Author Topic: Metro 12/2 rebuild  (Read 1564 times)

Tanman

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Re: Metro 12/2 rebuild
« Reply #30 on: September 19, 2021, 05:08:46 AM »
So I am in the rebuild stage and am test fitting the crank shaft and cam shaft, I set the clearance on the main bushings and there is very little play in the crank back and fourth almost imperceptible. But the crank seems difficult to turn, at least more than I would imagine it should be. Iím assuming that should rotate very easily with one hand at this point (no flywheels or rods attached).
Kubota ea300
Metro 12/2

38ac

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Re: Metro 12/2 rebuild
« Reply #31 on: September 19, 2021, 01:09:40 PM »
You should have about .010 end play. It is possible on a twin to have the crankshaft shoved into the center main via wrong number of shims on each outside housing. Another possibility is the shims are not up on the pilot that is machined in the housing thus pinching the crank. Always place the shims on the housing and hold them while guiding it in place. If this all checks out then loosen the  center main retaining bolt and the end housing nuts about one turn. Then knock the crank end ways with a mallet or hardwood block and hammer. Are tighten and check. Yes, the crankshaft should turn easily when correct.
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32 coupe

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Re: Metro 12/2 rebuild
« Reply #32 on: September 19, 2021, 05:30:54 PM »
When I rebuilt my 25/2 .
It has bushings and not roller bearings.

I ended up with several gaskets on each side to set
end play. What I found was that as I tightened the
bearing holder the clearance would change.
I spent a few hours tightening , spinning the crank by
hand, tightening the bolts, spinning the crank....

I think it is because the housing is so large the geometry changes
as the bolts are tightened.

Just what I found....your results may be different.


Edit....
I'm not sure I explained this as well as I should have. I'll try again.

What I experienced was not just end play but I noticed the entire bearing housing
would shift enough while tightening the bolts that the bearing would bind the crank.
I had  enough gaskets on each side that my plan was to remove gaskets and "sneak up"
on the end play. As I got closer to the end play and began to tighten the housing bolts closer
to torque is when I began to notice the pattern on tightened bolts would determine bearing clearance.
And yes the crank is straight.

The fact that the bearing itself is some 3" or better in length must come into play.
 It covers a pretty good area of the crank
unlike the roller bearings that cover what 1" or so ?  So when tightening the housing bolts  the housing
would shift enough that the housing was not parallel with the crank so the bearing would bind.

These engines are a hobby for me and not a job. I hate to think of the hours of time I spent on setting the
crankshaft into that twin. Time wise it was probibly over several weekends of play time. A few hours at a
time.  I have built engines my entire life. Lawn mowers to race cars, boats, aircraft.......I thought I knew
something untill I discovered these monsters. They are a different animal. 

I'm sure I could do one now in a few hours but don't know if I would want to !

I hope I explained this so everyone could understand what I'm trying to say.

Enjoy !




« Last Edit: September 19, 2021, 11:26:43 PM by 32 coupe »
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Tanman

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Re: Metro 12/2 rebuild
« Reply #33 on: September 20, 2021, 04:31:12 AM »
Thank you 32 and 38, I losses the housing bolts and the bolt holding the center breaking, spun it a few times and tightens everything back up (spinning it between tightening each side and center) and now it turns easy. Thanks again!
Kubota ea300
Metro 12/2

Tanman

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Re: Metro 12/2 rebuild
« Reply #34 on: September 28, 2021, 10:19:15 PM »
Well gents Iím on the re-assembly path and have come to the point of attaching the piston rods. The first piston measured .001 with plastigage but when torqued down to 55ftlbs would not turn (I did oil them up). I added one shim to each side of the cap and still too tight, added two total to each side and it spins freely. Can you add 1 to one side and 2 to the other? My shins came in a rebuild pack that came with the engine they are about as thick as a pop can sidewall (I can measure them if that helps us come to a clear answer).

CHEERS!
Kubota ea300
Metro 12/2