1963 atlas primary drive

Previously wrote:

I would like to replace my atlas chain driven primary drive with a belt drive. Is this possible? And if so any sugestions

first i should ask, WHY?

second, it wont be cheap.

how doyou change gearing on a belt drive?

canyou carry a spare link for one?

what are the advantages?

Hi John

I have fitted a Hemmings belt drive with commando clutch to a 650ss have rebuilt.

It makes the bike a lot smoother and also there is no oil leak from the primary drive!!!

I will accept its not cheap but I got £250-00 for my clutch on ebay so that went someway towards it.

How often do you change the gearing on your bike? that needs to be taken into account.

Talk to Mick Hemmings 01604 638505 if you have any quereies he is always willing to help.

Hope that helps

Hi John

Had no idea that you lived in the USA.

Mick Hemmings sends parts to the USA all the time so just look on his website and you will get all the deatails.

As for fitting it it is very easy and should be no problem to you if you are able to take the existing parts off of the bike.

Regards Nigel.

Hi John

Cant see your picture its just text.

Try sending again as a jpeg or pdf please.

Previously wrote:

Hi John

I have fitted a Hemmings belt drive with commando clutch to a 650ss have rebuilt.

It makes the bike a lot smoother and also there is no oil leak from the primary drive!!!

I will accept its not cheap but I got £250-00 for my clutch on ebay so that went someway towards it.

How often do you change the gearing on your bike? that needs to be taken into account.

Talk to Mick Hemmings 01604 638505 if you have any quereies he is always willing to help.

Hope that helps

Just for the record , currently preparing to change the engine sprocket and give my clutch aclean up. want a little more acceleration but still tall enough to keep the vibration down. it can be matched forones "normal" cruising RPM. with a belt drive you would have to do a lot more workchanging the gearbox sprocket to accomplish the same thing. for myself I appreciate this advantage. each onto his own.

Hi John

If you geta bit ofspare time, then do lookat some of the belt drive articles in the Technical section of this website. There are several that deal with the benefits and drawbacks of fitting sucha conversion.

In recent years I haveconvertedthree of myNortons to belt drive. Two Atlas's and a 650SS.

The bonus points, each time, were amuch smoother transmission, no oil leaks from the chaincase itself and a very light and easy clutch action. The other plus points were that when pulling off the chaincase cover,to check out the alternator, there was no oil to drain or drip on the garage floor, the belt never needed adjusting for tension and and showed no signs of serious wear after 5 years of hard use. Also, you can get pulleys of differing sizes to help adjust the gearing to suit your bike.

The possibles drawbacks:-

My first conversion kit was clearly geared to suit the smaller engined Dommies as, when first fitted to my Atlas,the engineran at 5000rpm for a 70mph cruising speed. Much too high for an Atlas. So this kit was donated to my 650SS which already had a 20t gearboxand 42t rear wheel sprockets to raise its gearing.

My next kit was ordered with a bigger engine pulley, 34t instead of 32t. This gave a primary drive ratio of exactly 2 to 1 and resulted in 4,400 revs for a 70mph cruse speed. Almost spot on.

Thiskit also came with a 1000mm long belt, which was too long and resulted in the gearbox having to be set as far back as the adjuster slots allowed. This in turn made the clutch rub against the outer primary case and also messed up the rear chain length.

Fortunately, you can now get belts of 980mm length which are about the right size to keep the clutch in the centre of the primary cover bulge. Also very useful is a spacer kit which pushes the primary cover about 6mm away from the inner. This stops the clutch centre nut cover from touching the outer when the clutch lever is pulled fully in. (When using a Commando clutch basket)

Thisfirst belt drive kit all came with longer alternator stator studs and spacers to push the stator outboard from the 30mm wide belt. There were two problems here. The studs supplied were too thin and allowed the stator to move sideways enough for it to touch the rotor. Secondly, when in place, the outer case also originallytouched the statorand pushed it against the rotor.I lost two expensive alternators before twigging a fix to cure both problems. The spacer kitmentioned above and some purpose made shouldered studs. Some belt drive kits now can be purchased with 25mm wide belts which also helps to sort out this difficulty.

I found out the hard way that someother very important points need to be considered. Especially when converting an Atlas to a primarybelt drive.

1) Your gearbox bearings must be in 'as new' condition. Any wear in the large main bearing or output drive sleeve gear will allow the gearbox mainshaft drive end to be pulled forward on accelerating hard and back when decelerating and using the rear brake. The change in angle of this shaft then causes the belt to track out and in on its respective pulleys and subsequently grind away on the alternator housing and primary outer cover.

2) You will need some way to hold the top gearbox mounting bolt in a fixed position once the belt tension is set. This could be by fitting an adjuster each side or some other means.

3) With the largerengine pulley fitted I found that the belt used to catch the top and bottom edges of the alternator housing. Some careful filing and buffing sorted this out.

4)If you are going to do some serious riding then you need to consider a means of keeping the pulleys and belt cool. You will be amazed at how much the pulleys expand when they get very hot, such as on long rides. The belts can then become over-tensioned and start to shed teeth. The spacer kit for the primary cover helps here as it allows air to flow past the seal.

There are plenty of belt drive conversion kits, for Nortons,on the market and most are now easy to fit and will do a good job. As a general rule the more you pay, the better the set-up. But............ be aware of the drawbacks mentioned and don't sell or give away your original primary gear. You might need it again, one day!!!