SOHC.co.uk Forums > CB500/550

Crank bearings good or bad

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Murf:
Plastigauging is very easy I am sure you can do it yourself and make a good job of it. Buy a set of plastigauge, about £13, for the mains you lay the crank back in the half shells in the crank case. Then lay a strip of plastigauge across each crank journal, not around the journal. Then carefully replace each bearing cap with its half shell bearing. Torque bolts to specified torque in stages evenly across all bolts.  Remove bolts, carefully remove bearing caps, you will see a flattened piece of plastigauge on each journal, match width to those shown on plastigauge instructions. This will equate to the clearance in the bearing, check this with specifications given in workshop manual.  If in spec and bearings are visually ok, no nicks, grooving or scouring then bearings should be ok to reuse.  If not then change.  I forgot to say wipe crank journal before putting plastigauge on it but do put a thin smear of oil on half shell to stop it sticking to plastigauge strip.

If you do resort to using a machine shop to do your engine, ensure you use someone that knows what they are doing, many say they do but many haven’t got a clue.

I am just looking up the bearings for the primary shaft for when I do my engine , sizes are 22x56x16.   25x52x15, needle roller is 25x29x17, I am going to check to see if they are normal or c3 spec. Will get back on that.

Acro1985:
The shop I am thinking of taking it to I have used before many years ago in fairness that was on a mini engine, but they have been going since the 50s and have a good reputation.

I will give the plastigauge a first though.

Let me know how you get on with the bearings

Acro1985:
Sorry another question.

My rocker cover appears to have a piece missing near the holes for the breather. I can only seem to find ones of earlier engines will they fit mine

McCabe-Thiele (Ted):
That damage looks really nasty on the cam cover - have you found any of the debris anywhere yet?

I assume you are going to the machine shop to have the crank measured accurately in thousands of a mm - good move.
You will need to buy Plastigauge of the right range o.025-0.076 mm.
Quite a few videos on U-tube on the process.

Acro1985:
No bits in the engine so I can only assume some one has run it like that 😱

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