Crankshaft Blues.

bergbro · Jul 23, 2015

Bro's
The mains on my 04 650 broke (snapped the boss off the bearing inner and jammed the counter balancer) motor ceased.
I am looking for some advice from those that know.
Here is what I have measured.
End float when assembled (50hrs ago) 0.45mm. with the factory shims removed. (I know.... it was not enough but as it was better than standard I let it fly).
Axial clearance on con rod is 0.381mm (research appears to indicate it should be 0.5-0.8mm).
Bearing shoulder to bearing shoulder..... at the pin side I measure 62.31mm. opposite the pin I measure 62.44mm.
Outside of the webs on the pin area is 60.00mm and opposite the pin is 59.82mm (obviously there has been a bit of flex going on).

Given that I have insufficient end float (looking for another 0.15mm at least)..
Can I safely reduce the axial clearance on the con rod to 0.231mm to gain the extra or is it better to machine the cases or reduce the boss on the crank?
Or maybe another solution?

Anyone got any input?

bushmechanic · Jul 23, 2015

best way IMHO is to rebalance the crank and remove the counterbalancer then you can have as much axial crank play as you like and use a 20mm wide roller bearing on the drive side

otherwise have to machine the RHS case out to get the clearance back not a very difficult job 30 min max for someone with a mill or you could do it yourself with a wood router and a carefully made jig, the deeper part of the bore that you are going to extend can be about 0.5 mm (check it) smaller diameter than the original (easy to set up) because of the radius on the bearing.

Id use 0.7-0.8mm axial play on the big end (lineaweavers rec), weld the pin and go to at least 0.8mm axial play on the crank/mains, need larger axial play on the big end if enlarging the axial play on crank

if you were super careful about certain bits not hitting other bits you might be able to machine the bearing inners down to a bit narrower but ive not tried it so i dunno how feasible it is.

edit: careful about the shape of the spacer in how it supports the bearing inner lip, it needs a funny radius lip to curl over the outer edge of the inner race.

bergbro · Jul 23, 2015

Bewdy.... thank you Bushie.
I decided against the removal of the balancer as I use the bike on backroads for a few hours at a time .
RHS case is the one to machine then.
Rough calcs suggest 1mm depth out of the case (add .5 to the rod and an extra .5 for the crank) should give me plenty to play with.
I understand what you mention about the radius in the hole..... sweet.

I don't understand the edit comment about the spacer needed to support the inner race unless it pertains to removal of the balancer and the required spacer to replace the balancer.

Cheers Bud.

now to make that jig.......hmmmm.

P.S. how much of the circle do I have welded? (ie a couple of spots or right the way around? %maybe?)

bushmechanic · Jul 23, 2015

sounds good, you may also find it easier to use large diam shims between the bearing outer and the case to adjust the crank axial play since its easier than removing the bearing inners

yes the spacer comment relates to the spacer you make in order to replace the counter balancer

crank welds .. can do 4 tacks it makes it easier to "keep" alignment more info post 35

http://husaberg.org/mechanical/17329-balancing-80mm-650-crank-4.html

bergbro · Jul 23, 2015

Thank you sir for the advice... most goodest.
The machining should not be a problem (incidentally is there a maximum crank axial play?) but the welding I am going to have to outsource as my gas or arc set will not be suitable.
Now to find a welder that can do the job to the required standard.

Cheers mate.
your a legend in the making.

bushmechanic · Jul 24, 2015

no worries Bro

ive used 1mm crank axial play on the 80mm crank, Dr_C was going to try more

for the 82mm crank we don't know what happens at really large floats but 0.8 to 1mm should still be very safe, if you aim for 0,8 then a bit either side of that is still ok

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