TZR50 - splitting the crankcase

[Caussados]

Hi

After nearly a year of my son riding his bike, I return with another problem that I hope someone can suggest something. The engine has wrecked the needle roller bearing on the gudgeon pin and damaged the surface of the con rod bearing, plus of course, leaving debris in the crankcase. I need to remove the crankshaft and have stripped down to the point of splitting the crankcase but the crank is holding tight in the bearing on the clutch side. The workshop manual says simply split the two halves by gently tapping! and shows the split halves such that the clutch side comes away from the crank. It is starting to move as oil has leaked oround the gearbox and I can see a slight gap opening, but it appears that the crankshaft is holding the two halves together. It won't take any general purpose puller. I have tried sharp hits on the crankshaft end with a copper hammer whilst prising the two halves (there is gap in the crankcase halves in front of the crank shaft that allows entry of a lever but obviously I don't want to overdo it).

Sorry its a bit long but I hope some of you experienced bike mechanics can help.

[Airhead]

First and foremost you must check and check again thet you have not left any case screws still fitted, it's and easy thing to miss as sometimes they can be quite hidden.

I have no experience of your bike so I can only say what I know of mine (also 2 stroke single with verically split cases)

my bike has two 8mm thres holes in an axis with the crank, one of these holes holds a bearing retainr in place. Now these holes can be used as an anchor point for some sort of tool that will push on the end of the shaft.

Here is the 'Yamaha' special tool for the task

And here is the OG version

Like I said, I dont know if this will help you, most or the difficulty will be to break the seal between the crankcases. If you do resort to striking the end of the shaft, try to protect the metal with some leather for example and it is always good practice to have the nut screwed on flush with the end of the shaft.

[Caussados]

Thanks for the reply OG. I understand what you say and have chacked that there are no remaining fixing screws. On this engine there is mention of a special tool to remove the crankshaft from the other half, but not the clutch side. The only nut left undone is adjacent to the gearbox input shaft and from the diagrams in the manual I believe it is the selector shaft with no attachment on the other end. I'm reluctant to loosen it incase I release something inside but perhaps I should try it and see if I can get any more movement I will examine carefully for possible threaded holes. I like your special tool, that's my kind of contraption too.

[Paulwhite]

the way iv done mine is to thread about 4 screws (in a cross) by 2 or 3 turns then turn the engine with the screws facing to the floor (depends which side the crank comes out), wedge the engine in the work bench (on top half of the engine casing) and tap the crank shaft poking out the top. it pushes the crank down the bearing that needs to be pulled,(bearing should be at the top) and splits the case, the screws stop it from hitting the floor! but iv only done that on my engine which was a xv 125 v2.

[Caussados]

Thanks guys

Job done with copper hammer in the end. Some crankcase bolts partially re-inserted and with my son holding the engine by the "top" half off the bench, struck the crank downwards and eventually it started to move. Same proczdure with the other half. Slight problem is that the bearings stayed on the shaft, any ideas on how to get them off or do I get new ones anyway as they have been operating in a metal soup?