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Duraforce Rebuild

4489 Views 12 Replies 6 Participants Last post by  LawnBoyDoc
As I was telling Sharkey earlier today, I am knee deep in my Duraforce rebuild. Its all apart and cleaned and I am just about to do a very very light hone on the cylinder for the new rings with my Flexhone (4 passes and one or two fast for cross hatching). I have pics I'll post later tonight, but it appears that the motor sat in a very humid environment or it was watered. Seems the bottom crank bearing had a bit of rust on the lower outside of the crank lip and partially on the bearing casing-couldn't see any on the ball bearings. I cleaned and oiled the crank bearings (both top and bottom ball bearing); the top crank bearing is butter smooth, the bottom crank bearing turns easliy-but it just has a "feel" to it. No where near as smooth as the top bearing.

What to do? It appears the Duraforce crank is ONE STOUT piece. BIG ball bearings!!. And although the bottom one seems a little less smooth it has no more free play than the top one. I don't think I could bend or hurt these bearings with a sledge hammer. Has anyone heard of a Duraforce crank bearing failure??

Also appears that the bearings and crank are one unit. Bearings are not...sold separately ($80.00 for the whole unit at mowpart). Anyone have any experience you can put me at ease or tell me to take out the wallet. :crybaby:
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Well i have 2 engines that have a good amount of play in them. I have heard that you can switch the bearings in these and people have done it.
Probably can...wouldn't want to try it or don't know how it would be done easily. I have VERY little play in each. Both top and bottom have about the same too.
I would put it back together and give it no more thought if they are tight enough to please you. DF cranks are tough units, it's the rod bearings and aluminum rod that concerns me. The DF mains are an improvement over the F series IMHO. After honing, check for burrs on the port edges as they can rough up a new set of rings and piston if they have a burr or sharp 90 degree edge. A wide port can have a ring bulge out into it a tad and catch the sharp edge. A small riffler file will do the trick of knocking off the sharp edge. Good luck!
Thanks. I think I was worried for nothing. I was thinking of taking a small file to de-chamfer ever so slightly the port edges prior to honing (I am using a Flexhone with the little balls).
Here are some pics.
Nasty crank...polished that up.

Here's what I found when I opened it up. Lots of moisture there at one time.

See the rusty crud at the bottom of the crank.

The Cylinder head.

Piston and rod were in great marks at all.

Cylinder head takin a diesel/kerosene bath.

These already had their bath...

LIke my little engine stand..!!
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Coming along nicely. Was it easier than you were expecting once you started tearing into the old fellow?
Yes Brad actually it is so much easier than the Honda cars I 've swapped and ripped apart (rebuilt). No worries about belts, hoses, timing gear, VTEC wires blah blah blah.

I did hit a stump on the lower crank bearing as the rust had invaded the ball bearings a bit. Sharkey and I discussed ways to clean up the ball bearings, but end play (side to side) play is negligible on both ends. So i'll clean up the bottom bearing, lube it up fresh and put it together today if I get the time. Tomorrow for sure.

More pics coming.
Nice pics, I don't see any deal breakers there, steel wool with do a good job of removing surface rust. The piston is not that bad either, but I like fresh ones with new rings and seals. You should have a runner there soon. Keep us informed.
Me too...I have new piston, wrist pin and rings.
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