Author Topic: CX500C problems (Read 6961 times)

mmtsquid · « **on:** August 15, 2007, 12:11:20 PM »

Just picked up a CX500C for my brother in law - after replacing the CDI unit, it started right up.
but, it backfires like crazy and has NO POWER.
I pulled the carbs, and they were pretty clean, jets clear, etc.
Plugs are very sooty.

Any ideas?

KB02 · « **Reply #1 on:** August 15, 2007, 01:07:16 PM »

Timing and Air filter come to mind.

Pull the air filter out and start it up. See if it runs better or worse.

Not sure if timing is adjustable on those. If it's CDI, probably not. But it does sound like an option if it is.

mlinder · « **Reply #2 on:** August 15, 2007, 03:11:13 PM »

What plugs are you running?

333 · « **Reply #3 on:** August 15, 2007, 05:29:22 PM »

You might want to double check the CDI wireing, including the pulsers. The symptoms you describe might be caused by the pulsers being reversed.

turtle · « **Reply #4 on:** August 15, 2007, 06:00:48 PM »

I've got one too. I'm not sure about your problems but you may like to post in the "Ask the Gurus" section on here:
http://australiancx.asn.au/forum/index.php.

mmtsquid · « **Reply #5 on:** August 16, 2007, 06:26:16 AM »

I pulled the air filter, and it ran worse.
I will try the other ideas this weekend - it has to be something simple!

mlinder · « **Reply #6 on:** August 16, 2007, 12:09:57 PM »

Quote from: mlinder on August 15, 2007, 03:11:13 PM

What plugs are you running?

well?

mmtsquid · « **Reply #7 on:** August 16, 2007, 01:27:58 PM »

Oh - the plugs are champion ra8hc.
I'm not sure if they are equivalent to D8EA or not..........

333 · « **Reply #8 on:** August 16, 2007, 05:36:07 PM »

Get the NGKs. The only bike that Champions work well in are old Triumphs.

bryanj · « **Reply #9 on:** August 17, 2007, 04:17:26 AM »

Put a NEW air filter in it, The CX was the only honda i ever came accross that needed regular replacement, also get fresh gas into the carbs as even a few days old goes off enough to give a bad start and the carbs are real pernikety on being clean

mlinder · « **Reply #10 on:** August 17, 2007, 11:19:15 AM »

The reason I asked is because, I think, the ra8hc is a resistor plug. You do NOT want a resistor plug.
A resistor plug will cause the issues you are having.
Replace with D8EA and see if your problem clears up.

The ra8hc is equivalent too the D7EV plug, which was replaced with the 5686 which is a resistor plug.
Again, resistor plugs will cause the kind of behavior you are describing, as there is too much resistance for a good spark.

mlinder · « **Reply #11 on:** August 17, 2007, 11:24:33 AM »

After more research, yes, the plugs you are running ar resistor spark plugs. Wrong kind.
http://www.championsparkplugs.com/more_info.asp?AAIA=&pid=4422

mmtsquid · « **Reply #12 on:** August 17, 2007, 11:48:19 AM »

God bless you all - I'll give it a shot tonight and let you know!

LoopsAndLogic · « **Reply #13 on:** August 20, 2007, 09:05:41 AM »

Sorry to hijack your thread, but is running NGK-R plugs in the SOHC-4's not recommend too, or is this just not recommended for CDI equipped bikes??

Thanks

LL

mlinder · « **Reply #14 on:** August 20, 2007, 09:25:01 AM »

Quote from: LoopsAndLogic on August 20, 2007, 09:05:41 AM

Sorry to hijack your thread, but is running NGK-R plugs in the SOHC-4's not recommend too, or is this just not recommended for CDI equipped bikes??

Thanks

LL

SOHC4's do not run resistor plugs.

TwoTired · « **Reply #15 on:** August 21, 2007, 03:15:43 PM »

Quote from: LoopsAndLogic on August 20, 2007, 09:05:41 AM

Sorry to hijack your thread, but is running NGK-R plugs in the SOHC-4's not recommend too, or is this just not recommended for CDI equipped bikes??

