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Discussion Starter #1
hey everyone,

i am experiencing an issue with my 1981 CX500 Deluxe dying shortly after firing it up. i'll attempt to lay out what has happened up to this point.

i was on my way back from the gas station a month or so ago after filling up my tires to ride around a bit; this was my first time starting it since winter, not sure that this has any bearing. on my way up a small hill through town the bike began to slow down on me even while twisting the throttle. the RPMs kept dipping down until the bike stalled. being a very short ride from home i proceeded to start it up to get it back ASAP. the bike died again, in the same manner, right before i arrived home. this time it would not start at all. the engine felt much hotter than usual and to my recollection the temperature gauge was not registering (still fully to the left). i sat and waited for about 15 minutes and the bike came back to life. when i got it back home the right side of the engine sounded louder than the usual valve "sewing machine" sound.

i didn't have much time to analyze the origin of the sound but i did take off the valve cover and nothing seemed to be loose or out of the ordinary. i left it sit until i had a little time today to check it out and do some reading. so today i started it up and got it to idle but it would die just like before - i wasn't expecting a miracle here, only stating that i started it up again to see if i noticed anything i missed last time. the louder than usual "sewing machine" sound was still there on the right side and the exhaust smelled very rich. i couldn't get it to run long enough to identify if the rich smell was only emanating from the right side or not. during my reading i had seen that someone, with perhaps a similar issue, checked the oil and there was a lot of metallic bits in it. this was not the case for me, as i could tell.

i'm just looking for ideas as to what this issue may be. i do not have the means to work on the motorcycle where i am at and usually work on it with my grandfather who is 2.5 hours away. he suggested that i reach out on the forum to see what the community may have to say as he has had success in the past on here with his GL500.

beyond suggestions as to what the issue may be i am hoping that some of you are in the northeast ohio area, akron/kent/cleveland, and have ideas as to some reputable shops around me that can pin-point/fix the problem.

best
bryan

i know more information is usually needed on these posts. so if i am not being descriptive enough or am missing an explanation of something, let me know. i am sure more can be coaxed out of me.

TL;DR:
- engine loses power/decreases in RPMs even when throttle is engaged
- temp gauge MAY not be working (wasn't able to run it long enough to see)
- louder than usual ticking/"sewing machine" sound coming from right side of engine
- exhaust smells rich (not sure if it is exclusively the right side)
 

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It sounds like a fuel problem to me. Either too much or not enough fuel.
The gassy smell makes me thing it is running rich on one side.
At this point check the oil and make sure the engine is not full of gasoline.
 
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Remember too, that the exhaust system with the Hbox will not give an accurate way to tell what cylinder is affected.
 

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Discussion Starter #4
@old okie, i'll look into the oil situation and see if it smells like gasoline now.

@ramprat06, thanks for the heads up. i would not have given that a thought. currently, the h box on my cx bit the dust and the two sides are separated.

should i adjust the pilot screw if it is running rich?

keep any other suggestions coming please.
 

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Do you know if the carb drains are clear?

You may have a high float level allowing fuel into the cylinder.

You can check your level by putting a piece of 4 mm clear line on the carb drain and opening the drain. Hold the clear line up the side of the carb and it will show you the fuel level which should be on, or a mm or so below the joint between bowl and carb body.
 

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Discussion Starter #6
@cxphreak, the drains were clear the last time i checked. i'll give the clear tubing level check a go.

the bike did take a tumble over winter as my roommate leaned against it. so perhaps the float is stuck.

the bike also emitted a few popping noises from the exhaust, i figure backfire. this could be attributed to a carb issue as well, yes?
 

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Someone help us on this but I think the pilot screw only affects the idle system.
Rich fuel mixture will not be cured by adjusting that screw. Bike should run
with the screw about 2 and 1/2 turns out. Tweak the screw to smooth out the idle.
 

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Discussion Starter #8
Okay. Developments.

I opened the right carb bowl into a clear tube. Once I got the bubbles out it sat much lower than the joint line. I started it in an attempt to get more fuel into the tube to see if it would level but it didn't. I closed the drain and checked the left side, it appeared level. During this time the motorcycle wouldn't idle. I had to spray started fluid for it to run several seconds each time.

Once I sealed the left carb drain I attempted to start it again. This time the bike maintained idle but at 2k RPM. Adjusting the idle screw made no difference, left or right did nothing. After turning the motorcycle off I adjusted the flat head that is at the center of the idle screw figuring I twisted it to far one way or another. When starting the bike this time the RPMs began to climb and not stop before I turned it off. I twisted the idle screw counter clockwise a bit and started the bike. This time it was back at 2k and wouldn't move when adjusting the idle screw, again.

