Special tools for rebuild and specs

[flyingscott]

Maybe I read it wrong, but I think the OP is looking for bearing clearance, not end float. As I said in my post, the spec for clearance, on roller bearings is zero. End float is a different story.

Chris.........

I am curious, I am not an engineer or anything but how long will the motor run with a 0 clearance.

 

[flyingscott]

Looking for bearing clearances is a waste of time. The only measurements that are important are the crank journal and the ID of the connecting rod.

 

[racerone]

Maybe tomorrow people will understand.-----Roller and needle bearing need clearance !!!----Some of you should ---google ----ball bearing c3 clearance ----Let me know what that tells ya.

 

[scatgo]

Looking for bearing clearances is a waste of time. The only measurements that are important are the crank journal and the ID of the connecting rod.

The crank journal minus the od of the connecting rod minus the diameter of the needle bearings will give you the clearance.Then just hook up a dial indicator and measure the up and down play of the rod with the bottom bolted to the crank. Measure in different locations of the crank. That would be the way to do it.

 

[scatgo]

I am curious, I am not an engineer or anything but how long will the motor run with a 0 clearance.

Not much longer than zero second. Once the metal heats up and expands things will bind and self destroy. This is why they give this infofmation. Very important!

 

[achris]

Not much longer than zero second. Once the metal heats up and expands things will bind and self destroy. This is why they give this infofmation. Very important!

Stop thinking 4 stroke!

Yes, the journals and bearings heat up and expand, but so does the rod, INCREASING its journal size to have a net difference of zero.

Geez Louise! :facepalm:

I have been through the Merc AND OMC training schools, and built DOZENS of these engines! Stop arguing with me, or go and build the thing with clearance in the bearings, see how long it lasts then!

I'm out!

 

[scatgo]

Maybe I read it wrong, but I think the OP is looking for bearing clearance, not end float. As I said in my post, the spec for clearance, on roller bearings is zero. End float is a different story.

Chris.........

http://www.fiberglassics.com/library...service001.pdf If any of you are interested go to the link. It will show the clearance for bearings, piston etc etc. This can be helpful to know. And VERY IMPORTANT if you are doing a rebuild. I just cant find this info for my engine.

 

[scatgo]

Stop thinking 4 stroke!

Yes, the journals and bearings heat up and expand, but so does the rod, INCREASING its journal size to have a net difference of zero.

Geez Louise! :facepalm:

I have been through the Merc AND OMC training schools, and built DOZENS of these engines! Stop arguing with me, or go and build the thing with clearance in the bearings, see how long it lasts then!

I'm out!

Sorry but I am not looking to stir it up. And yes they will both expand but not at the same rate. The rod has more mass than a tiny needle bearing. Of course the needle will expand faster and maybe more that the connecting rod. Therfore there has to be some room for that. And room for the film thickness of the mixed lube.

 

[scatgo]

Maybe tomorrow people will understand.-----Roller and needle bearing need clearance !!!----Some of you should ---google ----ball bearing c3 clearance ----Let me know what that tells ya.

This link tells it all. Ya need clearance!............. http://www.fiberglassics.com/library...service001.pdf

 

[scatgo]

Looking for bearing clearances is a waste of time. The only measurements that are important are the crank journal and the ID of the connecting rod.

That is good info. Thanks. if the rod is good and the journal things should fall into place as long as you have new bearings.

 

[F_R]

For anybody wanting to wade through over 100 pages of engineering-speak, here ya go---https://www.skf.com/binaries/327-129877/0901d19680495562-Super-precision-bearings-catalogue---13383_2-EN.pdf#cid-129877

I've only glanced at the above link. But I can testify that I once assembled a Torrington needle bearing onto a shaft with zero clearance. I soon learned not to do that again. Yes, some clearance is required, but it generally is built into the application, such as the rod bearings we've been arguing about. I still go by the maxim that they should look like brand new and if they do, they are good to go. Just my not-so-humble opinion.

 

[racerone]

F R----I agree roller and needle bearings need clearance.----The old story ----" when the students appear willing to learn , the teachers will show up " -----seems to ring true here.--------Anti friction bearings are usually round but do not need to be.-----Round shapes are the cheapest to manufacture !------Come to think of it a waterski is a bearing with water being the lubricant !

 

[F_R]

On the other side of the argument, there are bearings that are pre-loaded. I suppose the lubricant will only be a molecule thick in such cases. Anyhoo, outboard bearings simply are not that critical. That's why the service manuals don't give the specs.

 

[racerone]

Preloading of bearings often found on precision machine tools is a bit of " black magic ".------It cost time / money to set them up just right.-----It involves just the right bearing.----Just the right oil.-----The right temperature of operating conditions.----The right bearing housings that will stretch with the oil pressure generated by the bearing elements and the oil.-----There is more to fine machinery then saying roller bearings have " zero clearance " as some have suggested.