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Honda CX500 1980
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Discussion Starter · #1 ·
Hi all, had some issues lately with my cx500. About a month ago was riding on low oil level (indicator didn’t work). All the sudden my rear wheel locked. I’ve managed to push start it on the same run, drove to the nearest servo and filled it up with oil.
Was running for a couple more weeks but started to smoke a lot from exhausts. I figured it had to be ring damage due to low oil level.. not long later when riding back home it had lost most of its power. I’ve pulled over l, left the bike got a new battery (cause it was constantly going flat) and more oil. Got back to the bike next day, replaced battery thinking that lack of power might had been caused by low battery and faulty alternator. Took her for a spin, 3 min later rear wheel locked again when going 80km. Can’t start it anymore, won’t go in gear..
So I’m assuming engine seize possibly from melted rings? I took heads off and saw bits of metal on left piston, can’t move it not the crank. I’ve basically pulled apart most of the engine, both covers and now looking at clutch and gearbox.
Wondering if it might just be a matter of replacing pistons rings and cylinder rebore.
But this is where it gets tricky. Cause I can’t turn the crank I can’t align the pushrod bolts through the chamber in order to get to them. Not to mention the piston won’t move at all.
Any ideas how to remove the piston? And to determine if it’s not a snapped crank? Also do I need to take off timing chain in order to pull out gearbox? Also found that one of the timing chain bolts is shattered but this may have had happen with previous owner.
H E L P :)

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Piston rings are the least of your worries. You have no doubt locked up because of bearing failure. Whether it be main bearing or rod bearing, it doesn't matter as the crank and all bearings are toast. Finding another motor will be your cheapest and easiest fix.
 

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Honda CX500 1980
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Discussion Starter · #3 ·
Piston rings are the least of your worries. You have no doubt locked up because of bearing failure. Whether it be main bearing or rod bearing, it doesn't matter as the crank and all bearings are toast. Finding another motor will be your cheapest and easiest fix.
Thanks for your reply. I’m gonna try to pull out the pistons first, would you happen to have any answers to my questions?
Cheers
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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You don't need to remove the timing chain to remove the transmission, just the clutch. It comes out the front. You will need to remove the oil pump and it's chain to access and inspect the left conn rod.
Not sure why you're concerned about removing the timing chain. If you're planning to bore or re-sleeve the cylinders, you'll need to completely strip the block, anyway.
 
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That chain wear may not be on the PO. Have you been adjusting the chain tension at regular intervals?
 

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Your piston rings are not the reason you can't rotate the crank shaft. You have most likely spun a bearing and is holding your crank shaft from spinning. You don't need to remove the timing chain to remove the transmission as the transmission is removed from the front of the engine. Do you have a copy of the Factory Service Manual? It details this procedure very well. Since you have removed the heads, you can certainly remove the timing chain if you want to. You will still be able to try to turn the motor over without any fear of bending a valve.
 

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Also, very unlikely you have broke the crank shaft in half. If bearings and oversized piston rings were readily available I could see wanting to try and fix this motor but even the professional mechanics will tell you to look for another motor. I feel your pain, I had to put a different motor in my Silverwing last winter because I had the dreaded copper colored flakes in my oil and oil filter.
 

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It could be worse. I had to put a new engine in my Subaru.
 
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that also looks like it has been run hot
What's the give away there, Murray? The brown glazing inside the case? I see that in some engines, but haven't noticed a pattern.
 
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randall
if you look at the side of teh cylinder you can see the over heating patter in the sides of the block
then if you look athe picture of the piston you can see where water is seeping out of the seam between
the aluminum block and the cast in place sleeve in fact at one spot you can see the seam between them starting to open
then look in the water jacket and you can see heated on deposits and the headgasket looks cooked on
last look at the bottom of the cam gallery that is a rapid oil drain area yet it has burnt/coked deposits on the gallery
just my thoughts maybe the poster will tell me he has a working temp gauge and it never got hot
 

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'84 CX650E that is evolving into a GL500
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He's in Australia so shipping an engine from the US probably wouldn't make sense.

Mark: I agree with the others that replacing the engine is your best bet. It would be a lot less work and a lot less expensive in the long run.

BTW: These bikes don't have a low oil level indicator, just a low oil pressure light. It should light when the key is on and turn off when you start the engine. If it either doesn't light or doesn't turn off you should NOT ride the bike until you have fixed the problem.

