I have just stripped a Big 4 crank (God forgive me for my sins) and note that the big end outer eye has a Ransome and Marles bearing number (as does the one in the spare rod).
From this I assume that Norton did not manufacture their own big end assembly for this model but bought it in. The crank was set up with a crowded roller arrangement (no cage) and there is a single row of rollers a little more than twice as long as their diameter.
I have three questions...1 Is this the same big end assembly as that used for a 16H or is it particular to the Big 4?..2 Are the single row of rollers correct for this type?..3 Is this big end assembly available and if so, where from?...Thanks...Ian

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

Ransome and Marles? sounds like a lawn mower

The part numbers for 16H and big4 crankpins appear to be the same.

I have E mailed a possible source Rob

email (option): robmiller11@yahoo.co.uk

I may be able to help with Q1. According to R&M Application Data publication the R&M crankpin bearing reference for both 16H (1945-54) and Big4 (1946-54), and several other contemporary 350-600cc models, was DSP6938 (maker's part number E62-6A).

ChrisJ

Ian just use the Harley right side case rollers fitted up to 1955, they are the exact length and come in oversizes to enable you to clean up the rod or the race

email (option): davmax@ntlworld.com

That may be possible Dave..unfortunately both of the big ends I have are quite worn. As the Norton pin is fairly small I will have to work out how much material needs to be removed from the various bits and what size rollers would then be required..the possibility of 'overcrowding' the rollers has to be avoided.
That repair is one option..buying a replacement may be another and I can get an upgraded one made if necessary...Thanks for that info. Chris...that is the number on the outer race. I may try to see if Russell Motors have anything..Ian

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

The Big 4 should have the same crankpin and bearing as the 16H but there do seem to be several variants of taper on the pins and flywheels.

The original bearings were two rows of 1/4" x 1/4" rollers and the hardening on the most commonly found Hoffman pins is considered sufficient to allow a light grind and the fitment of oversize rollers.

It might be worth having a word with the NOC's Technical advice chap for pushrod singles - Mike Pemberton who trades as 'Pushrod Performance' - He likes modifying but is also a fount of knowledge on the standard specs.

http://www.pushrod-performance.co.uk/

I sold a NOS crankpin just the other day too....typical!!!

email (option): davmax@ntlworld.com

Thanks for that Rik..the crank I stripped today had very little taper(if any..I didn't look at that too closely). Interesting that they originally had two rows of rollers...I suspected that from the wear marks on the pin. It did come from India though so anything is possible!....Ian

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