Without knowing how much wear there is on the crank pin would make it impossible to suggest what size roller to use. I would also bet the connecting rod bearing sleeve is worn some and a little bit out of round and will require honing. You need to measure everything first.
It may be easier and cheaper to just get a new big end assembly.
I have had rollers that were too big center-less ground to the proper size for a 1929 AJS for which no new big ends were available and it is not cheap. Also had to have the crank pin ground smaller and the rod honed. At that point you can measure and see what size roller you need. The cost adds up fast! Putting new rollers in a big end which has wear on either the pin or sleeve, won't make it run very long.
Hello Bruce, thanks for the advice. I totally agree with your thoughts.
I was speaking to a lathe friend of mine, who told me that the crankpin is kinda worn out and needs replacement. Alternatively he said he will replace the bearings with a bush which will either be in Gun Metal or Phosphorous Bronze.
Which of the 2 is more preferable? All Royal Enfield motorcycles have this kind of a set up. Any suggestions
The Royal Enfield Big End floating bush is soft "White Metal" as used on normal car big end shells. Personally I'd contact Russell Motors or AMC classics and buy a proper new big end assembly.
The original crankpins were made of two pieces, pressed together. There were later made pins made from one piece that had an inherent problem, which has been addressed to my knowledge.....But worth asking and or getting advice about.
Big ends are very expensive but then I understand that's the way to go.
A friend suggested that he would use an aftermarket heavy duty roller bearing and ensure he would fit this to proper tolerances. I am however a little apprehensive.
Has anyone tried this sort of a modification?