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Discussion Starter · #1 ·
Hello posting from southwest Michigan here, to start everything off my project is to get a CX 500 to run for my dad for Fathersday. I don't know much about them but I am in school for mechanical engineering so I can manage with a wrench. I'm my garage I happen to have 2 nearly complete (all/most of the parts are there) and 1 other that does not have the plastics and my goal is to get one to run by Fathersday, and when I say run I mean I want the engine to turn over and stay at idle until I want it to turn off.

The only problem I have is I can get one of them to start if I take the spark plugs out and spray some starting fluid and put it all back together and it will turn over and run for about 5 seconds before it shuts off.

The other one turns over but not nearly fast enough for it to start. More like the cylinders are frozen.

If I was to start with the one that I can get to run with some starting fluid how would I go about testing what needs to be tested (electronically and mechanically) and what cleaning fluids should I use to maybe clean out the inside of the motor? Any help would be greatly appreciated, thanks guys I'm looking forward to the help.

P.S. I can post videos and pictures upon request
 
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If these bikes sit for more than a few months you can figure on pulling the carbs for a good cleaning first. (The idle or pilot jet clogs up first) Do a compression test with the throttle wide open and report back with the results. What are the mileages on the bikes odometers? How long did they sit neglected? Figure on replacing old tires before riding. Change the fluids. Download a factory service manual. Familiarize yourself with the term "Triple Bypass" as it relates to the CX/GL family. The older bikes have a plastic fan running off the front end of the cam shaft. They can crack and if they break, can damage the radiator on the back side. Cracks appear on the back side of the fan hub. You can pull the fan with the front axle used as a puller. Some folks upgrade to an electric fan set up from newer models. Head gaskets can leak. Mufflers rot out on the bottom. Water pump seals can leak with coolant running out of a weep hole on the back of the engine at the bottom of the pump. Problems can develop with vacuum operated petcocks. See if you have more than one hose at the petcock under the fuel tank. If the brakes stick, figure on overhauls of the caliper(s) and the master cylinder and you have to look for a blockage of a small hole inside the bottom of the brake fluid reservoir. Look for mice in the air filter box. Inspect the wire harness for any damage from critters or just age. If you take the rear wheel off, look at the drive splines. Are they covered with a black looking grease? That is what you want to see. Honda Black Moly 60% is what we use.
That should keep you busy for a while.
 

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Sounds like you have spark. so its fuel related. clean the carbs fresh gas and give a try again, let us know. Good luck Good son.
 

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If these bikes sit for more than a few months you can figure on pulling the carbs for a good cleaning first. (The idle or pilot jet clogs up first) Do a compression test with the throttle wide open and report back with the results. What are the mileages on the bikes odometers? How long did they sit neglected? Figure on replacing old tires before riding. Change the fluids. Download a factory service manual. Familiarize yourself with the term "Triple Bypass" as it relates to the CX/GL family. The older bikes have a plastic fan running off the front end of the cam shaft. They can crack and if they break, can damage the radiator on the back side. Cracks appear on the back side of the fan hub. You can pull the fan with the front axle used as a puller. Some folks upgrade to an electric fan set up from newer models. Head gaskets can leak. Mufflers rot out on the bottom. Water pump seals can leak with coolant running out of a weep hole on the back of the engine at the bottom of the pump. Problems can develop with vacuum operated petcocks. See if you have more than one hose at the petcock under the fuel tank. If the brakes stick, figure on overhauls of the caliper(s) and the master cylinder and you have to look for a blockage of a small hole inside the bottom of the brake fluid reservoir. Look for mice in the air filter box. Inspect the wire harness for any damage from critters or just age. If you take the rear wheel off, look at the drive splines. Are they covered with a black looking grease? That is what you want to see. Honda Black Moly 60% is what we use.
That should keep you busy for a while.
Com pre hen sive !
 

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Put in your profile where you are located. (city/state) That way if someone is nearby they and come and help you and mentor you through getting these bikes running. If they turn over and have spark, you are well on your way to getting them running. I would suggest that you get Larry's carb book and a ultrasonic cleaner and you will be running in no time. Also, clean the starter motor on the bike that turns over slowly. Theree are plenty of people on this forum that would be willing to help you out, but we need to know where you are located.
 

