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Honda CX500 1980
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Discussion Starter · #1 ·
Hi all!

I’m back with a few issues with my CX500 1980.
I’m just after an engine rebuild, had an engine seize big end bearings new piston rings. After rebuild worked fine a bit out of tune and smoke from right exhaust.
First issue I’ve experienced with it was when heavy accelerating my clutch would go stiff.
Not every time but every ride would happen. So once I accelerate hard try to pull clutch leaver it just wouldn’t move. Thought it might been rusty lines but then tried moving manually on the clutch cover and it would be stiff too. If I’d force
It eventually gear would engage, and funny thing when hitting rear break and accelerating repeatedly clutch would release.
Please help with ideas what it could be.

Second issue - my right cylinder seems to be out of tune. Not sure if my carbies need service or if it’s something with my valves, anyway I’m getting white smoke on cold start then when riding just the left cylinder is misfiring and smoking. You can build up speed slowly but when pulling down throttle it will choke. Bore is good and has new piston rings.
Amy ideas what it might be?

cheers guys looking forward to fixing issues with your help!
 

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Discussion Starter · #3 ·
read your sparkplugs. You may have a weeping head gasket.

Regarding the clutch I'm thinking a notched basket or a loose main clutch nut allowing the basket to float.
Thanks for your prompt reply.
Weeping head gasket would make sense, I did put new ones in though. Maybe I didn’t torque the head enough and came loose?

as for the clutch I’ll just take the cover off and Inspect the basket plus bolts. Is it those 4 bolts with springs?
 

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What was the source of the head gaskets?

If you didn't retorque aftermarket head gaskets they are likely beginning to fail. A retorque now MIGHT save the head gasket that is? weeping.

I was thinking the large special nut with the bellville washer that holds the whole clutch in. Though obviously the 4 lifter plate bolts can be checked first.
 

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Discussion Starter · #5 ·
What was the source of the head gaskets?

If you didn't retorque aftermarket head gaskets they are likely beginning to fail. A retorque now MIGHT save the head gasket that is? weeping.

I was thinking the large special nut with the bellville washer that holds the whole clutch in. Though obviously the 4 lifter plate bolts can be checked first.
I bought a rebuild kit on ebay.
Ah ok that makes sense I did struggle with tightening it as it requires a special tool? Taking it off was easier wracking off with hammer screwdriver.

I might not be making much sense as I was working on it over 6 months ago. I just had it shipped back up north and want to repair it again.

from what you’re saying it should all be just a matter of tightening up bolts, worse case scenario getting new gaskets?
 

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A special socket to fit the clutch nut can be made from a large socket with an angle grinder and file. While I am only guessing this is the issue it seems a good possibility. That nut does up to around 70 ft/lb. {58 - 72 from memory} A bit of an ask with no real leverage.

If you have to remove the basket I would recheck and inspect the entire clutch paying attention to any grooves worn into the basket that may need to be dressed out.

Read the plugs and if the bad cylinder looks suspiciously clean I think it will be the head gasket.

Retorque them regardless.

If the white smoke smells sweet it is likely coolant. If it smells fuelly you may have a weeping float valve.
 

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Discussion Starter · #7 ·
A special socket to fit the clutch nut can be made from a large socket with an angle grinder and file. While I am only guessing this is the issue it seems a good possibility. That nut does up to around 70 ft/lb. {58 - 72 from memory} A bit of an ask with no real leverage.

If you have to remove the basket I would recheck and inspect the entire clutch paying attention to any grooves worn into the basket that may need to be dressed out.

Read the plugs and if the bad cylinder looks suspiciously clean I think it will be the head gasket.

Retorque them regardless.

If the white smoke smells sweet it is likely coolant. If it smells fuelly you may have a weeping float valve.
I will keep you posted.
Thanks for your help makes so much sense.
 

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When you retorque the head you'll need to check valve adjustment also.
 
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Thanks Doug, I should have mentioned that.

I do the retorque at TDC compression stroke and check the clearances before retorquing the head and then check and adjust them again after the retorque. This gives a bit of a guide as to whether the gaskets are still compressing.

Remember to adjust the camchain while you're doing the left cylinder.
 

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consult the FSM for the correct way to remove the clutch internals. The four posts that the bolts screw in to like to snap off if you dont follow the correct procedure
 

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I'm not sure it's covered in the FSM, but best practice is to remove and install the clutch bolts simultaneously, about one turn at a time. It's tedious, but it keeps any lateral load off those posts.
 

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Discussion Starter · #12 ·
Hi guys I’m back, finally got my CX shipped to Exmouth.
First day first go - torqued up 4 bolts on head up to 54Nm. Wasn’t much play, just a tiny bit. Right cylinder is still misfiring, but have a feeling it’s a bit better after that. Whilst riding I’ll take off spark plug lead on left and right will run but not full power, and is choking a bit.
My question now is - should I go ahead take the head off and put some gasket putty or should I assume it’s that and order a new set of gaskets?

just another observation - if I accelerate gently engine builds up power, but if I rev hard it will jerk.

does this still sound like a weeping head? Spark plug was black..
 

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But wouldn’t that cause the oil to be milky?

I’ll try to chuck in the spark plug from other cylinder to see if that changes anything
Coolant in the combustion chamber makes for a clean spark plug and does nothing to the oil. Coolant in the oil makes a milkshake but does nothing to the spark plug.
 

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I like the color scheme on the tank, nice.
 

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