Now that I have my carbs apart...Pilot Jet Question

[Metallicat]

Well, I decided that letting gas sit in my tank and carbs for 4 months is probably not the best idea. So I drained my gas tank, started it last night and ran it until it died, and then today I disconnected the carbs from the intake flange and drained the floats. I actually removed the float bowls to get all of the gas out and then took out the pilot jets just to see what everyone is talking about as far as how small the jet passages are. Yup, they are small!

So...I read on another topic that there is a pilot jet adjustment screw on the bottom of the carb towards the engine side.

If there is such a screw, I sure can't find it on my sled.

I thought that since I have access to the carbs now I would check all of the adjustments - is there really a pilot jet screw on these sleds????

BTW - it isn't such a bad job to get to the pilots and drain the floats. Will probably do this in the spring for summer storage to get all of the fuel out of the carbs. There is a drain plug on the bottom of the carbs that works pretty good.

 

[Metallicat]

And...second question.

What is the purpose of the carb slides? The butterflies open up with the throttle but the slides are spring loaded and I assume they open based upon intake pressure levels.

What is their purpose? I have almost no knowledge about these type of carbs.

Thanks All!

 

[kinger]

Yes there is a pilot screw its on the float bowls you removed to look at the jets. Its a screw with a spring on it.

What do you mean carb slides? There are theg throttle plates and the choke is that what your thinking? I'm not a guru on carbs these are my first that I have had expericnce on.

 

[Metallicat]

The screw is ON the bowls? You mean on the exterior? Not on my sled. The only screw on the float bowl itself is the drain plug. Nothing else. Nada. See the pic below. The screw you see is the drain plug. The protrusion next to it is just part of the float bowl casting and is plugged. Sorry for the crappy image - but you get the idea.

On the intake side of the carb, in front of the butterfly valve, is a vertical slide valve which has a spring on top of it to control the opening speed. It is the valve that some people are using the Holtzman green slide springs on. It doesn't open with the throttle nor the choke, must be pressure actuated.

Yes there is a pilot screw its on the float bowls you removed to look at the jets. Its a screw with a spring on it.

What do you mean carb slides? There are theg throttle plates and the choke is that what your thinking? I'm not a guru on carbs these are my first that I have had expericnce on.

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[Metallicat]

Ok, think I just answered my own question by doing a little more searching on this site. The adjustment screw is accessed by removing the float bowl. From what I read earlier, it sounded like the screw was on the bottom exterior of the bowl.

 

[kinger]

Damn if my camera worked I would take a pict of mine the air screw is on the outside of the bowl. Maybe I'm confused between a air screw and a fuel screw. You can tell I just pull them apart blow them clean and install LOL

I'm not sure what the slides do either then! I should really sit down and study these things. Its just never a problem now that its dialed in.

 

[Metallicat]

Ok, then I think the carbs are different on the 2008 Vectors. There are definitely no air / fuel screws on the outside of the carb. There is a hole on the back side of the float bowl that is plugged with an amber resin / silicon type of substance. There are also 2 pencil-sized holes behind the float bowl on the engine side, but one is filled with an aluminum plug and the other with a brass plug. It appears that Yamaha has eliminated external pilot / carb adjustments on this sled. I am not going to pull the float bowls off again just to see if I have the internal screw as shown in my last pic...well maybe tomorrow if I feel ambitious.

The slides are strange, mostly because I am accustomed to 2 stroke carbs. They appear to function via vacuum pressure now that I look at them more closely. For me, there are so many mysteries about this sled. I don't understand why the oil reservoir is vented to the airbox, and why the airbox is vented to the cylinder head, and why there are slidey things in the carbs.

But it sure is fun to take everything apart and get to know the internals a little better.

 

[Mighty]

The slides regulate the amount of air drawn into the engine and do actuate by vacuum. Which is why you can get a little better throttle response by installing lighter slide springs. The carbs on your 2 strokes vari the air flow by a cable.
The venting is to evacuate the crank case pressure.

 

[Metallicat]

Thanks Mighty!

The slides regulate the amount of air drawn into the engine and do actuate by vacuum. Which is why you can get a little better throttle response by installing lighter slide springs. The carbs on your 2 strokes vari the air flow by a cable.
The venting is to evacuate the crank case pressure.

 

[Metallicat]

Thanks Mighty!

The slides regulate the amount of air drawn into the engine and do actuate by vacuum. Which is why you can get a little better throttle response by installing lighter slide springs. The carbs on your 2 strokes vari the air flow by a cable.
The venting is to evacuate the crank case pressure.

 

[RSV]

Damn if my camera worked I would take a pict of mine the air screw is on the outside of the bowl. Maybe I'm confused between a air screw and a fuel screw. You can tell I just pull them apart blow them clean and install LOL

Remember the RX-1 has Mikunis, while the RS has Keihin carbs... I don't know the difference between them, but this might be one of them?

 

[aVenture]

The slides regulate the amount of air drawn into the engine and do actuate by vacuum

The butterfly do regulate the amount of air drawn into the cylinder & is a mechanicaly linked device. The slide regulate the velocity of that air (that is its speed, density) by choking carb intake just before fuel metering. Doing this, keep a constant ventury across the jets & remove a nonlinearity known to the VM & TM device. For the same CFM in a pipe, small diameter is higher speed that large one. This is what the slide does... vary the aperture size to keep constant air speed even if the CFM changes. Yes it is actuated by a vacuum port... but also to a lesser amount by the air rushing to its front.

I cannot speculate for the effect of different springs.... but i know that the ears of the slides can get dirty & appear sticky. This can be seen during carb equalization. I had to clean it once at 12000 K. I used WD40 which i removed immediately... ??? worked.

 

[Srxspec]

Metallicat, you're not going crazy. The screw adjustment has an aluminum plug over it beginning in the model year 2006 if I remember correctly. The springs help in throttle response and acceleration!

 

[SRX Maine]

This is a break down for an 08 RS Venture and is exactly like an 07 Vector.
#5 is listed as pilot screw set.
Being located inside the bowl make no sence to me at all.
How would you adjust it when it's all together?
It must be under one of those external plugs and set by the factory then plugged off for some kind of governmental rules or emission control.
I know all the small products we sell at my shop come in that way
and we cannot tamper with those. (by law)
Say if a carb on a redmax trimmer need to be richer for idle, we are supposed to send the carb back to the factory or try a new carb

 

[kinger]

My bad I have worked on my RX carbs and our 05 vector carbs they were the same. Sorry for the confusion