Originally Posted by fyrstormer (Post 14326011)

I have a Picco engine that I've used for about a year and a half. It's a tiny engine so it sees a lot of near-redline running. I'm going to replace the crankcase so I can install ceramic bearings in it (I suck at removing used bearings from engines, I just can't get them to come out cleanly), and I was wondering if I need to replace the crankshaft to make sure the rotary intake valve will seal properly. The crankshaft is hardened steel whereas the crankcase is aluminum, so obviously the crankcase would wear faster than the crankshaft, but I don't actually know from experience if a used crankshaft can be reused with a new crankcase. Thoughts?

Originally Posted by fyrstormer (Post 14326417)

In lieu of a heat gun I tried the toaster-oven method, which didn't work even at the maximum temperature setting. Eventually I resorted to blowtorching the crankcase in the past to get the bearings out. I They still wouldn't dislodge, even after getting the entire assembly hot enough that it was smoking and the bearing seals were melting. Never had to do that with a Toki engine, the bearings always dropped out easily. I don't know what Picco does when they install their crankcase bearings, but they apparently really don't want them to ever be replaced.

The engine is discontinued, so I have two reasons for not replacing the engine outright: 1) new engines are getting harder to find, and 2) OFNA is currently offloading their spare parts at a huge discount so I ordered a bunch. No crankshafts though. Also, if I bought a new engine I'd still have to deal with the impossible-to-remove crank bearings, which I want to replace partly so I can use ceramic bearings for longer lifetime, and partly so I can use a metal-shielded front bearing because this engine keeps blowing off the rubber seals on the stock bearings. No idea why that's happening, but a metal shield will never come loose.

So anyway: How can I tell if a crankshaft is too worn to be reused with a new crankcase? What are the telltale signs?

Originally Posted by fyrstormer (Post 14326795)

Will do. Should I lightly sand the surface of the crank (say, with 1500-grit emery paper) to smooth any scuffing, or should I just use it as-is?

Oh, I should also mention that this particular engine apparently had a tendency to break crankshafts because they were hollowed-out a bit too much, so a crankshaft that hasn't broken in over a year is worth hanging on to if I can.

Originally Posted by fyrstormer (Post 14327136)

I was wondering if there was a tool specifically for nitro engine bearing extraction. I'll have to look into that, thanks.

The crankshaft is in good condition as far as I can tell. No oxidation except on the counterweight, and even that is just cosmetic. I'm just a stickler for details. I'll leave the crankshaft alone.

Originally Posted by fyrstormer (Post 14327848)

Noted. Thanks.

Does the crankcase need to be heated when installing bearings, or only when removing them? With everything else I've ever needed to press-fit bearings into, I was able to do it with the piece at room temperature.

Originally Posted by fyrstormer (Post 14328263)

Because I own neither a hair dryer nor a heat gun. :shrug: Never needed either one before.

Maybe I can freeze the bearings instead, to get a similar effect.