Bogging down

[rneal55555]

Just had to do the pick up coil wires my self one if mine broke clean off so the bike just quit. During trouble shooting my my yamaha shop manual says to check the pick up coils by measuring the resustance by unplugging the 4 wire plug on the TCI box you measure between the 2 wires with the same base color (white to white and yellow to yellow) they sould read 720 ohms. One of mine was open but if your checking for breaking wire You could put on the meter and suck on the vacum line to the advance to move it and watch for a change in resistance.

[Ken Talbot]

Nastydude - did you also remember to run a small wire and fluid and air through the pressed-in brass jet down the tube at the rear of the float bowl?


I'm not sure exactly which circuit this one is, but it is a critical fuel supply path at some part of the response curve. Being low down in the float bowl, it is easy for it to get plugged, and in your eagerness to get at the more fun part of the carbs, it is easy to overlook.

[pgg]

That sneaky passage connects to the 3rd air intake hole, the pilot circuits and the float valve too. To me it seems to be an air pressure equalizer. Can the 'carb gurus' tell me if I'm right?

[skids]

I do not claim to be any guru, but I think that is where the brass tube extends to draw fuel for the "choke". Follow the lines and you will see that it leads to the enrichening area. Work the choke back and forth when spraying up this tube. (rubber can be messed-up with carb spray)

Originally posted by pgg
That sneaky passage connects to the 3rd air intake hole, the pilot circuits and the float valve too. To me it seems to be an air pressure equalizer. Can the 'carb gurus' tell me if I'm right?

[pgg]

Yep - it's the choke supply alright. The diaphram draws it, the 3rd air hole lets it flow. Anyone got an X-ray machine?

[Nastydude]

yes i did and yes it is for the choke the when air is pushed through the brass pipe which goes into this hole in the rim of the float bowl (pictured) the choke valves will move.

[Winterhawk]

Good pic Ken.
I usually use one strand of wire off of an old cable. It's a really small hole and you have to work at it for sometimes 30min till you get contact cleaner to spray out of it. Also spray contact cleaner thru the mixture holes and look for the exits. Then the pilot jet hole with it removed and look for spray to come out in the clover type holes in front of the throttle plates. I always use steel wool in the float seats and spin it in there real good to remove traces of varnish. After the diaphroms are installed make sure they are not out of the groove a little. Easy to do so I always take the air hose hold it back about 6 inches spary air lightly in the vacuum opening and look for the slides to move the way they should. That with good manifolds would probably solve 50% of the problems on the forum maybe.

[pgg]

Hey Hawk, what's going on? Theres no link to merriams.

smartass kiwi.

[Winterhawk]

Sorry about that, but here is a link to my kids site instead.....LOL

Chads World

[Nastydude]

Some thing I may have over looked! Is there a carb genius out there thant might know what the two vacuume lines going to the breather do. in other words on a bike that runs good if you block or restrict flow through one or both of the lines what would be the effect on the engines operation.

[sidecarKev]

I think you are talking about the tubes that are to vent the bowls to atmosphere. Prevents vapor lock in the bowls. I think they were only on the 78 and 79 models. Are you talking about the tubes that go from the carbs to the airbox? I used a later years airbox and had to drill my own holes in the nipples.

Maybe your talking about something else. If so just ignore me.

[randy]

I'm with Kev on this one. Those vent tubes on 79 and earlier carbs provide atmospheric pressure for the float bowls. If you plug them, you'll flood the carbs. If you don't have the original airbox, put filters on the tubes so they can breath somewhat clean air.

Randy

[skids]

They are only on the 78 and 79 carbs. They break up the siphoning effect, allowing a truer float level. The newer carbs have the breathers located at the inlet bell perimeter and do the same thing through tiny pin holes located above the fuel chamber (if I remember correctly).

Originally posted by Nastydude
Some thing I may have over looked! Is there a carb genius out there thant might know what the two vacuume lines going to the breather do. in other words on a bike that runs good if you block or restrict flow through one or both of the lines what would be the effect on the engines operation.

[skids]

BTW, I noticed that someone recommended that the floats be set at 26mm, but I noticed that the original post was for a bike with 110's across the board. Something is inconsistent there. Older carb float heights and newer carb mains...

[sidecarKev]

I think it was me. I'm stuck in 1979.