Counterbalance Shaft Woodruff Key Dimensions

[Kenneth Webb]

Talked to George at Uptite yesterday about getting some woodruff keys for my 630 balance shaft. It has the stock key now and I want to replace it before tackling the Forever West run this summer. George is wrapped up for a while and recommended that I make some the way he does, by hand. You have to buy an SAE key and file it to fit. Sounds good, but I wonder if anyone has actual dimensions so that I can get a headstart before taking the bike down. Not really expecting an answer on this one, but thought I would ask.

 

[LRPct]

I woukdnt know off hand, but I bet if you search the thread in adv or supermotojunkie the answer is in thete somewhere... Sorry I couldnt help more.. fwiw, mine went on the 610 and I believe I replaced with the normal size metric and shes been great for another 10k+.. I think the real key is a snugged nut, secured/folded washer n loctite.. custom fit key sure dont hurt as well tho

 

[mtm100]

Not sure what your doing but you should be able to find all the Woodruff key info you need in the Machinery's handbook.
Whats wrong with the OEM key? What's better about the new reworked key? I assume if your filing a standard key somehow the difference is minor. If your just changing the thickness maybe you could set up several on a surface grinder to make a few. If you can't find someone local I could do that for you. Just a thought.

Talked to George at Uptite yesterday about getting some woodruff keys for my 630 balance shaft. It has the stock key now and I want to replace it before tackling the Forever West run this summer. George is wrapped up for a while and recommended that I make some the way he does, by hand. You have to buy an SAE key and file it to fit. Sounds good, but I wonder if anyone has actual dimensions so that I can get a headstart before taking the bike down. Not really expecting an answer on this one, but thought I would ask.

 

[Kenneth Webb]

Not sure what your doing but you should be able to find all the Woodruff key info you need in the Machinery's handbook.
Whats wrong with the OEM key? What's better about the new reworked key? I assume if your filing a standard key somehow the difference is minor. If your just changing the thickness maybe you could set up several on a surface grinder to make a few. If you can't find someone local I could do that for you. Just a thought.

Even before I finalized the purchase of my bike, George advised that the key would need to be replaced as there has been a history of sheering keys. Evidently the factory doesn't get the nut on the balancer tightened correctly and the load transfers to the key, damaging it, then sheering it. Happened to one of the riders on the Forever West ride over on ADVRider. The key is slightly undersized and leaves a little slop. Theoretically, the key is just a locator, but it also keeps the balancer from rotating if things loosen up a bit. At any rate, it is a good idea to make sure the key is a snug fit and to check the torque on the nut. Woodruff keys that I have replaced in the past "just" fit into the keyway. If it goes in there easily, it's too loose. I think the real problem is that the factory milled the keyway just a tad too wide, and the metric key is a little loose. An SAE key is too large, so you get to mill or file it down.

Thanks for the offer to do some grinding, but the only way I know to get a good fit is to do it with the shaft exposed and the bike right there to test fit. I don't know the keyway dimensions, or the dimensional clearance. Now, if I just happened to have a surface grinder sitting around in the garage..... I took vocational metal shop in high school and we had all the machines you'd ever need, plus the teacher and I were buds. The shop is gone, the teacher is gone, so no chance there. Way back when I was rebuilding the top end of an exotic racing motorcycle and managed to drop one of the valve spring keepers onto the dirty floor of the local Honda shop. No way to ever find it down there. I drove back to my high school and the shop instructor let me turn new ones on a lathe, then heat treat it. Worked great! Trying to get one from the manufacturer would have meant a LONG wait. Well, it looks like a long afternoon taking ten or twelve file strokes at a time to get the fit right.

 

[mtm100]

I'm a Mech Engineer with a machine shop. My dad was a tool maker so we've had a machine shop for over 40 years.
Made lots of crazy stuff. I build small internal combustion engines from scratch for fun.

Back to Woodruff keys. Your correct the key should never see a radial load. The taper and clamping force should hold the
flywheel in place. I know of the problem you mention. I had one of the first SM610's in the us and that was a concern.
I did replace the flywheel nut, retorqued and red loctited it. Never had a problem.

I doubt the factory cut the keyways wrong. But you are correct the key should fit snug.

A better way to thin the key than a file is to use a sheet of 320 sandpaper on a surface plate.
Then with one finger on the key slide it in a figure eight pattern. That keeps the key flat.
Very hard to do with a file. Lapping on sand paper is slow process and doesn't remove much
material. So patients is required. You can play with grits and any flat surface will work.
Table saw table, even a piece of glass will do. A little water on the sand paper helps too.

Good Luck,
Mark

Even before I finalized the purchase of my bike, George advised that the key would need to be replaced as there has been a history of sheering keys. Evidently the factory doesn't get the nut on the balancer tightened correctly and the load transfers to the key, damaging it, then sheering it. Happened to one of the riders on the Forever West ride over on ADVRider. The key is slightly undersized and leaves a little slop. Theoretically, the key is just a locator, but it also keeps the balancer from rotating if things loosen up a bit. At any rate, it is a good idea to make sure the key is a snug fit and to check the torque on the nut. Woodruff keys that I have replaced in the past "just" fit into the keyway. If it goes in there easily, it's too loose. I think the real problem is that the factory milled the keyway just a tad too wide, and the metric key is a little loose. An SAE key is too large, so you get to mill or file it down.

Thanks for the offer to do some grinding, but the only way I know to get a good fit is to do it with the shaft exposed and the bike right there to test fit. I don't know the keyway dimensions, or the dimensional clearance. Now, if I just happened to have a surface grinder sitting around in the garage..... I took vocational metal shop in high school and we had all the machines you'd ever need, plus the teacher and I were buds. The shop is gone, the teacher is gone, so no chance there. Way back when I was rebuilding the top end of an exotic racing motorcycle and managed to drop one of the valve spring keepers onto the dirty floor of the local Honda shop. No way to ever find it down there. I drove back to my high school and the shop instructor let me turn new ones on a lathe, then heat treat it. Worked great! Trying to get one from the manufacturer would have meant a LONG wait. Well, it looks like a long afternoon taking ten or twelve file strokes at a time to get the fit right.

 

[Stroker Ace]

Talked to George at Uptite yesterday about getting some woodruff keys for my 630 balance shaft. It has the stock key now and I want to replace it before tackling the Forever West run this summer. George is wrapped up for a while and recommended that I make some the way he does, by hand. You have to buy an SAE key and file it to fit. Sounds good, but I wonder if anyone has actual dimensions so that I can get a headstart before taking the bike down. Not really expecting an answer on this one, but thought I would ask.

Husky Part#65N121007 Copy this link!!! You can get all part#'s for everything here... https://www.halls-cycles.com/Catalog/Halls-Cycles-Husqvarna.aspx

It comes out about 3/16 x 3/4in. Get the next size up from the hardware store or auto parts store and file or sand to fit like George says. The stock one and the hardware store one I used is too small (but still working fine), Make sure the threads are DEAD CLEAN then use red locktite and tighten carefully with a 1/2" drive air impact gun, having the big nut tight is the secret!! The crank isn't tapered and the counterbalance drive gear only catches about 1/8" of the key, so if it works loose it shears off the inside 1/8" of the key. Fix it like I George says and your done.....