KZ900: Crankshaft Main Bearings, Replace or Not?

Hey all,

Question, since I have the cases open and all, should I just go ahead and replace the Crankshaft Main Bearings?

Are these a bitch to get out?

Special tools required i.e. gear puller?

What about pressing in, hows this done?

NOTE: these seem to roll fine, just researching and following up on it while waiting for other parts.

As always, thanks for your input...

Old Man Rock

Hey OMR; That's a really good question! I'm in the same boat with my Z1. The crank is pressed together and must be disassembles to R & R the bearings. Then of course, it must be pressed back together. I've looked at Falicon crank service and they list indexing, truing and welding service. What I don't know is if they replace all the bearings during this process. I believe they are roller bearings that use the parent material of the crankshaft as the inner bearing surface instead of a sleeve. So, what do they do if one journal is scored? Junk the crank? I don't know this for sure and I haven't had the courage to call Falicon yet as I'm a long way from needing the crankshaft. (Bike is still in one piece, just buying components now) I do know that the issue must be addressed as I'm not going to trust an orginal crank with all my new engine parts.

Got a 50 ton press in your garage? I'm pretty sure that will be required to disassemble and reassemble the crank.
And that's the easy part

You are also going to need the fixtures and measuring instruments to ensure that the crank is pressed back together correctly, as in absolutely true, not a job for anyone lacking the skills and experience (and tools/equipment).

Check out the KZ forum at dragbike.com for some discussions regarding crank builders. Not cheap :woohoo:

Yup... Been over to Falicon website... $$$$ Ouch!.

Since I'm not going over board with the cylinder and CAM combinations and the bearings seem good, probably leave this one alone.

The crank seems fine where I have no up & down play in the rods. Very slight side movement but from what I've researched this is normal. The up & down movement is the one to worry about. Bearings seem to roll fine.

Thanks guys,

OMR

Unless you are planning on making BIG HP I think you are wasting your money.
If you are starting out with a good crank you should be fine.
Just weld it and go.

FastKaw1... "Just weld it"

Is this something you did yourself or did you have it done by machinist?

If yourself, any tutorials/images on this?

OMR

I welded a couple 25 Yr. ago. Never had a problem with them.
I just bent a rod and welded it. You don't have to weld the hole joint
a 5/8-3/4 in. long weld will do. Up to about 150 HP.
That was a long time ago and thats how it was dun. Thats not how they do it today.
Only because there are much better welders out now, and I don't have one.
The Last one I had dun I sent out. $100 bucks out the door.
If I still had a arc welder I would not hesitate to do it again.
Weld a pin let it cool and weld the next. Takes all day.

I wish I had some pic. of the old days. Make us all LOL today.

I think the three or four most important thing to do for street motor are.
Weld crank
crank + cylinder studs and nuts (APE)
over shift bushing
If you are planning on doing a lot of hole shots a billet 2nd. gear is a good idea.

I hope this helps
ps have you trans magna fluxed before you put it back together... Worth every penny.

I just love beating dead horses. . . Ok, so I'll rephrase the question. If a person wanted to have the main bearings removed and replaced and the rod big end bearings looked at, where should the crank be sent? Does anyone know if a bad/scored bearing is found, does that junk the crank?
I don't think I need all the fancy stuff (indexing, etc) on my stock Z1 running the 1015/10.25CR kit. Might make 90 HP? I figure the 600-700 bucks saved could buy a few OEM rubber grommets and a decal or two (joke). Please let me hear your thoughts/experiences! Ride safe, Steve