Joins a 750 drive side crank case with 850 timing side?
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pierodn said:
Yes, it can be done, apparently, as we have seen an example on the forum (link) but it requires some machining otherwise the sump scavenge will be blanked off.
internal-sump-blockage-t20468.html#p264935
Hi Les,
thank you.
I mean.
I also have seen:
http://www.andover-norton.co.uk/SI%20Combat.htm
Ciao
Piero
thank you.
I mean.
I also have seen:
http://www.andover-norton.co.uk/SI%20Combat.htm
Ciao
Piero
pierodn said:
Sounds like you have the same issue as me. The timing side crankcase on my '72 developed a crack behind the cylinders. The welder destroyed it trying to repair. I picked up a matching set of '72 cases that I'm using now, but always looking for a timing side '72 case to retain the VIN number on the drive side. My timing side is already modified for oil pick up, so could use an 850 mate.
You could just unmatch your matching cases, and preserve the VIN number....
What do you do about the cylinder base studs, where the 750 has them and the 850 has provision for some through-bolts.
Can you just screw some base studs into the 850 case, and it all matches up to the 750 cylinder ?
What do you do about the cylinder base studs, where the 750 has them and the 850 has provision for some through-bolts.
Can you just screw some base studs into the 850 case, and it all matches up to the 750 cylinder ?
lcrken
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pierodn said:
The MKIII crankshaft main bearing spacing is wider than in pre-MKIII, so you would have to put a spacer in the main bearing bore in the MKIII half to get the right dimensions for an earlier crankshaft. It is possible to fit a pre-MKIII crankshaft to MKIII cases by putting shims in both the main bearing bores. It's been done in race bikes to use the stronger MKIII cases as replacements in a pre-MKIII engine. As pointed out above, the alternator arrangement is quite different, but most race bikes don't use the alternator anyhow. The primary cases are also not compatible, but again, most of the race bikes use belt drives, so that isn't too important either. In your case, if you are only using the MKIII timing side, mated to an earlier 750 drive side, none of that matters. Aside from the dowel pins, there might be other mismatch issues. That's a swap I've never tried. If you did make it fit, the mismatch in case contours would make it look a bit strange. You'd also have to either use some of the MKIII timing gears, or machine one of the earlier gears narrower to match the MKIII dimensions. All in all, it sounds like more work than it's worth.
Ken
Starting this up again. Just won eBay '73 850 cases and want to use the timing side to mate to my 201881 combat engine drive side case. My 750 drive side is already modified to move the oil pick up rearward. My only concern is crank alignment. No way really to line bore for this. Will have to determine a way to check alignment once I get the 850 cases. My timing side developed a nasty crack just below the cylinder joint.
I thought that it was a big no-no to use unmatched cases. The bottom side of each engine case has a factory stamped number. The number should the same on both the timing side and drive side engine cases. Or so I have been told.
I would be less concerned about the engine VIN matching the frame and tranny than I would be about mismatched engine cases.
I would be less concerned about the engine VIN matching the frame and tranny than I would be about mismatched engine cases.
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