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crank shaft play.. bearings are good.. w/pic >

crank shaft play.. bearings are good.. w/pic

crank shaft play.. bearings are good.. w/pic

Old 11-27-2010, 10:41 PM
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Default crank shaft play.. bearings are good.. w/pic



so here's the deal. ive inspected, ive located a extra crank, ive even bought back up bearings, its not the case, and its not the bearings.

the issue im having is horizontal play with the crank when my flywheel is chucked up. its not the bearing, its not the case.. its the crank. its almost like the crank is too long. i was wondering if the crank could be ground down? can you shim the crankshaft?

i get maybe .020" crank play. its not much, and it doesn't leak, just kinda concerns me.

something to worry about, or no?

Last edited by builtb16a; 11-27-2010 at 10:48 PM. Reason: edit photo
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Old 11-27-2010, 10:46 PM
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Originally Posted by builtb16a View Post


so here's the deal. ive inspected, ive located a extra crank, ive even bought back up bearings, its not the case, and its not the bearings.

the issue im having is horizontal play with the crank when my flywheel is chucked up. its not the bearing, its not the case.. its the crank. its almost like the crank is too long. i was wondering if the crank could be ground down? can you shim the crankshaft?

i get maybe .020" crank play. its not much, and it doesn't leak, just kinda concerns me.

something to worry about, or no?
make sur you are useing the right collet for flywheel, as long as its not hitting backplate i would say not to worry about it, if its a new mill, contact them and see if you can get a replacement.
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Old 11-27-2010, 10:56 PM
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its the right collet. the truck is a 8T2.0 and the motor is a turbo head losi 350.

ive tried bigger collets, but it just makes the flywheel stick out further away from the case as the losi collet.

i can tighten it down, but its just going to wedge the collet, against the bearing, and if the crank is too long, its just going to wiggle back and forth inside the case.

the flywheel is sinched down. its not going to budge. i dont' know if the rear bearing is moving, but i can see the front move without the flywheel mounted.
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Old 11-28-2010, 02:13 AM
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The crank is pulled against the inside (inner race) of the front bearing when you tighten down the flywheel so that part is always snugg. Make sure tho before you tighten the flywheel you pull the crank against the front bearing, install collet and push it against the bearing, then tighten flywheel.
This way it's installed correctly.
If theres still minimal play i wouldnt worry about it: i've seen it before with other engines. It has to do with tollerances of crank/bearings/case. Some engines are perfect, some engines have some resistance (because inner races of bearings are pulled towards eachother slightly) when you tighten the flywheel down and some have minimal play (does result in a really free engine).

I think it's mostly because of bearing tolerances. If you happen to have 2 bearings that allow just a tad bit more of horizontal play you will have the above.
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Old 11-28-2010, 03:54 AM
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Wrong thinking!

The crankshaft is indeed locked on the frnt bearing, if you do have some axial play then it must be 2 things. 1) the crankshaft was not pulled out to its maximum before pusing the collet to the bearing or 2) the front bearing has some play which is normal in cold conditions.

Then there is the issue of space of the shaft at the main bearing, it must be there!
The crankcase does expand more than the crankshaft, if you do remove all the play the crankshaft will be locked up, the space will give room for expansion.
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Old 11-28-2010, 08:34 AM
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Originally Posted by Ambros303 View Post
The crank is pulled against the inside (inner race) of the front bearing when you tighten down the flywheel so that part is always snugg. Make sure tho before you tighten the flywheel you pull the crank against the front bearing, install collet and push it against the bearing, then tighten flywheel.
This way it's installed correctly.
If theres still minimal play i wouldnt worry about it: i've seen it before with other engines. It has to do with tollerances of crank/bearings/case. Some engines are perfect, some engines have some resistance (because inner races of bearings are pulled towards eachother slightly) when you tighten the flywheel down and some have minimal play (does result in a really free engine).

I think it's mostly because of bearing tolerances. If you happen to have 2 bearings that allow just a tad bit more of horizontal play you will have the above.
Ambros303 has stated this perfectly.

