Crank grinding and undersize bearings

Posted: Fri May 29, 2020 5:32 pm

Wondering if anyone knows of a source for undersized bearings so a crank with bad main journals could be ground .25mm under. I’m also curious how deep the hardness is. If the journals are ground would the crank need to be re-hardened?

Cheers
Nich

Posted: Fri May 29, 2020 6:28 pm

I would like to know the answer to this myself as far as the hardness goes.

I remember a thread that Sonicrete had looked and looked for bearings but no luck. If you go with the thickest bearing. What do you end up with for clearance? I know Rex with T-Rex racing out of AUS runs his rod bearings at .002” clearance. He said that he has his machinist either grind the crank or he said he bored the rod to get the .002” I will send him an email and see which way he has done it? I’ll also ask what he knows about the hardness.

BTW Nich, I got the latest stack. I will try to get in the shop today and see how it fits. Be patient as I can only stand for a few minutes and then I have to lay back down. My back’s Fucked again.

Peace, Jim

Posted: Fri May 29, 2020 6:49 pm

Normally you weld the bad crank journal and machine it back to spec! Are all of your crank journals fubared?

Posted: Fri May 29, 2020 6:59 pm

I have had a crank hard welded up and regrouped. It’s about $400.00 per journal to have this done. Better to find another crank IMO. I had mine de-stroked otherwise I would have never done it.

Posted: Fri May 29, 2020 9:17 pm

Hi Nich,

perhaps, this can help

Carl Baguhn in Hamburg, Germany.

https://carlbaguhn.de/en/home.html

or this one, Kolbenschmitt -Rheinmetall
https://www.ms-motorservice.com/en/products-applications/products-in-the-engine/product/engine-bearings/#c92976

Regards

Kurt

Posted: Fri May 29, 2020 11:50 pm

JJam wrote:

I would like to know the answer to this myself as far as the hardness goes.

I remember a thread that Sonicrete had looked and looked for bearings but no luck. If you go with the thickest bearing. What do you end up with for clearance? I know Rex with T-Rex racing out of AUS runs his rod bearings at .002” clearance. He said that he has his machinist either grind the crank or he said he bored the rod to get the .002” I will send him an email and see which way he has done it? I’ll also ask what he knows about the hardness.

BTW Nich, I got the latest stack. I will try to get in the shop today and see how it fits. Be patient as I can only stand for a few minutes and then I have to lay back down. My back’s Fucked again.

Peace, Jim

I had thought about getting the thickest stock bearings and seeing if the main journals could be ground .001” to straighten them out. Definitely not easy to do with the crank grinder.

I saw you hurt your back. No worries. Let me know as soon as you can without hurting yourself more.

Take care Jim!

Posted: Fri May 29, 2020 11:54 pm

cbxsix wrote:

Normally you weld the bad crank journal and machine it back to spec! Are all of your crank journals fubared?

Like Jim said while this is possible it’s not very realistic. It would possibly be cheaper to have a run of bearings made than spending $1600-3200 to save a crank. They aren’t making any more of these (apart from Brent’s billet crank) so it would be nice to make marginal cranks useable again.

Cheers
Nich

Posted: Fri May 29, 2020 11:55 pm

k3po wrote:

Hi Nich,

perhaps, this can help

Carl Baguhn in Hamburg, Germany.

https://carlbaguhn.de/en/home.html

or this one, Kolbenschmitt -Rheinmetall
https://www.ms-motorservice.com/en/products-applications/products-in-the-engine/product/engine-bearings/#c92976

Regards

Kurt

Thanks for the links. I’ll check them out.

Twinstar Joined: Oct 27, 2013 Posts: 52 Location: germany

If you grind the crank 0,25mm you would have to nitride it again.

To get back the original hardenes.

Here are some Rod Bearings.

https://www.ebay.de/sch/m.html?_odkw=&_ssn=tongtong-motor&item=293126136978&_osacat=0&_from=R40&_trksid=m570.l1313&_nkw=CB400+CB450S+CB750&_sacat=0

But what quality ?

Regards,
Daniel

CB1100F Joined: Jun 18, 2006 Posts: 2511 Location: UK

One thing to bear in mind is the supplied Honda bearings are not a constant thickness around the radius of the shell
This was disgussed here many years ago

I have measured recently purchased and also found some NOS MA3 and MG5 centercode shells which were obviously manufactured long ago and many show the same varation

If you look at the photos you can see there is 0.025mm difference between the thickest and thinnest area on a new Yellow big end shell (13218 413 015), with a pair together that is going to be a bearing that is 0.05mm out of round (0.002'')

I suspect that when these shells are made they do not aim to make a certain size but grade the shells after manufacture then either use the thinnest or thickest area of the shell to select the colour code

The shells are measured with a 0-25mm micrometer with a 6mm ball attachment fitted

Posted: Sat May 30, 2020 10:46 am

what about King Engine bearings, do they make or can make anything?

Posted: Sat May 30, 2020 1:36 pm

cbx_daniel wrote:

If you grind the crank 0,25mm you would have to nitride it again.

To get back the original hardenes.

Here are some Rod Bearings.

https://www.ebay.de/sch/m.html?_odkw=&_ssn=tongtong-motor&item=293126136978&_osacat=0&_from=R40&_trksid=m570.l1313&_nkw=CB400+CB450S+CB750&_sacat=0

But what quality ?

Regards,
Daniel

I’ve seen the .25mm Chinese bearings on EBay. Not really considering that as an option. I might buy a set to inspect them if I can’t find anything else.

