Reassembling Carb - adjustments question

[Guest]

I'm starting to reassemble my first carb after cleaning (Carb 1) and I'm confused about a few things. I think part of it is that I'm reading posts about non-CV carbs and also I'm confused about the names for the pieces.

Here are my carb's pieces using the labels used in the "CV Carburetor Rebuild Guide" on BassCliff's site:


1) At the beginning of the guide, it says references to the "Pilot Air Screw" is actually the "Fuel Flow Screw". Is this referring to what I have labeled as the Air Screw or the Pilot Jet?

2) For what I have labeled as Pilot Jet, does this get screwed in all the way? I can't imagine this is something you have to adjust with since it is inside the carbs but I'm not sure. I assume what I have labeled as the Air Screw is what you start out with being "3 to 3.5 turns out" from seated all the way (as this is accessible outside the carb).

3) For measuring the float height: looking at the examples I've seen, I'm supposed to measure the middle of the float (on mine this is rounded somewhat - I can't tell from the example pictures I've seen whether that's normal or not). I assume I measure from the outermost surface below the gasket to the highest point of the curved section of the float. Is this correct?


On Carb 1, this seems to be right around the 22.4mm spec. I was kind of hoping it would be way off and explain my fuel overflow but I'm only on the first carb so...

[scott]

I also forgot to ask, do what I have labeled as the Main Jet and Air Jet also get screwed in all the way?

[tkent02]

All of the jets go in all the way, seated, they don't need to be reefed down. That screw is the mixture screw, it lets in a mixture of fuel and air. This mixture ratio is determined by the air jet and the pilot jet, air through the air jet and fuel from the pilot jet get mixed in a separate chamber, then go past that mixture screw into the venturi, through two or three tiny transition ports up by the crack in the throttle when it is just barely open.

For the mixture screw, more turns out is richer, it only has any effect at idle and very small throttle openings. Start with the screw about three turns out, you will later fine tune it from there.

[scott]

All of the jets go in all the way, seated, they don't need to be reefed down. That screw is the mixture screw, it lets in a mixture of fuel and air. This mixture ratio is determined by the air jet and the pilot jet, air through the air jet and fuel from the pilot jet get mixed in a separate chamber, then go past that mixture screw into the venturi, through two or three tiny transition ports up by the crack in the throttle when it is just barely open.

For the mixture screw, more turns out is richer, it only has any effect at idle and very small throttle openings. Start with the screw about three turns out, you will later fine tune it from there.

Okay - thanks! So when referring to CV carbs: Mixture Screw = Air Screw = Pilot Air Screw = Fuel Flow Screw. Some terms are more correct than others but they're referring to the same thing.

And the adjustable items on each carb are:

• Float Height (only accessible from INSIDE carb)
• Mixture Screw
• Throttle Valve Adjustment / Synchronizing Screws (on 3 of the carbs)

Then there's the single Idle Adjust Screw for the set of carbs.

This definitely helps clear some things up for me.

[tkent02]

Okay - thanks! So when referring to CV carbs: Mixture Screw = Air Screw = Pilot Air Screw = Fuel Flow Screw. Some terms are more correct than others but they're referring to the same thing.

Mixture screw is correct... All the other names are from people who don't really know how they work.

[hampshirehog]

If you carbs are overflowing take a good look at you float needle with a magnifying glass. You photo hints at a mark (ring) on it and it won't hold back the fuel if it is worn.

[scott]

Mixture screw is correct... All the other names are from people who don't really know how they work.

Got it

If you carbs are overflowing take a good look at you float needle with a magnifying glass. You photo hints at a mark (ring) on it and it won't hold back the fuel if it is worn.

Hmm I didn't notice that ring - it seems to be cosmetic but I wouldn't really know if it was worn down.