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Discussion Starter · #6 ·
I didn't clean the carbs yet but I decided to take a shot at the bike that was having the slow rotation when trying to start because that was the one that I know ran before storage. The only reason why I decided to do that was because the fuel light wasn't staying lit up after turning the key, which is what I saw in most of the startup videos on YouTube, where on the first bike I mentioned the light stays lit up red throughout the process of starting along with the oil light, reserve fuel light, and the neutral light. I was unable to get a compression gauge to do the test, I went to autozone and bought the most expensive one they had (because it had a bunch of fittings) and none of them fit. The mileages on the bikes doesn't seem correct to me because it says that there is over 300,000 miles on one and the other has roughly 150,000 which may be correct. All three of the CX500's we have have sat for almost 20 years, but I just replaces the oil and oil filters on two of them (the other is a donor bike) and I got a faster rotation on one bike and nothing changed on the other. The plastic fan doesn't seem to have anything wrong on either of the two bikes, no problem with the coolant leaking, on all of the bikes there is two hoses coming out of the petcocks, also the only problem with any of the brakes is that one of the rear brakes (when you press down the pedal) there is sort of a suction sound which i assume is the seal for the rear brake. And there is no signs of mice in the two bikes I think have a chance at running because they were stored in a garage covered up with moth ball bags zip tied around the frame. As far as the wire harness they both seemed in good condition just caked with dust which cleaned off very easily. As of right now I haven't had the chance to get the rear wheels off.

Points of interest:

The White Bike ------ (the one I got started for a couple of seconds) the red fuel light stays lit up when the key is turned on. When you flip the kill switch pretty fast between stop and run the rpm gauge will slowly move up to about 5000 rpm even though the bike isn't running. I took a inspection camera to the cylinder heads (after taking out the spark plugs) and the heads seem pretty clean compared to the other bike. This bike when you turn the throttle it doesn't snap back but rather slowly moves back which I assume can be fixed with some penetrating oil down the cables.

The Red Bike ----- Throttle seems like its brand new and lubricated correctly. When the key is turned on only the oil light and neutral light stay on until the ignition is pressed then the oil light turns off until I let go. When this one is all put together it doesn't turn over properly as it is very slow. When both spark plugs are removed it turns over faster but still not like the other bike. Even when there is just one spark plug in it still turns over faster, but once the second spark plug is replaced it slows down again immediately.
 

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Sounds like the red bike might need the starter opened up and looked at. I have seen one full of ground up carbon from the brushes on the armature. It wasn't repairable because the armature was too worn down. You could find enough voltage reaching the starter wire terminal but that won't tell you how much amperage is available through the wiring and the starter solenoid. If you swap batteries with the other bike does the starter RPM improve?
 

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Discussion Starter · #8 ·
I am actually using a car battery with jumper cables connected to the terminals so both bikes are using the same battery, I planned on swapping out the starter on the donor bike to the red one to see if there was any improvements there.
 

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Discussion Starter · #9 ·
Today I focused on white bike and I got the fuel light to turn off after taking apart all of the connectors and cleaning them. What I am running into now is I can't figure out how to get the fuel pump to prime which I think is why the carbs aren't getting any fuel. Other than that I think the bike should start right up. Any ideas on that fuel pump?
 

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No fuel pump. The petcock screen might be plugged. Drain the tank, remove the petcock. I'm guessing that you are going to find some interesting things.
 

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Discussion Starter · #12 ·
Yes, I didn't think there was a difference, but I'm guessing that I was wrong, the three bikes that I have are all 82 cx 500 turbos
 

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Discussion Starter · #14 ·
No fuel pump. The petcock screen might be plugged. Drain the tank, remove the petcock. I'm guessing that you are going to find some interesting things.
Already have done a complete drain and flush in the tanks, ran fuel straight through the petcock and had none issues with flow. And I was under the impression of a fuel pump because in one of the shop manuals there was a diagram pointing to one, but it makes sense since there is not one where it is shown.
 

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Discussion Starter · #15 ·
I can get some pictures up later tonight, I am actually using my phone at the moment and it wouldn't let me upload. But I will get those up as soon as I can
 

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Something is keeping the fuel from entering the bowls, possibly the floats are stuck? Open the drains on the bottoms of the float bowls and see if anything comes out.
 

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Already have done a complete drain and flush in the tanks, ran fuel straight through the petcock and had none issues with flow. And I was under the impression of a fuel pump because in one of the shop manuals there was a diagram pointing to one, but it makes sense since there is not one where it is shown.
If they are all Turbos there will be a fuel pump. Not to mention a tonne of other plumbing for the turbocharger, and no carburetors.

Without pics, this might help... which of these wheel types do the bikes have? Boomerang Comstars, presumably?

https://motofaction.org/motorcycles...eel-differences-honda-cx500-gl500-cx650-gl650
 

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Sounds like a good time to rebuild the carbs.
 

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Discussion Starter · #19 ·
Sounds like a good time to rebuild the carbs.
It is in fact the CX500TC so there is a fuel pump and no carbs. Although I do have brand new injectors on the white bike. Also just recently I powered up the donor bike and got the fuel pump to prime and spit out fuel, so tomorrow that pump will go on the white bike. Amd I'm guessing that will be the only thing needed for that bike to run!
I'm getting excited just thinking about the turbo running again!!
 

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Discussion Starter · #20 ·
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