Crank Bearings?

[mmaddix]

While riding my bike a few months ago I lost all electrical power and after looking into it the stator was bad. It was bad from the rotor on the end of the crank contracting in. Upon inspecting the crank I found it had play goin up and down which allowed it to contact the stator. Now I am going to have to replace the crank bearings which leads me to the questions:

Do I have to split the case to replace the crank bearings? Stupid question I know but I have to ask.

In your expert opinions do you think there is possibly anything else wrong that caused the rotor to contact the stator?

Thanks in advance for all the help.

[kboehringer]

Rotor Loose?

MMaddix,
First, THANK YOU FOR YOUR SERVICE, BTDT (USN 18+yrs).

It would seem much more likely that somehow the rotor came loose. It's only held to the crank by one bolt and the taper of the crank end to that of the rotor. Did you pull the rotor off and actually feel play in the crank?

IF you can actually FEEL looseness in the crank within the cases there has got to be some major damage in there! The relationship of the rotor & stator is close, but it ain't that close! In order for the crank to move that much I seriously doubt the motor would start without it sounding like the thing was about to come apart at the seams! The oil seals on the ends would also likely be shreaded and it would be peeing oil out both end seals.....

IF in fact there is this enormous play in the crank, then YES you have to split the cases to get to those bearings. You SHOULD NOT purchase bearings until after the crank has been removed and inspected. If the crank is damaged, which would be very likely if there is that much movement, the crank must be inspected by a machine shop to assure it is still straight and then cleaned and polished. That work will dictate the size of the bearings needed. OEM bearing are difficult but not impossible to find, there are a couple guys peddling them on flea-bay right now.

In my opinion, IF there is this enormous play in the crank, TOSS THE MOTOR. These are too easy to find for $200-300 (TOPS!). All the parts needed to perform the repair will far exceed (time, effort, $$$) the cost and ease of a replacement. If you are going to tear down that far, the parts needed to do it right are: Complete gaskets, rings, valve seals, crank & rod bearings, misc. seals, misc. roller bearings, machine shop fees, etc. etc.

As a matter of fact I HAVE a good assembled bottom end (cases, crank, rods) that could easily find a home in Beaufort, SC! You'd need to transfer your gears and etc. plus your top-end (cylinders, head, etc.). IF it turns out you need it, YOU can have it - SEMPER FI! We're not that far away from each other and we can work out some way to get it there. I bought that complete motor last year for $100. It's top end was garbage so the cylinder & up went in the trash, I pulled a beautiful set of gears out of it...

All that said, I still think the rotor somehow came loose on the shaft, contacted the stator and chewed it up. If that is the case, the few parts needed are easily found and easily replaced.

Sincerely,

[ViperRon]

Are you leaking oil like a sieve. Bearings get up and down play usually before side play and leak oil like crazy. No severe oil leak I'd look further before pulling it apart. Also if its that loose you should be able to shake it or slide it by hand or the tap of a soft wood mallet.

[Ranger_xs1100]

crank bearings

I have a complete brand new crank bearing kit here.
When you return home in January,
contact me and let me know what you need.
In the mean time, be safe over there,
wherever you are deployed,
And Thank You for your service!

[mack]

Crank Shaft

The crank actually doesn't sit on the bearing shells. There is an oil gap that is spec'd by the shell colours. The crank is held in place by the crank case seals at either end. You shouldn't have any side to side play because one of the bearing shells is a thrust style which prevents this. Now to answer your question, if the crank has movement other than rotation the culprit is most likely the crank case seals and these can be replaced without opening the cases. Oil leaks are usually the tell tale sign for worn seals but not always if it's the right side of the motor.

[trbig]

Mack, I hate to argue here, but the crank seals are just lips of rubber. No way in any shape or form do they "hold" a 45 lb hunk of steel. They are just a thin rubber lip trying to keep touching against your crank and keeping the slippery stuff inside the motor.

I could go into a long explanation here, but the crank bearing colors/sizes and number stamps on the crank only apply if you are installing a brand new crank that has never been run, or have had one reworked back to factory specs. Yes, the crank is supposed to be riding on a microscopic layer of oil, but the crank bearings and the crank itself are wear items, and gaps will happen over time as these parts wear together. Your crank is sitting on the bearings. Wear in these bearings is what would let your crank move.

A saddle bearing is installed to keep side movement (Parallel to the crank across the motor) down to a minimum, but a motor with many miles at all will have some movement, it just shouldn't be excessive with a clunking back and forth. Same with movement up or down or front to back. None is good, but I've gone a lot of miles with one that has just a bit of movement. You'll need 9 half shell bearings and 1 saddle bearing for a complete set.

That all being said, the rotor and stator are a very close fit. Improper assembly of the rotor to the crank end by just throwing it on there and tightening the nut can lead it to rub the stator. Been there, done that. But if you haven't touched the rotor and the crank is moving enough for it to rub, then yes, your only alternatives are new bearings, or a replacement motor. And yes, the cases need to be split, but that only seems like a big deal because you've maybe never done it? (I have pics on here somewhere of the process of putting one back together... just reverse for splitting.) Normally, you would have a lot of oil leakage, as suggested, before it would allow the rotor to rub, but no, not necessarily. As suggested, make sure it was your crank moving and not a loose rotor.

