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1982 CX500C (US)
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Discussion Starter #1 (Edited)
Bought a CX500C from a former co-op student of mine, someone had started to cafe it up a bit before him and he did some work as well. Odometer reads 26k or so (miles) so no idea if that's 26 or 126.

Sat for 2 years and he was moving so was selling, "ran fine" before sitting so currently working on air/fuel/spark as step one.

Wouldn't start when I got it, so replaced the battery, and took out the carbs and cleaned out the lower bowl side entirely, removed the 2 main jets and the "easy" emulsion tube, cleaned tons of green powder out of the right carb (likely 89 octane fuel with 10% ethanol that sat) and lots of gelled gas out of the left.

Got it to start up and it was only running on the right cylinder because of a poor connection from the spark cap to the wire, snugged that up and running on 2 cylinders now but stalls out at 4k-5k rpm. I haven't done the top end of the carb yet but I'm going to order 2 full rebuild kits and just do that as I didn't get to the diaphragm or the pilot jet at all, just the bottom side. It was previously converted to pods as well 2 owners ago so I need to check the main jet sizes as well although presumably it was re-jetted after the pod conversion. Float sticks on the right side (the green one) as well sometimes and needs a whack even after the cleaning so I'll need to tap that pin out and clean I think.

One thing I was hoping to get a question answered on is I'm getting black oil dripping out from the muffler connection on the kickstand side, and I don't know if it's oil making it through valve seals or something similar or if it's just residue in the exhaust. Oil is fairly clean (although will be changed this week) and the oil dripping out is very black but that might just be what happens as it makes it through the combustion chamber if it is sneaking past. The valve cover was previously overtorqued and repaired on the left side and there's gasket seal visible so I'll order some cover gaskets before I open it up, but was wondering if this is a symptom of valve stem seals / guides or if it's likely just residue.

New plugs installed as well, old plugs were quite black so maybe rich OR getting oil, not sure as they were black on both sides, have resistor plug caps so replaced with DE8A plugs.

Any help/tips greatly appreciated! It'll probably be next winter before I get brave enough for any of the big stuff (engine removal, etc) so for now looking at engine-in style things to check.
 

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The CDI test is not of use for this TI bike.
 

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1982 CX500C (US)
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Discussion Starter #6
The CDI test is not of use for this TI bike.
I did already do a swaptronic test on the TI coils as well when troubleshooting the left cylinder not firing and they seem to behave identically, and I tried to take some readings off the coils but the instructions I found elsewhere for testing the TI coils didn't seem to match up.


Maybe I need to run through the doable tests for the timing pickup coil resistance tests.
 

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... running on 2 cylinders now but stalls out at 4k-5k rpm.
Sometimes failing to run at higher speeds is due to a plugged air filter or plugged screen in the air box. It is simple to try a short run with the air filter removed.
Another problem may be the resistors in the plug caps. Have you examined them?
 

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1982 CX500C (US)
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Discussion Starter #8
I did already do a swaptronic test on the TI coils as well when troubleshooting the left cylinder not firing and they seem to behave identically, and I tried to take some readings off the coils but the instructions I found elsewhere for testing the TI coils didn't seem to match up.


Maybe I need to run through the doable tests for the timing pickup coil resistance tests.
Sometimes failing to run at higher speeds is due to a plugged air filter or plugged screen in the air box. It is simple to try a short run with the air filter removed.
Another problem may be the resistors in the plug caps. Have you examined them?
I haven't examined the resistors, but I did test that they are there as I needed to check before I put new plugs in with or without resistors.

I still haven't had the tops of the carbs opened though, so could the jet or needle on the top side still be an issue where the carbs were really gummed up? I can easily try running with the pods off too.

I tested what I -think- is the pickup coil resistance, the plug is under the seat and has 2 yellow and 2 blue on one side and ALL black on the other side. Testing the black side (which I thought was wrong - maybe?) 500 - 505ohms each, other side was something completely different.

