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March 3rd, 2009, 04:03 PM   #1
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Crank axial clearance.

Hey, im rebuilding my 04 fe 450 that had a knackered left main (roller). Im going for Enginehardwares method of using a roler on the right and a ball bearing on the left.

I want to get the axial clearance right as this is obviously important so went and bought the tool for taking the roller inner race on and off and a load of differnt sized shims.

Then i thought to myself, if i have a ballbearing on one side surely this will hold the crank tight and i wont be able to put the cases together, push the crank side to side and measure the clearance

Im thinking the way to do it would be to measure the crank and then the bearings in the cases then work out what shims to put in and hope its right?

Any advice?

cheers
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March 3rd, 2009, 04:42 PM   #2
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RE: Crank axial clearance.

hi rabno

i would prepare a crank with the c/b only on it and the rod in situ and then go to work. press the bearings in the cases and then drop the crank in and close it up. check for float now using a rubber hammer to give it a tap L to R and back. use any of the methods previouly mentioned to measure the float.

i would then shim up and take it that i did it right allowing say a tiny amount for error. then rebuild with the desired shim in there. when you pull the crank hard left that side won't expand and move but the RHS moves right and that is where the float and gap will be.

regards

Taffy
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March 4th, 2009, 03:51 AM   #3
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RE: Crank axial clearance.

taffy so that would work if the TMB ball had a slip fit on the crank ? or does it usually move if you hit it?

what about using an NU206 instead of an NJ206 ?

no inner race lip so don't have to worry about the "float"

FWIW I have seen a tech buliten from Hberg aust for installing the NTN TMB 6206 C3 ball LHS with an NJ206 RHS that says roughly:

press the crank to 59.90mm at the pin remove all shims from RHS of the crank but leave the 0.2mm shim on the LHS and put it together.

sounds like a no brainer but a bike put together at the local (jap) dealer with this tech buliten as a guide died a quick death. IMHO if you press the crank it will flex a bit and get bigger than 59.90 on the first startup. once its found its "happy place" it won't move much anymore but then how do you check the float? the dead bike had zero float and crank width measured 60.18

if the ball isn't a slip fit on the crank you could measure the "width" of the whole crank/bearings/balancer etc as assembled and then use a bore guage sort of thing to measure the distance twixt the bearing mounting flanges in the cases and go for 1mm "float" to be safe. can make a guage out of a long nut and 2 lengths of 3/8 threaded rod with the ends filed to small radius's

another potential problem is (I think) the TMB 6206 C3 has a larger OD as well so the "crush" is higher when installed in the same hole as an NJ206 C3

if we knew the ideal radial clearence as installed for the 2 bearing types then it does away with all the measuring of bearing housings and C numbers. FWIW there is a tech buliten in the DOC that says radial clearence as installed should be 0.04 to 0.05mm for the C3 skf Nj206. also says that if needed the bearing housings can be relieved with wet n dry

not sure if these tech bulitens should be taken as the shiznit in the way of advice but its a start..

HTH
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March 4th, 2009, 04:56 AM   #4
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RE: Crank axial clearance.

could you edit that bushy and use the following so i can understand you

ball
roller
open roller

it's so much easier to understand that way for other people. me hahahaha! i'm fine (ahem!).

regards

Taffy
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March 4th, 2009, 08:41 AM   #5
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RE: Crank axial clearance.

Thanks for the repys. So taffy are you saying even with the ktm ball bearing on the left side, a whack with a rubber mallet should move the crank enough for me to get an endfloat measurement?

cheers
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March 4th, 2009, 11:21 AM   #6
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RE: Crank axial clearance.

rabno

well that's what i have always done. the weak link when hitting the crank ends is going to be the friction between the bearing inner race and the shoulder/journal of the crank. giving it a 'slap' one way measuring, then slapping the other works for me. it also straightens the bearings which is why i can say that i've slapped cranks since 1977.

bushy
the 501 MX i did last year that was a '00 had a 6205 open roller on the right just as you say. it also had a collar on the left that the nut pulled hard on and drew the crank hard left against the bearing.

my "slapping" system works, i just didn't realise that i was the only one that did it?

regards

Taffy
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March 4th, 2009, 11:31 AM   #7
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RE: Crank axial clearance.

Ok thanks for the help, this was the lst thing i wasnt quite sure about so its off a engine building i go

cheers
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March 4th, 2009, 02:31 PM   #8
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RE: Crank axial clearance.

now remember that dowel on the left end of the crank. donchyu dare go near that! use a 10mm deep socket or summink over it to do make the impact.

regards

Taffy
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March 4th, 2009, 03:23 PM   #9
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RE: Crank axial clearance.

cheers for the heads up, i was thinking i would need to get something to avoid hitting the very end of the crank..
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March 4th, 2009, 03:54 PM   #10
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RE: Crank axial clearance.

bushy
the 501 MX i did last year that was a '00 had a 6205 open roller on the right just as you say. it also had a collar on the left that the nut pulled hard on and drew the crank hard left against the bearing.

ahh its a goot idea to have stuff wots not supposed to move tied down properly. if the closed ball isn't tight on the crank the collar seems like a must have if you wanted to use an open roller.. hey thats still confusing

Ive got an idea that when "correct" interference fits are obtained everything can move around when the motor is hot. if anything moves it closes up the float, motor cools and locks everything back in

rev it too hard when its cold with no float and boom

in JBS racings new hardened steel main bearing sleeves the bearings go in from outside the cases not from inside.

Taffy Im guessing that the LHS case needs to be heated to get that ball bearing in there ? I had to near melt this old 550 case to get it out.

hope it goes well rabno
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