Pto centering

[ted johnson]

Richard, the roller links stick out further than do the outer plates. The curve of the peanut across it's widest part should be .356 according to ANSI/ASME Spec B29.1. Chains should meet the above spec. If you take the radius, multiply it by two (to get .356), take the pitch diameter of the 9T sprocket, 1.097, subtract the .356 and you end up with a .741 dimension. This is the max. diameter you have left so that the chain will just touch the neck between drum and sprocket. Of course, you want to have some clearance, so a .688 diameter would be the max that I'd want to see. I had a flat washer under my clutch nut that was actually a bit bigger in diameter than the aforementioned .741 diameter, so that my chain was riding on the washer. I realized this was twisting my chain as it ran across the top sprocket, so I dug up a smaller one from ARP fasteners. I would like someone to measure the neck diameter on some 9T clutches to see how much the links can whack the neck when the chain is whipping around. I'm glad our AZ tracks are "open" enough so I can run a 10T. This means I have no clearance issues, plus I can run a needle bearing in my drum. As long as I put a dab of Moly disulfide grease on the needles once in a while, the needle runs for a very long time. I've also had folks tell me that a needle bearing running on the West Bend crank will cause problems. I've been running the same crank in my 610 for eight years, and there's no sign of wear. I run 10T needle bearing Max Torques and Rev Grips. TJ

[steve welte]

Ted I have had no problems on the duals running a 10t needle bearing inboard on the West bends (taper crank). Now if the crankpin wouldn't wear that would be great. Pits out at 11 o'clock. Down to 5 cranks left for 2  duals so in about a year i have no cranks to run.

[ted johnson]

Steve, I have had no luck looking for the stepped cranks that I like, either. Of course, I run the outboard clutches with the 10T and needle bearing. Ted

[Tom Day]

Steve, I have had no luck looking for the stepped cranks that I like, either. Of course, I run the outboard clutches with the 10T and needle bearing. Ted

Can you turn down a 3/4 crank?

[ted johnson]

Tom, I have no lathe access, nor access to a woodruff keyway cutter. I have cranks in both engines, so I'm covered for now. Thanks. TJ

[steve welte]

I studied that. You could run a 3/4 hub and turn down the end to accept the drum. The drilled hole would only go into 1/2 or the bearing surface. The other half would be sitting on solid shaft so I don't see where it wouldn't work. Problem being for Duals is the class calls of use of oil clutches. Good luck finding much of anything. singles it could be done.

[Tom Day]

I studied that. You could run a 3/4 hub and turn down the end to accept the drum. The drilled hole would only go into 1/2 or the bearing surface. The other half would be sitting on solid shaft so I don't see where it wouldn't work. Problem being for Duals is the class calls of use of oil clutches. Good luck finding much of anything. singles it could be done.

Steve,
  The old Burco hub for the straight Yamaha clutches is close to 3/4". I have one and also a straight shaft WB crank if you want to play with it.It would be a outboard drive of course. Got to be some of those old Burcos out there.

[doug tenney]

That's a tempting option (cut down 3/4" dia PTO's for use on karts).  However, the life of the clutch drum bearing surface will probably be shorter than normal, unless the new surface is case hardened.  Needle bearing manufacturers say that that shaft is supposed to have a hardness of HRC58 to 64.  Still worthwhile.

Steve, if you have access to a harness tester, it would be interesting to see what those crankpins measure.

[Terry Bentley]

This is interesting. Space chain has been around for about 45 years. When it first came available was the shiznits. All your chain problems were gone. Since most sprint applications were requiring a 9 tooth sprocket, chain life is still short, along with sprocket. But no kinking up or breaking so much.

A decade later 219 chains shows up and again is the fixall. Well almost. Chain life is increased now, but the 10 tooth 219 sprocket is smaller than a 9 tooth 35 sprocket. So the occasional sprocket shears off or more commonly the bushing wollers out or welds to crankshaft.

All is not lost Horstman comes out with an offset needle bearing in drum and gives more meat to keep sprocket from shearing off or bushing failing. So everything in hunkydory unless you have tight spots in chain from misalignment or piecing new and old chain together. Or worse, running a dry disk clutch. Oh well now that tiny little needle bearing is grinding a nice groove in the crankshaft.

Wow 35 chain is still used in 4 stroke racing and demand is good. Time to make an extreme version of the chain so it wont take a dump in middle of the race in case you forgot to turn your chain oiler on.

Now we have super sonic strong silver pro or g0ld on g0ld chain that has bigger links and even a real roller. It actually lasts a long time compared to days past. But how come my gears are shearing off? I just dont get it.

[steve welte]

Terry that last part is almost funny. I don't get it either. LOL. Doug we tested the cranks. They were indeed 56 rockwell. I've had 5 of the taper cranks fail in the crankpin. The new company or lastest I should say, US Motorpower, has never made one of them. They were made around 2000 and won't ever be offered again. It's all about time. I'll run what we got until there is nothing left to run and then we are done. I have yet to tear last seasons engine down to see how they fared. I switched from 10 oz of KL100 to 11 oz of straight Benol castor in hopes that may buy some extra time.

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It should be mentioned that g0ld on g0ld is RLV and sivler and black is EK. I have a package of tuck and run but haven't tested it yet. there may be slight differences on a 9 tooth. time will tell. I'm testing some black and silver and will be looking at the sleeve of the Max t soon now that tracks are opening up again.