sprag clutch fix... a how to

[hmmmnz]

well if you have a 500 follow this thread to remove the sprag.
if you have the 125 or any other bike with this type of sprag (ducati bmw ect ect) then you'll have to figure how to remove the sprag your self

and way once you have removed the sprag you'll find it looks like this



not to worry it is redeemable, and you dont have to spend a 100quid or a few hundred dollars to buy a new one

running around the circumfrance of the sprag in a groove in the center is a spring


basically lay the sprag flat and dig the spring out


now once the spring is out move the spring around untill you find the join, its the point where one side of the spring screws into the other,
now you have to cut about 1 inch (possibly more depending on how streched the spring is)
you have to cut the spring at the tail end of the spring!! you need the narrow end to screw back into the new cut end





after you have cut the spring then screw the 2 ends back togeather


funtimes, now slip the spring back onto the sprag

jobs a good'un
make sure the teeth (lobes) are all facing the same direction



and thats it. jobs done
nice and easy, time to re-install

[Nozz]

After going through this procedure, I will have to do it again! Maybe I did not snip off enough of the spring, but after a couple of dozen successful starts, it is spinning again. Hopefully it will be a quicker R&R this time!

[hmmmnz]

yeah, you have to snip quite a bit off if its been stretched a bit, make sure its nice and tight,
and kill your bike with the de-compression lever, rather than the kill switch or key, as the kick back stretches the spring,

[DAVID THOMPSON]

the unit in the 125cc bikes is very different
dave

[Nozz]

OK, I got back to the sprag. The spring had come undone . After putting it all together again I have to wonder if there is a trick to the spring fastening. I tried to unwind it so it would wind against itself when I screwed the ends together, but it didn't seem to want to cooperate, so I just screwed it hand tight and put on the assembly. Second question; is there a direction for the little sprag parts to be facing? In other words, in your picture the little lines on the teeth seem to be on the left, does that go upside in or upside out?? Thanks for your help! I'm going to post another question about my crank problem on the other bike. Now I am fired up to get that one back on the road with the cam and carb!

[comanche91]

I'm going to post another question about my crank problem on the other bike. Now I am fired up to get that one back on the road with the cam and carb!

Off topic: What's the number of the cam you'll be using Nozz? I'm getting ready to do the same (#865). -Don

[Nozz]

Don, I'll note the number on it and pass it along. I am having the crank shaft re-trued right now and all the parts are at another fellow's shop. When I take the crank back to him I will get the info on the cam.

[comanche91]

Okay - thanks.

[MZCountryRider]

I posted a link to this procedure and the one about removing the sprague clutch as well on the ATK discussion group. They found it a great help and I'll pass along their thanks to hmmmnz. One ATK guy did mention something that might be of interest here, his tip:

"Rather than fixing the spring as shown in the links, you can replace it with the spring from an oil seal part # 21098 that can be purchased from either an industrial bearing retailer or Napa Auto Parts."

Edit: for those of you not in the USA and/or who don't have access to a NAPA, it appears that 21098 is the front crankshaft seal for a Jaguar V12. Any bearing dealer should be able to get it though - Chicago Rawhide brand #21098.

[comanche91]

for those of you not in the USA and/or who don't have access to a NAPA, it appears that 21098 is the front crankshaft seal for a Jaguar V12. Any bearing dealer should be able to get it though - Chicago Rawhide brand #21098.

Good info. The 21098 oil seal is an SKF part number, so it should be readily available in Europe. Another identical oil seal is the NATIONAL P/N 450867, available at Advance Auto and many others. About $10.

[hmmmnz]

very good,
i think i have a part number kicking about for one i did on a gagiva with the same sprag clutch,
the spring cost me 10cents (nz)
ill post the numbers if i find the packaging

[Nozz]

This lesson has been a gift that keeps on giving! My spring broke apart again, and I tracked down the National Seal part # referenced above, only to find that the spring inside it is a bit sturdier, and will not fit the groove. Back to the drawing board... A trip to the bearing house and/or a call to Ron Wood is in order. HMMNZ, did you find the spring part # you mentioned??

[comanche91]

Damn, the NATIONAL P/N 450867 is a direct replacement seal for the SKF 21098. I guess the springs are not though. Did you try the SKF 21098 oil seal from NAPA?

[Nozz]

I'll check on that one. I guess I needed an excuse to get back in and replace the gasket!