CB72/77 Crankshaft bearings

SMBH · Post by **SMBH** » Sun Jul 05, 2015 5:18 am

I would like to share we you my ideas for the replacment of the 2 Honda CB72/77 outer crankshaft main bearing after looking at the silly prices and if you can get them for the bearing.

Here is the way I intend to go the left side Honda bearing size is 30 X 77 X 19 so I purchased a STD 6306 bearing 30 X 72 X 19 off Ebay £4.40 and had a local machine shop turn up a sleeve and put the hole for the knock pin (see below pics)

So now I have just purchased a STD sealed 6206 bearing 30 X 62 X 16 for the right side cost £2.20 incl p/p Ebay a little cheaper than the Honda 30 x 65 x 16 they sell.

Here's pics of the Left side modded bearing -

Not got round to the right side yet waiting for my £2.20 bearing from Ebay.

Sleeves will be locked in with bearing lock.

One last thing I noticed the knock pins on some of the holes were very loose in the crankcase castings there was a lot of side play not a good thing if you want to hold a bearing in place so I have used some bearing lock to hold them tight.

Your thoughts guys good or bad no not the bad im going to use them any way.

mike in idaho · Post by **mike in idaho** » Sun Jul 05, 2015 10:21 am

Any bearing clearance markings on the new part? With the bearing a press-fit on the shaft you might want to go with more clearance than standard. C3 clearance would probably be about right.

G-Man · Post by **G-Man** » Sun Jul 05, 2015 1:30 pm

Mike

That's the route I was going to take. Steel or alloy for the sleeve?

Sorry I didn't get around to it for you yet......

G

SMBH · Post by **SMBH** » Sun Jul 05, 2015 1:35 pm

mike in idaho wrote:Any bearing clearance markings on the new part? With the bearing a press-fit on the shaft you might want to go with more clearance than standard. C3 clearance would probably be about right.

No markings on the bearing other than NSK 6306 On the box it has 6306CM D 5.
My crankshaft is at S.E.P for reconditioning so no way of trying the bearing on the shaft if its tight then that's ok for me if it's loose then bearing lock, this bike in my hands will see little miles and not a lot of speed at my age I have done with speeding.

Thanks for your reply.

SMBH · Post by **SMBH** » Sun Jul 05, 2015 1:59 pm

G-Man wrote:Mike

That's the route I was going to take. Steel or alloy for the sleeve?

Sorry I didn't get around to it for you yet......

G

Alloy, machine shop said it would be best., they made it very tight so I will put the bearing in the fridge and use a hot air gun on the sleeve to fit it and some bearing lock.

No problem Graham I had to have a new first gear bush made infact I had two made and they made a very nice job of them, so I got them to made the bearing sleeve while they were at it.

Also looking at replacing the other side with a 6206 STD bearing and sleeve.

While I have your attention the right side outer bearing the smaller of the crank shaft bearings 30 x 62 x 16 has a hole for lokating the knock pin, the hole in the bearing on my bearing is 6mm offset from centre and the knock pin is stepped down to 5mm so when the bearing is installed there is a lot of play is this so ?
Also the oil hole is covered when the bearing is installed and the inner side of the bearing is sealed not allowing oil into the bearing so all that is left is the very small channel by the bearing, im thinking of removing that inner seal.
Your thoughts on it would be very welcomed.

LOUD MOUSE · Post by **LOUD MOUSE** » Sun Jul 05, 2015 7:25 pm

HERE I GO AND IF I OFFEND YOU, YOU MAY BE THE PERSON THIS IS ADDRESSED TO!
I'm amused by some things I see that are Over Kill to fix or repair a simple part in these engines when plenty parts are out here and $$$ seem to be the Road Block. to some ?????????????????
As I see what comes next I never see any $$$ saved.
To me it seems that in the end more $$$$ and time are spent for simple repairs.
I am impressed at how some are so capable to use tools or have parts made at machine shops that the average sole who wants to JUST GET ONE RUNNING AND RIDE ABLE will never have but salivate (drool) at the process shown on this forum.
Yes I'm impressed on how a SPECIAL FITTING can be made to allow a Bearing that doesn't cost all that much can be changed but WILL BE SPECIAL in ones engine.
I shutter to wonder how much if any $$$ you save with all the things I've observed in the last months.
I can and have rebuilt several REALLY SORRY engines for +- $950.00 US and the sad thing with this the cost to ship is usually near $100.00.
If I wasn't so lazy I'd show all the simple ways to take these engines apart and then how easy they go back together.
Special Tools! Hammer, flat chisel, vise grip pliers, HAMMER DRIVE to loosen/remove Screws jis #3 screwdriver, long point punch, wood to put on the 2 Deadheaded Nuts at the engine center to split the cases, Bass rods to knock the cams out of the head. Sharp Putty Knife to remove gasket maternal.
Probably the tool most will not have is a Torque Wrench but OLD FOLKS have learned how to KNOW WHEN THAT NUT/BOLT is good and tight and will DO THE JOB! I HAVE 3. OTHER MAY NOT!
What allows me to be happy as I rebuild engines is that I understand "IT'S JUST A MACHINE" AND PAYING ATTENTION TO WHETHER A PART IS GOOD OR BAD is #1.I don't do things to fix a non existent problems or Puff Up my Chest with SPECIAL REPAIRS when the very simple HONDA parts are still out here and as many of you know I sell them at reasonable prices.
Most of you who I address this diatribe to have purchased HARD TO GET PART from me.
ENOUGH!!!!!!!!!!!!!!!!!!!!...............lm

SMBH wrote:
G-Man wrote:Mike

That's the route I was going to take. Steel or alloy for the sleeve?

Sorry I didn't get around to it for you yet......

G
Alloy, machine shop said it would be best., they made it very tight so I will put the bearing in the fridge and use a hot air gun on the sleeve to fit it and some bearing lock.

No problem Graham I had to have a new first gear bush made infact I had two made and they made a very nice job of them, so I got them to made the bearing sleeve while they were at it.

Also looking at replacing the other side with a 6206 STD bearing and sleeve.

While I have your attention the right side outer bearing the smaller of the crank shaft bearings 30 x 62 x 16 has a hole for lokating the knock pin, the hole in the bearing on my bearing is 6mm offset from centre and the knock pin is stepped down to 5mm so when the bearing is installed there is a lot of play is this so ?
Also the oil hole is covered when the bearing is installed and the inner side of the bearing is sealed not allowing oil into the bearing so all that is left is the very small channel by the bearing, im thinking of removing that inner seal.
Your thoughts on it would be very welcomed.

Steverino · Post by **Steverino** » Sun Jul 05, 2015 10:00 pm

LM
I have three or four torque wrenches but I prefer to go by feel. Especially with all the aluminum. I've never ruined threads, on my old Hondas anyway. I would really hate to feel threads give way while I'm trying to get up to a certain reading on my wrench. I definitely use my torque wrench and follow sequences on my old car motors though. And Thanks for ID ing my Scrambler Seat.
Steve