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Discussion Starter · #1 ·
Hey all,



Have a summer project to do for a friend. I've worked on my 1981 GS850 alot before so I know some mechanical things. I'm no wizard though. After picking up this 78 cx500 that was sitting for a while (not sure how long) we did some basic restoration. In order to see if the engine was siezed or "locked" before we attempted to started it, we tried using that 17mm nut to crank it. The wrench did turn about probably about 1/2 of the diameter. Then it went into the pesky lockup and is frozen there. And yes, the spark plugs are out.



Second...the gears were working in fine order. Neutral was good and could go up and down the gears if we rolled the rear wheel while on the center stand...untill the above problem starter. Now the shifter feels as though it's in 5th. No room to shift up, but room to shift downward. When you "shift down" nothing happens and remains in that gear; whether the wheel is moving or not.



Thanks for your help in advance,



Kev
 

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hmm

interesting

normally when you rock the back wheel back and forth you can change gears and

find neutral

if its stuck in gear it may be why you cant rotate the motor

have you tried turning the motor with the clutch in?
 

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Discussion Starter · #3 ·
I have tried with the clutch engaged and dis. Was waiting for a new cable to come in since the last one was frozen. It rolls with a good amount of resistance when the clutch is pulled in. Probably from sitting and clutch slipping. I don't think it has to do with the engine being locked, but I could be wrong.
 

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I'd have a look at the gear change lever and see if its loose or

slipped on the splines thereby preventing you shifting gears

Also check the lever doesnt foul on the case.

If you can get it into neutral by wiggling tbe back wheel and lever

you can then see if the engine will spin more freely.

Its usually very easy to do, if you cant then you may have to think about

dropping the engine and looking inside
 

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Put some light weight oil down the plug hole and let it sit for the night. If worst comes to worst, take the head off and use a block of wood and a hammer to get the piston to move. What's the oil like? If it sat for a long time, the best thing would be to take the motor out and replace some rubber. The mechanical seal is dry, and so it will probably be ruined just by spinning the motor by hand. It really isnt that much work to get the motor out. I can fit all the tools required in one hand. Although a jack is nice. Some just use a milk crate.
 

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Agree with whats been said. Maybe the bore is slightly rusty or dirty, if the piston has been down for a long time. When you cranked it over by hand, you moved the piston into the "dirty" area, and it has seized there. Rip the head off and tap the piston down with a block of wood, then wet/dry or hone the cyl bore before attempting to spin the engine again.

As NateDawg said, a handful of tools and a milk crate. Easy as pie. Get into bother? call us here on the forum, we will help you out.
 

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Discussion Starter · #7 ·
Agree with whats been said. Maybe the bore is slightly rusty or dirty, if the piston has been down for a long time. When you cranked it over by hand, you moved the piston into the "dirty" area, and it has seized there. Rip the head off and tap the piston down with a block of wood, then wet/dry or hone the cyl bore before attempting to spin the engine again.

As NateDawg said, a handful of tools and a milk crate. Easy as pie. Get into bother? call us here on the forum, we will help you out.


Sounds like a likely and relatively easy problem to deal with. Don't have such an issue with that besides for the fact I haven't dealt with these types of engines before. If the piston becomes free, will this fix the shifting problem though? I feel like these issues aren't related.

The oil seemed pretty good when it was first drained. Good color besides for a little white stuff mixed in.



Any advice is well appreciated.



Kev
 

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These clutch plates sit in oil. Same oil as motor lubricant. My bike runs well, but I can feel a difference in the clutch from cold to op temp. Sometimes when cold, if I left it in 1st gear, neutral can be a pain to get into. Goes away once the clutch plates have been fully oiled. Some would suggest taking out the clutch basket and soaking the whole thing in oil. I would be happy if you just took the cover off and threw WD-40 all over in there. I would bet you have more of a dry clutch problem than a trans problem.
 

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Kev, if you haven't done so, head to the General Discussion section and find the Quick Reference thread. You will find downloadable factory service manuals there, as well as a butt load of other helpful items.



It almost sounds like there is a lodged part that is preventing the crankshaft from moving, so tread carefully. The gang here will guide you as you get into it.



Joel in the Couve
 

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Discussion Starter · #11 ·
After looking at the manual and searching I can't find much. All I'm trying to do is remove this head...I feel like I'm missing something here which is kind of frustrating. Do I need an allen key that big to take off that ?bolt? underneath the rocker once their taken off? It also looks like there might be a bolt connecting to the radiator behind tht shroud.



Kev
 

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NO, dont undo it. It's not required. From memory (..and I drink a lot), there are 4 head bolts going thru the rocker gear, the inlet stubs, the exhaust bolts and the head should come off. Please correct me, Oh guru's of the twisted twin. The head will be stubborn to remove. I usually stick a hammer handle in the exhaust port and lift.



The "Allen" bolt is there from the factory, I believe it is used in the casting process, something to do with the coolant, I believe. Dont quote me, though.
 

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Discussion Starter · #13 ·
NO, dont undo it. It's not required. From memory (..and I drink a lot), there are 4 head bolts going thru the rocker gear, the inlet stubs, the exhaust bolts and the head should come off. Please correct me, Oh guru's of the twisted twin. The head will be stubborn to remove. I usually stick a hammer handle in the exhaust port and lift.



The "Allen" bolt is there from the factory, I believe it is used in the casting process, something to do with the coolant, I believe. Dont quote me, though.


Yea I figured it out. After eating some dinner and cooling my nerves I get them off.



I wont have time to really work on it, but I attempted to knock the pistons out of their "frozen" spot with wood. Didn't work =/ Maybe a bigger hammer would help, but I don't want to force anything and make a bigger problem. The piston had some carbon build up and a little rust like oil color looking liquid resting on top.



Any ideas??



Kev
 

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If you could throw some pics up it would make it easier for us to see what youre 'seeing", and who knows, one of the geniouses here may spot something right away
 

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im pretty new to this but the one problem i did have and fixed was the cam chain tensioner. it got obliterated and the pieces prevented my being able to shift at all. im thinking that pieces could be preventing your shifting as well as the cam chain moving. just a thought. hope im not just guessing on this one, just tring to give back since ive been helped so much already
 

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the fact the engine turned a bit initially made me wonder at the rusted piston idea

and didnt fancy that

The broken cam chain or tensioner idea sounds a good contender

I'd have a flutter on that meself



PICS !!



Show us what ya got
 

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The shifter lever isn't bumping into the exhaust is it?
 

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And you tried turning the nut backwards right? I'm guessing you tried going the opposite way of what you did earlier, but just thought I'd check in case...
 

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just another note. the 78's were known for a faulty cam chain tensioner. youll want to make sure the engine serial has the stamp that indicated a recall was done to fix that problem. either way the triple bypass is something youll want to investigate. cam chain, mech seal and stator. theyll need doing eventually.
 

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Discussion Starter · #20 ·
Hey guys,



Just got back home and I'm glad you all put your thoughts into this one. The cam chain sounds like a possibility, but didn't hear anything break when I attempted to turn the engine over manually.



Here's what I'm looking at on the right side when I initially pulled the head off.

 
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