Vintage Motorcycle Eccentrics

I pulled the engine from the 175 - I will split cases and make sure all is good. It took less than 10 minutes to take it out after what I already had taken off.
But I want to finish assembling the 65cc mini engine first. I don’t want to do another engine with it still sitting there (I already did the AJP engine, bumping the 65). It won’t take long to finish, cases are already together, clutch on.

I have taken the 175 engine apart. The countershaft sprocket was a bugger. I did finally get it off, the woodruff key was sheared. I do not know if when pulling it, or it already had sheared. The shaft is tapered also.

I am sourcing bearings etc. The gearbox oil had water in it- and I didn’t trust the bearings without inspecting. Some where not great, so I will just replace them all.

Initial cleanup and measuring bearings.

I think I have all the parts for the 175 now. Only thing I am having difficulty in sourcing is the small end con rod bearing.
But all the rest of the bearings, gaskets, seals and all cleaned up.


I got a 125 complete engine (most parts the same) that would not turn over from rust- cheap.With some work, I got the cylinder off and everything but the rings looks usable. I have not taken it any further apart- and will not for some time. But I could use the con rod bearing if I cannot source one- it is quite good.

Fun working on these weird old machines isn't it. I have a set of plates for rebuilding KTM cranks. You are welcome to them if you can use them.

a riding buddy just had some question on his crank true (spring broke and jammed inbetween primary and clutch gear).
I don’t think he was going to rebuild though.
I will check…

I started to put the engine back together.
But when cleaning some parts I had not done yet- I found the kickstart shaft had some bad splines. I didn’t notice it before. It worked fine, but seems silly to not replace when it is all apart and a NOS part is $17.

So I have as much as I can do until I get that new shaft and install. Then I can put in the crank bearings, bearings on other case side and pop them together.

For such a small motor the cases are beefy, and beautiful castings too.

It is quite a nice engine. Not a bunch of power, but the size of the main bearings for such a moderate output engine is impressive. Bigger than the ones on my Beta 300 that has a LOT more power.
The 125cc engine is the same, with a longer stroke and bigger bore- not much difference other than that.

The shifter desmodronic drum is actuated differently than others I have seen. You can see the small gear on the end with two marks on it. That matches up to the shift shaft (that the lever goes on and has interesting return springs setup). It has to be ‘timed’ since the shifter gear is only a part of a circle. They have a inspection hole in the case to make sure it is right when the cases are together.
It works well, but the others I’ve worked on have the drum go through the case and the shift lever setup attached on the outer case someplace. Right hand shift with ‘1’ up of course.