Rear crank bearing carrier installation woes.

Are ya having a problem with your rig? We'll try to help. Share your tech tips and experiences here. Dr. Billy Glaser, author of the "Unofficial 750 Ural Service Manual" site myural.com, is moderating this section.
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eastbloc
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Rear crank bearing carrier installation woes.

Post by eastbloc » Tue Mar 10, 2020 7:39 am

I'm having a hard time getting the bearing plate on my '02 750 to seat without pushing the crank forward. I don't remember having this problem working on my 650's.

I see some old threads with gobium mentioning building a "crank locking tool", and videos being referenced that are no longer viewable publicly.

Anyone have any bright ideas?
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Re: Rear crank bearing carrier installation woes.

Post by stagewex » Tue Mar 10, 2020 9:22 am

Why don't you just contact Van/Gobium.
Here's his "Le Moto" site. I'm not sure if he has kept this updated but if you go to the header drop-down menu that says "more" a lot of his videos are still viewable:

https://lemoto.info
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Re: Rear crank bearing carrier installation woes.

Post by rougaroo » Tue Mar 10, 2020 9:25 am

Van did a video on this somewhere in the electrons using an improvised tool, and Lutz makes an elegant tool for this that he shows on his site. There is also a dealer tool for it. It's basically a three-legged bearing puller where the center screws into the front of the crank and the legs screw into the case.

(Found Van's video: [youtube]https://www.youtube.com/watch?v=SG6aqvJk-3s[/youtube]

The 750 crank needs to be pulled in, not pushed. You pull the bearing forward until it is 7mm from the front. Under no circumstances should you force the crank in from the rear using a hammer, despite what Billy G says on myural.com.

With both cranks being multi-part - 3 for the 750, 5 for the 650 - it's really important not to stress the crank. Lutz has documented how difficult it is to true them, and here on SS we've all seen the consequences of bearing failure. Anything that pinches, untrues them, or binds them should be avoided at all costs. Unless, of course, you want to be doing that job again in 10,000mi.

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Re: Rear crank bearing carrier installation woes.

Post by eastbloc » Tue Mar 10, 2020 9:45 am

The crank is already installed. I'm just trying to get the rear bearing plate back on after replacing the bearing. The problem is that putting pressure on the bearing pushes the crank forward and out of position.

It seems that I need some way of either immobilizing the crank to prevent it from moving forward, or a tool that would enable me to press the bearing against the rear end of the crank rather than the motor housing.
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Re: Rear crank bearing carrier installation woes.

Post by Snakeoil » Tue Mar 10, 2020 11:03 am

The points made about pulling the crank into the bearing versus pushing on it should not be ignored. I've never done a 750 crank installation, but have done a 650 and I remember the comments that the 650 is much easier than the 750 for this particular reason. And I've done plenty of other complex bearing/shaft installations where issues like this existed. Following the correct procedure is key to a successful assembly.

Van's vid makes it abundantly clear.

To pull the crank into the bearing, I would think you could take a tube that presses on the inner race and extends beyond the end of the crank. Weld a cap on the end with a hole to allow a bolt to thread into the flywheel bolt hole in the crank. Now with a nut on that bolt, draw the crank into the bearing. I don't know if the carrier is a press fit into the case. If so, you will have to heat the case so the carrier will slip in without preloading that bearing. Granted, once the carrier is home, you should be able to relieve any preload by pulling the crank bearing home on the crank. But that cover may simply slip into place if positioned squarely.

Hope this did not muddy the waters.
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Re: Rear crank bearing carrier installation woes.

Post by eastbloc » Tue Mar 10, 2020 11:32 am

I'm confused. Do I need to remove the crank fully, press the bearing plate onto the rear, and then pull the crank back into the front of the motor with the rear already installed?

Is it not possible on the 750 to replace the rear bearing without removing the crank?

EDIT: Okay, yes, I see now, watching the video in full is illuminating. Thanks for pointing me to it.
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Re: Rear crank bearing carrier installation woes.

Post by eastbloc » Tue Mar 10, 2020 11:48 am

Van sent me this video which shows the rear:

https://www.youtube.com/watch?v=NAnhzat ... 51beHEJLRs
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Re: Rear crank bearing carrier installation woes.

