MAR engine strip

[syncro16]

Hi all, first time poster here...

I have just bought a couple of Ossa's to have a go at duffers trials of some sort.  I need to remove the RHS crank case half to get a little bit of welding done (very small and barely necessary, but I am a bit OCD with such things...)

Anyway, I have a question. The manual seems to show that it is entirely possible to remove the RHS crankcase half whilst leaving/not disturbing the crank and gearbox shafts clutch and what have you in the LHS crankcase half, is this the case?

Of course, as this engine is a complete unknown quantity and I have not bought it running I could find out that having split it i need to replace a shed load of stuff.  We shall see.

Thanks all

[woody]

On 20/03/2017 at 6:01 PM, syncro16 said:

Anyway, I have a question. The manual seems to show that it is entirely possible to remove the RHS crankcase half whilst leaving/not disturbing the crank and gearbox shafts clutch and what have you in the LHS crankcase half, is this the case?

I guess you can if you don't remove the clutch but if the engine is unknown then I would be replacing the mains as a minimum which means clutch off and a complete strip in which case, when you split the cases the shafts will stay in the RH case. That is the case that you also reassemble into when putting it back together.

You'll need to buy or improvise a puller to remove the tapered fit sleeve from the crank that holds the clutch cush drive assembly. These can be a very tight fit and difficult to remove.

When you split the cases do it very gently to keep all the shafts in the RH casing as if they fall out they have shims on both ends and you need to make a note of which shim goes where to make reassembly easier. You don't want them all over the bench / floor.They aren't just on the two gear shafts, they can be on the selector drum too and they are also on each end of the kickstart shaft. They are also on the crankshaft.

[syncro16]

Thanks Woody

Predictably, having pulled it apart a little, it definitely needs new crank seals at least, the bottom end was covered in gear oil.  So Id just as well go the whole hog.

One more thing, the piston and bore are largely unmarked but it seems loose in the cylinder - Is that relatively normal? are they generally a bit piston-slappy?

also, the conrod has next to no up and down play but is very sloppy left to right? is that to be expected too?

 

Ta

[woody]

They aren't piston slappy no, if everything is right they run without noise.

Conrod does have side to side movement, they are designed like that, you have to centre the crank with shims when assembling