Oil on belt primary drive

I've not see the Hemmings belt but if it is of Synchronous type and non rubber material then oil won't affect it in the slightest and in fact the belt will then provide for a more more efficient and less energy sapping drive compared to dry.

" We " in work used to run HEAVY industrial equipment with synchronous belt drives and they never had issue with any oil / grease / sludge / water type contamination even when submerged for prolonged periods.

I'd not sweat over it, others will advise I'm sure.

The key with these belts is correct tension and pulley alignment so time spent here will not be wasted !!!

When incorrect the belt will suffer and the drive segments will snap like a carrot.

We used laser alignment ( as when aligning motor and pump shafts ) but that is probably OTT for the Norton.

Yes. Replace it. Last time I looked Hemmings use a Gates toothed belt which does not tolerate oil. It will lilely survive for a while and then break at the most inopportune moment.

Attached photos show my RGM primary drive conversion to belt drive. One photo shows it fitted inside the original tin cases and the second inside a tasty RGM alloy cover. Both have run quite happily for over 10,000 miles despite having all kinds of rubbish thrown at them. 

I went for the open alloy cover, not just for the looks, but also because a good airflow through the drive helps to cool the pulleys and limit the amount of expansion due to heat from the engine. This has worked for me despite having to run the belt with just 30mm of play in it as a result of having a fixed position gearbox. 

The standard Commando primary covers plus a belt-drive conversion need at least 40mm of play in the belt or it will probably lose teeth or break. Adding some form of cooling such as mesh inspection covers or even drilled holes in the covers will help.

The owner of the small garage where I take my car told me that some modern engines have internal rubber cam belts!  Worst of both worlds - he has seen engines with 30,000 miles and the rubber belts have started to rot and rubber blocked the sump oil pump scavenger!  Perhaps bad manufacturing batches?  I find it hard to believe that the big manufacturers would make such serious mistakes with material selection?

I thought the real benefit of belt drive was to avoid the need for oil so, for example, cam belts could be external.  And changed in 25 minutes by the roadside.

@Philip Hannam

That RGM belt is of a different material  and profile to the Hemmings one I have, admittedly a few years old now, Mine is black rubber with round tooth profile.

Free play in the drive belt is best set when the bike is hot (go for a 10 mile ride). Because the alloy pulley wheels expand this might well equate to 40mm when cold. And +1 about cooling.

@David Cooper

That garage owner is yanking your plank. And sadly the days where you could change a Cortina OHC cam belt at the side of the road are long gone. Nowadays, if the belt breaks the engine is more likely than not buggered. And there's a lot of stuff to remove before you can get at the belt.

Hi Nick,

Did Mick Hemmings provide his own belts or just fit those from RGM or others?

My experience is with the RGM belt conversion (60000 miles on a Commando) is that they are fine in oil, which is just as well, since after a bit of wet sumping the oil pushes by the crank seal on start up and into the primary drive.

As stated above - the worst thing to do to a belt is run it too tight, slack is good.

Regards - Paul.

Getting a bit off topic but I stand corrected on timing belts running in oil. Seems like a damn silly idea but for those that are interested see:
https://fordtransit.org/forum/viewtopic.php?f=64&t=204983&p=1750970&hilit=oil+timing+belt#p1750970