If you go to replace the crank bearings, since your motor does have wear and since there is such a negligible difference between the different bearing thicknesses, it has been advised to just go with the thickest ones (Blue) if you can find them, and if not, just any matching set. Use a good motor assembly lube to protect things on the first startup afterwards, and put in a couple new crank bearings. Connecting rod bearings are up to you, but I've been into a whole lot of these motors and never seen, nor heard of a bad con-rod bearing. Probably why they are becoming unobtainium. Replacements were really just never needed. For my first few motors, I'd replace them, but the old ones would look the same as the new ones.

Hope this helps a bit.

[trbig]

Correction: Improper assembly of the rotor to the crank end by just throwing it on there and tightening the BOLT can lead it to rub the stator.

[mack]

Yep

I agree, no argument here. All that you've said is true. I probably didn't articulate as well as I could have. The shell colours and stamps on the case is a reference to the spec'd oil clearance at the time of assembly for sure. Also I will confirm that jumping to blue across the board on a rebuild is the way to go. I've done five now and that's sop for me. As for the seals yes again on the primary function however I went through about ten feet of plasti guage on the last motor and found that those seals do have an impact on the clearance in the shells. However I am man enough to admit that I have never broke in the motor then disassembled it again to verify that the new seals hadn't settled slightly.

[trbig]

GEH!!!! More typos, sorry.

Use a good motor assembly lube to protect things on the first startup afterwards, and put in a couple new crank bearings.

That was supposed to read "Put in a couple new crank SEALS." Sorry. Also, probably not a bad idea for a new cam chain as well since you're that far in. You could even buy one that isn't split (No master links to worry about) since you'll be removing the crank anyway.

[mack]

The

last motor I did I used AMSOIL break in oil for five hundred miles. It's very thin and revealed a lot during the break in aspect. I found several leaks where the torque was spec but the mating surfaces where not perfect. Re torqued and haven't had any leaks since. PS. I buy sheets of gasket maker and I know this will start a discussion but I try to stick with what the manf. intended and don't go with tubed gasket makers etc. I like to cut my own from the template provided my this site.

[trbig]

PS. I buy sheets of gasket maker and I know this will start a discussion but I try to stick with what the manf. intended and don't go with tubed gasket makers etc.

Agreed. That just comes down to a personal decision. I used to cut out my own gaskets as well, but have had just as good or better luck PERSONALLY with just the liquid gasket. YMMV.

[mmaddix]

As a matter of fact I HAVE a good assembled bottom end (cases, crank, rods) that could easily find a home in Beaufort, SC! You'd need to transfer your gears and etc. plus your top-end (cylinders, head, etc.). IF it turns out you need it, YOU can have it - SEMPER FI! We're not that far away from each other and we can work out some way to get it there. I bought that complete motor last year for $100. It's top end was garbage so the cylinder & up went in the trash, I pulled a beautiful set of gears out of it...

kboehringer,

First, thank for what you did for this country brother...even if you were Navy haha 😎.

I'll definitely look into the rotor. I did have it off to replace the crank seal but I don't remember how long ago it was because I've done the crank seals on a few different motors. I'll take the rotor off and see if it is the rotor or the crank that has the play in it.

My motor does have some noise but it's coming from the top end. It's not any crazy amount of noise. I need to adjust the valves which I also plan on doing once I get this thing running again.

I have 2 other motors. 1 is the original motor to the bike, it wasn't in the bike when I got it. I don't know what if anything is wrong with it other than the parts I have cannibalize off of it. The second motor has a head with a bent valve, I bent it tapping a sparkplug hole 😔. I know the bottom end is good but it's a 78 engine and I need to look into putting newer heads on it(80, 81 I think) . I read on here somewhere that it will change the compression. I just need to do the research before I actually do it but I digress. I would gladly take the bottom end from you. I will contact you when I get back. I'll give you something for it at least.

[mmaddix]

Are you leaking oil like a sieve. Bearings get up and down play usually before side play and leak oil like crazy. No severe oil leak I'd look further before pulling it apart. Also if its that loose you should be able to shake it or slide it by hand or the tap of a soft wood mallet.

VipeRon,
I've replaced the crank seals but I still had oil leakage so it probably is just play in the crank going up and down but I'm going to check into it some more.

[mmaddix]

I have a complete brand new crank bearing kit here.
When you return home in January,
contact me and let me know what you need.
In the mean time, be safe over there,
wherever you are deployed,
And Thank You for your service!

Thanks man, I'll definitely contact you when I find out what I need. What color bearings do you have available? I appreciate the gratitude for my service, thank you

[mmaddix]

Mack, I hate to argue here, but the crank seals are just lips of rubber. No way in any shape or form do they "hold" a 45 lb hunk of steel. They are just a thin rubber lip trying to keep touching against your crank and keeping the slippery stuff inside the motor.
...
Hope this helps a bit.

Trbig,

I agree about the crank seals.

I have never split the case before but I will do it in this monitor if it is needed. I just want to get another motor in my bike while I'm doing it so I can ride.

Thanks fir all the great info.