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Old 06-17-2013, 10:29 PM   #29
Brevis illi vita est
Joined: Jun 2010
Oddometer: 4,609
Originally Posted by rustygardhouse View Post
So where to begin...

I didn't forget: with all the variation in the castings of the carb body & float bowl as well as the gasket & gasket compression, the marks are only a relative measure of fuel level so I can easily see the changes. The marks are adjusted so they actual read from the edge of the bowl down which removes casting variation in the depth of the bowl.

I tried to follow the Bing recommended method as well as Snowbum's lift the float method. Of the two I think Snowbum's is the better method. the thing that both of these methods depend on is floats of the same volume & buoyancy.

I just hate lying on my side trying to figure if some faint line on the float is level with the bottom surface of the carb body. I even used the float bowl bail to hold the float in position but to me it's just too inconsistent.

I'm running 'older' floats & they certainly are not the same volume. When set to the Snowbum method, there is a difference in the fuel level.

Yes, I have new floats on order... But if I can figure this out, I can make old floats work as well.

I also tried Snowbum's stick in the bowl with a notch & got tired of it.

When I read the marks, I place the bowl in the same place & in the same orientation to reduce variations from unlevel surfaces. Like I said, the marks aren't absolute but they do let me know how much I've changed the fuel level as I tweak the fuel level.

so the first thing I do is take two reference readings before I start playing with the level.

I really like the idea of a clear float bowl to see where the fuel level is wrt to the jet stock. This doesn't really have to mimic the bowl just its gasket profile. It could have scribe marks on its side for fuel level reference.

Some days it's fun to be a mech design eng ne aircraft mech ne logger. Give me a bit & I'll whip up a model.

Fuel level & performance...

The left carb is being a problem child. It was running lean though the needle & main jet. As I increased the fuel level by 1mm the needle jet came alive but the main is still way too lean 14s at the cross over, 17s at wot. Basically, the bike is running on the right cylinder.

One of the things that concerns me is that with the rake of the R65 carbs, the fuel level can get high enough that the idle ports are below the fuel level. I think I'm seeing this on the right side as the idle screw seems to have lost it's effectiveness.

Did I cover everyone's questions?

Here's a gotcha: When I got this bike a year ago, I had the shop lash the valves & check the timing. Well, in a fit of 'just in case' I thought I'd check the valve lash & timing.


Left exhaust was set to 0.012" but the rest were fine.

Can't find the timing mark with my timing light. The marks are there, I've repainted them with bright yellow nail polish but I can't see them. The mark I do see is ~60 away from the timing marks.

I'm wondering if the flywheel was put on one hole over the last time the clutch was done.

Anyone know if it's possible to install the flywheel one hole over?
Man, I don't want to harsh on ya or hurt your feelings, but you don't seem to get it.

The only thing that matters is the distance from the surface of the fuel to the opening in the main jet. if the bowl is six feet wide and 10 feet deep and cocked 20 degrees sideways, it all the same. Dimensions of the bowl, volume, perpendicularity to gravity, casting variations, color, creed, religion, marital satus or sexual orientation mean nothing. They have no effect on the distance from the surface of the fuel to the opening of the main jet.

So get rid of the bowl, O.K.? It's distracting you.

Never measure the correlate of something when you can measure the thing itself. if you want your motor to be well balanced and to run smoothly, measure that balance directly. Vacuum is not balance. Mixture is not balance. You toys/tools have good uses, but you are not using them for those. measure the power output of each side directly. It's rather simple to do.

So too with the distance betwen the surface of the ful in the and the openig of the jet. What you are really after is pressure but this is difficult enough to measure that you go for the correlate of height. And long as your fuel densities are pretty consistent your correlation coefficients will be strong. Atmospheric pressure cancels out BTW.

Putting little makrs on something merely reveals that you have never been a tradesman that knows how to do thing. I have been / am one, as well as a scientist, engineer, social worker and artist. However, to humor you, and because I am hurting your feelings anyway, I have made some marks on the carb body. I know how close the fuel can get to the body before it goes out the overflow tube (may height) and I know how far away it can be without uncovering thee idle jet and killing that circuit. (min height). So I knw the istance range for the marks. BTW, it can't flood out the idle ports in the venturi, they are above the overflow.

Just for you (and I mean that, this is why they are on the inside):

I could make those so they would have .01mm resolution. It's just an example so I don't care to. But they are engraved, marked and for real.

Now look what happens:

Such a fit!. Floats are totally free. The only reason it's glass is so you can see when the float shuts off. Your method is to hold the jar up and turn on the gas. pop the bail off first to get it out of your hair. When the float shuts off the gas, you turn off the petcock and lower the jar collecting whatever drains from the line without changing the high water mark on the body. Then lower the jar completely and read the high water mark. If you were a tradesman you would simply capture that mark rather than reading divisions. More accurate---but also sort of a trade secret.

jar is pretty deep and you are only interested in what is happening in the top half inch, so keep it pretty full.

The surface of the fuel is always level no matter what the jar does. The float always shuts off at the same point even if you wiggle or lower the jar during the test. This jar is a nice size because you can hold it against the carb bottom to steady it. And you can get them in any grocery store. And they have nice lids you can reuse.

Match the levels on both sides for starters. If you are way out on mixtures after that look for some other problem. Do not just sweep it under the rug by diddling the fuel levels.

Bob (snowbum) knows a great deal in a number of fields. He also knows shit in some of them. I like the guy personally, but I respect his limitations. I have not read his float setting stuff in recent memory nor have I recorded it. I suspect I started to read it once, realized this was something he was too clueless about, stopped and moved to something else.

if you are going to try the float-touches-needle-and-gives-monkey-joy position, you sit on a stool, pop the carb off without disturbing the cable and hold it at 45d. so you can see easily but the float won't swing too fast.

Good luck...Mr. Phelps.
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