At first, I thought a main bearing seized on me. So I ordered a complete engine rebuild kit, and started disassembling it. I came to find that the clutch lifter rod was toast from (presumably) the pin bearing back behind the casings. I haven’t split the cases yet because now I need more parts.
Interesting wear pattern. I’m wondering if something got loose in there, and that is just where it got trapped? I am really surprised that the rod can spin that much. Was the ball in place in the pressure plate? Is the clutch end of that rod somehow damaged too?
Many moons ago, when I put a clutch in a 60’s car and got a good look at the parts: I decided forevermore to spend as little time as possible with the clutch pedal pressed. Have carried that over to motorcycles, and karting too. I never sit more than a couple of seconds with the clutch cable in tension, preferring neutral in the gearbox as a better alternative.
All – thanks for your input…and Ray, thanks for the encouragement! Once I get the rest of the parts for the engine, I will dive into the cases and figure out what the heck happened.
Alan – the ball was in place in the pressure plate. In fact everything came apart quite nicely. I was concerned when I saw metal shavings come from the oil, but hopefully the metal came from just that rod and no where internally.
Lets say the pin bearing failing was the cause of this. Could have the debris from the bearing gotten trapped somewhere in another bearing or gear inside the casing? After the engine locked up on me, I got it back to neutral from 5th gear. So I’m praying everything inside there is alright.
I got a new crankshaft assembly assuming that the old one was done…but it seems to have a tight side-to-side tolerance (much like the new one). How do I check to see if the rod was stretched? Perhaps I could reuse the old crank? I say “old”…but it was new as of last December. Thoughts?
BTW – the piston and cylinder look great! Still has a nice crosshatch in the cylinder (though I will get it honed anyways and rebuild the top end).
I’ve heard some people drill holes on the piston where the exhaust bridge would be in contact with for added lubrication and cooling. How difficult is that to do? Do I even bother?
you can use the CR125 manual for the model year to check all the various clearances, tolerances and lengths of things. I’d say it is likely that your used crank is just fine and that it may only need a balancing/straightening. That is, if it isn’t your crank that is the problem..
I also wouldn’t bother honing the cylinder if the lining appears fine. Unless you actually smeared aluminum (from a melted piston) up the side or broke off something in there, it should be fine.
this site has info on drilling holes for lubricating the piston. I don’t see any reason why you wouldn’t (unless your race org doesn’t allow it).
BTW – if you’ve never split the cases before. You either need the honda tool to do it or a big f’in hammer (and subsequently damaged crank assembly) and a lot of patience. After the first time, and after honing your crank for future dis-assembly, you’ll have no problem separating the cases.