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Discussion Starter #1
I realised I post it in the wrong place to begin with. re posted here...

Hello, My name is Meir. from Holland. im new to the forum and was hoping to get some advice on an issue with my cx650e, 1983. I purchased this bike a few months back in a bad shape, but she was running. I customised 2 bikes already and am accumulating experience as I go. I built a R100RT '79 and a Shadow VT1100c '92. I fell in love with the CX models. when I got the CX650 it wasn't running perfect, idle was rough, lots of noise from the monoshock, bad cold starting, worn tires, etc.
after about 300km I decided to get to work and get her ready to become a daily commuter:

that's what I did:
  • compression test, 165psi on left, 160 on the right.
  • change clutch cable, was very tight, works perfect now.
  • Oil filter, Oil,
  • removed and cleaned the gunky carbs. new jets, needles, O rings, all according to factory specs
  • accelerator pump tested and good.
  • carb synchronisation to perfection. no gap at all..
  • changed the sparks (NGK as per the specs)
  • replaced the spark plug caps (one was cracked)
  • replaced the left hand intake rubber sleeves between the carb and the head as the rubber was cracked
  • removed the air cleaner box and installed KN filter pods on the carbs.
  • ran a hose from the breather to under the swingarm, pipe is now open and breaths well.
  • removed the original air pressured mono shock and replaced it with a YSS shock that looks and behaves great.
  • installed two new Metzeler tires.
  • Overhauled the prolink, new seals, moly grease and even powder coating.
Very excited to go on a ride now, engine turns from first attempt. I take her for a spin and after 2 km I blow the right hand side head gasket.
push her back home, all frustrated and start with the next operation:

  • flush of the coolant, drain the oil
  • New head gaskets on both sides, oil control O rings
  • New thermostat (had none at all...), water pipes O rings, etc
  • cleaned the heads, did valve clearances to spec. on both sides
start the bike, she turns again from first touch. I let her warm up, check all settings. idle perfect. trying to Rev, engine stalls at about 4k rev's and won't go further for a about 2 seconds and than suddenly pick up. I try to ride, put first gear, and problem is worse. including headlight flashing as if it doesn't get enough power.

I tested the coils, they both give strong spark and both have same resistance. shortened the spark leads by 1cm on each side to expose new copper and re installed. tested the resistance of the pulser by the two yellow wires, perfect. checked ignition timing through the inspection hall for both sides and although it was spraying oil like shit I could see both sides were on time. recleaned the carbs, put them back in, still the same. checked all ground connections, all good. checked charging of the battery at acceleration and its perfect.

can somebody tell wtf is going on and what did I miss?
and apologies for the long story.

thanks, Meir
 

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You put K&N`s on but didn`t re-jet? :unsure:

Run the bike at the engine speed where the problem appears for at least 20 - 30 seconds, kill the engine and coast to a stop, remove the plugs. What do they look like?
 

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Discussion Starter #4
Sounds like a sticky automatic timing unit. You can check the advance with a timing light.

Are you sure the jets went back in the right place?

78 into the carb body. 118 into the brass emulsion tube.
hi Mark, yes, the jets went back to their correct place. twice.
 

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Discussion Starter #5
You put K&N`s on but didn`t re-jet? :unsure:

Run the bike at the engine speed where the problem appears for at least 20 - 30 seconds, kill the engine and coast to a stop, remove the plugs. What do they look like?
Hello Jah, I started with larger secondary jets #122 and thought this was the problem, went back to the original #118, same problem.
 

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Discussion Starter #7
Are the K&N pod filters blocking the vent port by the sliders?
Not at all. The KN's have a rubber boot/sleeve with no inner disturbance or groove so the ports are fully open. its only hugging the outer surface of the carb body.
I did have the idea that maybe the float bowl is emptied at 4k revs, so maybe the float needle gets stuck? but if I keep the throttle steady for a couple of seconds she will suddenly rev up and will go much higher with no interruption, so I doubt it fuel supply...or is it? im trying to exhaust all options before I go and drop the engine for the ATU...
note, she only boggs at around 4k.
when cleaning the carbs I replaced the float needles, but not the floats as they were at spec.
or should I add a shim to the jet needle to raise it a little? my spark plugs look healthy in color by the way.
 

