fyrstormer

iTrader: (1)

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?

35Plus21

I believe it's OK to use the old crankshaft. I would think that money-wise is it really the best solution to replace crankcase/crankshaft/bearings? You are propably also replacing the conrod/pin/clips. The total cost starts to get near a new engine???

-X-

35Plus21

... so I think either change the bearings/conrod/pin/clips or buy a new engine. The bearing-chnge is easy if you have the tools and a heat gun.

-X-

fyrstormer

iTrader: (1)

(double post)

fyrstormer

iTrader: (1)

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. 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?

blis

The cranks don't wear much, there's a little scuffing on the shaft from the bearings but that's usually it. The crank pin is where the wear affects the engine, if this has worn then the rod won't be happy no matter what so check the pin.

fyrstormer

iTrader: (1)

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.

blis

Nup, you can't put back what you've removed so leave it unless it's harmful. Mild scotchbrite or polish if you really must, if there's pitting from rust your expectations have to be realistic. Generally give it a good clean with toothbrush and brake cleaner/WD/CRC/Inox to get rid of oxide, you dont want to touch the metal itself.

Clean it, lube it up and get the digital calipers out and do some measuring.

Try and find someone with same crank and compare.

PS: If you are in and out of engines, then go and find the Hudy bearing extractor, pay the bucks and do it. Took me 8 years of knocking blocks on chopping boards with oven gloves. In an instant of buying and using the Hudy tool, the foolishness of old ways really hit home strong. Also, DO NOT install a ceramic bearing without a good bearing tool. Keeping it square on the way in and applying pressure uniformly is what it's about. You can feel the hair dryer and heat working too and the overall experience is a better feel of the tolerances in your engine block. Best investment for someone who's into the nitty gritty

fyrstormer

iTrader: (1)

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.

blis

Note: The Hudy tool itself can do both .12 and .21 and sold with the choice of one size of collar, which means the tool only removes one engine type of bearing. So to remove both you must buy the "other" sized collar separately.

fyrstormer

iTrader: (1)

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.

blis

You can do it cold but why would you, if you have a hair dryer or heat gun handy and apply heat while installing, you'll feel the difference as the bearing tension eases and glides in true. Same applies with removal.

fyrstormer

iTrader: (1)

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.

nitrodude

iTrader: (8)

Toaster oven...

wingracer

iTrader: (24)

I've done bearings on a stove top before. Just set the case on a burner, crank up the heat and give it a few minutes. Usually pop right out.

I also borrowed the pizza oven at the track's next door italian place once but that's a whole different story