fuel leak 1974 super rat

[sbraatz3]

I suppose it's not a leak, but when I start the bike and rev it up it there is sometimes a puddle of fuel under the bike. It seems to be coming from the air vent tube (if that's correct) off the bottom of the carb. It seems like it's only when I first start it then it doesn't do it. Is this normal?

[Dale]

No, this is not normal, but is very common. Most likely your float needle valve is not sealing up. This can be really bad if you leave the bike with the petcocks on, the fuel flow will not shut off and can fill your crankcase full of fuel. This valve can be worn or quite possibly it has a bit of dirt or debris under it, keeping it from sealing. Worn valves can sometimes be cleaned up and saved, but I prefer to just change them out. Have you cleaned the carb? And, do you have an inline fuel filter installed? You will definately want both.

Edit: Another thought... If it only happens on startup and not when left unattended with the petcocks on, then it could be as simple as the float level set too high. Easy to check when cleaning the carb.

[sbraatz3]

DDVORAK - It seems intermittent. I can leave the pet cocks open and there is no leakage. Just seems after I start it up initially. I did take the carb apart and cleaned it up as much as I could. I'm not a motorhead, I can take things apart, clean them up and reassemble. I will have to brush up on my terminology and what part is what. When I took it apart I did have to clean the bowl floats off pretty good. There didn't slide up and down too well. I'm pretty sure those regulate the fuel allowed into the bowl? I did unscrew one other part that I wasn't sure of it's function. I cleaned it and screwed it back in. I'll have to look at the schematics so I can better explain myself. One of the petcocks was frozen shut so I drilled through the plastic insert. That one I can't shut off. I also had to remove the filter on the top part of both of them. I did hook up a inline filter. Don't laugh but I couldn't wait so I grabbed one from Fleet Farm from the lawn and garden section. Not the one that is actively sold on here. So with that said, I think I'll look at the part names on the schematics so I can figure out exactly what you were talking about.

How do you check the float level? Don't they just slide up and down as needed? How would you adjust that?

[Dale]

Your inline filter sounds fine. As long as it does its job...

Yes the floats serve as the trigger to shut off the fuel supply when the bowl is full. They work in conjunction with the float valve and seat in addition to the float arm and pin. There is a tang on the float arm that can be carefully bent to adjust the float shutoff level. There is a technical measurement, but standard practice is to turn the carb upside down in your hand and note the position of the float arm. It should be parallel to the of bowl gasket surface. Remove the pin and arm to bend the tang and re-check until the parallel position is obtained.

As for the float valve and seat. This is a two piece unit with the seat screwed down to the carb base with a red gasket on the threads. The valve is a small piece that sits down in the seat. It has a pin that is spring loaded on one end and a sharp point where it mates with the seat. It is the pin that makes contact with the float arm tang and it is this valve and seat that must seal to shut off your fuel supply at the correct level.
Dale

[sbraatz3]

Thanks Dale, I will definitely reevaluate all of these things. When I get some time tomorrow. Thanks for taking the time to explain these things. It's very much appreciated.

Shaun

[sbraatz3]

Dale I'm pretty sure I grasp what you're saying. Question?


The pin that is in the float valve seat iso spring loaded, could you explain that to me because I didn't see any spring opposite the pointy side of the pin.

Shaun

[Dale]

Here is a picture of it. The spring loaded pin is an intregal part of the float valve and the spring is not visable. Hope this helps.

When you have it apart, check the pointed end for a smooth surface. It should not have any worn grooves in any direction on that surface. Also check the mating surface down in the seat itself. The seats will often corrode over time and will not provide a good seal even when cleaned. Both surfaces must be in ideal shape to get the necessary seal.
Dale

[sbraatz3]

If I remember correctly, the pin on mine was flat on the non pointy end. I might be wrong but I'll take it apart and ccheck it again. I know the pointy end had some areas of discoloration which could have wearing or buildup.

Shaun

[Dale]

Hummm, if you find that yours does not have a pin sticking up then you have found the source of your leak. The picture is of a used valve from a 98 Super Rat just like yours...
Dale

[sbraatz3]

Dale, Would this also explain the fuel ( I assume) getting into my gear case. I checked that today and it looked diluted and fizzy on the dipstick or could that be another problem? I also noticed oil spatter from the exhaust on my basement wall .

[Dale]

Yes, it sure could. I think you have two issues here. One is that the float valve not sealing and the other is the petcock that you can not shut off. I would sure address the petcock too. Not only will the crankcase fill up with fuel, but so will the exhaust. Any extra fuel that finds it way to the exhaust will quickly become black oil splattered all over anything in the way of the exhaust outlet. What you don't want to happen is to have enough fuel leak into either the case or exhaust to create a hazarous situation!

Both items are easy enough to fix.

[sbraatz3]

Ok, the float valve and pin look to be good. I was wrong about the spring. It's definitely there and seems to function. I did check the float arm's position and it seems to be about 1/8 to 1/4 higher then the surface of the carb where the bowl and carb meet. I'm assuming the "tang" is the center part of the arm that sits on the pin/spring? I did notice some sediment in carb, I had previously clean all out. I should probably get the proper filter, new float valve and pin also. Ah, good thing i have plenty of winter to make it right!

[sbraatz3]

[Dale]

Yes, you are correct on the tang. Be very careful not to bend anything except the tang itself. You are looking to get the float arm(s) to sit parallel to the gasket surface. You might not need anything except the adjustment, another cleaning and then the petcock fixed.

For a good filter, just go to any motorcycle dealership and get a small inline fuel filter. The clear ones are best in order to see the fuel and any sediments. There will be a small metallic cone inside that is the actual filter and look for an arrow to indicate the proper flow direction.
Dale

[Dale]

After seeing your picture, yes it is quite a ways out of adjustment. This would allow too high of a fuel level. Remember that you have the carb upside down for this view. When it is all assembled and installed the floats would have further to rise to actuate the float valve and shut off the fuel thereby making the fuel level too high.

[sbraatz3]

Dale, the other thing that came to me, when I reassmbled the floats in the bowl, I'm not sure if I had them orientated correctly. Should the little studs that hit the arm to be closer to the bottom or should the they be up higher with the tapered part of the float towards the bottom. I guess that is one thing I didn't pay any attention to when I took it apart nor when I put it together. I looked at the schematic but it was hard for me to tell which way it sits in there. Thanks again!

Shaun

[Dale]

I have been there...
The rounded part of the floats fit into the bottom of the bowl and the notched sides, with the pin, sit close to the float arm. So, drop the floats over their respective guide studs, rounded bottom first.

[sbraatz3]

Here is my new float valve setting. Does this loak like the correct calibration?

[Dale]

Yes, that looks much better and should work fine.

[sbraatz3]

Ok, Good! I'll get it all back together tomorrow and see if I have different results. I'll let you know how it turned out. Thanks again for taking the time to explain things and being patient with me!

Shaun

[Bullfrog]

Shaun:

For a self proclaimed "non motorhead" . . . you are doing just fine! Nice job on adjusting the float level.

Ed