thought i was all ready for chucking the rebuilt engine back in soon, after emptying honda and tyga and a couple of forum member spares bins i'm back with another one
was checking the oil pump tonight for the o rings etc and the crankcases



i was thinking they dont match and i remember when the cases were in bits that the small hole was an oil way on to the crank bearings,

just realised what it is, the engine is a 28sp engine, from the manual it looks like the pump also feeds oil directly onto the clutch end outer crank bearing, does the 21 not get oil directly onto the bearings? the pump must be differant on a 22 and 28 and ive got the std 22 pump, which effectively means that there has been an open hole to the crankcase and no direct oiling, no wonder the bearings were f####d. i'm a bit hacked off now

can someone confirm my logic, might be a good reminder to others that 21 and 28 engines are not totally compatable.

so looking for a 28 oil pump and orings,

cheers
brendan


Last edited by ricey3 on Sun Feb 22, 2009 7:32 pm; edited 1 time in total

from what I recall, the earlier model MC21's didnt' have the oil galley for the right side bearings. Honda introduced this in I think 1993 (could be wrong on the year) and followed this into the MC28 model.

So if your engine case has the oil galley hole, and your pump doesn't have the feeder then your end bearing won't be getting the additional oil.

Now you could be in the situation I was in where I had an early model MC21 (with no hole in the cases) but an MC28 oil pump. Took me a little while to figure out why I was getting oil all over everything. Tried to epoxy the oil pump hole, but ended up simple pulling the system and went with pre-mix.
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Charles Gallant

I understand now!

Thats not the water pump drain hole I thought you were talking about.

You can either block the hole and run a early '21 pump or use a later '21 pump (it has the extra feed) or find a '28 pump.
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If I have to take the carbs off once more...

that's confirmed it then as the chassis number brings it up as an early 21 but it has the 28 engine in. so it either a 28 or late 21 pump required. bloody bike