IMG_2783.jpeg IMG_2782.jpeg

I had a look at the pods and I don't think they're blocking the atmospheric ports and running with them off same result.
 

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1983 cx650E
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856 Posts
Leaking valve seals isn't a typical problem with these engines, but it can happen.
 

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1982 CX500C (US)
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Discussion Starter #10
Leaking valve seals isn't a typical problem with these engines, but it can happen.
It's only 5C (40F or so) in the garage, so it could just be condensation mixed with carbon in the exhaust and not oil, so that'd be nice. :D
 

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1983 cx650E
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The later models had vacuum diaphragm petcocks that would get pinholes after time. It usually manifest itself on the road by shutting down via fuel starvation after a accelerated period. Letting it sit would allow the carbs to fill again and the ride to continue a few miles again.

Doesn't seem to match your problem but something to keep in mind.

Yours sounds carb or electrical related.

Does it shut down suddenly at 4500 (electrical) or does it stumble and sputter it's way off? (Fuel)
 

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As nolimitz has already stated, get Larry’s carb book and rebuild your carbs correctly to start with. You will be chasing your tail if you don’t do things correctly.
 

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1982 CX500C (US)
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Discussion Starter #14
The later models had vacuum diaphragm petcocks that would get pinholes after time. It usually manifest itself on the road by shutting down via fuel starvation after a accelerated period. Letting it sit would allow the carbs to fill again and the ride to continue a few miles again.

Doesn't seem to match your problem but something to keep in mind.

Yours sounds carb or electrical related.

Does it shut down suddenly at 4500 (electrical) or does it stumble and sputter it's way off? (Fuel)
I’ll pop a video on here but more sputtering based on rpm/throttle and if I roll off I can stop it from dying, so definitely more feels like carbs.
I’ll get the carb kits ordered with the ACV and accelerator pump diaphragms and order Larry’s book and go from there!

Any reason I should drop $105 US on CX Master Carb Kit (B) vs $25 US (for a pair) of Ultimate Carburetor Carb Repair Rebuild Kit for Honda 1980-82 1981 CX500C CX500 | eBay ?
 

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1982 CX500C (US)
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Discussion Starter #16
Thanks, so I'll order up those cheaper kits to get new rubber all around and try to re-use as much of the original brass as possible, I'm sure I can find someone I know with an ultrasonic cleaner.

So here's a quick vid:

It definitely seems like not getting enough fuel, because it will start ok choked or open, stalls out at 4500rpm while choked and won't go past 3k even when a bit warm while open, so that sounds like too lean / fuel not getting through. Choke was on in the video and I went to re-do with it off and notice it wouldn't even get to 4500 then, usually choke limits you!

I can get this kit in Canada - Honda CX500C 1980-82 CX500D 1980-81 CX Carburetor Rebuild Kit Carb Kit Deluxe | eBay - given what needs do be done I feel like it'd be better to have spare rubber plugs, new ACV and accelerator pump rubber, etc?
 

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It looks like you have already taken the carbs off the bike. If so, I'd suggest checking the ACV and accelerator pump diaphragms for condition. If the rubber is in good shape you could reuse them. When I did my GL500 carbs I reused all the parts and just did a cleaning. Been running fine for the last few years.
 

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1982 CX500C (US)
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Discussion Starter #19
It looks like you have already taken the carbs off the bike. If so, I'd suggest checking the ACV and accelerator pump diaphragms for condition. If the rubber is in good shape you could reuse them. When I did my GL500 carbs I reused all the parts and just did a cleaning. Been running fine for the last few years.
I mean they looked ok, the ACV ones for sure (although I'll double check them) and the pump one was ok although maybe a little scalloped on the bottom. Not torn or warped, but if I can get a kit with all new rubber for cheap and they're apart doesn't it make sense to just swap it all out? It seems like the OG brass stuff is preferred but what about rubber? Seems like new rubber would always be good.
 

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I believe that there have been problems with aftermarket ACVs, although I can't find the thread at the moment.
 
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