, Cheers Bill.

 

[Oldhaven]

Are you sure it is timed on the correct lobe on the magnet, backfire sounds like wrong lobe to me?

It is timed with the rear number one cylinder on the lobe at 6 o'clock. That is the one that has the long following duration between it and the front cylinder lobe at about 11 o'clock . I did accidentally time it on the exhaust stroke tdc once early in this process, due to confusion with the degree wheel while finding tdc. I only did that once. Now I always check the rockers to make sure. I also have done the brass segment check Bill suggested. Ok there. I was a bit put off by the new manual advance end cover since it had the points cover spring post towards the rear, but this is fine since the magneto now has more end cover mounting holes. The slack wire advance requires re drilling since the cable abutment covers the original hole.

All this seems moot now since the magneto which runs fine on the bench is back to a no spark condition on the machine

 

[Oldhaven]

It has a good 5mm gap spark at low rpm but nothing when installed. I am going to try installing the ground strap Davidd used, even though I get continuity between the mag body and the cases. I am using the rather thick triangular Cometic gasket, and the studs were put in with loctite low strength. Who knows? Also will try cleaning the points and probably Champion plugs as I am using NGK B7ES now. I have little hope any of this will make a difference. After that little experiment, the next step is to put on the Norton dual points arrangement I have now completed. It was to be a backup and it appears the time has come. I am tired of troubleshooting magneto problems after waiting all winter to start up the Rapide. I have a new Alton and am running all LED lights except for the headlight, so I should be fine. I can get to that mid week.

Thanks to all again for the support and advice

Ron

 

[Bill Thomas]

Sorry Ron, You must be going mad, Have you checked the the brass strip on both cylinders, Brass in the middle as points are opening, Cheers Bill.

 

[Oldhaven]

Sorry Ron, You must be going mad, Have you checked the the brass strip on both cylinders, Brass in the middle as points are opening, Cheers Bill.

My wife says I must be the most patient man on earth. So far the magneto has not grown wings and come flying out of the barn.
I think if the brass segment was wrong it would not look good on the bench for both cylinders, but I will check the front cylinder too anyway. I believe it will have less brass segment left on the front than the rear if I have learned enough about magnetos and 50 degree v twins.

 

[Bill Thomas]

I am sure you know that once a plug is wet, It should go in the Bin, I know they cost money, The other old trick is heating the plugs up with a blow gun although by the time there back in you would think they were cold again, Are you sure you have compression on both cylinders ie you can turn the pushrods TDC on firing stroke, It's driving me nuts !!, I have a spare mag' and a D distributor, But you are a Bit far away, Sorry Bill.

 

[Oldhaven]

I am sure you know that once a plug is wet, It should go in the Bin, I know they cost money, The other old trick is heating the plugs up with a blow gun although by the time there back in you would think they were cold again, Are you sure you have compression on both cylinders ie you can turn the pushrods TDC on firing stroke, It's driving me nuts !!, I have a spare mag' and a D distributor, But you are a Bit far away, Sorry Bill.

Hi Bill,
You have said before that wet plugs will never be good again . In this case the same plugs that do not fire on the bike will when I take the whole mess off and move it to the vise I use for testing at the bench. Is this wet plugs thing only for ones that have been run a while and have soot, or even for new ones? You are right, that could get expensive if tickling the carbs too much gets the plugs wet.
Thanks for the offer of spares, but my next try with points and coil should tell me a lot. I will be sure to put a ground step on the points housing as well, as I am getting paranoid

 

[Bill Thomas]

Hello Ron, I think T.T. said, It's a compression thing, A plug can work on the bench but when it's under pressure the spark get's blown out !! when wet, In the old days, In the garages I worked at, They had plug test machines that has compressed air going into them, and you could see the spark under pressure,The spark could happen right up inside, Which is no good !. The other thing, If you think you have flooded, Switch the petrol OFF and spin the engine over with valve lifter held in and the throttle open, Then after a bit try and start it as normal, Don't put the petrol on yet !!, With luck it could fire for a few bangs, Which would tell you that it was flooded, I hope you are starting by letting the the valve lifter go as the kicker gets to the bottom, It is much better for you. Good Luck, Bill.