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Discussion Starter · #1 ·
My 1980 CX500 custom has a constant flow of air bubbles in the coolant expansion tank. I noticed this tonight when riding home tonight and the amount of air bubbles increases with increase in rpm's. I let the bike cool down and started it again to see the if the amount of the air bubbles reamained the same, it did pretty much. Checking the motor oil and it is fine, not murky or discolored in any way. Also checked the coolant, new engine ice this year with right cylinder head gasket and it also looks good.



So looking for advice. Head gasket, water pump seal or is there something else I should be investigating.



Regards,

Bill Martin

Cincinnati, OH



1980 CX500c

1982 CB900c
 

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Are they vibration bubbles? or possibly does your radiator to reservoir hose have a hole in it and is blowing air when it circulates coolant?
 

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Sounds like a head gasket leak to me. Do a compression test. Open the reservoir cap and take a sniff when its bubbling. Smell like exhaust gases?
 

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Sorry, but, I agree with Pappa. Head gasket split, and is forcing air (compression) into water galleries. Compression test should show it. Best of luck.
 

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Discussion Starter · #5 ·
I just checked and the hose is good, I think there is head gasket (again) work in the future. Will do a compression test today and post the results.



Quick question, should I replace the water pump mechanical seal with the head gasket repair?



The bike's history is been sitting in a barn for 20 plus years. Had less than 5,000 miles on it. When I picked it up the right head gasket was blow and the kid was runnning it a bit, no coolant in the system though. All in all it took the abuse so I bought it and only did the right side head gasket, along with all the fluids. Ran good for 400 miles, now I see bubbles.



Regards,

Bill Martin

Cincinnati, OH



1980 CX500c

1982 CB900c
 

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I probably wouldn't replace the water pump seal if it isn't leaking or weeping. But I do agree on the head gasket being the likely culprit. Since these heads are away from the seal, you don't have to even get close to the water pump to change a head gasket. I am a firm believer in "If it isn't broke, don't fix it". That's not to say that if you are doing the stator, you should reuse the seal, but don't just open it up for fun. Do a compression, or better, a leak down test. That should point you in the right direction.
 

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Try one of those test kits to see if combustion gasses are getting into the coolant. You put a little coolant in a test vial, add a few drops of something and if it changes color that means a head gasket leak is probable.
 

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Discussion Starter · #8 ·
I just bought a compression test guauge and the right side is 120, left is maybe 60. I did the test after warming the engine. So the left side it is and you folks were spot on, head hasket.



The reason I was asking about the water pump seal was because the previous owner ran the bike without coolant. I replaced the right head gasket, thermostat, orings and radiator cap but never did open the impeller. Just wondering if the heat would have hurt the seal and since the coolant is out and I am going to rebuild the carbs the water pump is like right there. But, taking your advice I am going to leave it alone and do the head gasket only. If the water pump acts up I'll have something to do next weekend.



Thank you all for your informative advice, I can only hope to help others now that I have joined this forum.



Best Regards,

Bill Martin

Cincinnati, OH



1980 CX500c

1982 CB900c
 

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Even the right side seems a little low. I think normal is about 170 +/- 10%. Did you use a push in gage? They don't seal as well. And the throttle needs to be fully open for the test to be accurate.
 

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Hi Bill

the Europsort motor in my bike had been stood for some time when I got it

and I had similar things happen to me when I eventually

( 2 years, no big hurry I had other bikes)

got it all assembled and on the road.

I renewed the gasket on one side and when it happened to the other side I found the head

bolt tightness was less than optimum and I was lucky and got away with just torquing them down more.
 

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Discussion Starter · #11 ·
I used the screw in type to measure the compression and did not open the throttle at all. Will give it another go and check the bolts on the left side as well.



Just found an 81 Silverwing GL 500 on craigslist with 7,500 miles on it. Just have to go see it, and the wife is out of town. So are you folks as good on GL 500's?



Bill Martin

Cincinnati, OH



'80 CX500c '82 CB900C
 

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Heck, if your head gasket is leaking you can probably smell it in your exhaust. It will be different. Also, look for small glassy looking beads around the muffler outlet. I noticed these two signs way back in 1979 on my 78 CX500. I fixed it myself, under warranty, and got paid for my labor. I worked at the dealership as a tech.
 

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Just found an 81 Silverwing GL 500 on craigslist with 7,500 miles on it. Just have to go see it, and the wife is out of town. So are you folks as good on GL 500's?


GL & CX - no real difference to us as they aren't really that different.
 

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If it sat so long and it doesn't weep from the mech seal, verify that the weep hole is unobstructed. Sometimes a PO has 'fixed' a leaking seal with a dab of silicone.



R
 

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Discussion Starter · #15 ·
To Reg in Bristol, thanks for the tip to check the head bolts, they all needed quite a bit of attention. Redid the compression test and both are at 160+ with full throttle open (thank you Blue Fox). Going out for a gentle ride and see how she behaves. Will post the results.



Regards,

Bill Martin

Cincinati OH
 

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If the air bubbles continue or not renew the Radiator cap.Take the old one to Autozone.Do NOT pay top dollar for a so called,"Honda" one.They are a stock car Rad cap(13 Lbs PSI .9 bar) as is the thermostat.
 

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Discussion Starter · #17 ·
Bummer.. just did a quick ride and the bubbles are back.



Shep, I did replace with a new Honda cap, should I replace with one from Autozone? I also am thinking that once the bike cools overnight I'll re-tourque the left cylinder head bolts again.



Bill Martin

Cincinnati, OH
 

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Bill another sympton of the prob I had was the expansion bottle level kept

rising and eventually oveflowing

Obviuosly I was losing coolant over time as well

It was worse on long runs while in town use it wasnt so apparent

the temp gauge would often look normal unless I let the coolant level drop

there was no water in the engine oil and I figured gasses from the combustion

chamber were leaking past the gasket and pressurising the coolant.

Strictly speaking a new gasket would be the usual path but I took a chance the second time and so far so good, it all looks fine.

Same rad cap/radiator I've had for 10 years BTW

it was on the bike I built in 2000/2001

they dont go wrong much
 

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Bummer.. just did a quick ride and the bubbles are back.



Shep, I did replace with a new Honda cap, should I replace with one from Autozone? I also am thinking that once the bike cools overnight I'll re-tourque the left cylinder head bolts again.



Bill Martin

Cincinnati, OH


Probably already time to retorque, they settle in quickly.
 

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Possble that the head is cracked on the intake side? It wouldn't fog but you may see coolant in the cylinder. However these guys are probably right with the head gasket.



If it is indeed a blown head gasket will it be obvious that it was by looking at the head gasket.



NOTE: John heads don't like to come off very easy on these engines. Someone mentioned loosen the head enough to crank the bike over but not loose enough to throw the head across the room, bend pushrods and whatever else. And just crank enough and no more.



This method should generate some responses. (As a disclaimer I have never removed a head this way, and I read it on the old forum).




Bill have you considered asking John for a head gasket?
 
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