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Discussion Starter · #1 ·
Well I took the bike out today and the ride was short, maybe 30 minutes? I went to pick up some resistive plugs after doing the Brass Rod Mod to the Plug Caps. Currently I am still running the standard 8KEA plugs, picked up Champions version of the 8RKEA's and I have yet to install them.



Note that the bike started to hiccup when riding prior to doing the Brass Rod Mod.



When I got to the parts store I rolled up and the idle slowly dropped and stalled in the time it took me to find neutral to park it. It started but needed coaxing from the throttle to stay running--hand off the throttle, RPM's drop and she would stall. Every light needed some throttle to keep the motor going.



Acceleration is skittish anywhere even after 4K and 5K...when you get above 6 and 7K it seems to go, but not like I remember it did.



I checked the temps with the infrared gun, and the right side head just above the intake was 190F and the right side was around 178F.



It was cooler than usual this morning, but the temperature gauge found the middle, and then dropped back and never got to the middle again, and hung at about 75% of the thin-lined low zone.



I just got in and have not checked some of the more obvious things like replacing the fuel filter, checking the carbs to ensure they are clean (I did rebuild them the Cargill way) float levels etc.



I have my road test on the 25th of this month and would like to sort it out before then!!



I've read up a little by searching for my 'symptoms' and I think I am heading down the path of diagnosing the coils, CDI Unit, Pulsor, or Stator. What do you all think this sounds like? I am not too smart with electrical, but if I have the info I have a nice multimeter and should be able to trouble shoot the obvious if given some proper instruction.



thansk guys!
 

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Have you checked the air cut-off valves? If there is a hole in one of them it can cause the symptoms you describe. If you take them out and hold them up to a bright light it is the best way to check for pinholes.
 

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Discussion Starter · #3 ·
Have you checked the air cut-off valves? If there is a hole in one of them it can cause the symptoms you describe. If you take them out and hold them up to a bright light it is the best way to check for pinholes.


These were replaced when I rebuilt the carbs about 7 months ago with new ACV's...they were the ones from Sirius Consolidated and were of the solid rubber variety. I will add that to my list of items to check though. Thanks Allan.
 

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Have you checked the air cut-off valves? If there is a hole in one of them it can cause the symptoms you describe. If you take them out and hold them up to a bright light it is the best way to check for pinholes.




QFT....I had the same symptoms when I first bought my bike and rode it home. I also had a leak in my carb boots. Check those...air leak could ruin your day for sure. Try spraying carb cleaner around them...any change in RPM=leak.
 

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Discussion Starter · #6 ·
I will check for vacuum leaks as well. I am buggered because she was running peak for nearly 900 or so miles and then just fell flat. My gut is telling me 30 year old electronics.
 

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Discussion Starter · #8 ·
Well the first thing I checked were the plugs--and the look REALLY LEAN, as in NO brown lean. I had decent golden brown before doing the Brass Rod Mod. Is it possible that the MOD has improved the spark that much that I will need to retune?
 

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Discussion Starter · #9 ·
would like to thank Allen for posting the excellent Pic of the CDI Resistance checks between all of the pins...



1 to 5, 108.5 ohms

2 to 5, 94.8 ohms

3 to 5, 202.5 ohms

4 to 5, 106.6 ohms

6 to 5, 94.1 ohms

7 to 5, 204.2 ohms



8 to 9, 83.1 ohms

5 to 9, 422 ohms



...now these were measured cold, but were all pretty much in the middle of the ranges specified for each test.



I checked the charging voltage, 14.85V at 1100 rpm...all continuity tests for the Stator were positive, and resistance measurements averaged 1.5 to 1.6 ohms between pins 1 to 2, 2 to 3, and 1 to 3.



I started the bike after swapping out plugs to the resistive types, and proceeded to pull the boots to see if the engine would keep running. I pulled the right boot and the motor stopped instantly.



I replaced the boot, started the bike, pulled the left boot and the bike kept running. I am guessing this tells me that the left coil is bad? Can someone confirm for me?



Here are some pics of the coils...







So if this is telling me one of the coils is bad, what are some decent coils to buy? Do they come with new Plug Caps as well?
 

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You should put a spark plug in the left cap and hold the plug against against a good ground (not the valve cover)to see if it is sparking,,so far all that you can tell is that the left side is not working,,it could be a fuel issue. If you have no spark on the plug then it would point to coil or some other electrical problem. If there is spark then it is probably a fuel issue.



P.S. Thank Reg for that pic,,he is the one who made it.
 

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Discussion Starter · #11 ·
You should put a spark plug in the left cap and hold the plug against against a good ground (not the valve cover)to see if it is sparking,,so far all that you can tell is that the left side is not working,,it could be a fuel issue. If you have no spark on the plug then it would point to coil or some other electrical problem. If there is spark then it is probably a fuel issue.



P.S. Thank Reg for that pic,,he is the one who made it.


Its funny that you mention NOT to used the valve cover...I did that and found that both plugs were generating spark which confused me. I will check a frame ground.



I will check fuel as well...would the best way be to crank with kill switch off, full choke, pull the plug and see if its wet?



