Loose Crankshaft Bearings, and My Fix

GoldenMotor.com

Pilotgeek

New Member
Apr 6, 2011
403
0
0
Green Bay, WI
I'm pretty sure my engine has had this issue from the start, but only recently did it start getting bad enough to tear it apart. I found out that not only were my crank bearings very bad, but the crankshaft fit too loosely into the bearings. At its worst, the crank would just spin inside the bearings without the bearings themselves rotating at all. Mind you, there wasn't that much clearance, with the brand new bearings maybe only about .001-.002" but it was enough to make it run poorly and make an annoying clicking or chattering noise. It also caused my crank seals to prematurely wear out after only about 200-300 miles.

Because My crankshaft was otherwise perfect and nicely balanced, I didn't want to order a new crankshaft. So my solution was to add poor-man's knurling to the crankshaft. Just take a small punch, and in a checkerboard pattern, make tiny punches all around the bearing surface of the crank. This pushes the surrounding area up slightly, causing it to fit tightly inside the bearings. It worked, and I ended up having to lightly hammer the crankshaft to push it into the bearings, so I know it's tight (but not too tight). Everything rotates very smoothly now.

 

Pilotgeek

New Member
Apr 6, 2011
403
0
0
Green Bay, WI
This worked out very well. I put about 300 miles on since this rebuild and the crankshaft is still tight in the bearings. I never had the crankshaft balanced, I just ended up with a good one.
 

tooljunkie

Member
Apr 4, 2012
663
5
16
Manitoba,Canada
i you ever need to go this route again,you may want to consider Loctite stud and bearing mount in addition to the knurling.
i have used it to mount slip fit bearings many times.
its great you showed how to save an otherwise useless crank.
works well on trailer wheel bearings also.
 

Pilotgeek

New Member
Apr 6, 2011
403
0
0
Green Bay, WI
Yeah, I was going to try some of that Loctite, and I'll be sure to try it if I ever need to do this again. I researched how to fix that type of problem and I heard a few good things about using the loctite made for this. However, I was in a hurry to get it back together, and tried just the knurling. I'm sure the Loctite would have provided a better crank seal and better security / longevity, but just the knurling ended up being "good enough" so far. I know many would have just tossed the crank in the garbage, but that's not my style.
 

skaaltel

New Member
Aug 13, 2012
1
0
0
canada
I have the exact same problem on my snowmobile. I found your post through google and I've actually gone through all the trouble of registering just to say to you sir: you win an internet! I'm going to try this :)
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
22
0
memphis Tn
Outstanding old-school fix! Why, back in my day, we had to ride coal-burning motorbicycles! You youngsters don't know how good you have it! lol...