Topic: Standard bearings on CB750 Transmission / Ebay Undersize crank shells

[AshimotoK0]

Given that I  have the facilities for free to get bearings grooved, which 'off the shelf' bearings can I safely use on my CB750K0 gearbox? Which ones should have the suffix 'HS' and what does that mean?

Anyone see or have used these shells? Is it true about the 'depth of the nitride' hardening described?

http://cgi.ebay.com/ebaymotors/HONDA-CB750-SOHC-CB750-CB900-CB1100-CBX-CRANK-BEARINGS_W0QQcmdZViewItemQQ_trksidZp3286Q2ec0Q2em14QQhashZitem518bcd00d8QQitemZ350237819096QQptZMotorcyclesQ5fPartsQ5fAccessories

[AshimotoK0]

ANYONE got any comments particularly regarding the Ebay shells and nitriding depth. Thx Ash

[MRieck]

It would be cheaper to buy a used crank by the time you pay for the bearings AND crank work.

[AshimotoK0]

Yes I do agree but the only decent low mileage cranks seem to come from your side of the pond and shipping here alone can be $200 on a crank and rods. It has also been stated many times on this site that the only option is to use Honda shells and that undersize shells don't exist. However, by the looks of the EBay sale they now are. The other problem with used cranks is peoples perception of what is good and what is bad, plus you always have to get new main shell bearings anyway as they are either the wrong letter code for your crankcases or they get sold off or thrown away with the crankcases. I have yet to see a crank for sale accompanied by a Plastigauge set of measurements of the clearances, which is what I would do if I were selling one.

[754]

ash, you are getting  mixed up..

 Changing crank means using Crank CODE & Case CODE Combined to select bearings, previous case / clearance has NOTHING to do with the swap.

As I said before mic the journal, as selecting a size based on what the crank was previous to slight wear, may mean the codes will not provide corect clearance (in some instances)

 Codes are a system of grading and IDing actual hole & journal sizes WHEN NEW.. as they are not always identical. Read & reread the bearing section in manual, to better understand.

[AshimotoK0]

Thanks - yes I think I understand - You mean that wear on the journals means that the original shells if replaced with the same codes may not give correct clearance. What I am hoping to do is  get a crank off this guy, who is a toolmaker and has this bike for sale :

 http://cgi.ebay.co.uk/1971-Honda-CB750-K1_W0QQitemZ140340551585QQcmdZViewItemQQptZUK_Motorcycles?hash=item20acf2dfa1&_trksid=p3286.c0.m14

The original crank from the bike had done 20k and he replaced all of the shells last year  (120GBP) and only used the engine for 1500miles and then fitted the 'hot' engine in the Ebay listing . His crankcase bearing codes were all A's and my case codes are all A's too, apart from one which is a B. If he has done everything correctly, does this mean I can just change the shells fitted to the one journal which is different (after mic-ing up of course and using the selection chart) ? Of course I have the Plastigauge already and would check using this. You guys have really cheap decent used cranks over there but it's a nightmare in the UK trying to get a decent one.