Pinion Bearing Install

[vmx1963]

I know the usual practice is to install the crank and then push the pinion bearing into the case over the crank shaft with the special tool, but is there any problem with pressing the bearing into the case first and then installing the crank?

Cheers

VMX1963
Western Australia
VMX KTM

[Kip Kern]

I usually "dry fit" the crank, gasket in cases(screws properly torqued) less pinion bearing, to achieve proper end play measurement for the crank.  You can't get a proper end play from the crank with the pinion bearing installed.  Also after the cases are built and you do push the pinion gear on, it initially is placed flush with the case.  You then install the pinion gear assy and when torquing the pinion gear, this properly seats the bearing.  Also, the crank pushes in really hard when the bearing is already in place. Wow, I feel better;)

[vmx1963]

Thanks Kip, I asked because I noticed that the crank is quite stiff to turn once the pinion bearing is installed, though I haven't seated the bearing right down against the spacer yet.  

Another question, the manual says the crank width should be -2.135" measured over the webs - does that refer to the raised shoulder on either side of the crank that the shims sit against?  I just got my crank back from the shop and if I measure the width between those shoulders it's 2.173". I think it needs to be pressed another 1mm.

VMX1963
Western Australia
VMX KTM

[Big Mac]

Not sure the right answer on where to measure the width of the webs, but I asked the rod rebuilder to measure the Before width and make very sure that the After width was the same-- and it worked fine. The end play check after "dry" installation with no pinion gear bearing is the best test to be sure it's not too tight or loose.

There aren't too many of the pinion bearing install tools around. Someone mentioned drawing it in by torqeuing down the pinion nut bit by bit, which should work well. If you install the pinion bearing and try to push the crank through it, you risk collapsing the webs out of alignment. The guy who rebuilt my crank shimmed between the webs to reinforce all and pressed the crank in thru the installed pinion gear with a press--worked fine. Mac

[john durrill]

VMX,
 I this crank a 175 or 250 ?
The 175 uses a very thin thrust washer on each side of the rod. Did you put a new rod kit in? If you did check the thickness of the old kit thrust washers and eyeball the new ones. If the new ones are are  thicker then thats the problem. The rod should have between .011 and .018 of a inch side clearance ( we try for 14 to 15) between the crank web and thrust washer measured with a feeler gauge.
 Hope this helped,
John D.

[vmx1963]

Thanks John & Big Mac.  John, it's a 175 with new rod so I'll check the clearance between the web and thrust washers on the big end.  

I'm still confused about where to measure the width of the crank to get the same spec as the manual - is it meaured flush from outside web to outside web, or do you measure between the shoulders that the crank shims sit against?  Wish I could draw a picture here [B)]

VMX1963
Western Australia
VMX KTM

[john durrill]

VMX,
Each crank is different, at least the ones we have rebuilt.
 As long as it will fit in the cases with the gasket and case screws tight, it should be ok. Thats why we have to shim the inner races to have the right crank end play. I think its .004 to .006 of an inch.                              side to side on that crank. but will look and send you the right #'s
 If the rod kit was not NOS then that could very well be the problem.
 The thrust washers are special on that kit. If they are too thick then crank web to case clearance is not right. The webs will be too close to the cases and stand a chance of hitting under running conditions or the cases will not mate right.
 Its been 2 years since we did my sons 175. We had a time finding a rod kit. Euro Rods sold one but the thrust washers were too thick. They were trying to find a source for the thin ones at that time. The kit is the same as the Sachs 125 B engine except for the washers.  
 Let us know how it turns out and what you find.
John D.