timing side bush

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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timing side bush

Postby Paul R » Wed May 16, 2018 8:15 pm

Hi all Hope some kind soul can shed some light on this for me . The workshop manual gives specs to ream a new timing side bush but does not seem to give any info as to what is an acceptable running clearance between the bush and the shaft . The reason I ask is that I suspect there is some wear to the shaft itself ( there is about 2 thou difference on 2 of the shafts I have ) . It would make sense to ream the bush to suit the size of the shaft rather than just " go at it" . Any one any thoughts on this ? Kind regards . Paul.

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Re: timing side bush

Postby Ozmadman » Wed May 16, 2018 9:21 pm

I took mine to a local engineer who fitted the bush. He will need the crank and both crankcase halves to line it all up correctly. Cost me £70 because of the time setting it all up and having to make a sleeve to replicate the main bearing on the other side
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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Re: timing side bush

Postby clanger9 » Wed May 16, 2018 9:32 pm

Unlike Paul's, mine was a perfect fit "out of the box" - no reaming needed.
If your undersize shaft is worn, it'll likely be worn oval. Does it measure the same all the way round? If not, I don't think you can really get away with under-reaming the bush to compensate...

PS: running clearance for a bronze bush like this will likely be around 0.0015" - or in Brit engineering terms "more than 1 thou and less than 2..."
1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: timing side bush

Postby Paul R » Thu May 17, 2018 9:29 am

Thanks guys . Will check out shaft for ovality . Can then check running clearance is within the 1 to 2 thou range . I have a lathe so will be able to make up a temporary drive side bush if needed to get it all properly in line before reaming . Regards Paul.

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Re: timing side bush

Postby Ozmadman » Thu May 17, 2018 10:08 am

Paul R wrote:Thanks guys . I have a lathe so will be able to make up a temporary drive side bush if needed to get it all properly in line before reaming . Regards Paul.
Or,,, just fit the one of the bearings in the case?
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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