Belt drive.

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arc

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Oct 30, 2008
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O.K guys i'm going to fit a belt drive but there are so many choices!!!!(74 mk2a) so here's the question is there any one which stands out from the pack????..........................Thanks in advance for your replies and hopefully helping me make my mind up?...............Cheers Andy
 
Steve Maney's ones are very good! Steel back, so no chewing up fibre plates. Never had a problem with them. Years ago I had one from a company with big ads in all the magazines, sell lots of rubbish on EBay etc...you know the one! the pulleys weren't even anodised, so didn't last long!!
 
This exact question was asked, and answered with many good points, less than a week ago.

Do a search and reap the benefits.
 
I have a Norvil for many years...no problema! and you can choose different ratios.
Just make sure to vent the primary
Philippe
 
I have a Norvil for many years with no problema. And you can choose different ratios.
Just make sure you vent the primary.
Philippe
 
yes , but with a HTD belt 36 teeth on the front pulley is about the maximum in a std primary case .
More than 36 and the belt may rub against the stator studs .[/quote]

True as far as it concerns a pre MK3 case. The MK3 case will take up to 40 teeth front pulley.
 
Norvil belt here for the past 10 years.
I used to vent the primary by removing the inspection covers, but after giving it considerable thought for the past six years
I have run with the covers all in place. And it gets hot here in the southwest US.

From talking to industrial engineers, the belt itself can tolerate more heat than a sealed primary can build up.
So does it come down to the rotor and stator not being able to stand the heat?
I doubt it because that same rotor and stator are totally sealed in a primary with a chain, and I doubt very much that
some ATF fluid which itself would be as hot as the primary would "cool" the alternator.

So why exactly then do some people believe that venting a belt primary is necessary?
 
I would think that the lube in the primary would transfer quite a bit of that heat to the primary cover where it could dissipate against the cooler outside atmosphere.

Whether that is NECESSARY, I have no idea.
 
highdesert said:
Norvil belt here for the past 10 years.

So why exactly then do some people believe that venting a belt primary is necessary?
Click to expand...

I would suspect you would get some cooling affect on the alternator when bathed in ATF/oil. With a sealed primary and belt drive you would get none.

Of course it would help to know the optimal operating temperature for the alternator. I always assume the cooler the better but that is not based on any facts. :mrgreen:
 
I've run a Norvil belt drive on my Manx with a Bob Newby front pulley with zero problems for two seasons. I spent some time in the paddock taking a look at the primaries of other race bikes and found that several had very little ventilation. They essentially just had enough to vent the case slightly. All reported no problems whatsoever. I'm also running a Norvil belt drive on my Commando.

The belt is a Gates Powergrip HTD. The trick with these belts is that they make many different sizes, but some are only carried in specific countries. I have a local bearing supply that carries Gates HTD belts, but they don't carry the size I need for the Manx. I have to order it from England. The size for my Commando is available here. I'm told that some specific sizes are only carried in Germany. I guess it's based upon popularity or size equivalents for specific regions of the world.
 
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