timming side bushing

[Drew Back]

Just got my crank back from shop have to go .20 over on the big end however I was wondering what timming side should measure my crank is at 1.37 the old one is completely shot and very loose..

[duTch]

 Not sure on measurement, but I think the general consensus on the T/S main is don't adhere to sizes- just ensure the journal is round, with an extra undersize bush and line-ream the bush to suit

[muskrat]

G'day Drew.
You will need a more accurate measurement of the crank. 1.37?". The std timing side bush bore is 1.370" so the crank journal would be 1.369" - 1.3685". As duTch said, best to ream an undersize bush to fit the crank. The normal undersize bush is 0.010". It must be line reamed with the cases together and dead true to the drive side bearing, so it will be another trip back to the machinist . I shoot for 1 to 1.5 thou clearance.
Cheers

[Drew Back]

Upon careful re measure and glasses it is 1.369 I spoke to my dealer and will drop the cases off next week..

[muskrat]

That's a good std size then. Lucky bugga.
Cheers.

[orabanda]

When the old bush is removed, measure the bore in the casing for out of round.

My experience is that it is common to be 0.010"- 0.014"out of round. I put this down to the stresses created by a flexing 28 pound crankshaft, spinning at up to 5,000 rpm (or more, in Musky's case).

I get the housing bored oversize, until it cheans up, then make the bush to suit (with interference fit from 0.0015"- 0.002.

The issue with the casing bushing being out of round, is that you will lose some oil flow around the outside of the bush; not good.

If you take the timing cover off, remove oil pump, and blow air into the oil delivery port to the crankshaft, and air blows out of the line between the crankcase housing, and the OD of the timing bush, then your crankcase bore for the timing bush, is out of round. 

Richard