Hello folks. No doubt like everybody else I am well and truly fed up with the Covid situation and I am sorting the newly acquired 1955 B31 ready taking to the road as soon as we are allowed. Well, assuming I get a decent amount of miles under my belt on the bikes (B31; AJS 1938 38/26; Honda 1988 XBR500) this coming summer I was wondering how I am going to fill in the winter months? Then I had an idea. I have a complete but well worn 1956/7 B33 engine and a separate, quite rusty flywheel assembly. Both need new big ends.
I have never changed a big end before. I have a well equipped workshop, lathe etc and wonder if I could successfully replace the big ends. I have all the necessary tools but have I the knowledge? I have re-built dozens of bikes but never changed a roller big end. Is it a step too far or will it require a professional person to do this job?
Has any one tried and succeeded? Any information on the way forward would be welcome.
Also am I correct in assuming that the crank assembly is the same for both the B31 and B33, just that the bores are are different?
Ride safe all.
The big end bearing is the same as is the mains but the flywheels are different weights and balance factors. Different part numbers. The outer race of the big end needs pressing out of the con rod and the new one pressing in. I tried to do mine with a vice with no luck. You need a press.I am trying to do what you are as well.
I have done this on my B31, the only part I had to outsource was the honing of the conrod race.
Check out the WM20 website http://wdbsa.nl/
especially the technical section and Dave Plumb's articles such as
http://wdbsa.nl/crankshaft%20rebuild.htm
A press may be needed for the AJS a nd Honda but not the B31.
Have fun!
Pete
Sorry, didn't register with me that idie 's reference to a press was in relation to the conrod race. You may well need one for this! The big end pin does not need a press to fit to the flywheels.