Posted: Sat May 30, 2020 1:39 pm

krgood0 wrote:

One thing to bear in mind is the supplied Honda bearings are not a constant thickness around the radius of the shell
This was disgussed here many years ago

I have measured recently purchased and also found some NOS MA3 and MG5 centercode shells which were obviously manufactured long ago and many show the same varation

If you look at the photos you can see there is 0.025mm difference between the thickest and thinnest area on a new Yellow big end shell (13218 413 015), with a pair together that is going to be a bearing that is 0.05mm out of round (0.002'')

I suspect that when these shells are made they do not aim to make a certain size but grade the shells after manufacture then either use the thinnest or thickest area of the shell to select the colour code

The shells are measured with a 0-25mm micrometer with a 6mm ball attachment fitted

That how most bearings are made. The end use determines the amount and location of the variation in wall thickness.

Posted: Sat May 30, 2020 1:46 pm

Lindy wrote:

what about King Engine bearings, do they make or can make anything?

King, ACL, Mahle/Clevite are all possibilities for custom manufacture. I don’t think they already make bearings for these engines. I did quite a bit of searching for an existing bearing and didn’t find anything. That’s why I started this thread. I thought maybe someone here could confirm whether they exist or not. With the exception of the Chinese eBay bearings it looks like we’re headed towards not.

CB1100F Joined: Jun 18, 2006 Posts: 2511 Location: UK

I remember Sonicrete searched high and low for bearings many years ago and came up with nothing

Obviously Honda had them made as a special order to their spec along with the grooved gearbox bearings with the 2mm wide location grooves

Posted: Sat May 30, 2020 5:27 pm

So the Chinese bearings are .25mm which is .0098” thicker than what Honda sells? Am I understanding that correctly? That’s plenty or room to grind the crank. What am I missing?

Posted: Sat May 30, 2020 6:05 pm

You’re not missing anything. I don’t want to use no name Chinese bearings unless that’s the only option. I would prefer to use reputable race quality bearings.

Posted: Sat May 30, 2020 6:41 pm

^ Can't say I blame you. I looked for years, never found a replacement. Custom sounds interesting, but expensive.

CB1100F Joined: Jun 18, 2006 Posts: 2511 Location: UK

JJam wrote:

So the Chinese bearings are .25mm which is .0098” thicker than what Honda sells? Am I understanding that correctly? That’s plenty or room to grind the crank. What am I missing?

You are missing nothing just depends on what quality the Chinese bearings are, untill someone trys we will never know,I remember from when i used to rebuild car engines in the 1970's there was always oversize bearings available for crank grinding

The only way to test the hardness of the crank would be to have one tested, then grind it and test it again, probably be safer to have 10 or so ground to get a better picture

I guess the time will come when even Honda will not be suppling the CB750/900F shells, as the CB1100F MG5 and CB1100R MA3 were phased out long ago which many now use the 750/900 ones, so owners will be looking for an alternatiive and maybe grindin and using Chinese bearings may be the only option

I guess Honda thought their cranks would be long lasting which most have been so they never had oversize bearings made, and i guess with a few different colours available cost would have been prohibitive

Posted: Sat May 30, 2020 7:15 pm

genesound wrote:

^ Can't say I blame you. I looked for years, never found a replacement. Custom sounds interesting, but expensive.

Right! However the stock bearings are fairly expensive anyway and sometimes custom parts are affordable. Only one way to find out!

Posted: Sat May 30, 2020 7:21 pm

^ True that! Keep us posted!

Posted: Sun May 31, 2020 3:24 am

I will have to dig around to find them but I have an assortment of FJ1200 bearings,
rod and main, left over from building Legend car motors. its possible
that they might be the same sizes as Hondas since there
are other part that interchange Honda/Yamaha. they should be readily available since
Yamaha still produces these motors for Inex/600 racing as I recall.

Posted: Sun May 31, 2020 3:37 pm

Nich,
I just had a look into servicemanuals of Suzuki Bandit 1200 (GSF1200S 1996-2000). The Dimensions of the Crankcase I.D. and Crankshaft journal O.D. are the same spec as the CB's.
When there are undersized bearings for this bike, this could be a try.

Regards
Kurt

Posted: Sun May 31, 2020 4:36 pm

Both of those possibilities are ver interesting!

Posted: Sun May 31, 2020 5:42 pm

my factory FJ shop manual gives no dimensions, just
clearance specs. but a crank measured 36mm main
journals and 38mm rod journals (pins). a 900C crank
I have measured 36mm both crank and main, as well
a CBX crank. I see no reason* the Suzuki bearings wouldn't work.
my guess is that, like pistons, all 4 Japanese brands use
the same bearing mfg.

*shell width ?

Posted: Mon Jun 01, 2020 2:56 pm

I found bearings that would work years ago (can't remember if it was bandit or Hayabusa bearings, something like that. The issue I ran into was was width across the bearing and Tang location. Not a nail in the coffin but more than I wanted to mess with.

Posted: Mon Jun 01, 2020 5:19 pm

Also, I seem to remember our rod and main bearings having the tangs on opposite sides, but I wouldn't swear to it, it's been a while.

Posted: Mon Jun 01, 2020 5:20 pm

nathanhouse wrote:

I found bearings that would work years ago (can't remember if it was bandit or Hayabusa bearings, something like that. The issue I ran into was was width across the bearing and Tang location. Not a nail in the coffin but more than I wanted to mess with.

That sort of what I’m expecting to run into. Might be able to find something that fits the housing bore and the journal but might have other dimensional issues.

Posted: Mon Jun 01, 2020 6:36 pm

genesound wrote:

Also, I seem to remember our rod and main bearings having the tangs on opposite sides, but I wouldn't swear to it, it's been a while.

Pretty sure that's correct but I too would have to go check.