From what I keep reading, that float needle valve and seat is the most likely cause of my problem. After I get through taking apart all the carbs / cleaning / reassembly, I'm hoping 1 will stick out as obviously worse than the others or that the new float needle valve seat O-rings fix the issue. Since it sounds like an OEM replacement float needle valve and seat is the way to go, I don't want to replace all of them at more than $30 / each if I don't have to. That may be my only option though.

Redman mentioned installing the carbs on the bike without the airbox so I could see which carb was leaking. I assume I could just set the petcock to PRI and that I wouldn't have to actually start the bike but that may not be right.

[tkent02]

From what I keep reading, that float needle valve and seat is the most likely cause of my problem.

What exactly was the problem?

Leaking fuel when the engine is running? From where?

[scott]

What exactly was the problem?

Leaking fuel when the engine is running? From where?

The primary problem I'm trying to address is fuel in the oil - I haven't noticed any exterior leaks. I'm sure there will be other issues to tackle but I haven't ridden the bike yet.

When I first got the bike, I started it up and warmed it up. I noticed a fuel smell and checked the oil crankcase which smelled of fuel (although the oil level did not seem TOO high). I had read so much about old petcocks causing problems so I replaced the petcock with a new OEM part and changed the oil.

Then I started it up and let it warm up a bit (maybe a few minutes - did not ride it). I did have to give it some throttle to keep it from stalling before it warmed up but I assume that's a separate issue. I put it back on the center stand and checked the oil again - the level was over the sight glass already. So I assume I have a fuel leak from the carbs.

In hindsight, I probably didn't need to replace the petcock but now I don't have to worry about that at least. So ... now I've moved on to cleaning the carbs, replacing the O-rings and checking the float height.

[Tom R]

Does the new oil smell like gas? Is it possible you accidentally overfilled the crankcase?
A needle valve and orings don't seem like they could leak enough fuel to flood a crankcase in only a few minutes of running. Did you find any floats stuck open? Even then that sounds too quick. And it ran? idled?

[scott]

Does the new oil smell like gas?

This was almost a month ago - I THINK I smelled the crankcase but I might have just assumed it was fuel when I saw the level was high. I just opened the oil crankcase now - it actually smells a bit different than gas right now (but what else could it be). This will probably sound crazy .. but right now it has a pickle-like smell. Maybe that's just a factor of it sitting for several weeks.

Is it possible you accidentally overfilled the crankcase?

I guess it's possible. I filled it on the center stand up to the Full line (which is how I checked it when it read above the sight glass). Is there something I should do differently?

A needle valve and orings don't seem like they could leak enough fuel to flood a crankcase in only a few minutes of running.

I was a little surprised too (especially since it seemed worse than before I replaced the petcock). It took a couple tries to get it started but I definitely ran it less than 5 minutes (it took several minutes of me holding a bit of throttle on to get it warmed without stalling. I know I shouldn't need to do that but the choke did not seem to have much of an effect (if any effect). After the couple minutes of throttle, the choke seemed to have more of an effect.

Did you find any floats stuck open?

I've only cleaned Carb #1 so far although I'm not sure what a stuck float looks like. Would that mean the needle valve seemed stuck out of the valve seat? Or that the spring in the needle valve wouldn't depress? Neither were the case on this first carb at least.

[Tom R]

Pickled crankcase - the first time I've ever heard of one.
I've never seen a stuck float either; probably as common as a Yeti, but I have heard of that before. Since you have the nitrophyl floats it's even less likely they're sunken and stuck open; but you never know.
Still baffled about filling the crankcase with fuel.
When you reassembled carbs, did you put the rubber plugs back on the pilot jet openings?

[scott]

Pickled crankcase - the first time I've ever heard of one.

Ha - I'm probably way off with that description - it just didn't smell as specifically "fuel-like" as when I first decided I was getting fuel in the oil.

When you reassembled carbs, did you put the rubber plugs back on the pilot jet openings?

I'm still waiting on some parts to arrive so I don't have the carbs completely reassembled yet. New pilot jet plugs are one of the things on the way.