Tuning Carburetors CO Carbon Monoxide Levels

Paul Sutton

Paul Sutton

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I am interested in knowing if Yamaha ever recommended a Carbon Monoxide range for tuning the XS650. Perhaps someone out there has experience tuning their older motorcycle's carburetors using a Carbon Monoxide analyzer?

Thank you.
 
Yamaha actually was the first OEM, IIRC, that actually required dealers to have an EGA; circa '79 or so. CO & HC; can't remember the specs...

Edit: CO was a % (maybe 10), HC was ppm (remember goal was low as possible)
 
Thank you jpdevol. It would be nice to see the spec for the XS650SH which was set quite lean. I wonder if 1.5% is too low?
 
There was a manual...

I recall that we actually removed the blind plugs and richened the factory fuel screw setting to not only improve performance (warm-up, idle, etc) but reduce the HC's - CO was increased from factory setting (and the book)
 
Thank you Mike. After searching for a coup[le of hours I see a trend of 3 - 5% which fits your Gunson recommendation. I have also seen higher values were max torque is required at the expense of fuel economy. I shall measure my Virago carburetors today to see where they are set, but it would be nice to see a Yamaha document to see just what they set their more modern XS650s at where they were set lean for EPA reasons.
 
jpdevol,

Great video...:hump:...!!! At 8:16 they state that most Yamaha 4-Cycle engines will have a Carbon Monoxide specification of 3% when running at idle. I rechecked the Virago today after a 20 mile ride and got Rear Cylinder = 3.0% and Front Cylinder = 3.2% so things are remaining stable.

Thank you for taking the time to find this technical video from Yamaha.
 
Yep, when I was in High School and working at the local Yamaha Shop (late 70's/early80's), we received a new fangled, very large blue rolling electronic cart. I remember my Service Manager being very intrigued as he was getting familiar with it.

It was our new exhaust gas analyzer that took forever to warm up and get ready to use....had probes for the exhaust pipes, etc.

I remember watching him test and tweak several different problem children bikes on it when they wouldnt quite run right due to the new uber lean factory settings for the US market....several 650's included.
 

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