Norton MK III 850 electric start belt drive

I purchased 2 RGM belt drive kits for 2 X 1975 Norton MK III 850 electric start . The top of the belt is rubbing the starter sprocket on both bikes and cannot be adjusted to prevent this. We are a classic motorcycle restoration shop and very experienced with Nortons but the first with a primary belt drive for this model. RGM is not responding to several requests for assistance. We can see how the belt drives would be OK for non electric start, but they simply do not fit 1975 Norton MK III 850 electric start without this rubbing taking place. The crankshaft and gearbox output shaft orientation cannot be changed to enable the belt to be guided off the starter sprocket as both engine and gearbox are fixed between the same 2 mounting plates. Does anyone know of a fix for this without fitting an additional ( and expensive) guide to the clutch basket or the crank drive sprocket? I can send pictures if the explanation doesn't suffice Thanks K

RGM normally respond to emails very quickly, your emails may be in a spam folder so give them a ring, Roger is very knowledgeable about how their products work.

Wish I could get any cooperation at all k

Kevin,

Not sure if you are asking about tension or side to side interference

The only way to change and get the correct tension on a MkIII belt drive is to:

- change the size of the belt
- change the size of the front sprocket
- change the size of the clutch basket
- a combination of the above

In other words, you have the first select the closest ratio you are wanting to use, get a belt size to work as well as possible and even then, you may have to change the front or clutch basket a tooth or so just to get it right. As you mention, there are no other ways to adjust the tension since the gearbox is fixed

If your issue is side to side adjustment, there is no way to do this either. There is a slight chance the upper and or lower gear box holes are somewhat worn and oval and that the clutch basket is therefore not aligned with the front sprocket, pushing the belt in or outward

Also, if you are considering running this cavity dry....think twice. There are some parts in the MkIII primary that require lubrication and without it, possible lock up and some serious consequences.

Good luck

Matt / Colorado Norton Works

http://www.coloradonortonworks.com

Go to a duplex big pin Merc chain......simples

I bought a RGM MKIII belt a LONG time ago and once I got it, I eventually decided against using it. Primarily because of over the years and all the discussion of the delicate nature of the starter mechanism...sprag especially and other supporting machinery that would not get the life blood needed (oil).
Aside from the poor judgement to use one...Did you not receive the eccentric bolt/shaft adjuster? My original kit had one? Is it ineffective to adequately tighten it to make it not quite touch?

FWIW you can still use it on a regular commando.

Do you have a 28/55 set?

Thanks for all responses. The problem is the outside belt interference with the starter gear on both bikes. I do not understand how RGM can sell them for Norton MK III 850 electric start when this problem exists. I can see how they would work with non electric start but most important after a lot of one way correspondence they don't appear to have the answer and I am largely been ignored. K

The bigger question is how things can be expected to work with no lubrication to the sprag bearing, as pointed out above.
Strange that RGM would sell a dry belt drive for a MK3, sounds like a non-starter, if you will pardon the pun.

Would it happen to be a run-in-oil belt drive?
There are some belts that will run dry or in oil.

Glen

The RGM kits are very well made and use the Synchroflex belts which are excellent quality and are unusual in that they can be run wet.

...which kinda defeats many of the benefits of fitting a belt drive in my opinion.


If you want to run the kit dry, RGM recommend two options:

1) that you use the 'start assist' very occasionally but only with very regular lubrication of the e-start components
(I would really not find this an attractive proposition, as dried out equals locked up)

2) that you remove the electric start components, and start your bike using the kickstart

Personally, I don't find any of these options appealing and if I was in this situation myself would be following the route of andychain

starting is NOT where the lack of lube is the trouble . the trouble is when it is in freewheel where the sprag and bearing in the crank assembly runs dry.

gtiller said:

If you want to run the kit dry, RGM recommend two options:

1) that you use the 'start assist' very occasionally but only with very regular lubrication of the e-start components
(I would really not find this an attractive proposition, as dried out equals locked up)

Click to expand...

On their website, RGM show 2 kits for Mk3, one of which seems particularly designed for keeping the starter motor.
BELTMK3SM BELT DRIVE KIT FOR FOR MK3 COMMANDO WITH SPECIAL TENSIONER AND SPECIAL DESIGN OF FRONT PULLEY WHICH ALLOWS THE RETENTION OF THE STARTER MOTOR
It costs 20 pounds more than the other kit. Could you not just order the special pulley for an extra 20?
http://www.rgmmotors.co.uk/main.htm

Mr. Rick said:

On their website, RGM show 2 kits for Mk3, one of which seems particularly designed for keeping the starter motor.
BELTMK3SM BELT DRIVE KIT FOR FOR MK3 COMMANDO WITH SPECIAL TENSIONER AND SPECIAL DESIGN OF FRONT PULLEY WHICH ALLOWS THE RETENTION OF THE STARTER MOTOR
It costs 20 pounds more than the other kit. Could you not just order the special pulley for an extra 20?

Click to expand...

The "1975 Norton MK III 850 electric start" kits purchased by Kevin j Wilson must already have the 'special Mk3 front pulley' as it wouldn't be possible to fit the starter crank drive gear and sprag using a 'standard' pulley.

Old Britts sells a belt drive tensioner that is supposed to be very well proven.

Thanks for all of responses The kit was ordered for the MK III electric start. The belt simply does not clear the starter sprocket and never will with this setup. Anyway ..finally a positive response from RGM they are taking them back for a full refund. Thanks Again Merry Christmas... Kevin

A little bit off track but has there been any issues with belt alignment on MK3's? or should I say misalignment.

I bought a Belt Drive Kit for my MK 111 from Norvil and it states that the belt MUST be run dry. I was a bit surprised at this as i expected it to be able to be run wet because of the Sprag. I dont think that would last 5 min without any lube. Looks like i have wasted my money and will end up running the stock set up as i still want to be able to use the electric starter which i have already upgraded. My fault i guess but i dont think Norvil should be selling these kits for the MK111 in their current form. :?

A (PROPERLY ADJUSTED & LUBRICATED) roller chain is a very efficient and durable power transmission method. The ongoing belt drive infatuation is baffling.