If you have a lathe you can also turn the parts for removing crank pins, as well as make your own alignment pins for reassembly. I guess you have figured out, unless you do a lot of crankshaft work, it's much cheaper to farm out crank rebuilding.If you have a Big Lathe, you can Center the Crank between centers to check Runout, or make a Stand.
======================================================================If you have a lathe you can also turn the parts for removing crank pins, as well as make your own alignment pins for reassembly. I guess you have figured out, unless you do a lot of crankshaft work, it's much cheaper to farm out crank rebuilding.
I have a lathe and have trued cranks between centers but I can tell you it's easier with the typical "roller bearings on a V-block stand"...much easier.
==============================================================Aren't you friends with Steeve Beetie? Just send it to him.
=============================================================================Taking apart is not hard, its putting back together straight and true. A side note, I worked next to a machine shop with a BIG press. It killed two people. Both times shrapnel form misaligned parts blew through the workers chests like a shotgun blast. One was a car U-joint, one was a bearing. Insurance made them put a big cage around it. Be careful.
Rebuilding the crank on the two cycle engine is not something for a home mechanic to do. You need special equipment the dissemble and re-assemble the crank and not have it our of true.
Take it to your local snowmobile shop.
I do have a milling machine, lathe and a machinist background. But I don't do enough cranks to venture into rebuilding them myself.======================================================================
Yes, if you have your own Mill, and Lathe, you can make some of these Parts. There are some 3D Modeled parts needed on www.Grabcad.com you could just download, and take to a Machine shop and have made, maybe by a friend, neighbor, etc. Lot's of cheap Scrap Metal in junk/salvage yards for pennies on the dollar.
So far, that's only $325 for the Tools. Just rebuilding (1) Crank can cost $250 in labor, and $250 in Parts, on average. So No, (1) Crank probably isn't worth it, but (2) Cranks, Yes. Also, allows you to rebuild others for $$$ for yourself, paying off them tools.
Yes, the Roller Bearing Stand, and V-Block Stands, are easier to True a Crank, than using a Lathe, but I haven't found their Prices yet, or any good Plans to build your own yet!
I have a 12" x 37" Lathe, myself. I probably got 8-10 Cranks to do right now.
Just showing what Basic Tools are needed for doing Rotax's. Some other Types of Engine Cranks may require a 40+ Ton Hyd. Press.
Another Tool Needed is a BFH (Big Fricking Hammer).
=================================================================I do have a milling machine, lathe and a machinist background. But I don't do enough cranks to venture into rebuilding them myself.
Oh, that BFH has to be softer than the crank or you'll end up with an expensive piece of scrap metal. I like lead hammers myself but that's probably because I make my own.
I've got a need for a press now so I think l check out the 20t rig from HF. I've got a couple PWC cranks to practice on so this might be interesting. I'm in the same boat, if I can put a couple of engines together for an ultralight, I'll be thrilled.=================================================================
Sounds like you got Half the Tools needed already, and Machine Tools to make the other's you would need. None of those Truing Stands look that complicated. Me, I just want to do Skidoo/Rotax Singles, and older Twins anyway, maybe do some old Kawasaki's.
I've rebuilt 4-1/2 PWC engines over the past couple years and the all had bad cranks/con rods. Nobody wants to touch those so they are the best deals. On one rebuild, the center bearings ( roller bearings) were seized. The outer race was blue so they got pretty hot. Back in my dirtbike racing days, a crank rebuild was not a regular event but it did happen. The age old enemies of two-stroke engines are dirt and (lack of) lubrication.Must be missing something, ......Are the bearings bad? They are hardened, not to say can not be bad but in 40 years working on many motorcycles I have never had to re-build a crank.
Because of marginal lubrication in the first place, sometimes an engine thinks it ran out of oil even when it didn't.forgot the oil? Of course if you forget/run out of the oil,... the engine is toast.
There are situations where I would install a used crank in an engine. An engine in a flying machine isn't one of them. Sometimes, key components are hard to inspect without breaking the crank down.After you buy the specialty bearings, maybe new crank pins/rods etc, would it make more sense to get one at the junk yard or buy an overhauled crank?