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checked ignition timing through the inspection hall for both sides and although it was spraying oil like shit I could see both sides were on time.
Meir when checking the timing hold a tube, for example a toilet paper roll, over the port. That will cut down on the oil spray.
When you checked the timing were you using a timing light? If so you should be able to see the timing changing with engine RPM if the ATU is functioning properly.
 

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When you next get the carbs off blow into the arc-shaped port in the top of the intake side of the carb and check that the vacuum pistons are moving freely.
You can do this with a moderate jet of air from a compressor if you have one or with your mouth if not.
You should be able to hear and see the pistons rise and top-out and then thunk back down with moderate airflow.
I`d still do a plug chop at the affected engine speed/load, though. Don`t just assume your mixture is correct - investigate with actual results under actual conditions. Two sizes larger may not of been enough, and reverting back to std with pods fitted will deffo be lean.
 

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..also check for the proper operation of the vac tap - it could be fuel starvation caused by a vac tap not delivering fuel.
Hose from carb to tap OK? Hoses hooked up correctly on tap (two hoses, vac and vent)?
Remove fuel delivery hose and blow into vent hose n check for good fuel flow..
It`s a good idea to mod the vac taps to manual operation.
 

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Discussion Starter #11
ok gents, first let me thank you all for contributing here.
I know for certain my carbs are good: spark color checked, all ports of the carb were cleaned and air blown, including the pistons reacting smoothly to air blown through the intake ports. I also made sure the vacuum hose from the right hand carb is connected to where it should be on the tap and not to where the drain hose should be connected.

im using a xenon timing lamp to check timing. I did the toilet paper tube thing this morning and found out that left cylinder is advancing properly (I can see the II at the port when revving) while the right hand cylinder is not really getting there until it manages to pass the 4k...
is this a symptom of an ATU?
 

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The ATU should advance both sides the same in operation.

There is a specified air gap though between the rotor and the left and right pulse generators and differences in this from one side to the other may be an issue. Perhaps the pulse generator plate has moved?

I would recommend testing the pulse generators per the FSM - both hot and cold.

You can also check the igniters by swapping them side to side, recheck the timing and see if the fault follows.

Murray may have more for you. I don't see many of these ignition systems mainly seeing early 500s.
 

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sounding like a dodgy igniter or coil to me ....
 

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Discussion Starter #17
ok, I just swapped the ignitors and the problem remains. I also did the timing test (again), using a toilet paper carton roll. I was obviously using an external battery which is fully charged. the results are as follows: for the right hand cylinder the II marks are slightly below the notch on the body of the engine case. for the left hand they are slightly above. meaning that the two do not nicely align on both sides of the notch. the pulse generator resistance readings are per the spec tolerance. very frustrating as im not sure how accurate the marks should align as we talk about mm's here and if this is really gonna screw the mid range so much...
 

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that is pretty normal for it to be off a bit as long as they are both advancing

i would check by cleaning the spark plug caps and if the resistors are there do the brass rod mod

and check the coils for proper high tension wire connection cracks and proper resistance
 

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Discussion Starter #20
Hello Murray, thanks for jumping in. the carb slides/pistons are freely moving and reacting to the air pressure through the air intake ports. I did place two new spark caps as one of the old pair was cracked. I also exposed new copper on the leads prior to screwing them in. I did test the coils for resistance, they both measure to about 19ohm on my multimeter. the service manual says it should be between 2-3 but only if using the Sanwa or Kowa meters for accurate readings...I just have a standard (brand new) mm. a couple of days ago I took the coils assembly including leads, caps and sparks to a Honda bike dealer here. the guy told me that if they fire up and the engine is running than it should all be good. not sure if he has a deep understanding of older bikes though...is there another way to test coils?
alternatively could it be that I have fuel starvation in mid range and need to raise the jet needle a little? note, all of the issues I have are when the bike is stationary. the issues im describing are not while riding. trying to ride her its worse and I don't get too far
 
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