I'm going to look at the owners manual to see how the mechanics of the idle screw work since I may be doing something wrong here as the only result I got was it climbing and I have no clue why...yet.

Beyond this the right side exhaust feels weaker than the right. This is something that I've noticed when I first started the bike up after winter. So my grandpa and I are thinking it may be within the ignition system. The first test was sticking the screw driver shaft into the plug wire and hovering it above the valve cover for the left and right wires. The spark coming from the lines seems equivalent. I'm going to check the plugs themselves next but I'll need to purchase an extension for my ratchet to reach the plug.

TL;DR
- Good news the bike is idling now though I haven't a clue what changed other than draining both bowls. (I also gave the right bowl a few knocks out of aggregation)
- the RPMs won't go below 2k even when adjusting the idle screw
- the right side exhaust feels weaker than the left

Thanks to everyone who has chimed in so far. I appreciate the advice.
 

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Discussion Starter #9
Apologies. Reading the manual now. It was the throttle stop screw that I was adjusting CCW and CW with no results other than using a flat head to twist the screw in the middle of it in which case it began to climb in RPMs.
 

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you might want to check that the air admission hole in the gas tank cap is open. Doesnt take much vaccuum in the tank to stop gas flow.
 

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Discussion Starter #11
I just drained the right carb again into the tube. It's level with the joint now.

I think it's getting a constant stream of fuel because it will idle steady now.

I killed the battery with all the fiddling. It's on the trickle charger now to get it ready for me troubleshooting.
 

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Discussion Starter #12
Okay. Hopefully the original respondents and whomever else is out there can keep this ball rolling.

- The motorcycle now runs consistently.
- The temperature gauge is confirmed functional and when the bike ran for ~10 minutes it stayed steady.
- The plugs were swapped from left>right and right>left. That did not make the right side exhaust perk up.
- Both plugs were very black.
- It seems as though the ride side exhaust is inconsistent and has a stutter compared to the left side.
- The tach will not go below 2k even when the throttle screw is turned completely clockwise.
- The throttle cable is not stuck. When twisted is snaps back to its resting state.
- The choke is not stuck either.

It seems that the pilot screw may want a slight twist out to achieve the proper idle. That is my very novice analysis of the idling situation.

The plugs seem to be suffering from dry fouling but the exhaust does not smell rich anymore. Perhaps it is still running rich but not as extreme as when I began this troubleshooting.

IMG_3932.JPG

Walk around the bike

Bike shut down and start up

Curious bit of smoke coming from exhaust joint that went away after a minute or two of running
 

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1981 CX500 Deluxe idling too high

hey everyone,

i am having difficulty getting my bike to idle below 2k RPM. adjusting the throttle screw completely clockwise does not drop it further than 2k RPM.

the right side exhaust is also weaker than the left. the spark plug wires were checked and they had good spark and the spark plugs were swapped from one side to another with no difference.

please allow me to link you to my original post that may be best suited for the Technical Help and not the regional section. it already has some contributions that i have followed through on.

**Mod Edit--removed link after merging the two threads.**

thanks!
bryan
 

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Apologies. Reading the manual now. It was the throttle stop screw that I was adjusting CCW and CW with no results other than using a flat head to twist the screw in the middle of it in which case it began to climb in RPMs.
If the throttle stop screw has no effect on idle speed, check your throttle cable adjustment for the correct amount of free play.

Move the handle bars fully side to side does the idle speed change?

Also check that the choke cable is installed correctly and that when the choke knob is pushed down the choke is fully opened and the fast idle cam is disengaged.
 

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Discussion Starter #17
I was doing some reading on the forum about that issue last night. But I wasn't necessarily following where that apparatus is located. Is this it, with the screw, sitting below the throttle? If so, it seems to clack onto that nudger when it snaps back to a "resting" state. Is this the screw people were speaking about only twisting a touch to readjust this, that a little goes a long way for it?
 

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Discussion Starter #18
Alright. It seems the issue was the barrel of the choke not being seated completely in its hole. So it wasn't fully disengaged. The tach now responds completely to the throttle adjustment screw.

The rich smell of the exhaust is still here though. So next is adjust the air/fuel of the carbs?

Thanks for causing me to look closer than what I had been. Silly misses.
 

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Discussion Starter #19
The right side exhaust is still weaker than the left and inconsistent too. May try to run it to a local shop to diagnose tomorrow. Give it your best guesses too. Then I can look into them if I have the ability with my limited number of hand tools.
 
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