Timing side bush.

[Brad]

Hello All.
At around 50mph with a warm engine, I get a distinctive rattle/rumble when I just ease the throttle. I have had the cylinder off recently and am sure that the big and little ends are fine. I get a very good oil return to the tank which seems almost too good, and it made me wonder if oil was "leaking" out of the timing side bush/shaft and reducing the flow to the big end and at the same time draining quickly to the crankcase where it is scavenged in virtually a continuous flow. I have the timing side covers and cams off and find that a lever under the timing pinion with a suitable block of wood shows some vertical movement in the shaft. A 5 thou feeler guage easily slides between the bush/shaft. Bearing in mind there is still oil in the bush, does this sound excessive. I guess with no oil present this play would be considerably more. Any comments and advice would be most welcome.

[alanengineer]

A 5 thou feeler gauge wrapped around a shaft that small is huge. i dont think i have come across one that worn

[Rob Harknett]

Not sure about timing bush play. However, could the rattle be coming from the SR 1 auto advance unit. To stop this slip a bit of cable sleeving over the bob weight stops. Another mystery rattle I have had, has been rocker nuts coming a bit loose.

[Brad]

A 5 thou feeler gauge wrapped around a shaft that small is huge. i dont think i have come across one that worn

Not wrapped around the shaft alanengineer, just slid into the gap at the top of the shaft

[Brad]

Not sure about timing bush play. However, could the rattle be coming from the SR 1 auto advance unit. To stop this slip a bit of cable sleeving over the bob weight stops. Another mystery rattle I have had, has been rocker nuts coming a bit loose.

Thanks Rob, but I am quite confident in the above but I do need to find out what the bush/axle clearance should be.
Regards

[alanengineer]

I would guess at 1/2thou and no more than 1 thou. Otherwise it would give the teeth a hard time chattering with each other

[Brad]

I would guess at 1/2thou and no more than 1 thou. Otherwise it would give the teeth a hard time chattering with each other

Thanks Alan, that was one of my concerns as well.

[Rob Harknett]

http://archives.jampot.dk/book/Workshop ... ndards.pdf
The bike may not be WD, but this book of WD inspection/tolerances may prove interesting. In particular, WD tolerance accepted for the bush in question.

[Brad]

http://archives.jampot.dk/book/Workshop ... ndards.pdf
The bike may not be WD, but this book of WD inspection/tolerances may prove interesting. In particular, WD tolerance accepted for the bush in question.

Thanks for that Rob. Where do you find all this valuable stuff? If I am reading it correctly I see acceptable clearance between axle and bus is given as both .005 and .006. for the given engines. I would have thought that this could well be valid for my 1955 engine and when still wet with oil I can get a 005. feeler between the shaft and bush at the top of the shaft. Although not very precise it certainly demonstrates that play exists and this would be greater with no oil present. I am in the process of a strip down for closer examination of the bottom end.

[Brad]

....."clearance between axle and bus"...... I seem to have dropped an h.