1983 carb trouble?

[RonE]

I bought an 83 with 26K miles on it back in May. It ran great for the first 1,000 miles then started missing and gas milage dropped from 38-40 to 23-26. Local dealer messed with it some but I wouldn't let them experiment on it, based on previous experience(!) with them. Ran a bunch of yamaha carb cleaner in it and it ran worse, ran some Sea Foam and it ran worse yet. Based on the exhaust I surmised it was running way to rich so I took the top off the air cleaner box and it runs better than ever! (with a lot of intake noise) It is of course running lean at times and hesitates a bit because of it but gas mileage is back and it doesn't miss & cutout.

 

Now, I'm sure I've isolated the issue but I've no idea what to do next. Any suggestions would be appreciated.

[Yammer Dan]

What does the filter look like?

[RonE]

Filter looks clean, previous owner says he changed it "a while back", it seems to ride okay in the box with the lid off.

[Yammer Dan]

Filter looks clean, previous owner says he changed it "a while back", it seems to ride okay in the box with the lid off.

 

 

Most of these things don't like to run with the Lid off.

[RonE]

That's not what I'd prefer, but with the lid on it won't hardly run at all.

[Yammer Dan]

Something not right there. Are the pilot jets still plugged?

[Venturous Randy]

My first suggestion with you running a bunch of stuff thru your carbs is to put in new sparkplugs and check the caps and wires. The caps have a resistor in them that can get corroded and cause all kinds of problems.

RandyA

[mbrood]

The CV carbs NEED to see a specific restriction to air intake which the opening in the airbox lid provides... you can pull the filter and put the airbox lid back on and recheck... if there's a difference you would do well to toss the air filter.

[mrich12000]

:smash2:Check the carb diaphrams. You have a bad float in one of the carbs. Check the vacum readings on each carb, although you cannot fix this problem without a carb kit..y 2 pence..

[RonE]

Thanks to all of you for your suggestions, here's where I am now:

 

Yammer, I don't know much about carburation to know what action to take about your response "Are the pilot jets still plugged? "

 

Randya, I've changed the spark plugs & checked the wires, all cylinders seem to have good spark, and as I said with the air box top off it runs great

 

Mbrood, last night I tried running with the filter out & the lid back on, and it's awful, no decernable difference with the filter in or out with the lid on, I guess that means the filter isn't the problem.

 

Mrich12000, that sounds reasonable to my uneducated mind, I assume I'd need to get the "kit" from my dealer(?). My assumption is that it is getting way to much gas to run with the normal air intake.

 

Additional info: I noticed while messing with it last night that the outside of the #1 boot only has some gas, or something wet on it. Also, the carb drain hose on #1 is cracked & won't stay in place, I assume this isn't a performance issue tho.

 

Thanks to all of you!

 

RonE

[Yammer Dan]

Factory put plugs over Pilot Jet adjustment screws. There is a thread here on how to drill them out and remove and set Pilot screws. Might make a difference. Maybe one of these screws has decided to back out of there??

[dingy]

Pull the air cleaner lid off and remove the air filter.

 

Start the bike.

 

Look down into the top of the carb bank and rev the engine.

 

Do all 4 air sliders move at about the same amount? These will retract into body as engine is reved.

 

Gary

[MikesBike]

Are you sure the carbs are all the way down into their sockets? A wet carb is also the same symptom I had... Take off the filter box and loosen the socket clamps, give the tops of the carbs a good hard push, you should feel one or more carbs "pop" into its socket. This can't be done with the air box on as you can't apply enough force to make them seat.

[Yammer Dan]

Are you sure the carbs are all the way down into their sockets? A wet carb is also the same symptom I had... Take off the filter box and loosen the socket clamps, give the tops of the carbs a good hard push, you should feel one or more carbs "pop" into its socket. This can't be done with the air box on as you can't apply enough force to make them seat.

 

 

Good point to check if the carbs have been off. You never know.

[mbrood]

Sounds to me like they opened up the fuel idle mixture jet (CCW) and now you are too rich from 1k to about 2.5K rpm, which is why taking the airbox cover off (more air) makes her run better. These should be 2.25 to 2.5 turns BACK from a gentle seat...

 

The "brass sleeves" are found on unmolested carbs and have to be drilled out to get to the fuel idle mixture jets.

http://www.bergall.org/temp/venture/1stcarbs3.jpg

[jasonm.]

Pilot jets plugged usually cause LEAN issues. You are suddenly running rich. You have likely one or more bad float needles,Or floats. But not bad enough to flood the carb. I had one bad needle and bad float and my mileage went down 20%. These needles are rubber. They don't last forever. Especially with ethanol fuels. And SeaFoam is not a cure all...