SOHC.co.uk Forums > CB750
Oil pressure issue / motor rebuild
Seabeowner:
Goods over £135 attract a whole variety of different rates for different goods from different countries. It's a minefield. Best to try to stick under the £135 if you can and then it's just VAT and admin.
Mind you I have had two deliveries from Cruzinimage recently and both slipped through unnoticed. But I've always had to pay when it's come from the US.
AshimotoK0:
You will always pay the duty if you buy from Yamiya as they are squeaky clean on customs declaration that's why I always get my 'man in Japan' Chris to ship them for me. Lets face it a lot of those parts look like they are probably worth 2 quid in value not 200.
MrDavo:
I may have to take you up on that if I bugger any of them up, at least now I know I got the right shells. The day started well with plastiguaging the shells, I used green first but it squeezed to wide, another go with the red I should've used first, I got it to be 1.5 thou clearance imperial, .038 mill, within the manufacturing tolerance.
It ended up being a mixed day. The first knockback was finding the metal ring around the oil seal in the middle was well and truly stuck, ill take it round to the engineer bikers I know before I damage something.
The second knockback is far more serious- I didn't really appreciate that its one thing to undo the conrods in site with the barrels still on, another to get the caps back on without pushing the bolts up the rods, let alone start the nuts on the threads, all the time trying not to damage the expensive new shells. Suddenly I'm not convinced it's possible but I'll keep trying. I've got the two central rods on and tight, but I'm close but no cigar with the outside pair, I'll have another bash tomorrow.
MrDavo:
Well that was a disaster.
I managed to get the rods attached to the crank, lubed all the shells and put the cases together, all fine. Torqued up the main bolts around the crank, as I did when I plastiguaged (bear in mind I couldn't turn the crank then or I'd have ruined the plasticine) and guess what.
It's locked up solid. :( I opened it up again to see if any shells had moved or overlapped but no. I tried again, all moves until you nip up the first bolts, the 2 long center ones under the crank, then all was solid again.
I think I need professional help.
ETA: just a thought before I throw in the towel - I used lashings of redline assembly compound on the crank journals - given that the clearance was only 1.5 thou, could it be that the goop can't escape sideways and is causing a hydraulic lock when tightened up. Wishful thinking maybe but I could try again with most of it wiped off.
AshimotoK0:
Hmm sounds like you are having fun Dave. The crank I sold you definitely turned over OK in the engine it came out of and the main bearing shells all looked great. Have you tried lubricating the bearings and placing the crank in each half individually and rotating slowly to check that nothing is fouling? Also have you checked that you have matching top and bottom halves ( 2 halves should have the same stampings / markings top and bottom). I smell a bit of a rat that your original shells picked up so badly as it's very rare for shells to wear down almost to the copper like your original ones did, even if the wrong shells had been fitted. The 4-cyl 70's Honda crankcases are line bored in production so you can't mix top and bottom halves from other engines, like you can with Honda twins. Could it be that it's had chain damage and somebody has fitted another crankcase half?
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