Mk3 Belt Drive Suggestions

Chris,

I personally don't think its the sprag that is the main concern. Sure, it can blow up and cause some damage but it doesn't necessarily lock things up.

The bearing that can cause you some serious trouble is the needle bearing inside the crank gear (06-4731). If this doesn't get lubrication, it can/will lock up on the crank race, that in turn locks up on the crank

When that crank gear locks up, it will engage the starter and this is when you are in trouble.

Black skid marks as Comstock talks about will be the result and you can only hope that you are on a straight when it happens.

To go in and occasionally lubricate is risky. How will you determine that its time to lubricate ? When this primary fails, it will do so in a matter of seconds.

The bottom line is that it doesnt matter if you use the starter or not. This is not what will cause the failure. Running the bike will

I don't think that any oil leak is worth the possible consequence of running a dry primary on the MkIII. This wont just break the machine.....it may break you as well

Matt / Colorado Norton Works

http://www.cokloradonortonworks.com

Thanks much for the reply Matt. First with Jim's comment and now yours, the belt drive is no longer an option!

Thanks to everyone for helping me avoid a serious mechanical, and potentially dangerous, situation...

Nice site Colorado Norton Works, check the spelling on the forum.

Converting to belt drive and running a wet primary makes absolutely no sense to me. I don't see any benefit in a belt drive OTHER than the ability to run a dry primary. If you have to keep lubricant in there for the Estart anyway, why go to the expense?

Re that...how does the clutch bearing survive in a belt drive since there is no lubricant? I assume the oem bearing is replaced with a sealed/lubricated one?

mike996 said:

Converting to belt drive and running a wet primary makes absolutely no sense to me. I don't see any benefit in a belt drive OTHER than the ability to run a dry primary. If you have to keep lubricant in there for the Estart anyway, why go to the expense?

Re that...how does the clutch bearing survive in a belt drive since there is no lubricant? I assume the oem bearing is replaced with a sealed/lubricated one?

Click to expand...

yes you change the clutch bearing to a sealed type ,,,,,,,,,,,,,baz

To answer : Big weight savings and smoother running .

Big weight savings and smoother running .

Click to expand...

no leak primary

no need to remove clutch plates and clean the oil off from time to time

CNW said:

The bearing that can cause you some serious trouble is the needle bearing inside the crank gear (06-4731). If this doesn't get lubrication, it can/will lock up on the crank race, that in turn locks up on the crank

When that crank gear locks up, it will engage the starter and this is when you are in trouble.

Black skid marks as Comstock talks about will be the result and you can only hope that you are on a straight when it happens.

To go in and occasionally lubricate is risky. How will you determine that its time to lubricate ? When this primary fails, it will do so in a matter of seconds.

The bottom line is that it doesnt matter if you use the starter or not. This is not what will cause the failure. Running the bike will

I don't think that any oil leak is worth the possible consequence of running a dry primary on the MkIII. This wont just break the machine.....it may break you as well

Click to expand...

Matt -

Consdering installing a belt on my 850 Mk III. With the e-start removed from the bike, I am I correct that there is no need for the associated crank gear, and therefore should be no issue?

Cheers, Wiill

Wiill,

No problem running a belt drive in a MkIII if you remove the associated starter gears. The one tricky part is that you have no way of adjusting the belt tension (like on a pre MkIII), so its critical that you get the perfect size sprocket/belt combination.

Good luck

Matt / Colorado Norton Works

www.coloradonortonworks.com

I suppose you could slot the upper gearcase bolt holes in the cradle, add a screw-type adjuster and tension the belt? (Mimicking the older system)

Danno said:

I suppose you could slot the upper gearcase bolt holes in the cradle, add a screw-type adjuster and tension the belt? (Mimicking the older system)

Click to expand...

Well, you can but it wont allow much movement since your shift shaft has to be considered as well. Don't want that to bind up. You would also have to remove and open up the main shaft seal area where it goes into the primary.

Matt / Colorado Norton Works

http://www.coloradonortonworks.com

Yeah, I forgot about the sliding mainshaft opening in the older primaries. Mine is such a mishmash with MK III motor and trans with E-start removed and shifter converted back to the right. The MK III crossover shaft is already at a silly angle.

A few helpful tips:

If you clean the primary cover mating surfaces (brake cleaner is a good idea), install a new gasket that's lightly coated in both sides with Permatex #82180 Ultra Black, and replace the phillips screws with allen head screws (OldBritts has these as a kit), you will eliminate ALL primary cover leakage. Keep that Ultra Black in your tool box. You'll find many uses!

Use only Ford Type F transmission fluid in the primary. If the crank seal leaks engine oil into the primary and fouls the clutch plates, drain the primary and then put in one cup of kerosene. Take the bike for a VERY short ride - 1 block or so is plenty, just enough to shift a few times. Drain the kerosene out of the primary and put in the Type F. Now take the bike for a slightly longer ride, maybe a mile or so, then change the Type F again to make sure all the kerosene is out. Your clutch plates have been cleaned and slippage has been eliminated, without having to remove the primary cover and disassemble the clutch.

I picked these tips up over the years and they helped me to get along much better with the wet primary on my MkIII.

Thanks everyone... don't know what I'd do without this site.

Been in touch with Steve Maney and he guarentees a 912 size belt with his race kit will fit an 850 Mk III with no adjustment... he says the race kit on an 850 MkIII still allow the stock alternator as well due to the longer crank...

Given the favorable exchange rate at the moment I'm going to put an order in. Leaking primary is only one consideration amongst the several other advantages. Bike has been off the road for two seasons after it went down due to a driver hooking a left hander into me. This was only two weeks before I was moving states, and the Navy has been moving me around every year since then, because of that and welcoming a baby I haven't got my shop set back up. Finally getting a new tank in a few weeks... since the bike is sitting anyways this seems a good time to upgrade.

Cheers, Will