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Discussion Starter · #1 ·
I am beyond frustrated with this motor...

Ever since I installed the GL650 motor into my cx500 frame, I've had an issue that seems to be progressively getting worse. I am led to believe its an issue with the left cylinder, but I will get to that in a bit...

Specs:
GL650 motor, 175psi on each cylinder when last checked a few months back
Murrays Carbs
Rae-san ignition, stock ignition
DC3-1 ignition coils
DR8EA plugs
Brass rod mod
Converted to manual chain tensioner with low mileage chain from the pulled cx500 motor

While riding the bike, especially on the highway, the bike sounded normal, but I could feel a subtle surging as I maintained constant throttle. This progressively got worse to the point the bike would stutter once you started getting around 5500rpm, and kept getting worse till about 7500rpm. If you went WOT, the bike would generally power through the stuttering, though thats not how I usually ride haha...

I had the carbs sent to murray where he cleaned them, synced them, and sent them back. No change.

I started diagnosing the ignition system with Ray. We found huge amounts of interference on the signal lines using my oscilloscope, which we thought was from the stator. However, it turns out I had a failing spark plug that was causing all the noise. Put new DR8EA copper plugs in, and all seemed better...for about a day. The stuttering came right back like it was turned back on per se.

Not knowing if it was truly an ignition issue, I cobbled the stock ignition back together using the power supply from Rays system, cx500 TI modules, and the GL650 mechanical bits.....Nope. Issue is not ignition related.

Setting the bike on the center stand and holding the throttle around 6k-7k, it keeps "coughing" / popping out the exhaust pipe, with a small puff of black smoke following out the pipe, but only on the left side. This kinda leads me to believe that I either have a burned valve, or maybe an issue with the cam?

The stuttering, while its trying to push past it, it sounds like something is trying to "enable" in the engine, if that makes any sense. Once said thing "enables" the bike feels like it picks up a decent amount of power.

I've attached a short 2 minute clip of me riding the bike and holding it at the point where it stutters.

At this point, I'm willing to check ANYTHING. I have this feeling that I may have to drop the engine, but if all I need to do is pull a head, I'd be ecstatic.

 

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I might have asked you this before in a previous thread about this same issue but just in case I didn’t, have you checked the resistance of your spark plug caps after doing the brass rod mod. My personal experience with these spark plug caps when they get corroded is that they seem impossible to get cleaned enough to function properly. I bought two new one from DSS earlier this year and just wish I would’ve done it sooner.
 

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Discussion Starter · #3 ·
I might have asked you this before in a previous thread about this same issue but just in case I didn’t, have you checked the resistance of your spark plug caps after doing the brass rod mod. My personal experience with these spark plug caps when they get corroded is that they seem impossible to get cleaned enough to function properly. I bought two new one from DSS earlier this year and just wish I would’ve done it sooner.
No, though the stuttering was never an issue with the cx500 motor. I had the brass rods installed with the cx500 motor for years with no issue. I'll give them a check tomorrow though.
 

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with the cx500 motor -were you running the DC3s or CDI coils ?
the left fires after the right - crosstalk from the right firing - triggering into the left hence shows up much more than the left firing triggering into the right due to the much larger gap - ie 280 degrees vs 80.

The DC3's are still common between the two test cases - but also as mentioned the plug caps can be at issue too. especially given that faulty / plug that was in there.

Rayman
 

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To my amateur mechanic’s ear that sure sounds like an ignition issue. I have neither a scope or the knowledge to interpret one, but I would expect your scope would show an anomaly during misfiring that would narrow your suspect list. I believe Ray’s later gear has an RPM limiter feature, if yours has that function could it be over zealous? Additionally, have you tried a SECOND set of new plugs? Though rare, a bad new plug is not unheard of. When it finally gets sorted the satisfaction will quickly eclipse the frustration, in my experience.
 

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we did check rev limit and lots of other stuff - as that was my first theory -
The issue is its now running the stock GL650 ignition setup ie mechanical advacner / pulsers and standard TAI boxes - and still doing the same thing -
hence the only ignition points of commonality are the coils, plug caps, leads and plugs .

Cheers
Rayman
 

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Discussion Starter · #7 ·
with the cx500 motor -were you running the DC3s or CDI coils ?
the left fires after the right - crosstalk from the right firing - triggering into the left hence shows up much more than the left firing triggering into the right due to the much larger gap - ie 280 degrees vs 80.

The DC3's are still common between the two test cases - but also as mentioned the plug caps can be at issue too. especially given that faulty / plug that was in there.

Rayman
I was running cdi coils as I dont think the cdi and TAI coils are compatible with one another.

If I were to try different coils, all I have to use right now are old car coils. I assume they would work as they also use the +12v / ground trigger...

To eliminate the possibility of crosstalk, should I unbolt the DC3's from the frame? Currently they are bolted to the factory location, with the use of small 90* brackets I made.
 

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I would think on the TAI system of the stock GL a TAI coil would be the correct choice? Not the CDI coils? Sorry if I’m muddying the water with my limited info. I’m trying to learn from this exercise, as I’m sure many others are.
 
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Discussion Starter · #9 ·
I would think on the TAI system of the stock GL a TAI coil would be the correct choice? Not the CDI coils? Sorry if I’m muddying the water with my limited info. I’m trying to learn from this exercise, as I’m sure many others are.
you are correct. cdi coils are not compatible with tai bikes.
 

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Ok couple of things to think about here. The cdi coils mount using steel brackets on either side of the spine bur it sort of forms a magnetic loop. So the coils are coupled magnetically.
On the 650 the coils are physically closer together but are not magnetically coupled as the mounting brackets that hold the coils are aluminium. They are also mounted in opposite directions.

