Magneto belt drive conversion

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Magneto belt drive conversion

Postby Jdraper » Wed May 29, 2019 8:26 am

I seem to recall someone selling toothed belt drive conversion for heavyweight singles with N1 magnetos. Has anyone used one of these?

Jeremy

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Re: Magneto belt drive conversion

Postby SPRIDDLER » Wed May 29, 2019 8:37 am

I've no knowledge of that conversion but am interested as to why you want or need to do that....... The mag chain drive is rarely problematic.....
:?

EDIT:
It has just occurred to me that perhaps you are referring to a belt conversion for the primary drive on a mag ign engine. This has been mentioned quite a few times on here and the general considerations are:
The width of the belt requiring a wider/modified outer chaincase...?
The clutch rollers need oil.
Driving the dynamo chain...? (Some mag ign bikes had an alternator).

A further (yet irrelevant) thought...
The N1 has manual advance/retard.
Your '55 would have been fitted originally with an auto advance/retard mag. An over-tight chain can inhibit the functioning of the auto A/R unit. The necessary tension required for a belt would be undesirable.
I poke badgers with spoons.

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Re: Magneto belt drive conversion

Postby Jdraper » Wed May 29, 2019 3:56 pm

No, it was the magneto drive and I have tracked down a clip on you tube -

https://www.youtube.com/watch?v=LLUwAyFw3-E

I suppose I was thinking the same question as to 'why', but I can think of a few plusses - slightly more accurate timing, less chaos if a chain snaps, slightly quieter, no oil/grease required so cleaner. There are a number of plus points that come to mind. I was asking if anyone had tried the kit and if so, what benefits have they seen. Unfortunately my 18S is a '55, so has an SR1 with auto advance unit so the kit, as described wouldn't fit, but I do have a N1-4 lurking somewhere...

Jeremy

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Re: Magneto belt drive conversion

Postby SPRIDDLER » Wed May 29, 2019 8:09 pm

The link doesn't work for me.
Youtube error (640x431).jpg


However, they're all logical plusses in theory but IMHO entirely unnecessary for practical purpose.
In my experience it's a solution to problems that don't exist....
Sufficiently accurate timing is easily achievable with a chain.
Grease doesn't leak out of the chain housing.
I've never had a mag chain break (they are endless and under minimal stress).
I can't hear the chain noise above my valve gear chatter and rattling dentures ;)

Happy to be corrected though.
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Re: Magneto belt drive conversion

Postby Jdraper » Wed May 29, 2019 8:57 pm

You've got the right link from your screen shot, looks like a problem elsewhere in the digital domain. Try cutting & pasting into a new window..

Just got my '55 back on the road after a (very, very) long layoff. I'd forgotten why we need lockwire on the tank bolts.

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Re: Magneto belt drive conversion

Postby 56G80S » Sat Jun 01, 2019 5:36 pm

Link worked fine - too well. Just lost 30 minutes watching run on clips about work done on Matchless engines!

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Re: Magneto belt drive conversion

Postby Dave T » Sat Jun 01, 2019 9:33 pm

The belt does look very spindly, I think I would rather trust a chain. What is the service life of the belt, replacement will be mileage or time dependent, has anyone ever changed a chain in good condition simply because it was old :?:

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Re: Magneto belt drive conversion

Postby 56G80S » Sun Jun 02, 2019 11:14 am

Good question, Dave.

Purely for the age reason I bought one the other year to replace the "real" Renolds that was on when I bought the Matchless back in the mid '70s. There was almost no stretch at all.

But the Regina chain was a bit tight and I had to "adjust" the earlier (incorrect) barrel to move the SR1 back. And then refitted the Renolds chain! To quote Rob Harknett, it will outlast me and I wasted my money.

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Re: Magneto belt drive conversion

Postby Dave T » Sun Jun 02, 2019 11:39 am

Well, I'm glad that it's not just me that does things like that, keep up the good work :D

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Re: Magneto belt drive conversion

Postby SPRIDDLER » Sun Jun 02, 2019 11:43 am

For whatever reason the link opens fine now. It's a tidy piece of work and wouldn't be harmful.
A belt conversion would be a more useful alternative for the dynamo drive chain as it would probably do less damage if it broke or clashed with the primary drive chain. Obviously the dual engine sprocket makes a dynamo belt drive a bit of a challenge.
I've not had a dynamo or mag chain break, nor have I replaced or had a camshaft chain break on any of my MG's and other cars but a main dealer-replaced cam belt broke after 6 months on my Ford Sierra with very costly consequences.
I poke badgers with spoons.

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