There is an advert in the wanted section for a model 19 con rod measuring 7.5 inches between centres of big end and small end when checking my spares iv found a norton singles crank assy 8 inches between centres does anybody know what bike this belongs to
Probably a Big 4 rod John
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con rod lengths
I'm sure this will have been posted before but here goes:
6.1/2" con rod is for M50 with 88mm stroke
7" con rod is for ES2 and presumably M18 with 100mm stroke
7.1/2" con rod is for 19R and 19S with 113mm stroke
8" con rod is for 16H with 100mm stroke and also for Big 4 with 113mm stroke
(I'm pretty certain that pre-war 633cc Big 4 also used the 8" long rod for 120mm stroke)
The OHV engines always had a slightly bigger crankpin and thinner con rod liner than the SV engines which accommodated additional full complement rollers)
AJS / Matchless con rods are slightly wider and stronger around the big end eye
7.3/8" for both 350 and 500 until early 50's and then changed to 6.7/8"
(I use 7.3/8" rods with INA type big ends in both my 19S road bike engines and also in the old 19R racing outfit back in the 80's)
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Con rod lengths
Thanks for your post on con rod lengths its cleared up something thats been puzzling me about a crank that I have which I thought was off a big four but now I know is off a 16H
Regards G.Roberts
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Probably a Big 4 rod
John