Honda cx500c 1982 running problems

[rekievit]

Looking for a little help with this,
My friend purchased a cx 500c, the guy he bought it from jump started it and ran fine. So he put in a new battery, filled the tank, added some seafoam, reconnected the manifolds (they were off for some reason) put in a new air filter and we started working on it.
We ran into some problems though, the bike started to backfire and didn't sound quite right. We sprayed some water on the headers and the right header was not hot at all, maybe warm to the touch and the other got hot very fast.
We checked for spark and both had it, we swapped plugs to no effect. And replaced the resistors in the caps (they are known to be problematic).
Here is where it is now. With the bike running, pulling the cap on the right cylinder has no effect on the engine. Pulling the left cap kills the engine. When starting, if the choke is all the way out and the left cap is pulled the bike will start and run on the right cylinder only for a short time, it will begin to rev (never putting choke back in) and then die.

We took off the carbs for now and they look clean, but we will take them apart to look some more.
If the right cylinder is only firing when the choke is out does that mean its not getting enough gas through that specific carb?
Any ideas?

[randy]

If the right cylinder is only firing when the choke is out does that mean its not getting enough gas through that specific carb?


Pretty good guess.....pilot circuits are probably clogged from sitting. Give the carbs a thorough cleaning and synching and you should be OK.

[fredintoon]

Looking for a little help with this,
My friend purchased a cx 500c, the guy he bought it from jump started it and ran fine. So he put in a new battery, filled the tank, added some seafoam, reconnected the manifolds (they were off for some reason) put in a new air filter and we started working on it. - - -

Hi Rekievit,
um, which manifolds were disconnected that allowed the seller to start the bike in the first place?

[rekievit]

Ha... I meant the carb boots to the airbox
It would be pretty hard to run without the manifolds

Thanks randy for the advice well check it out

Anyone else got any suggestions? Not that I doubt randy, but were just trying to get as many ideas as possible.

[boyat68]

It may be that all you need to do is re-synch the carbs as the PO may have retarded the idle screw on one carb more than the other while removing the carbs? boots??? Then again it might be as Randy said a cleaning may be in order as fuel could be blocked into the carb. On my 400 I have a synch screw that adjust the right carb to follow the left carbs throttle adjust screw.

[tarzan]

You already have the smart idea.If you have spark at both cylinders,and only one cyl fires,I would say that probably it is the carb that runs the dead cyl.And Randy is pretty savy with these bikes from what Ive seen here on XS11 so I would go with that advise.

[rekievit]

thanks guys,
since the carbs are off the bike now we will check for any blockage, then sync when replacing
hopefully all goes well and we find something,

[rekievit]

Update

Well...we got problems.
We cleaned the carbs really well. They looked clean initially but even so all rubber was removed, they were soaked over night, and reassembled.
I then bench synced them using a bread tie wire.
This is what happened.
We mounted them on the bike (left the boots off because we wanted to spray some more carb cleaner), the bike fired up with the choke off, then put it back in, but idled at 3000, and the throttle adjustment knob had no effect in either direction. On top of that the right cylinder would still not fire. After removing the left cylinder cap the bike would start using the right cylinder only if the choke we all the way out and only for a short time.
As another test we switched the coils around. This time the bike still ran on only the left cylinder but the idle was now perfect at 1100 and the throttle adjuster know worked correctly.
Whats the deal?

I know the carbs are clean, im thinking a timing issue or something else. This is above my knowledge and have no idea. Please help.

[tarzan]

Well there are a couple things you can do.
1-Run a compression test and find out how that is.
2-If moving the coils made a difference but didnt move the dead cylinder,maybe you have a bad wire or connection that works intermitantly.
3.While it is running spray a little fuel ,wd-40 ,or something flamable into the cylinder that isnt firing to see if it will fire.If it does ,your carb on that cylinder is still restricted.
4-remove the timing cover on the left side and check for a short in a pickup coil wire

[randy]

The CX500 is a 2-cylinder. Your ignition is obviously working 'cause it will run on only the right cylinder, but only with help from the choke. Your pilot circuit in that carb is still plugged.

[rekievit]

The CX500 is a 2-cylinder. Your ignition is obviously working 'cause it will run on only the right cylinder, but only with help from the choke. Your pilot circuit in that carb is still plugged.

I agree with you in that all the symptoms point to that and that is the simplest solution, but short of running a wire through the circuit i don't have any ideas on how to get it unplugged. We also blew air through the passageways and none seemed obviously blocked. Any ideas on how to clean this out.
What we did - soaked in vinegar overnight, blew out with carb cleaner, blew out with air.

tarzan - i don't have a compression tester but maybe should pick one up, the cylinder will work when the choke is out though so it has some compression. Ill also double check the electrical connections but, unless i'm mistaken, i don't think this bike has the pick up coils that are problematic like the xs11's.

question: If that cylinder runs with the choke out, would it be possible to compensate by screwing out the idle screw? Or would that not be a big enough adjustment? Obviously fixing the problem would be better but I would be willing to try a quick fix like this.

[rekievit]

Another Update

Some more testing results for your consideration:
Sprayed some combustible stuff into the right (problem) carb and that cylinder fired up the revs.
Sprayed some around the manifold and that also increased the revs, so we took it apart and was missing an oring in between the engine and the metal mount on the manifold. A trip to the hardware store fixed that.
Good news, now the bike can run on the right cylinder only without the choke, but not strongly.
When both plugs are connected the left cylinder still does all the work and the left pipe gets much hotter than the right. There is a backfiring like sound which i think is the right cylinder trying to fire or firing intermittently.
Messing with the idle screws and the throttle plate sync screw between the two didn't really do anything.
So the carbs are back off for another cleaning.
I'll let you know what happens but feel free to chime in with any ideas, or something i may have overlooked.

[randy]

While you have the carbs off, change your plugs. They may be fouled from all the choked running.

[cywelchjr]

Some more testing results for your consideration:
Sprayed some combustible stuff into the right (problem) carb and that cylinder fired up the revs.
Sprayed some around the manifold and that also increased the revs, so we took it apart and was missing an oring in between the engine and the metal mount on the manifold. A trip to the hardware store fixed that.
Good news, now the bike can run on the right cylinder only without the choke, but not strongly.
When both plugs are connected the left cylinder still does all the work and the left pipe gets much hotter than the right. There is a backfiring like sound which i think is the right cylinder trying to fire or firing intermittently.
Messing with the idle screws and the throttle plate sync screw between the two didn't really do anything.
So the carbs are back off for another cleaning.
I'll let you know what happens but feel free to chime in with any ideas, or something i may have overlooked.

Double check that you don't have any vacuum leaks, as that will cause what sounds like a lean condition. Make sure that when you spray into the idle jet that it comes out by the butterfly valve, if it doesn't then the idle circuit is probably still partially plugged.

[rekievit]

cleaning results

Thanks Randy, will do.
Cy - Thanks for the ideas. After fitting the o-ring we sprayed some more around the manifolds with no resultant rpm climb so i think at least there shouldn't be any more major air leaks. I cleaned again too with this result.

They should be clean now. What I did was fill a rubber ear syringe with carb cleaner from an aerosol can. I then placed it up where the idle screw sits and blasted it. There was solution spraying from all three tiny holes under the butterfly valve.
I then placed the ear syringe into where the idle jet sits and blasted it again, solution came out where the air cutoff valve is. Plugging that with my finger ans squeezing again caused solution to come out of the three holes I previously mentioned and the place where the idle screw sits.
Idle circuit should be good yes?

Thanks guys, I appreciate it.