Cylinder 1 getting hot.

[DEmily]

Hey all,

I have benn working on this 79 xs1100F through the winter. I just got it out to fire it up. Idles fine , kind of stumbles when you excelerate. After letting it idel for a while it began to idel eratically. At that point I noticed the exhaust pipe for # 1 was turning brown at the head. The other cylinders looked fine. Am I looking at a lean mix on this cylinder? I had to drill out the pilot holes as the previous owner, ( my brother) broke the pilot screws off in the carbs. Any ideas?

[steelcat]

What do your plugs look like? How are the intake boots?

[DEmily]

Steelcat,

I had to wait for it to cool. Just took them out. The number 1 is nothing but carbon. The rest look good. As for the boots, they have external cracking, but seemed solid inside.

[steelcat]

Ussually if you are running too hot / too lean the plug will be white ash. I'd still check the boots with wd40 or starting fluid. Then check the sycn. of the carbs. You may also be having a sticking float.

[DEmily]

I'll check the boots as you suggested. But I am really puzzled that the cyl. is running so hot yet it appears to be rich or floading.

[TopCatGr58]

Too hot??

Someone correct me if I'm wrong, but I thought too hot a cylinder produced a "BLUE" colored pipe, not a brown? And like was mentioned, the plug should be white, not carboned black!! And with a hesitation, that sounds more like too rich, where as lean I thought didn't stutter, but would just run out of pull near top end? I ran mine lean and had great response and pull up to 8.5K.

With having to drill out the Pilot screw holes, did you drill them ALL out so that they are all even, or just the #1?? Last year I had an occasional sticking float/needle valve and one cylinder would get flooded, had horrible low end response, had to give it full throttle to get it to respond, then it was like a light switch, on or off, no inbetween! Good luck.
T.C.

[DEmily]

Topcat,

When I said brown on the exhaust, what I should have said was almost a brass/bluish color. The exhaust are brandnew MAC 4/2. The number one is the only pipe that turned and it only ran for about 15 to 20 minutes before it turned colors. As for the pilots, I had to drill them all.

[ratbyk]

Pipe Color

I would suggest that the number one pipe is coloring over the others because #1 carb is running too rich. Could be dirt on needle and seat or float level to high. Not all of the fuel is burning in the cylinder. Some of the unburned hydrocarbons are then burning inside the header pipe after leaving the cylinder and finding some oxygen to allow combustion to complete.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

[DEmily]

ratbyk,

No that makes sense. It's too bad I had to toast my new pipes.
I'll start on that carb first thing. When I did the cards I used a micrometer to set the floats, and the seats and needles are new. Can any other situation cause the floading on that cylinder?

[ratbyk]

Needles & Seats

A good trick to use before you put the bowls back on the carbs is to turn the carbs upside down. Hook a piece of fuel line to the fuel inlet "t's" and blow in the hose. If the needle and seat is working you should not be able to blow. If you can move air then pull the needle back out and examine really closely. Maybe even use a magnifying glas. If unable to find anything (marks,dirt,hair whatever) then I have lapped the needle lightly into the seat using valve grinding/lapping compound. I have had good luck with this. In fact I have not bought needles and seats for anything for years. I have just reseated them.
Ken/Sooke

[DEmily]

ratbyk,

Thats a great tip. I keep that in mind when I examine the float settings. Thanks for you assistance.

If anyone else has any helpful tips or guidance for diagnosing or correcting this problem, I would be greatful.

[skids]

It is possible that the bike blued the pipe at midrange or high rpm speeds and then carboned the plug while idling or whe the choke is on. These carbs have to tuned for mains, midrange (not sure how to do the non adjustable main needles for 80 and 81's) and pilot circuit, in that order.

[DEmily]

OK, I may have found something in the previous posting. I have individual air breather and have the lines that ran ro the old air box plugged. On a posting from last year, Skid stated the following:



The plugged air box nipples were for later carbs that incorporated the breather into an extra hole around the perimeter in the inlet bell of the carbs. Plugging the breather hoses on the older carbs will make the mains slurp fuel with the engine vacuum!

Is this true for the 79 F?

[dfrooney]

IIRC:

"older carbs" refer to '78 and '79.
"newer carbs" refers to '80 and up

so in your case, if they were plugged, you would see a rich condition.

P.S. - I am not a carb expert...you may want to wait for someone to confirm this before you do anything.

[skids]

I remember a fellow that had a hell of a time with carbs flooding and he sent them to the carb god, Rick Jemmison. Rick finally determined that the breather line had a plug in it causing all of the problems. The 78 and 79 carbs had those hoses.