Topic: 1972 cb500/four with no gear changing and back wheel gets stuck

[Hondawggie]

Picked up a beater 1972 cb500/4 today.  I've been looking for a '71 500/4 but ran out of patience and the price was right.  One-owner bike, it got neglected but kept as a sentimental item after he passed in 1995 in a (non-motor-vehicle) accident.

I removed the rear brake rod leading from the rear brake pedal to the brake arm mounted on the rear wheel hub.  Sprayed Amazing Blaster on the rear hub brake arm's shaft,  and was able to tap the rear hub brake arm back and forth.

Bike is now up on center stand.  The chain is off the bike.

When I tapped it towards the front of the bike, sure enough the brake is coming on because the rear wheel won't move.

I tap the rear hub brake arm rearward and the back wheel spins freely but only about 1/10th of a full wheel rotation!  It hits a hard mechanical stop in both directions of rotation.  

I move the wheel like the bike's moving forward or backward.  It hits a hard mechanical stop in both directions.  I used a flashlight and found nothing on the outside of the rear wheel that could cause the wheel to spin only 1/10th of  rotation.

Any ideas?  I can't take the rear wheel off tonight, and tomorrow it's raining -- I'm dying to know any sort of speculation on this 'wheel stuck' problem as I might have to wait 3 days before it stops raining here.  


ALSO:  The shift lever moves up and down the full amount of movement and will not catch 1st, or 2nd, and I can't spin the countershaft so it must be stuck in a gear.  No impact damage in that area to indicate something banged into the shif lever; the shift pedal, left footpeg, gas tank left side, motor left side, etc. are fine.   What might cause the shifter to be unable to engage a gear?

I don't think it's much of a serious problem -- the bike only has 11,400 miles or so,  simply was not run since 1995.   I checked the crankcase -- plenty of oil, no smell of gas or any non-oil smell.  It doesn't even smell like very old oil.  Then again I've never been inside a 500/4 gearbox.  But the miles are low and it has not turned over, it is evident from the condition of the rest of the bike.

p.s. these are just the first of many problems this beater has, but it has potential!  All original down to the exhausts which are in fair-to-poor shape.

[DavePhipps]

Can you rotate the wheel when the the clutch lever is pulled, or do you get the same behavior?

[bryanj]

Sounds like its not in neutral to me

[florence]

This happened to mine out on the road.  It turned out that the brake lining had come away from the shoe!

[Jordan]

Since the chain is off, it has to be something inside the rear wheel assembly, brake lining, bearings, axle, tire rubbing or those rubber balance thingy's or any combo thereof. Just my guess, good luck and have fun with it.

[bryanj]

Sorry missed the bit about chain off, in that case brake lining fell off, same linings as 450 and 500 twin plus all 500/550 fours

[Hondawggie]

I've got unexpected dry weather and will try to get the wheel off -- wow, 'brake lining detaching' I guess it sounds about right but I didn't know they did that.


Okay -- why does the shift lever freely move up and down but I cannot get it into neutral?  Is there a way to troubleshoot that by removing engine side plates without having to pull the motor?

The symptom is (see my first original post in this thread) I can move the shift lever up and down through the full range of motion, but the front chain sprocket (countershaft sprocket) will not move as if it is stuck in a gear, and the shifter shaft will not make a the gear change happen.

Or do I have to yank the motor and disassemble the transmission to find the problem?

[Duanob]

You should take the rear wheel off and a part anyway at least to check your brake pads. You will probably find your problem then.

As far as the shift problem. cb500 trannys are notoriously weak. Sounds like you will be digging into it more than you wanted to. Could be a broken shift fork.

On the subject has anybody ever swapped a cb550 trans for the 500? Would be a good upgrade if it fits. I think the cases are the same.

[dave500]

the shift fork mechanism is changed,you have to use the entire bottom end not just internals

[Hondawggie]

FOUND THE 'NO REAR-WHEEL-ROTATION' problem.

Here it is:  photos I took today show the brake linings
1) separated from the metal chassis of the 2 brake shoes
2) and not only did the brake linings separate from their rightful home -- they found a new home, stuck to the inside of the hub directly on the braking surface.

QUESTION:  how do you *safely* remove the brake liners and not damage the hub's braking surface that they're stuck to?





THIS PHOTO shows where the brake linings are *supposed* to be (notice the ridge on the brake show -- there would be no such ridge if the brake lining was still there)


Sure the heck am glad I only spent $75 on this beauty.  After the brake problem, I have to fix the shifting and the motor is stuck too.

Thanks for the feedback on the shift shaft, sounds like a teardown.
Is it possible to do that with the motor in the frame (I suspect not.) ??

[Kong]

Get a nice little clean sharp chisel and put it right on the edge to pry the two parts apart and give it a good rap with your ball-peen.  There's nothing holding them there but corrosion.  You should be able to pop them off without doing any damage.  New shoes are cheap.

[DavePhipps]

Neutral is a bear to find on the 500. I have to have the bike off, roll it forward a bit and then shift into neutral. Some call this a mechanical problem. I'll call it ....bike personality, at least till I get enough money fix it.
As I alway tell people with 500's, check the clutch lifter rod. It goes from the left crankcase through the engine to the clutch lifter plate in the right side crankcase. They are notorious for snapping.

[camelman]

You clutch plates are likely stuck from sitting so long.  Typical situation.  Get your rear wheel fixed and back on.  Then, pull in the clutch lever and push the bike back and forth with all your might.  The clutch will break free.  Once it is free, you'll have much more luck getting into neutral.

Camelman

[Stev-o]

Spray some PB Blaster on the rear hub, and as Kong suggested, get after it with a hammer & chisel. It'll pop off.

Sorry, but that tranny repair won't be as easy as the brake.

[bryanj]

Both shafts have to turn to get a decent geatchange on the 500 so try again when the wheel is sorted and back in with a chain on,still bet it aint in neutral at present tho'

[dave500]

i wouldnt say neutral is a bear to find on the 500,same as any bike if its stationary,itll need to be rocked back and forth if it isnt running,this will rotate and connect the dogs that will naturaly clash otherwise and give a numb gear shift feel,many guys here havent spent time on dirt bikes and are yet to experience the less than perfect world of gear selection on these older bikes,its a "knack to be learned"even on new bikes a little rocking back and forth may be required to square up the dog engagement on a stationary bike.,do it with out using the clutch,too many people think pulling the clutch totally isolates something,i dont even declutch up shifting,i do on downshifts though to soften the blow.