1150 low rpm not on all 4 cyl

[not a biker]

i think i have a burnt valve or a dead low speed circut in one carb. last summer i checked the valve adj and not one valve was out of specks. it went from a slight rough idle to now it feels like it is on 3 cyl until about 1,500 rpm . i hope the 26 year old carbs that have never been touched are the problem. hard to believe a pampered 1150 with only 15,000 miles on it has a burnt valve. a guess a compressinn test will tell. what is your guess.

[salty_monk]

Probably a blocked pilot circuit is my guess.... Have you tried putting a lot of seafoam in a tank of gas & riding it 100 miles or so?

Dan

[chef1366]

Check the spark plugs first and the connection on the boots.

[Dave8338]

HMMMMM... Bill may have the right answer in the plugs/wires/caps.
I have had similar problems on a sled and it turned out to be the plug wire itself.

The fact that the carbs have never been off leads me to believe they have been cared for.

OH...how old is the fuel in the bike?

[blowerbike]

burnt valves don't happen.
fresh plugs and then clean the carbs correctly if its still a triple.

[trippivot]

not a biker
not a mechanic either

no, odds are that valve is not burned.

old oil, old spark plugs, and best old gas causing plugged carburetor fuel circuits

none of which "pampered" bikes ever have in them.

[mike_of_bbg]

Carb sync? Maybe one butterfly isn't open enough until throttle applied...

[Nessism]

Probably a blocked pilot circuit is my guess.... Have you tried putting a lot of seafoam in a tank of gas & riding it 100 miles or so?

Dan

This is my guess as well but I suggest cleaning the carbs off the bike, replacing the old/hard 25 year old O-rings, and performing a vacuum sync. Pay me now or pay me later. Maintenance is good.

[not a biker]

not a biker
not a mechanic either

no, odds are that valve is not burned.

old oil, old spark plugs, and best old gas causing plugged carburetor fuel circuits

none of which "pampered" bikes ever have in them.

well yes i am a mechanic, was a buick tune up mechanic in 1975, opened my own shop in 1991.
installed new spark plugs at the same time i checked the the valve adj. one had a little darker color than the others , but not black or wet. my first plan is to remove the spark plugs, test the comp. if good i will remove the pilot jet adj screw on the cyl that the spark plug is colored. carb spray that circut. re install adj screw and see what happens. if it still runs poorly under 1,500 rpm i will go threw the carbs. i doubt it is a bad spark plug wire becouse above 1,500 rpm all is good. thank you for your input

[not a biker]

i spun the engine over without the choke on to listen to the engine turning over without running. it does not sound like it has a low cylinder.GOOD. i started it up and kept touching the exhaust pipes, they all get warm equally.GOOD. i backed out the pilot jet screws 1/2 turn and it runs better in the garage. i will road test it as soon as it stops raining.
the pilot screws are about2 1/4 turns out now. they were all at 1 1/2 to 1 3/4 before. no speck for pilot jet adj in my factory repair manual. i guess cuzz it is suposed to stay sealed

[Steve]

i spun the engine over without the choke on to listen to the engine turning over without running. it does not sound like it has a low cylinder.

Not sure how a "low cylinder" sounds, so I'll just address the first part.
How would the "choke" change the way then engine sounds when cranking? I know you said you are a mechanic, so please realize that the "choke" on our bikes does not operate like the choke on a car. On a car, there is a plate that turns to cover the inlet of the carb, choking it down, forcing the extra vacuum below it to draw more fuel (and less air) through the jets to richen up the mixture. On our bikes, activating the "choke" moves a plunger that uncovers a separate fuel and air circuit that bypasses the throttle butterfly. It relies on the closed throttle for the vacuum to draw the fuel up from the float bowl to mix with the air, then into the cylinder.

the pilot screws are about2 1/4 turns out now. they were all at 1 1/2 to 1 3/4 before. no speck for pilot jet adj in my factory repair manual. i guess cuzz it is suposed to stay sealed

You are right, they were meant to be sealed at the factory and stay that way, too bad it wasn't the proper setting for good running. I am going to suggest that you turn the screws out even further. Most of us will suggest that after cleaning the carbs, you start somewhere between 2.5 and 3 turns out as a starting point, then adjusting the mixture once the bike is warm.

Oh, also keep in mind that not all the screws are going to end up at the same setting. I forget the exect numbers right now, but when I got "Freebie" up and running, I seem to remember that two carbs were set to about 2.5 turns, one at 2 and one at about 1.5. I have it recorded at home, in my service log, so I can reference it next time I have to work on the bike.

.

[not a biker]

my stock 1150 is so cold blooded it will not start cold unless the choke lever is on. being lazy i just wanted to spin the engine over without it starting. to listen to the sound of one cyl low on compression [ yes you can do this] it cranks very evenly . this is not as good as a real compression test, but it is a fast way to get a idea if you need to do a compression test. at this point i think it is the carb on one cylinder or maybe a coil and wire. just maybe the pilot adj will do the trick. it has been raining for 4 days here in so cal and i am getting cabin fever.