carbs again what should I do???

[Duster]

79 SX11 special. I've replaced the intake boots, cleaned and overhauled the carbs to factory, new filter bench sync the carbs so now it runs great. But #2#3#4 are rich, way rich at low rpm and maybe some at high. #1 looks great. Turning down the idle adj. causes stumbling on excellaration. Now the questions:

Should I; sync the carbs running and fix the problem?
Adjust the needle clip on #2,3,4..higher. XXX
Replace the pilot jet and main jet to a smaller one on
#2,3,4 ?? If so where do i find one.
Could floats be to high on #2,3,4
or Clean the plugs every 60 miles. XX

and What is normal cyclinder compression

None of my ideas go along with anything I've read so far. It doesn't make sence to mix jets to reduce fuel..

Hot in Texas. Duster Guy

[Snow]

definately check the float levels right off. Don't go changing jets to fix a problem somewhere else, you'll just be adding to your headache. Try cleaning the pressed-in main Air jets with carb cleaner (you might take out the pilots and mains beforehand though, maybe even emulsion tubes) and use compressed air to dry. Be careful not to use the air on floats.

[Bob Falter]

<<Should I; sync the carbs running and fix the problem?>>

I agree with Snow, check the float levels first. Then, what do you mean by sync the carbs running? If you only synced the carbs with the wire method, yes, you should sync the carbs with the motor running. The wire method was a waste of time when I did me 79. When I did it I thought that the carbs where way off because I had to turn some adjustment a long way. Then it never ran very good so I sync them the way Yamaha says to do it. I ended up moving all those adjust back to about where they were before. I know that this means one of my carbs (can’t remember which) has the butterfly running a lot further open than the rest (a lot being a couple of degrees). But it runs great and the plugs look good (light brown).

[Duster]

Thanks. I checked the float level again and it's about a 1/4 inch from the top. sync. the carbs. while running and still have too rich on #2,3,4. Should I lower the level a little more and see if that helps?
Duster.

[jchigbee]

I would suggest checking out these two web sites http://www.motorcyclecarbs.com/ and http://www.factorypro.com//tech/carbtun.html

[Bob Falter]

I assume, since you said the level was about a ¼” from the top, that you are checking this level with a clear hose attached to the bottom of the carb float bowl. How did you do that on your 79? I wanted to set mine that way but the 79 carbs don’t have a connection for the hose. On my 79 I had to checked the level by turning the carb upside down, with the float bowl off, and measuring from the float bowl gasket surface up to the bottom of the float. This measurement should be 1.012 +/- 0.04 inches (25.7 +/- 1.0 mm) per Yamaha.

Another thought, maybe there is something wrong with your air cleaner box, or exhaust, that is restricting air, in or out, of 2, 3, and 4? Or a vacuum leak into #1?

[Duster]

Thanks for the info.. I have got to try lowering fuel level on the three carbs. Bob: My carb. drains have a #8 short bolt in the bottom with just enough lip on them to place a large clear hose on the drain. But the hose will not stay on easy. You can use a 1/4 inch plastic L that conects hoses. Place the smallest hose you can on one end with about 1/8" sticking out. Screw this into the bottom of the float bowl then place the longer clear hose on carfully. I think it was 1/4" L ?? I found one made of plastic that I was able to shorten the ends for more room..

Duster

[Bob Falter]

Duster,

Looked at my carbs, think I know what you mean. Not much of a lip there but I think I will give it a try. Thanks for the info.

[Geezer]

Check the vacuum diaphragms on the carb slides. If there are holes in them you will have these problems. The damaged spots usually look a little worn but not worn through but they can still leak. He comes the disgusting part; you have to suck on the damaged part to see if you can get air through it.

The carb slides are a weak point and very expensive to replace.

Geezer