August 5, 20224 yr Hi I have an otherwise very good M80 slimline but with a mullered crankshaft. Can anyone tell me if the crankshaft from a 175 Sherpa (M221) will be more or less a straight swop. Thanks in anticipation. Sparks2
August 6, 20224 yr 9 hours ago, sparks2 said: Hi I have an otherwise very good M80 slimline but with a mullered crankshaft. Can anyone tell me if the crankshaft from a 175 Sherpa (M221) will be more or less a straight swop. Thanks in anticipation. Sparks2 Not certain, but I think the M221 might have two ball bearings on the drive side while the M80 has one ball bearing so the bearing seat on the M221 crankshaft might be too long for the M80 motor. This may not be a show stopper though. It just might mean that you also need some other M221 parts as well as the crankshaft. The other thing to think about is that the 175 crankshaft will probably have different size balance holes in the crank wheels to suit the (lighter) 175 piston. What is it that is stopping you using the M80 crankshaft? (be a bit more specific than whatever being mullered is)
August 6, 20224 yr I would guess that being "mullered" has the same meaning as being Johnstoned, so messed up - broken - destroyed beyond repair.
August 6, 20224 yr Author Hi Thanks for the replies The M80 has chewed the wooduff, crank and drive sprocket. Failing the M221, I have a couple of poor 325 engines that might need new big end & con rods Failing the 325, as a final resort I have a good M49 engine. Regards Sparks
August 6, 20224 yr 51 minutes ago, sparks2 said: Hi Thanks for the replies The M80 has chewed the wooduff, crank and drive sprocket. Failing the M221, I have a couple of poor 325 engines that might need new big end & con rods Failing the 325, as a final resort I have a good M49 engine. Regards Sparks So it's just the drive end of the crankshaft that is damaged? It's probably more common for the magneto end to be damaged by the bearing seat wearing the crankshaft down. I've got some with damaged magneto ends and good drive ends so you might be lucky and find a model 80 crank with a good drive end somewhere near you. My comment about the balance holes in the crank wheels also applies to 325 crankshafts being different to 250 crankshafts. Another thing is that early 325 crankshafts have the same diameter crank wheels as the model 80 but after about 75/76, the 325 got bigger crank wheels which will not fit in the M80 cases.
August 6, 20224 yr Author Should have said the 325s are probably a M159 and a M199 So they are probably no go. Yes, the magneto end has a smaller woodruff key and is known to fail. But in this case it's the main drive end. I will probably have to strip the M221 down to see. Has anyone come across this problem before and is there a repair scheme? Thanks for your help. Sparks
August 6, 20224 yr 11 minutes ago, sparks2 said: Should have said the 325s are probably a M159 and a M199 So they are probably no go. Yes, the magneto end has a smaller woodruff key and is known to fail. But in this case it's the main drive end. I will probably have to strip the M221 down to see. Has anyone come across this problem before and is there a repair scheme? Thanks for your help. Sparks I didn't mention the key or keyway on the left end. Yes it's common for the key on the right hand end to fail and chew out the keyways and the shaft because it's a dodgy design and people sometimes don't tension the nut properly or they sometimes fit a key that's too long. Depending on the amount of damage, you might be able to get away with machining the keyways wider in the crankshaft and the sprocket and fit a wider key.
August 6, 20224 yr I don't have one loose to measure now but I think the 221 crank is too big to fit an M80 as the 221 is a sleeved down later 250 motor and the cranks from around '75 onwards are a bigger diameter, 250 and 325 In Motion is worth a try as they have a lot of cranks, either full or halves
August 7, 20224 yr Author Thanks Woody, I'll try Dave Renham. Thanks everbody for your replies. Regards Sparks
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