So things to try. Reverse wires on one coil. Reverse direction of one coil.
Reduce magnetic coupling by using some non magnetic spacers between coils and the mounting tubes and brass or stainless bolts between the two.
Quick test would be to unbolt and separate/ rest o the heads and see if things change.

Rayman
 

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Discussion Starter · #11 ·
Ok couple of things to think about here. The cdi coils mount using steel brackets on either side of the spine bur it sort of forms a magnetic loop. So the coils are coupled magnetically.
On the 650 the coils are physically closer together but are not magnetically coupled as the mounting brackets that hold the coils are aluminium. They are also mounted in opposite directions.

So things to try. Reverse wires on one coil. Reverse direction of one coil.
Reduce magnetic coupling by using some non magnetic spacers between coils and the mounting tubes and brass or stainless bolts between the two.
Quick test would be to unbolt and separate/ rest o the heads and see if things change.

Rayman
Do the DC3-1 coils have a polarity? I know the dual posts ones dont, but I'm pretty sure the single post coils do. Will it hurt them to reverse the polarity?
 

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It depends on how they are wound and if they have a diode in them.
Given they show a polarity.. make sure it's correct and turn one around or better magnetically separate to see if a change.

Rayman
 

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Discussion Starter · #14 ·
View attachment 215125
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It depends on how they are wound and if they have a diode in them.
Given they show a polarity.. make sure it's correct and turn one around or better magnetically separate to see if a change.

Rayman
Just out of curiosity, wouldnt the brass rivets be enough to magnetically separate them from the frame?

Looking at the stock cx650c bracket, the coil leads face the same way, not opposite.

Also, if this is a weird magnetic issue, why are the cdi coils not affected by being bolted to the frame, whereas the ti ones are?

Rectangle Cylinder Font Gas Automotive lighting

Bicycle part Jewellery Personal protective equipment Body jewelry Auto part
 

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Discussion Starter · #15 ·
Small update. Decided to go the extra mile and eliminate the DC3-1 coils from the equation and connected two car coils to the bike.

Aaaaaand.... No change. Nothing.

Checked the spark plug caps and the brass rods looked a tiny bit tarnished, but nothing crazy. Cleaned them up and put them back in.

Any thing else I should check?
 

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the brass rivets will give a small "air gap" but magnetism has that whole action at a distance thing - so while its a start, it could be better.
Ive seen the coils mounted in opposing directions on brackets - but they were different brackets from memory with the coils closer together - might be from 500 Eu / GL or something -

re the CDI versus TI - the CDI coil acts as a transformer - there is a direct drive primary to secondary - not much magnetic field is built up as the currents are relatively low and fast.
The TAI setup stores energy in the magnetic field - hence the dwell time for the current to build up to about 4-5Amps - this field is much stronger and under the wrong circumstances can loop through both coils rather than jsut one - then spark occurs when its collapsed and "sucked back in" -( not correct but works for the purposes of visualization). Obviously if both coils see the collapsing of the field - both can generate spark.

we are in the twilight zone on this one so it pays to rule out the weird edge cases / theories as well as the normal ones. - which you've now done -
so I'd say we are looking at a valve or similar issue.

these things are so frustrating.
Rayman
 

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Small update. Decided to go the extra mile and eliminate the DC3-1 coils from the equation and connected two car coils to the bike.

Aaaaaand.... No change. Nothing.

Checked the spark plug caps and the brass rods looked a tiny bit tarnished, but nothing crazy. Cleaned them up and put them back in.

Any thing else I should check?
Cleaning and visually inspecting the spark plug caps is fine but did you ever check the resistance with a meter?
 

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Discussion Starter · #18 ·
Cleaning and visually inspecting the spark plug caps is fine but did you ever check the resistance with a meter?
Left is 7.3ohm, right is 3.8ohm. I'd expect them to be closer to 0, so lemme see if I can clean them up a bit more.

Also, I know Murray sets his carbs a bit rich, but damn is this rich 😅 this is with like 1 mile on the new plugs
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Sooty plugs can be a rich mixture - or it can be a weak spark prompting poor combustion.

Have you done a test for spark strength?
 

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Discussion Starter · #20 ·
Sooty plugs can be a rich mixture - or it can be a weak spark prompting poor combustion.

Have you done a test for spark strength?
I know this isnt the proper way of checking... but I pulled a boot off to see if itd arc from the boot to ground, but instead the old toyota ignition coil had a fat blue arc from the tower, jumped an inch or so to ground. The other coil Im using is a performance pertronix flamethrower coil. I can only imagine the size of the spark from that...

Another update.

After checking the caps, I went ahead and cleaned the brass with a bit of sandpaper, and sprayed some deoxit down into the cap in case there was some corrosion. Put them back together and...huh, one of the boots is now reading 1.5megaohm, and was increasing the longer I held the leads on. Said boot was also on the left cylinder that I thought had a bad spark plug. Cool, did I just find an intermittent issue?

Since I dont have spare cx500 boots laying around, I grabbed a pair of known good non-resistor toyota boots and installed them, still using the car coils.

Aaaaaaand. Nope. Still stutters.

What Im still trying to understand is, when it clears the stuttering, the sound of the engine changes drastically, and it picks up a bunch of power until redline. Almost like the bike has a really crappy version of vtec...

As of now, the entire ignition system has been changed. plugs, boots, wires, coils, modules, etc.

I pulled the valve covers off, pulled the plugs and cranked the engine over to watch the valve movement. Granted, the bike idles fine, and the starter spins slower than idle, but everything looked fine, and moved smoothly.

Not sure what to check next.
 
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