Topic: '71 CB500/4 engine locked up - part 2

[nomath]

Tonight I pulled the clutch cover and clutch basket to try and determine if my '71 CB500/4 had a locked up tranny or a locked up engine.  Take it easy on me please - I'm a CB-newbie.

Problem: The engine will not turn over via the kicker.  Kicker lever tip drops about an inch or so prior to engaging, then stops solid.  With the bike on the center stand and in gear (any gear), I can't rotate the engine by rotating the back wheel - either direction.  Plugs are removed, tank and carbs were bone dry when I got it.  Tank and carbs now removed.  There is no battery and no starter button, so I can't test if the starter will move the engine.  I was given the bike and have never heard it run.  When I first got it the motor would turn over via the kicker.  It did so a few times, then locked hard.  Nothing was done to the bike between when it worked and now.  Odometer shows 36K miles and I have maintenance records.

Troubleshooting done tonight: Removed clutch cover and basket.  With the tranny in gear when I rotate the rear wheel the center shaft on which the clutch basket mounts rotates.

Q: Can I then conclude that the tranny is not the cause?

Next: the clutch basket has a large gear milled into its inside (back, or twards the center of the bike side) surface.  This large gear engages a smaller gear just forward of the clutch basket.

Q: Is this smaller gear the mechanism by which the outer clutch basket is driven?

Next: this smaller gear is locked.  It has some mechanical play (I can rotate it a degree or so), but it will not rotate.

Q: Does this implies that the problem is with the engine, correct?

Q: What should I look for next?  Pull the head and see if she turns over?
Q: If so, can I pull the head with the motor in the bike?
Q: If so and pulling the head does not unlock the motor, pull the barrel assembly to get a better look at the crank?  If so, can that be done with the engine in the bike?
Q: Am I waaaaaaay off base here?  So far off that the light from "base"  takes a thousand years to get to me?

Any help would be really appreciated.

Thanks in advance,
doug (who's stumbling his way through a non running CB)

[pmpski_1]

I'm sure some of the experts will be along in a bit to answer your questions. In the meantime did you remove the timing cover and try to crank it that way? You should be able to turn the crank there.

[TwoTired]

I'm sure some of the experts will be along in a bit to answer your questions. In the meantime did you remove the timing cover and try to crank it that way? You should be able to turn the crank there.

The bolt head behind the timing cover will turn a free spinning engine.  But, that bolt will shear off the spark advancer if too much pressure is applied.

[TwoTired]

Troubleshooting done tonight: Removed clutch cover and basket.  With the tranny in gear when I rotate the rear wheel the center shaft on which the clutch basket mounts rotates.

Q: Can I then conclude that the tranny is not the cause? 

Maybe, probably.  I think I'd cycle through all the gear positions to gain confidence there is no specific gear issues.

Q: Is this smaller gear the mechanism by which the outer clutch basket is driven?

yes

Next: this smaller gear is locked. It has some mechanical play (I can rotate it a degree or so), but it will not rotate.

Q: Does this implies that the problem is with the engine, correct?

That small gear is on the main shaft.  That shaft is internally connected to the crankshaft with a chain.  The mechanical play you feel is likely the chain slack as there is no tensioner on the CB500.

Q: What should I look for next? Pull the head and see if she turns over?

I'd pull all the tappet covers just to see if any valves have stuck open.  I'd also look into the spark plug holes to see if something looks awry.
But, yes, you will probably have to pull the head.

Q: If so, can I pull the head with the motor in the bike?

Yes.  I'd worry about the two bolts on the cam holding the chain sprocket.  If the crank won't rotate, neither will the sprocket.  If the sprocket won't rotate, you can't get the bolts out.  Break the chain, then.

Q: If so and pulling the head does not unlock the motor, pull the barrel assembly to get a better look at the crank? If so, can that be done with the engine in the bike?

With the head off you can see the piston/cylinders.  If rusty, the pistons lock to the barrels.  I can't imagine getting the cylinder block off without freeing the pistons.  penetrating oil, battery acid, etc.

Are you doing this without any kind of shop manual?  Why not make it challenging and don a blindfold!
Think of the stories you could tell?   

[oldbiker]

You say 'When you first got the bike ,the engine would turn' so I don't think the motor is seized. I tend to think either the primary chain or the cam chain has broken and locked the engine. since you say the clutch basket will turn from the back wheel with the gears engaged, I think this puts the emphasis on the primary chain. Unfortunately this means a complete strip down of the engine but with a bike that has stood for quite a while, this is advisable anyway.

[bryanj]

More likely that something has broken and dropped into the primary chain rather than primary chain itself broken. As the 500 runs a Hy-Vo primary chain breakage unless under exreme load is very rare. You can remove both head and cylinders with the engine still in the frame , which is probably a good idea as you need to hold the engine down to get the clyinders off. Take a small grinder to a cam chain link to remove chain and aither use a 500T rivet link or beter still replace the cam chain. A manual is a MUST as is a new gasket kit, Top end minimum preferably Full.

[Paul]

I wonder would it be of any benifit to remove the sump and try'n get a look up there with a flashlight.
The gears and the kick start mechanisim can be seen.. just in case an old spanner falls out.
Probably won't be able to see anything unless really obvious but it's an easier start than pulling the head before the next step.

[nomath]

Thanks to everyone who replied.