The crank can "free float" fore and aft in the rear bearing by design.
The only thing that could allow excess movement would be the front bearing, the bearing outer race moving back and forth in the case, or the crank not being fully drawn to the back of the inner race when the flywheel is tightened. I always expand my collet slightly with a hobby knife or small screw driver and pull my crankshaft forward while sliding the cone firmly against the front bearing. If there is no gap between the collet and the bearing when moving it fore and aft, the play has to be in the bearing or the bearing is moving in the case.

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Old 11-28-2010, 12:03 PM
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cool guys, i don't think im going to put much worry into it anymore. now, vertical play would have my concern, and would put alot of stress on the conrod and piston, but im ok with a little axial play.

my collet is snug, and the crank was pulled all the way through, its just the crank is a tid bit longer than ive come across and its sloppy in the case.

now i don't know at 220-240. it might not be as noticeable, and the front bearing isn't leaking, so i guess just keep an eye on it.
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Old 11-28-2010, 01:59 PM
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Originally Posted by builtb16a View Post
cool guys, i don't think im going to put much worry into it anymore. now, vertical play would have my concern, and would put alot of stress on the conrod and piston, but im ok with a little axial play.

my collet is snug, and the crank was pulled all the way through, its just the crank is a tid bit longer than ive come across and its sloppy in the case.

now i don't know at 220-240. it might not be as noticeable, and the front bearing isn't leaking, so i guess just keep an eye on it.
Its impossible for a crank to be too long and allow axial movement like you describe...if the crank is truly pulled all the way forward it will butt up against either the front or rear bearing locking it from coming forward...and if your collet is snug it will lock it against your front bearing and prevent it from moving back...the only way possible for it to move if its truly pushed all the way forward is if the inner races of your bearing allows movement.... You need to fix this if the crank is not all the way forward, as this kind of movement can allow your conrod to come into contact with the backplate.........There is no way the crank is too long, and even if it was you would still be able to lock it in place... If i were you I would pull the flywheel off and install while you push on the crank from the inside of the engine...if it moves then it means you have movement in the bearings, it can be nothing else.
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Old 11-28-2010, 02:35 PM
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ok, well, the engine has ide say 3 gallons on it. its on its 1st pinch.

the only way the crank isn't installed correctly, is if the rear bearing isnt' all the way in. now, you would think after 3 gallons, it would move by now, but its not. the only movement is the physical crankshaft, and visually the front.

the crank is pulled through, and the collet is tight on the crank. with the flywheel chucked up, its still moving. only thought is the crank main journal is too long. the collet is tight on the front bearing inner race, and the crank is flush on the rear main. only solution to eliminate play is to shim the crank at the rear, or take some material off the crank where the front main race sits on the crank. the flywheel, or the collet isn't going to get any tighter.
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Old 11-28-2010, 03:04 PM
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Originally Posted by builtb16a View Post
ok, well, the engine has ide say 3 gallons on it. its on its 1st pinch.

the only way the crank isn't installed correctly, is if the rear bearing isnt' all the way in. now, you would think after 3 gallons, it would move by now, but its not. the only movement is the physical crankshaft, and visually the front.

the crank is pulled through, and the collet is tight on the crank. with the flywheel chucked up, its still moving. only thought is the crank main journal is too long. the collet is tight on the front bearing inner race, and the crank is flush on the rear main. only solution to eliminate play is to shim the crank at the rear, or take some material off the crank where the front main race sits on the crank. the flywheel, or the collet isn't going to get any tighter.
Please trust me on this, its for your own benefit..
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Old 11-28-2010, 03:34 PM
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These are some pretty experienced engine dudes built, I would listen to them.

Make sure to pull the crank all the way forward when installing the collet. If you want to you can even pull the backplate off of the engine and push the crank forward from inside. If you've got the crank all the way forward and the collet set properly and the flywheel tightened properly, the only play you could possibly have is coming from the front bearing.
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Old 11-28-2010, 03:42 PM
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i appreciate everyones input, and i'll break down the motor again, and inspect my assembly.
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