THANKS REG!! Great stuff.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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I am guessing this tells me that the left coil is bad? Can someone confirm for me?
The left and right coils are interchangeable. They just have different colored leads. Swap them to find out if the fault is in the coil or the CDI. You can also swap the plug caps to verify those.





R
 

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Discussion Starter · #13 ·
well using the frame as a ground, both plugs generate quite a bit of spark. I will try swapping left & right as you have mentioned Randall, and also check fuel delivery...maybe a float needle is hung up?
 

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Discussion Starter · #14 ·
well I physcially swapped the left coil with the right, as well as the pink and yellow leads so the pink was now mated to yellow, and yellow to pink. Started the bike, and pulled the right boot and the bike stalled same as before, pulled the left and the bike kept running.
 

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Are you using the spark plug that is in the left side of the engine to test it for spark? If you tested using a different spark plug,, test the plug that is in the engine to make sure the plug is firing, if it is sparking then you probably have a fuel issue,,after reading this thread over it could be as simple as a piece of dirt or rust in the main(112) jet , or also could be a clogged idle jet or idle circuit.



I think I remember reading that you cleaned the carbs,,do you have a fuel filter installed?



Also as mentioned above you should check for air leaks, especially on the left side. I use an unlit propane torch and move it all around the connections between the carbs and the intakes, the rubber intakes themselves and around the intake to head connections.

You should also check around the acv cover for leaks the same way.
 

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Discussion Starter · #16 ·
Are you using the spark plug that is in the left side of the engine to test it for spark? If you tested using a different spark plug,, test the plug that is in the engine to make sure the plug is firing, if it is sparking then you probably have a fuel issue,,after reading this thread over it could be as simple as a piece of dirt or rust in the main(112) jet , or also could be a clogged idle jet or idle circuit.



I think I remember reading that you cleaned the carbs,,do you have a fuel filter installed?



Also as mentioned above you should check for air leaks, especially on the left side. I use an unlit propane torch and move it all around the connections between the carbs and the intakes, the rubber intakes themselves and around the intake to head connections.

You should also check around the acv cover for leaks the same way.


I will go test the motor by switching the plugs...even though they are new, doesnt mean they work. I did clean the carbs per the letter via Larry's awesome book...I do have an inline fuel filter. I will check the carbs now though becuase there was a breif period when I was foolin around after JUST rebuilding the carbs that I did not have the filter in line.



So I think with the resistance checks on the CDI all coming back good, proof of spark from both coils, swapping the coils left to right, and with the same issue pulling the right boot and having the motor stall would tell me my left cylinder is not getting ANY fuel at all. It should be noted that after I swapped them, I pulled the plugs and there is little to NO carbon on the left plug, and the right plug is starting is golden brown look already just idling for a couple minutes.



would you agree? No fuel to the left cylinder.
 

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Yes it sounds like at low rpm you are getting no fuel on the left side.



You should however, test the left spark plug just in case it happened to be a faulty one,,it has happened before. Swapping the plugs left and right should rule it out.
 

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Discussion Starter · #18 ·
So I think it all adds up now...left the already swapped coils in place, exchanged the plugs, pulled the right plug cap and she died. Plugs are fine.



Looking at my riding notes from Saturday the temperature gauge never quite got to its normal middle spot...only 1/3 of the way on the dial. Temperature right cylinder was much hotter than usual, left was cooler.



No fuel to left cylinder. now I can't wait to get home from work tomorrow and tear into my carbs and find out what sort of crap is in there and what is happening internally.



Will keep you guys updated and thanks for everyone's help on this one. Will save me a lot of money.



Its funny how we like to go to the hardest bits first such as coils, CDI, Stator, etc...and in this case I think it has come down to fuel delivery. Though it can be argued that if I did not confirm that all other components were working or tested to be OK...it would not have been so easy to determine the fuel issue.



Night all...this guy's beat.
 

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Now, the only part of the ignition system that can still be considered suspect is the CDI box.




There is an old mechanics maxim that says that 90% of carb problems are in the distributor.




I'd swap in a known good unit if possible to rule this out but it is beginning to seem the problem really is the carbs.



I suppose just for starters I'd be opening the carb drains to check that fuel is in fact making it to the left float bowl.



If it is I guess you're going to have to get even more intimate with that left carb.
 

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Discussion Starter · #20 ·
Now, the only part of the ignition system that can still be considered suspect is the CDI box.




There is an old mechanics maxim that says that 90% of carb problems are in the distributor.




I'd swap in a known good unit if possible to rule this out but it is beginning to seem the problem really is the carbs.



I suppose just for starters I'd be opening the carb drains to check that fuel is in fact making it to the left float bowl.



If it is I guess you're going to have to get even more intimate with that left carb.


Quick question for you...

since I have no spare CDI, and though nearly all signs point to the fuel deivery, I did do the resistance checks on the CDI and all came back Nominal and well within the acceptable ranges. Granted the CDI was checked cold, any reason how or why it could possibly still be the CDI and NOT fuel delivery?



Thanks for all your help on this one btw!
 
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