illf8ed said:
rvich said:
I wonder if you could modify that to accept an oil seal like the 9815 being used on kick start shafts. Do you have the diameter handy? Of course going to a belt drive...yada yada yada...
Russ
One thing I just realized, timing belts on cars are something that need to be replaced roughly every 100,000 miles. When I see an engine with a timing chain, it's a relief. So why is a drive belt better than a triple row chain? Weight, quiet yada yada yada.
Dave
Bits from a few different stories about commando primaries:
In about 1970 or early 1971 when I had my first 70 "roadster"... I had beat the hell out of it like a ninja. I finally blew the chain off the front sprocket and it trashed the steel felt oil seal carriers. At that time I did not know the carriers were available. My dad, a highly skilled toolmaker/machinist, made some thin tapered aluminum discs with a bore to hold the felt. It was made in two halves and was had maybe .015 of seperation that was closed up by 3 or 4 little #4 screws to make a sealed and secure, but sliding carrier, against the machined inner and outer surfaces of the primary. It could have easily been made with a "real seal" built in instead of the felt. In a wet environment I don't see the tranny shaft speed as being high enough to not be entirely effective and long lasting.
In the late 80's when I was at a Lotus rally in Corning NY near Watkins Glenn. There at the track I met Carl Hockinson a Norton race guy. His belt drive story goes as follows. He used to drag race a commando for many years before going to road racing. He would go to New England dragway and with a triplex primary chain would trash a gearbox almost every weekend. He finally put a belt drive in it as they were fairly new on the market at the time...
From then on he would then go the whole season on one gearbox......
He was so enthused about them he gave me a Fair spares catalog. and urged me to try one.
I did get one and in addition to a full gearbox rebuild, I tried it. This is the ocassion that prompted me to make my clutch rod seal that I read about in the norton news, since no one was selling them.
I am absolutely convinced the MASS of the chain and clutch basket along with the energy of resonant chain whip is the cause for much gear face brinnelling/sprauling and not the shock of drag race starts. If you look at many gearboxes you will see gear face damage on commandos but much less on featherbed bikes with only light single primary chain.
Drive a bike with a belt right after installation and most alert riders can sense a huge difference by the elimination of the heavy chain whip. I pit crewed for almost 10 years for vintage racers and this is also very evident when you go to a race track and observe the open primaries and actually pay attention to the chain/belt motion.
I would pretty much put a belt drive on any commando I plan to KEEP and RIDE... trailer queens don't need them.