Right side spark plug black cant adjust idle

Thanks everyone for your feedback on the tight 1st mainshaft gear I took the shaft and gear to a machine shop and they took about 2 thou off the shaft splines and it fit like a glove. I have another question On my restored 850 interstate I have been unable to adjust the idle on the right side carb. The carbs are brand new Amals. The spark plug on the right side is consistently black the left side is a perfect light brown and adjusts fine. There is no affect when adjusting the air jet Every now and then when idling and I give it gas I get a little puff of smoke out the right side. It is almost like oil is running down the valve guide and contaminating the plug but the plug is not wet. The motor was completely rebuilt but I did not install the valves myself. Any ideas. Thx Drummer99

I have a similar problem on my 750.

Initially a lot of smoke on start up (white, right cyl.). When I cured the wetsumping this stopped. The right plug would foul and stop sparking, bike would run as a single, (when wetsumping).

The carbs are old Amals with new slides etc. Bike idles at 800rpm, pulls cleanly from idle, carbs are balanced both visual and tactile means as well as on a manometer. However the right plug remains black, but does not foul.

I changed the right valve seal using the old rope trick and a home made tool.

My analysis is that (mentioned in another post), the cylinder head pressurises from the downstroke of the pistons, oil is blown past a leaky valve stem or valve guide. Mixes with the fuel mixture and produces a rich mixture, oil displaces air in the burn, hence black plug.

When the bike was wetsumping the cylinder head was flooded with oil on start up, (watched this happen with covers off). If I take the plugs out and spin the motor I can hear a leaky type noise. If I take intake cover off, it stops. Thumb over the retaining nut hole, I feel the pressure in the cyl head and hear the noise again (just on the right side).

Some point need to take the head off and investigate. Weather too nice! Couple of other clues, oil consumption and oil stains in the right inlet.

Have you checked to float height as it may be wrong even on new Amals. I know as i have had trouble myself with float hitting carb body almost an black traces of smoke in exhaust an airscrew having no effect.

Guys thx for the input I will check the float height easiest thing to do You say you have the bike idling at 800 RPM I cannot keep it idling unless I get up to around 1200 or so What is the rope trick Did you change the valve seal with the head still on the bike? Thx Drummer99

Drummer99 said:

Guys thx for the input I will check the float height easiest thing to do You say you have the bike idling at 800 RPM I cannot keep it idling unless I get up to around 1200 or so What is the rope trick Did you change the valve seal with the head still on the bike? Thx Drummer99

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Rope trick or how to replace valve seals without removing the head: valve-seal-replacing-t7362-15.html#p329799

The Burlen premiers are know to typically come with fabrication debris in them, it can easily clog one of your low speed jets and/or a drilled passage, and you will not get adjustable idle mixture due to the blockage.