Post by Peter Pan » Tue Mar 10, 2020 12:02 pm

Claus showed me his way to assemble...use heat and cold...work fast.
Pieces nearly drop into place.
Last summer in NC on Medio Tico's rig it took me the conventional way Push pull 0,1mm at a time a full day and a lot of sweat to assemble his crank.
After Claus's instruction in Hamburg it took much less and most of all, no fear anymore when I assembled my own rig after 7 month waiting for my return and time to get hands on it.
(Cool inner parts in fridge. Heat outer part with preheated plug or torch. Use headless guide screws for aligning and good assembly oil(paste).)
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Re: Rear crank bearing carrier installation woes.

Post by rougaroo » Tue Mar 10, 2020 12:20 pm

Heat/cool is one of my favorite tricks for bearings all over the bike. It is amazing how much more easily the parts assemble.

Over the years my wife has gotten used to opening the freezer and seeing parts of final drive cases, bearings, all sorts of stuff. Note for folks who may be doing this: hot doesn't mean "red hot". The part that you heat only needs to be hot enough that it is uncomfortable to hold, not so hot you can't hold it at all.

Van's second video is of Sergei showing how to install the rear bearing and plate the right way. What you're doing is stabilizing the crank so no pinching force is applied to it and then tapping the plate down onto the crank. It's yet another lesson in the old, "It's easy if you know how."

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Last edited by rougaroo on Tue Mar 10, 2020 12:27 pm, edited 1 time in total.
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Re: Rear crank bearing carrier installation woes.

Post by eastbloc » Tue Mar 10, 2020 12:25 pm

I did try heating the bearing but it didn't help much because I did not immobilize the crank.

Based on Van's feedback and the video above, I ordered a 300mm M24x2.0 threaded rod and some nuts from McMaster-Carr. This will be enough to make two tools for immobilizing the crank while installing the bearing plate.
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Re: Rear crank bearing carrier installation woes.

Post by Peter Pan » Tue Mar 10, 2020 12:37 pm

My wife doesn't like the smell of steel parts in her oven.
(Stress relieve of machined parts diminishes the bending potential in the next machining step.)
Says this prussian blue eyed Prussian with Prussian blue on his hands.
(once upon the time, and if this word wide paranoia continues: soon again)
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Re: Rear crank bearing carrier installation woes.

Post by Snakeoil » Tue Mar 10, 2020 7:01 pm

I fully agree about the use of moderate heat. Normally, aluminum should not be taken above the boiling point of water, which makes for an easy test. Lightly spritz the part and if the water pops and flashes to steam instantly, you are at your heat limit. By spritz I mean dip your fingers in water and snap them to spray the water on the part. You'll know immediately.

The vid of Sergei makes things clearer. The carrier is not a press fit, but more of what is called a line fit. It's what you might call a perfect fit but because it is aluminum and very difficult to align 100% by hand, needs to be tapped in place a little at a time.

I suspect that Klaus heats the case and the bearing at the same time while avoiding any heat on the carrier (tricky to do). This will allow the bearing to slip onto the crank and the carrier into the case.

What is not clear is if the bearing is a slip fit onto the crank. I suspect it is because there is a snap ring to retain it on the crank. If it is a slip fit, then simply heating the case should allow the carrier and bearing to drop into the case and onto the crank.

Please post your experience here when you go thru the process.
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Re: Rear crank bearing carrier installation woes.

Post by eastbloc » Tue Mar 10, 2020 7:34 pm

I'll keep you posted. What's clear is that the procedure at myural.com is incorrect:

http://myural.com/installing_the_cranks ... earing.htm

Doing it this way will push the crank forward just as I experienced here. I was lucky that the jugs were removed or I could have tweaked the crank arms as the crank worked its way forward with each blow.

As per the video of Sergei, it is necessary to immobilize the crank before the bearing plate can be driven home.
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Re: Rear crank bearing carrier installation woes.

Post by Desantnik-VDV » Tue Mar 10, 2020 8:35 pm

Here is a video from Eugene Bykovsky, who also uses a tool to pull (650) crank in. No hitting with hammer. Can this help?:
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Re: Rear crank bearing carrier installation woes.

Post by eastbloc » Tue Mar 10, 2020 10:39 pm

Desantnik-VDV wrote:
Tue Mar 10, 2020 8:35 pm
Here is a video from Eugene Bykovsky, who also uses a tool to pull (650) crank in. No hitting with hammer. Can this help?:
Not quite, that's the wrong end. I actually have the factory tool for that part.
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