Crankshaft drag advise

sandman768
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sandman768
I'm learning how to rebuild bottom ends..very low hr 92 rm 250, had been sitting a long time, crank is original, not rebuilt, very tight. I split cases to replace main bearings & seals & water pump seal. Did everything by the manual, froze bearings, heated cases, bearings dropped right into cases nicely, I gave them a light tap with a socket. Crank dropped in to bearings very nicely, I used crank puller just to make sure crank was in bearings/cases. Very thing went together really nice & easy. Crank spins like butter. Problem: when I tighten down drive gear bolt, the crank spins but not as freely as when bolt is not tight. I have read other post on this topic & I tried using rubber mallet on crank ends, but does not seem to help...thanks for any advise...
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40
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40 2/19/2017 1:24pm
2/19/2017 1:24pm
Does tightening the bolt pull the entire crank toward the right case? Is there the same clearance on each side of the crank to the cases after tightening the bolt?
Also, if you had the transmission and crank assembled in the right case, sometimes tightening the left case bolts will push/slide the crank toward the right due to main bearing drag.
sandman768
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sandman768 2/19/2017 1:37pm
2/19/2017 1:37pm
Crank appears centered in the case halfs, I installed everything into the rt side case first. everything went together very easy, figured I was good to go, appears there is a slight amount the crank could move to the rt side, when I put the drive gear on, it is not flush with the crank end. The crank end is slightly recessed into the drive gear, so when bolt is tightend it appears putting pressure on the crank or bearing.
40
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40 2/19/2017 1:46pm
2/19/2017 1:46pm
There should be a spacer under the primary drive gear which makes contact with the oil seal and the main bearing inner race. Tightening the primary drive gear bolt should not normally pull the crank if the spacer is correctly installed. We have seen the crank pushed to the right by tightening the left side case bolts before, but the primary drive gear bolt is unusual.
Paw Paw 271
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Paw Paw 271 2/19/2017 2:03pm
2/19/2017 2:03pm
Take a rubber mallet or dead blow hammer and strike the crank on the stator side, as it sounds like the sleeve is pulling the crank and thus putting pressure on the left crank bearing. Even with out doing this , the crank should settle during the first few heat cycles of the assembled engine.

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sandman768
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sandman768 2/19/2017 2:11pm
2/19/2017 2:11pm
40 wrote:
There should be a spacer under the primary drive gear which makes contact with the oil seal and the main bearing inner race. Tightening the primary...
There should be a spacer under the primary drive gear which makes contact with the oil seal and the main bearing inner race. Tightening the primary drive gear bolt should not normally pull the crank if the spacer is correctly installed. We have seen the crank pushed to the right by tightening the left side case bolts before, but the primary drive gear bolt is unusual.
You are correct, the spacer is installed correctly, it just slips over the crank end, then the drive gear butts against it, only 1 way to install it. With both the spacer & drive gear installed on the crank end, the crank end is recessed about 1mm into the drive gear, so when the bolt in tightend down it is pulling the crank to the right....I gave it some pretty good whacks with rubber mallet, it got a little better, but still dragging some when bolt is tightend. This is the kind of stuff the u tube videos don"t mention! Thanks for the advise 40.... l
sandman768
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sandman768 2/19/2017 2:25pm
2/19/2017 2:25pm
Paw Paw 271 wrote:
Take a rubber mallet or dead blow hammer and strike the crank on the stator side, as it sounds like the sleeve is pulling the crank...
Take a rubber mallet or dead blow hammer and strike the crank on the stator side, as it sounds like the sleeve is pulling the crank and thus putting pressure on the left crank bearing. Even with out doing this , the crank should settle during the first few heat cycles of the assembled engine.

Paw Paw
That is Exactly what is happening PawPaw...I struck the stator side crank about as hard as I"m comfortable doing, whenever I use a hammer on something I"m usually sorry afterwards! I have read the same advice on previous post about this issue. The crank is not "hard" to spin, but definetly not as easy when drive gear bolt is Tightend. Thanks for chiming in....
40
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40 2/19/2017 2:45pm
2/19/2017 2:45pm Edited Date/Time 2/19/2017 2:48pm
Also, since you used the cool the bearing/heat the case method to install the new main bearings, are you 100% certain that the bearings went all the way into their races- flush to the bottom? If they are sticking up only a few thousandths, this will cause drag when the case halves are tightened together..
sandman768
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sandman768 2/19/2017 2:57pm
2/19/2017 2:57pm
40 wrote:
Also, since you used the cool the bearing/heat the case method to install the new main bearings, are you 100% certain that the bearings went all...
Also, since you used the cool the bearing/heat the case method to install the new main bearings, are you 100% certain that the bearings went all the way into their races- flush to the bottom? If they are sticking up only a few thousandths, this will cause drag when the case halves are tightened together..
The bearings dropped right into pockets nice, but I did give them a few taps with correct side large socket just to make sure they were bottomed out. With case halfs bolts all tightend, the crank spins like butter, it is when the drive gear bolt is tightend that the crank gets slight drag. I even put my crank installer tool back in the right side to try & pull crank to the rt a bit & the crank did not move over, I did not crank on it super tight but pretty good pressure.
xnationalwrench 2/20/2017 4:17pm
2/20/2017 4:17pm
If you use a hammer on the crank put the nut om the end of the crank so the crank threads will not mushroom.
sandman768
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sandman768 2/20/2017 5:50pm
2/20/2017 5:50pm
xnationalwrench wrote:
If you use a hammer on the crank put the nut om the end of the crank so the crank threads will not mushroom.
I used a brass hammer & had a nut on the end of shaft...I"m satisfied with the way the crank spins now. I really appreciate everyone's input!

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