What could this be?

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What could this be?

Postby Tims500 » Fri Dec 20, 2013 6:09 pm

My 1980 CX500 Delux right cylinder won't fire consistently when first starting cold. The colder it is, the worse it is. While trouble shooting I pulled the plug wire while running and it didn't change. However, when putting it back on it started to fire. If I hold the wire away from the top of the plug it starts firing! If I hold it out it arks and fires, cylinder warms up and then its OK. Coil? Yes, I've changed the plug. I do have a multi-tester but don't know what it should read. I don't have a compression tester, what should be the range for compression at 35K miles?

Tim...
USA 1980 CX500 Deluxe
Tims500
 
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Re: What could this be?

Postby Gman » Sat Dec 21, 2013 12:08 am

Swap the plug caps with each other.If the problem swaps then it's the plug caps.
Check the Electrical section on here for the Spark plug resistor cleaning if they are that type.I use NGK resistor plugs with,"None" resistor plug caps from Wemoto,

http://www.wemoto.com/bikes/honda/cx_500_a/79-80/

or even off eBay.They are worth renewing anyway as they are most likely 30+ years old and only waiting to fail.
If this doesn't get it there are other causes like the carbs but try the easy stuff 1st.
General info here,

http://www.pdsrecording.site90.com/cxgl500/Plugs.htm

:)
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Re: What could this be?

Postby Tims500 » Fri Dec 27, 2013 3:07 am

I did get a new cap from Ebay. BTW the new one has a much larger post that goes in the wire so you can go back without replacing the wire. I noticed that sometimes it falters at higher RPM's. Its really odd. I'll swap out plugs (again) with a different brand, don't remember what's in there now. Will be reading tonight before I head to the parts store.

Thank's and have a Happy New Year!

Tim...
USA 1980 CX500 Deluxe
Tims500
 
Posts: 10
Joined: Wed Feb 06, 2013 4:05 am

Re: What could this be?

Postby Gman » Fri Dec 27, 2013 12:58 pm

Another cause can be a damaged or missing,"Spoiler".

This is the air-dam on top of the engine made of rubber and metal.It deflects the heat away from the coils,that are very sensitive to heat.This would not cause problems when cold but can cause problems once the engine has warmed up.I've repaired one of mine with some thick Car mat rubber cut to suit and self tappers added to the orginal rubber to make up for the bits that had degraded and fell off.

Just something to think about and check :)
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