TOPIC: One Plug Black

Greetings All,

I'm a long time member, but short on posts. Today my concern is with my '73 850 Interstate.
I bought it in 1974 and have clocked about 12,000 miles of easy riding. The ignition system is fired by Boyer. I pulled the plugs and found the right side shows a light, even coating of black carbon deposit. The left plug is exceptionally clean with only a very slight tinge of black evenly on all surfaces (center porcelain is off white).

This plug condition has always been typical since I've owned the machine. I've used a few various plug types over the decades. I did search our site for prior discussion but with no luck. I've replaced both exhaust pipes several years ago and recall the right side with a deeper blue color than the left side. Currently the pipes are quite even showing a medium straw coloration.

I'm simply looking for opinions on what I might do to make both sides fire correctly. My first guess is the throttle needle setting on the carb slide....right vs left. It starts good and runs good but still concerned.

Thanks for any help,
Dave

Engine carb and ignition is one of my strong points. The full diagnosis is fairly straight forward.. Air -fuel- compression- ignition.
simple compression and leak down test will give data in this area. Great if there is no mechanical defects found.
Boyer Ei should give even timing between right and left side.
Carbs & cables are a strong possibility for unequal running. Just the cables off a bit makes one side run cool and that can lead to a black plug on the lazy side.
Old plastic floats running on E10 gas could be dying causing uneven jetting.(fuel level.
A good excuse to run it on the brake dyno and get an EGT readout. (exhaust gas temperature) the cool side will be the black one.
Give a call if you want a chat 978-626-1378
cheers
Dave

Hi Dave....

I selected "quick reply" as this time of day I'm in from the farm and not at my best for thinking & speaking.
I do want to thank you for your prompt reply. I will call and feel very fortunate to have your attention.

Give me your best time to chat and I'll be sure to call.

Thanks again,
Dave

I'm up usually quite early between 4 and 5 most of the time but always by 6 and drinking coffee. I am working on research and maintenance issues all day and even tonight I am only quitting now and putting the tools inside.Checking emails before going upstairs to do the dishes .
I don't use a cell phone so call when you want but if you email me first, when you will call, approx I'll listen up for the shop phone.t.
Dave

Good Morning,

We're on the same clock....4-5 am with coffee....no cell here either. You said Email you first so I "quick replied" as I don't see your email address in the forum. I can call from here on my land line around 6:30 if that works for you.

Thanks again for your reply.

Dave

Up and at um
computer on and e-mail check
going for the 2nd cup
Trash day here.... put out by the road.