Topic: CB650 feels like skipping sprocket teeth in 5th gear?

[bryanj]

You CANNOT fit just a half case, the top and bottom are machined as pairs

[Motohead1]

I vote for new motor, your glitter likely had done a lot of damage.

Yea I know.  Im being really optimistic.

[denward17]

Will a 750 motor fit in that frame?   asking for a friend.....

[newday777]

I have seen the pins knocked back down and epoxy used on the top, problem is if its alowed the bearing to float endwise how much damage has been done to the gears, repairing a gearbox gets very expensive very quickly!

Assuming I need lower case halfs

If you are thinking just the half with the hole.... that is a bad assumption. And you know what Assume means?

Both case halves are a matched set, upper and lower case halves. (Not including the cylinder bore.)

[bryanj]

Nope 750 wont, 550 might

[Motohead1]

Started tearing it apart but it actually dosent look to bad.  dogs are rounded slightly on the 5th gear engagement but most all the glitter is aluminum from the gear grinding into the case.   video shows the dogs that where dragging each other in neutral that was giving me that noise.   I will get the top end apart and off this weekend coming and get it split.   if it looks good in there and nothing is wiped I might just do the bottom case halfs and whatever else the trans needs and call it good.   time will tell.

[bryanj]

Probably all caused by that bearing not being located on the peg and allowing side play, it does not takemuch wear for a Honda gear dog set to give problems, in your situation i would still look for a complete lower halh assembled or complete engine keeping your parts for emergency spares

[Motohead1]

Still digging out from this this operation popeye hurricane but found a few minutes to pop the cylinders off today.   Looks like I can see where all that plastic in the pan came from when I did the first oil change.     So I will need all the seals and gaskets.  Is there preference for full engine seal kit?  or what to stay away from I should say.    Im either gonna fix this one or I am tempted to pick up a complete lower half from a 1980 that is just 90 miles away for $300.  Its loaded with all the lower guts still.   That would get me back up and running quicker.  Either way I need a full seal kit.

[bryanj]

Honda never did a seal kit, they all came seperate.
Dave Silver might do kit, he does for the 500 and 550

[fizzlebottom]

Oh man. Here's the bad news. Unless you LUCKY on eBay, CMSNL, or DSS, then you're going to find that the world is running almost empty of SOHC CB650 cam chain tensioners and guides. No one makes anything, and it is a trial to wait for a good condition one to pop up.

But, maybe it isn't the most intensely critical part if you replace the chain. If it never gets loose enough to slap against the sides then you'll get another 20k miles out of it. Or not? I really don't know at this point. The scarcity of parts is getting to me. I bought a new bike earlier this summer cause I'm tired of sitting on the edge of my seat waiting for the shoe to drop on impossible parts.

[Motohead1]

Yall are gonna love this.   So here is what I found followed by my theory of what happened.   

The mainshaft bearing on the clutch side I noticed was about an 1/8 inch gap from the gear.   looking at the assembly the bearing supposed to be pressed up against the gear bottomed out against it.   There is no shims or anything between.  I just had an air gap. 
On the  rh side of the mainshaft bearing where I found the needle bearing dowel popped through the case I squeezed the dowel back through and because of the bearing gap on the LH side of the shaft the loaded shaft would not sit back in there.   I pressed the bearing flush on the shaft and it all sits in there perfect and no more case grinding or dog engagement issues.   Im gonna clean this thing up and JB weld it where it popped through the case.

Now on to my theory.   I have no experience with cb650 motors but I have rebuilt and tore down many other engines.    I dont think this case has ever been split.  I say this as every bolt broke torque properly there were no leaks or aftermarket seals and many other clues that to me say its never been apart. 

So with that said I think this was a factory install screw up.  It would have run fine for a long time till that shaft started migrating to the right cause by every single clutch engagement.  The oil feed hole in the shaft to the clutch might be misaligned enough to cause disengagement issues like starved for oil in the basket after high rpm possibly or some other factor I am not thinking about that would be affected by the whole basket and shaft migrated by an 1/8th of an inch or more.   

Anyway those are my findings. Let me know what you think   Ill post pics later when I get a chance.  I am waiting on seals and looking for a shift lever and Ill slap it back together.

[bryanj]

I very much doubt Honda got it wrong, somebody in the last 40 years has been in there and done it wrong

[Motohead1]

See here before and after bearing pressed home.

[PeWe]

Warranty??

[Motohead1]

haha about as good a chance for warranty as a backwards installed c-clip on the transmission.       

I found all newish shift forks for cheap should be here in a few days then just waiting on crank seals.