I do have a Clymer manual and used it to ensure I pulled only the fasteners necessary when I removed the side covers.  Unfortunately the pictures aren't as good as my Honda shop manual for my GL1100 and GL1000 - maybe I'm spoiled.  The Clymer doen't help much w/diagnosis, especially for a complete newbie like me. 

I'll order the gasket set - does anyone have preferences?  I've seen sets on eBay for (relative to Goldwing sets - that's the only point of refernce I have - they're cheap), I have a great local independent shop, or I can go to my local Honda dealer (my last choice).  If there is a particular brand of gasket set that is a great value (or one that I should stay away from) I'd appreciate the advice.

Again - thanks to everyone.  I'll get going back on it tonight.

doug

[lakeboi]

Doug,

Just wondering how the rebuild of your '71 CB500 went.  I'm facing the same situation now.  I can crank the engine over one rotation but then it locks.  Were you able to find your problem by pulling the head off?  How difficult was it to put back together?

Any info would be great!
Brian

[csendker]

I do have a Clymer manual and used it to ensure I pulled only the fasteners necessary when I removed the side covers.  Unfortunately the pictures aren't as good as my Honda shop manual for my GL1100

Download the 500 Shop Manual here --> http://www.sohc4.us/forums/index.php?topic=426.msg2552#msg2552

[nomath]

I do have a Clymer manual and used it to ensure I pulled only the fasteners necessary when I removed the side covers.  Unfortunately the pictures aren't as good as my Honda shop manual for my GL1100

Download the 500 Shop Manual here --> http://www.sohc4.us/forums/index.php?topic=426.msg2552#msg2552

To be honest, I haven't done anything on it since this post.  I've been working on the project '75 Goldwing in mys spare time (work has been unusually busy of late).  I did get a second engine for the 500 - a complete junkyard special   

I'll get back to it eventually.

doug

[cb500 maniac]

i've fixed siezed pistons with a hammer before.....seriously! never tried it on a 4-cylinder but i've used a piece of wood and a sledge hammer to free up dirt bike motors. of course, if you have a broken peice of something buggering up your primary chain or your cam chain then this wont help, but may releive some frustration and anger to smack it around anyway....I know i've been close to shooting a few of my project bikes before.

[lakeboi]

I'm about ready to do just that.  My pistons are moving....at least one rotation...and then something is locking it up.  May be that something has fallen on one of the chains?

Thinking about giving it one really big push!

[bryanj]

DONT DO IT you are just gonna have to bite the bullet and stri[p down as far as the base gasket to find out what went wrong DO NOT make the mistake of leaving the cylinders on if you find something wrong with the head----the base gasket will leak later!

[nomath]

I'm about ready to do just that.  My pistons are moving....at least one rotation...and then something is locking it up.  May be that something has fallen on one of the chains?

Thinking about giving it one really big push!

I figured since I'd have to pull the barrels to find whatever is boogering up the works, I might as well do a complete rebuild while I'm in there.  The CB is now sitting in the corner of my shop, waiting in line behind the '75 Goldwing.  When I get too frustrated with the 'wing, I can just hop over to the CB 

doug

[Boomologist]

If the engine will rotate almost one revolution then stop you most likely have a valve that is stuck open and the piston is hitting it. This would be caused by a broken valve, stuck valve, broken valve spring or broken/jumped out of time cam chain. There is also the remote possibility that something got dropped into the cylinder.

[lakeboi]

quick question....I've pulled the head cover and can now see the valve springs.  This is what I've found....All of the valve springs are tight (no play or movement) except for one of the intake valves.  Can I assume that is my "bad" valve.  I'm hoping this is my problem as all of the pistons appear to be moving (not seized up).

Trying to find in the Clymers manual how to remove them.

[merc2dogs]

  Unless I'm reading this wrong, as far as I know there's only one way for a valve spring to get loose, and that's for a valve to drop, afraid you may find some more issues when you pull the head. 

would also fit in with the turns both ways but stops at about the same point.

 If you had it running you may have had valves hanging up, and kissed one of them which could cause pistion damage, if you're lucky it just hung up after shutdown and is sticking out far enough to stop the piston, DON'T force the engine to turn, that may turn a quick pull down and clean up job into a  real repair job.
 
ken

[smashme33]

 Motor oil in it when you got it? Coulda been dry when you were kickin it over at first?

[cb500 maniac]

that's a bummer about your stuck valve, but at least you found your issue....too bad honda never went with the torsion-bar vavlve springs they put in the 450's in all their bikes.....ingenius design, just a piece of high-tensil steel rod that springs the valve back by way of radial torque.....one huge advantage: with coil springs you eventually set up a harmoic at high rpm's and float the valves....with torsion bars you have no harmonic issues, so there's no break up at high revs! anyone know why this never made it into the 500/550 and 750 motors?! i'd be interested to know.

[acid_rein]

My engine was locked up what I did to free it was take out the spark plugs and spray in some pb Blaster let it soak for a day or so. I also used a long extention and gave a couple taps on the cylinders through the spark plug holes to free it. changed the oil and it spins fine now. I got other issues. I think I may need a new ignition coil. another tip once you get the engine loose. When you break into those carbs get you a .009 guitar string wire and clean out your pilot jets no doubt those are clogged. They unscrew from the bottom of the carburetor pretty easy. Good Luck.