Thanks

LL

SOHC4s came with resistors on the plug caps instead of the spark plugs. If you want to run resistor plugs replace the plug caps with zero resistor types. The spark voltage capability of the stock SOHC4 is rather low by today's standards. Adding extra resistance to the ignition path requires more voltage development in the coil to overcome the spark spark gap. When the plugs are new, this is seldom an issue. But, plugs require more voltage to fire as they age, and approach the upper limit on the coil capability. Adding inline resistance exacerbates the issue and sooner spark plug replacement.

Note that some resistance is a good thing as it broadens the spark duration at the gap and reduces coil heating. But, it is analogous to air in your tires, too much-bad, too little-bad, just right- good.

Cheers,

mlinder · « **Reply #16 on:** August 21, 2007, 03:26:12 PM »

Quote from: mmtsquid on August 17, 2007, 11:48:19 AM

God bless you all - I'll give it a shot tonight and let you know!

So... how'd it go?

LoopsAndLogic · « **Reply #17 on:** August 23, 2007, 03:13:52 PM »

Get rid of the NGK-R's. Got it!!

I hope it all works out for you with your CX. I use to own one. Great bike!!

LL

mmtsquid · « **Reply #18 on:** August 27, 2007, 05:09:27 AM »

Well, it made a LITTLE bit of difference.........
Now, left cylinder runs great, right cylinder cuts in occasionally - but when its running, it REALLY pulls!
I was out of town for a week, so I'll play more this coming weekend......

upperlake04 · « **Reply #19 on:** August 28, 2007, 09:54:06 PM »

Some SOHCs, for sure the 1978 750F3s for the Canadian market, apparently do use resistor plugs. Here's a link to the NGK website which explains the symbol code stamped on the plugs and page 43 from the 78F Owners Manual.
http://www.ngksparkplugs.com/techinfo/spark_plugs/partnumberkey.pdf

TwoTired · « **Reply #20 on:** August 29, 2007, 06:23:39 PM »

So the question is...
Do the Canadian F3s have resistor plug caps?

upperlake04 · « **Reply #21 on:** August 29, 2007, 08:24:07 PM »

I don't know. Maybe you can tell me. #1 cap is marked Nichiwa VDO5F, as are the rest, and if I am using the meter correctly has 6.7ohms resistance.

TwoTired · « **Reply #22 on:** August 29, 2007, 11:29:59 PM »

Was your F3 first sold in Canada?

Your measurements indicate a resistor plug cap. But, the 750 values are usually 5K +/- 10%.

I wonder if the Canadian government had a stipulation for distribution into Canada? Is there, was there, a spark plug Mfg in Canada during the 70s? Was RFI a political football for that era?

I don't know of a technical reason why Canada would need extra resistance in the HT leads (Besides RFI). You'll have to change plugs sooner, unless you have a high energy spark system.

Cheers,

upperlake04 · « **Reply #23 on:** August 30, 2007, 10:54:21 AM »

TT - this F3s history is unknown to me. Starting in 1977, all new vehicles sold here were required to have the metric speedometer scale dominant. That would be a clue, but this one had mismatched replacement gauges when I bought it.
The caps measure 5.3, 6.1, 4.4 and 4.8 ohms on the 200K scale.
A quick look at a business guide shows NGK to have a factory in Canada now which does not export but as for the RFI situation in the 70's, I have no idea. A reasonable theory though.
From what you've written, it appears a switch to non-resistor plugs at the next change might be slightly beneficial.

mmtsquid · « **Reply #24 on:** September 04, 2007, 05:31:02 AM »

OK< now I'm stumped - The bike woll only run on one cylinder!
The right fires right up, but left only fires occasionally - both sides are getting good spark, carbs are very clean.
What else could it be?

??

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Author Topic: CX500C problems (Read 6961 times)

upperlake04

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