So to go open like that how does it affect the clutch. Do you need a new one that operates dry or will the wet one work dry?
And does it affect clutch life. I would assume it shortens the lifespan somewhat wouldn't it.
And what about debris getting in there.
I certainly like the look of it

 

I'm waiting for some answers o this topic too.

 

I'm thinking of a PM primary drive, is the clutch pull stiffer with this unit? I hear some have a lockup clutch where the pull is light

 

There are quite a few different makers of belt primaries, both open and closed. They run from $400+ on up into several thousands of samoleans. Some of the closed kits use the original clutch plates, except they are now run dry. Most, both closed and open, use a complete new clutch set-up. Since they are pretty much all different, any comments on a particular belt drive apply only to that drive.

I've run a few closed systems, one on a '72 Sporty, one on a '78 Shovel, and one on my current '87 Sloptail. The Sporty was a very early model, ran wet as the Sporty primary & tranny used the same juice (same as now), and there was even a valve between the primary & engine crankcase. It also used a square toothed Gilmer drive belt. And no, it didn't slip in the oil...

The Shovel was a simple system. The clutch hub and engine sprocket were replaced. The stock clutch was reused. System was run dry. I did replace the plates with Barnett wet-or-dry plates; they worked better than the stock plates.

The Sloptail is a Rivera Primo Brute III enclosed set-up. I carved up the outer primary so the innards are pretty much exposed; call it a semi-open unit, LOL. It uses the Rivera Pro clutch. It's pretty solid, but as with any open primary, the clutch is a little noisy.

Open primaries are for two reasons - you need a wider than stock belt to soak up some serious horsepower, or you like the looks. Guess there are three reasons, the previous two, and the combo of them.

If you run a completely exposed unit and go down, it will be expensive. I remember one brother who even bent the crankshaft. It was over a year before he could ride so we had plenty of time to patch the bike. If your open unit has the backing plate, and the fancy covers, they'll help protect things in a lay-down. Can't say as I've really seen a problem with crap getting into the works and messing things up. It's possible, but I live down a 1/4 mile iron ore-gravel drive and haven't had a problem.

Maintenance-wise the belts require less - no chain adjustments and no primary juice to change. If you run an enclosed unit make sure it is well ventilated as heat will kill the belt. Replace the inner primary bearing with a sealed unit.

One last - a wide set-up hanging off the side will change the balance of the bike. After a couple rides you'll not notice it unless you think about it. It's a physics thing, and physics always wins.

 

Great info, thanks. I'm looking at the open primary for style, but I keep making engine improvement so it will end up working out for both reasons. Cost is kinda prohibitive- $2500 is enough for a decent custom paint job, but it would look hot on my bike.