Welcome to the forum. Please add your location to your profile and your bike's model and model year to your signature so that you don't have to remember to tell us every time and we don't have to keep asking when you forget (see Forum Settings link in my signature).

And welcome to the world of antique vehicle ownership (they own us, not the other way around). Your bike is about 4 decades old and the Previous Owners may or may not have done the maintenance necessary to keep it safe & reliable so it is highly recommended to download the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and go through all of the service procedures, regardless of whether your bike has reached the specified mileage.
I also recommend looking on all rubber parts with suspicion because rubber does not age gracefully. Check the date codes on your tires and replace them if they are over 5 years old no matter how good they look & feel (old rubber simply cannot flow around the irregularities in the asphalt well enough to grip, especially if it is cool or wet). If your bike still has the original rubber brake line(s) (should be replaced every 2 or 3 fluid changes = 5 or 6 years) I recommend shopping for modern stainless braided ones (they last practically forever and double the life of the fluid). And don't forget things like the rad hoses and the boot between the engine and swingarm (they can crack on the bottom where you don't see it).
 

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Discussion Starter · #15 ·
He's in Australia so shipping an engine from the US probably wouldn't make sense.

Mark: I agree with the others that replacing the engine is your best bet. It would be a lot less work and a lot less expensive in the long run.

BTW: These bikes don't have a low oil level indicator, just a low oil pressure light. It should light when the key is on and turn off when you start the engine. If it either doesn't light or doesn't turn off you should NOT ride the bike until you have fixed the problem.

Welcome to the forum. Please add your location to your profile and your bike's model and model year to your signature so that you don't have to remember to tell us every time and we don't have to keep asking when you forget (see Forum Settings link in my signature).

And welcome to the world of antique vehicle ownership (they own us, not the other way around). Your bike is about 4 decades old and the Previous Owners may or may not have done the maintenance necessary to keep it safe & reliable so it is highly recommended to download the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and go through all of the service procedures, regardless of whether your bike has reached the specified mileage.
I also recommend looking on all rubber parts with suspicion because rubber does not age gracefully. Check the date codes on your tires and replace them if they are over 5 years old no matter how good they look & feel (old rubber simply cannot flow around the irregularities in the asphalt well enough to grip, especially if it is cool or wet). If your bike still has the original rubber brake line(s) (should be replaced every 2 or 3 fluid changes = 5 or 6 years) I recommend shopping for modern stainless braided ones (they last practically forever and double the life of the fluid). And don't forget things like the rad hoses and the boot between the engine and swingarm (they can crack on the bottom where you don't see it).
Thank you for the advise. I’ve updated my account info.
As for my issue, I agree that getting a new engine would be cheaper and faster. However it’s not easy to find one in Australia, I’d have to get a whole motorbike and swap it. Might as well get a new one and make it my next project.
mum gonna try to fix it though, heaps of parts online. Once I’m back from camping I’ll try to pull out the clutch gearbox and get to the pushrods. If the pistons pop out then recon has to be the crank shaft.. let’s see how it goes.
Happy to be here, so unfortunate about the circumstances though :) but once she’s back on the road will have other discussions.

thanks everyone I shall update soon!
 

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Discussion Starter · #16 ·
when you put a new engine in hook up the oil light and temp gauge
that also looks like it has been run hot
where are you i have some engines
Well mate I’m in Western Australia tell me more about your engines :)
 

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Discussion Starter · #17 ·
randall
if you look at the side of teh cylinder you can see the over heating patter in the sides of the block
then if you look athe picture of the piston you can see where water is seeping out of the seam between
the aluminum block and the cast in place sleeve in fact at one spot you can see the seam between them starting to open
then look in the water jacket and you can see heated on deposits and the headgasket looks cooked on
last look at the bottom of the cam gallery that is a rapid oil drain area yet it has burnt/coked deposits on the gallery
just my thoughts maybe the poster will tell me he has a working temp gauge and it never got hot
Water didn’t sip through, it dripped down when taking off the head
 

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Even though engines are hard to come by in your area, I think you will find the engines are still easier to come by than all the parts you’ll need. I don’t mean to be rude but the fact that you limped it along without oil in it says you are relatively new to internal combustion engines. The work your motor needs might be a little over your head.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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It's too bad you're nowhere near CXPhreak in Adelaide.
 
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