Topic: CB550 rear wheel locks up

[dirtroad]

Hi everyone,
So I finished my 550 cafe couple weeks ago and she runs great. I completely overhauled the engine with everything that was replaceable within my budget and all the gaskets, oil seals etc etc. So tonight I took her for a spin cruising at around 80km/h when suddenly the rear wheel locks up solid!. Needles to say I pulled a 80m skid mark and the havoc caused by the smoke and traffic piling up nearly cost my life. Eventually had to push her home.
Now for the strange thing. With the bike in neutral everything turns freely and I can push the bike like it should except when I lean the bike over to the right she locks up again. Lean to the left she "releases" again but lean to the right she locks up.  When locked up even pulling the clutch makes no difference.
PLEASE any help will be much appreciated.
Thanks

[crazypj]

Either a broken brake shoe or a broken transmission.
It's easy enough to pull wheel and check brakes and wheel bearings
 If they are OK it's going to be motor out.
Pretty sure that if front sprocket was loose it would destroy cover before locking up wheel

[dirtroad]

Thanks for that, the brakes was first thing I checked. It's definitely inside the transmission where things get stuck. Just can't figure out why it would stick leaning right but not leaning left. Weird.

[bikebitzofvt]

Thats pretty unusual...  Glad you survived the super slide!!!
Perhaps something is messed up in the shift linkage??
Good luck

[dave500]

drop the pan and have a look,the little clip on the kick start mechanism might have popped of?or its trying to select two gears at once?with it on the centre stand and the pan off and spark plugs out, use the kicker by hand and try to run through all the gears watching whats going on.

[few-regrets]

That happened to me at the wrong end of an 1/8 mile dragstrip at about 100 MPH a zillion years ago on a K2 750. The "lean and release" thing sounds just like it. Turned out to be a shift fork that was bent so bad that it was goin for two gears at once. My foot shifter had about 1/2" of sloppy play (in n out sliding) afterwards. Does yours have a buncha play? I used to launch the bike than go for the gears with my left hand since I was already laying on the tank - never used the clutch at all. Which is why it broke and now that I think of it - it makes me wonder how I ever lived to be so damn old. That was dumb.

[scottly]

I had a 750 that went into gear by itself, while on the side-stand, while I was taking a compression test. The bike suddenly moved forward, which folded up the stand, and fell on me, pinning me against the garage wall, with one leg pinned under the bike. I had a hell of a time getting free. When I split the cases, I found 2 snap-rings on one of the transmission shafts were not in their grooves, that allowed a stationary gear to slide sideways and engage it's mate. The most puzzling thing was it appeared that the cases had never been apart before, and the snap-rings and grooves were not worn or traumatized. 

[dirtroad]

Wow that's some scary stuff I'm really lucky not to have come off or be hit from behind by one of our notorious taxi drivers here in South Africa. So looks like I'll take the oil pan off today and do a gear by gear inspection. I'm really gonna have a hard time trusting this bike now which is the sad part. Thing is parts like shifters and transmission stuff is all but impossible to come by down here. I'll post some pics once surgery starts.
Thanks for all the help guys!

[scottly]

By the way, welcome to the forums! You ought to put your location in your profile. I think there are other members from S.A.

[dirtroad]

Oh crap Removed the oil pan and guess what I found lying inside...one of the small shift forks  Yes you guessed it, when I replaced the shift fork shaft I put the small retainer plate in the wrong way around. Shocking but I remembered now how this happened. I did the transmission inspection and replacement and then got busy with other things on the bike. It was only weeks later when I assembled the gear shift mechanism, clutch etc so that little shaft was long forgotten. When I fitted the little retainer plate if fitted "perfectly" albeit 180deg wrond way around.
Well hard lesson learned and going to be expensive as well. Also found bits of gear teeth in the oil pan. Out with engine now, split cases and see the bank manager.
I was indeed lucky, this could have caused me my life had it happened round a fast corner.

[dave500]

bummer man!as you said it could have been worse,try and find a complete old engine or bottom end maybe to use as parts,i have one here but freight would kill it.

[crazypj]

Oh crap Removed the oil pan and guess what I found lying inside...one of the small shift forks  Yes you guessed it, when I replaced the shift fork shaft I put the small retainer plate in the wrong way around. Shocking but I remembered now how this happened. I did the transmission inspection and replacement and then got busy with other things on the bike. It was only weeks later when I assembled the gear shift mechanism, clutch etc so that little shaft was long forgotten. When I fitted the little retainer plate if fitted "perfectly" albeit 180deg wrond way around.
Well hard lesson learned and going to be expensive as well. Also found bits of gear teeth in the oil pan. Out with engine now, split cases and see the bank manager.
I was indeed lucky, this could have caused me my life had it happened round a fast corner.

 I had exactly the same thing happen.
Bearing/shift drum retainer behind clutch has a 'tab' to hold shift fork shaft in.

 I did wonder if that could be your problem but didn't think it could lock/unlock
Had a friend help me with engine build and he put plate on backwards (I was 'damaged'  from flipping MX bike )
 I had been doing 110+ about an hour before transmission locked up when selector fell into gears.(luckily only around 20mph) Never let anyone help me with a transmission since then.
 It was expensive, I spent about $600 in parts, mainshaft was slightly bent.
 Sucked as I had just replaced everything 

[dirtroad]

Hi again,
OK got the transmission out and now the search begins for replacement gears. I can still get the one circled in red below, seems fairly available. However the one in black circle is dicontinued. eBay has some trannys available but the shipping to South Africa will be too much.
Question for the experts. What is the compatability between the CB550 gearbox and say 500, 650, 750 CB models. At least then I can hunt the local market with a bigger scope.

[bryanj]

Sorry, has to be 550 or nothing, Have you tried Dave Silver for the gears? I remember one of them was modified and needed to be replaced as a "pair" so check for part number upgrades as well

[dave500]

hey bryanj i thought the gears were the same only the primary reduction was taller on the 550?the oil pump on the counter shaft is a different thing,are the individual ratios different?

[bryanj]

Some gears are the same but its too complicated to say which are and which arnt. Also when i tried to build a "NOS" box for a 500 a few years ago i found one "Pair" were modified and had to be used together as the tooth profile was changed, cant remember which. Some 650 gears will fit but not all just to make it even more complicated.

To the first poster with the problem, I am in UK and if you find a box on ebay.co.uk i will happily act as a post office and send on to you, i think UK post office still does surface snail mail as against US that only does airmail now

[dave500]

thought that might be the case bryanj

[dirtroad]

Hi folks,
Belated update. After scrounging the local secondhand market I finally found replacement gears for the two that got damaged. Replacing them went smoothly and this time I was anal about getting things correct, or so I thought. Took her for a spin on Saturday, 1st gear fine no problem, shifting into 2nd, no problem, then trying to go to 3rd there's a bit of gear noise and then she goes straight into 4th! WTF??? I'm so dissapointed and rip the engine out AGAIN, split the cases and do inspection. I turn the shaft slowly while shifting by hand (clutch everything is off) and sure enough it seem to go from 2nd to neutral, sticky sticky and then into 4th.
I don't have enough experience to spot the cause of the problem per se but the effects of it is obvious.
Maybe only option is complete transmission instead of mixing and matching?