By Count Johnny
#91906
Morning Chaps

Of late (given that I haven't ridden Slo Poke, so much) the Bob Newby belt drive clutch has had a tendency to stick, from cold.

Usually, this breaks free by dropping it into gear with the aid of a slope but, yesterday, it wouldn't break free at all.

Removal of the plates revealed that two plates were stuck solid and that there was considerable corrosion within the clutch and primary chain case caused (I'm guessing, because the chain case is well sealed) by condensation.

Does anyone have any thoughts on how one might prevent this? My first thought was running it in ATF, but I don't think the belt will like this. As I say. Any thoughts?
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By stinkwheel
#91908
Maybe needs the chaincase to be not sealed? So condensation can escape? I'd imagine there could still be a small amount of blowpast from the crankcase.

I know a lot of people run belt primaries open on other bikes. I do remember my mate having a belt primary on his A65 and he left the caps off the cover.

It'll be hot when parked up so if it's being parked up somewhere dry, it shouldn't get condensation forming.
By mauri
#91909
a vent for the primairy was one of the first mod's i did.
the condensation it mostly due to there being an alternator in the same casing.

in my trials wich has a pre 56 primary casing, hence no alternator it has no need for a vent.

the vent does not have to be much, on mine its a 4mm hole.
after that the condensattion problem was gone.
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By Rushour
#91931
The BNR clutches have different plates for wet and dry and the belt would not appreciate ATF fluid! I would suggest some sort of breather to let air circulate around if you are going to store the bike.
By Count Johnny
#91942
Thanks for your responses, chaps.

I've had a bit of an email dialogue, with Bob Newby, who confirms our suspicion that it is condensation within the primary chain case, that is causing the problem. He also added that the friction plates are hydroscopic, so would have a tendency to attract moisture, which is then sandwiched against the steel plates, causing corrosion.

As per the responses, above, he recommends some venting (at least while the bike is parked) which could be easily arranged by removing the oil filler plug. He also suggested tie-wrapping the clutch lever 'open' and assures me that this will not compromise the springs.

Finally, he also has some special clutch plates (which are intended for extreme racing applications) made from a higher chromium content steel which would - as a bonus - also be more resistant to rust.

I hope this is helpful, should anyone else experience the same problem.
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By Adrian
#91945
I don't now if they'd fit the BNR drive or clutch basket pulleys, either in length or tooth form, but Tony Hayward's Triumph belt drive kits use (I think) a urethane belt which is oil-compatible.

I foresee Slo Poke being equipped with a neat custom breather for the primary chaincase, you can't just ride around with the level plug unscrewed and maintain any style! :lol:

A.
By Andy C
#91947
Simple solution - ride the bike more often :mrgreen:

Only joking, sounds like you have a solution, the BNR clutch on my bullet runs in oil so dont have this problem.
By vince
#91949
Hi, drill a 4 mm hole in the fillercap, that way you can always return to original spec without marring the cases. Vince
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By stinkwheel
#91950
Buy a cheap primary chaincase from India and cut fretwork into it. Can be shonky as you like because it doesn't need to seal.

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