Carbon fouled plugs (1982 XJ1100J)

[jeffnew29]

Hi Guys. New owner,"new bike"...XJ1OOJ Maxim.My plugs are fouled with carbon (totally black even on threads) after about rwo weeks.I knew it would run rich at Denver elevation but was surprised at the fouling. Are the carbs the same on the XJ VS XS series?Should I rebuild them and rejet? Is there any easy fix adjustment? Runs terrible

[jeffnew29]

Engine Knock?

Wondering if my clatter in the upper engine is not valves but engine knock from carbon buildup? Sort of sounds like a diesel and becomes worse as engine heats up.

[bikerphil]

Is the air filter plugged up? You can run some Seafoam in the gas to clean things up in the engine and carbs. Also if you haven't already, unscrew the spark plug caps and trim 1/4" off of each wire and screw them back on. Corrosion at the ends can cause weak spark and misfiring. It's best to start with simple stuff first before digging in too deep. Upper end noise could be a loose cam chain. If you adjust this make sure you read the manual carefully before proceeding.

[jeffnew29]

So the spark plugs cap just screws off? Will xhexk it out. Thanks

[petejw]

What have you got your mixture screws set at?
maybe screwing them in half turn or so might help.

[XJOK2PLAY]

Jeffnew29,

Carbs are set up & jetted differently on an XJ compared to other XS's.

All kinds of info here... do a thread search obout carbs... should find charts, etc.

Floats should set up at 22 mm w/o gasket.

Synching and pilot adjustments are critical, and will solve an entire list of carb problems.

What octane gas are you running up there?
Does it sound like pinging, timing chain noise, or knocking?

Stock air box or pods?

[jeffnew29]

stock air box,valves were adjusted, premium fuel, sort of a diesel/clanging sound that gets progressively worse after warmup...did try a fuel additive (Lucas)

[jeffnew29]

read out of sync carbs can cause engine noises?

Thanks XJOK2PLAY

[Yahman]

It's best to set the floats according to the book, with a tube connected to the float bowl and held up to the side of the carb. The carbs must be level front to back and side to side. It's more accurate because even if the floats are all set to the same height, the fuel level can be different.

You will also need a special tool to sync the carbs on an XJ, they have the YICS system that needs to be blocked off before you adjust the carbs in any way.

Larry

[tarzan]

I just talked to a friend of mine that I sold my '80 XS11 Special to earlier in the summer.He lives in Denver and the bike is completely stock including jets.
He says it runs excellent.
So I would think you have a carb issue.IE incorrect fuel ratio,restricted air jets or some other malady.