I have a B31 crank which needs some TLC and having read Dave’s treatise I think I can work up the courage to have a go. Just a few additional questions though. How critical is the 10-12 thou side play on the conrod and can I dispense with the crankpin nut lock washers (31-300) and use loctite intead –one is already missing from the assembly I have-?

Cheers
Pete

Hi Pete...The side float figure is reasonably flexible but shouldn't be less than .010". If it works out like that on assembly you can surface grind some off the sides of the conrod big end eye to correct it.
You can dispense with the big end locking plates...Ian

email (option): ian@wright52.plus.com

Thanks Ian, time to get my big hammer out then
Cheers
Pete

Hi Pete..When the flywheels are 'trued up' after big end work BSA specify a maximum run out of .005" on the flywheel faces and .002" on the mainshafts.
The .005" figure is not so important but the .002"(max) mainshaft figure must be achieved unless you like engines that vibrate a lot and are mechanically noisy...
When fitting the crankpin by hand to the flywheels check that you have the correct clearance between the shoulders on the pin and the flywheel faces (before fitting and tightening the nuts)..this is important to ensure correct fit and function when everything is tightened up...Ian

email (option): ian@wright52.plus.com

If you can get the run out to about 0.001" it should be fine, but the closer to absolute zero the better as it will be smoother running. It isn't always possible to get it this close, but try to get it as close as you can.

email (option): davmax@ntlworld.com

Pete C
My B31 crank needed some attention, and while I am confident doing most engine work, I decided to drive up to Dave Plumb's place and let him do it as he has the experience and jigs etc. (Dave's place is closer to me than Ian's)
He was happy to show me how it was done, and also did some honning work that needed to be done to complete the job.
I went there with a knackerd crank and left with good one, the cost was better than reasonable, the engine has now done 1,000 miles, and hardly vibrates at all.

email (option): Gasboy@btinternet.com

Dave,

Would you ever consider filming what you do when rebuilding and balancing a crank? I'd certainly be interested and be willing pay for that video.

cheers, Scott

I'd do it for free, but there is no cranks in for work at the moment, As soon as I get one in, I'll do it. Unless you live anywhere near me. I'm up in Cheshire in the UK

email (option): davmax@ntlworld.com

I'm across the pond Dave otherwise I'd gladly bring a crank over ... and film it myself for others. Many thanks!! Scott