Plain bearings

Pulled the T150v apart yesterday. The primary chainwheel shock absorber rubbers, with only a few thousand miles, simply disintegrated. They then leaked out of the chainwheel and befouled the primary case. Since on the Trident the engine breathes through the DS ball bearing into the case, the oil carried the residue into the crankcase and thence onward to the oil tank, on to
the filter and to the crank.
The crank shows wear but not horrible wear and is still round. The insert bearings show some marks but nothing untoward.
I probably could have done a few short duration oil and filter changes and beat the reaper. But better to be safe than sorry.
Now cometh the question: currently the bearings in place are from LP Williams marketed as Race Quality. From what I understand this means they are harder than standard. Since it is all apart and I am not too worried about cost, should I replace with standard
inserts? They cost almost three times less but as I say cost isn't the issue. What is best is. Bike is a 850 Nova and used on the street
not the track.
I await advise!

It's always good to know what clearance you've got , " Classic Triumph from aussie recommend. 0005 -.001 max , you might only be able to obtain that by grinding to suit . I have a T160 and one day it will be good to freshen it up , cheers

Onder said:

Now cometh the question: currently the bearings in place are from LP Williams marketed as Race Quality. From what I understand this means they are harder than standard. Since it is all apart and I am not too worried about cost, should I replace with standard
inserts?

Click to expand...

Assuming this follows what is produced for AN, RGM and SRM for Norton and BSA's then the 'Race' quality will be trimetallic and 'Standard' will be bimetallic. Trimetallic have a higher yield strength to cope with the higher loads but have a very thin and soft top layer which wears out quickly, not a problem on an engine with frequent teardowns so you can inspect the bearings. The bimetallic has a lower yield strength but yield strength is like a dam, the dam wall could be low or high but if the water level never breaches the wall there is no issue. Where the bimetallic wins is the top layer is thicker and harder so wear rates are lower.

So for a road bike the Standard bearing makes more sense, couple that with a high oil film strength oil which reduces the risk of crank to bearing contact and you are sorted.

Roger that, thanks.

kommando said:

Assuming this follows what is produced for AN, RGM and SRM for Norton and BSA's then the 'Race' quality will be trimetallic and 'Standard' will be bimetallic. Trimetallic have a higher yield strength to cope with the higher loads but have a very thin and soft top layer which wears out quickly, not a problem on an engine with frequent teardowns so you can inspect the bearings. The bimetallic has a lower yield strength but yield strength is like a dam, the dam wall could be low or high but if the water level never breaches the wall there is no issue. Where the bimetallic wins is the top layer is thicker and harder so wear rates are lower.

So for a road bike the Standard bearing makes more sense, couple that with a high oil film strength oil which reduces the risk of crank to bearing contact and you are sorted.

Click to expand...

Nice, clear explanation.
Thanks....