Dirt Squirt Float Level

[go_hercules]

Anyone know the correct float level for a 1973 chrome tank Dirt Squirt 100? Thanks very much.

[Hydraulic Jack]

Float arm level with bowl mating surface when turned upside down.

[go_hercules]

Wow. You mean there is no actual dimension? I think I picture what you are saying, but do you know if there is a picture anywhere I could see? Thanks a lot.

[Bullfrog]

There is a dimension offered somewhere, but I can't find it (didn't actually look) . . . and you don't need it.

Just follow the recommendation on the photo. The photo is not of a Dirt Squirt carb . . . but the rule of thumb applies (and works) for the Dirt Squirt.


Ed

[go_hercules]

i see what you mean. Just a second ago I discovered an old Resonator page that says the measurement on a Mikuni 20 is 7/8 inch. https://www.strictlyhodaka.com/v/vspfil ... Mikuni.pdf

I will see if your method and that figure come out the same for curiosity sake.

[Hydraulic Jack]

Doesn't matter what the measurement is unless you have the correct dimension for the correct version of Mikini, but all the dimensions will leave you with a parallel arm.

[go_hercules]

Hydraulic Jack, I checked the float level thing on the Dirt Squirt. Like I mentioned, I found a reference on a Hodaka Resonator page saying the float level was 7/8 on the 20mm carb. When I set my float at 7/8, the float arm is not at all parallel. Now, when I set the float arm parallel like you mentioned, the float level measures out right at 1 inch. This would effectively lower the actual fuel level in the bowl, correct ???

[Bullfrog]

While I too am virtually certain that the "parallel" setting would work just fine . . . I don't have a machine with a 20mm carb to check it out. In which case, sticking to the published spec in the Resonator seems prudent. That spec has been around a long time . . . and has been used a long time without complaint.
Ed

[go_hercules]

Yeah, it just made me curious because I have been having problems adjusting my air screw. All the way in, all the way out makes no difference. i just finished testing crankcase leakdown which is good. Went through the carb again, checking every single passage by blowing through and blocking each one. Even checked the choke circuit fuel and air passages to make sure no fuel was leaking through there. Keeps loading up at idle. That is why it was interesting that by adjusting the float arm parallel, and thus lowering the fuel level I now have with the 7/8 setting might lean my idle mixture some. What do you think?

[Bullfrog]

While I am still a bit concerned about having no effect from radical pilot air screw adjustments, it sounds like you have assured that all passages in the carb are cleaned out. (the sort of "standard" problem is that the pilot jet or the pilot air passage is plugged, so the pilot air screw can do nothing . . . but you have fixed that)

It is possible that the pilot jet is wayeeeee oversize or drilled out by a previous owner - so you might check that.

If the pilot jet checks out, then float adjustment to "parallel" is certainly in order . . . and would follow what seems to be a Mikuni design standard for their carbs.

Ed

[go_hercules]

The pilot jet is the standard 25 and looks good, but I will check to see if it might be oversized. I am setting the air screw at normal idle. Is that correct, or should the idle be bumped up or down when tuning it? I never was sure if that even made a difference. Thanks.

[Bullfrog]

I'd recommend setting the pilot air screw at 1.5 turns out, that is the target setting (1 turn out to 2 turns out is ok, with the target at 1.5). Then you can do your tuning ("in" or "out") from that setting. Remember to make adjustments in 1/4 turn increments and give sometime for the engine settle in to it's new condition and to judge whether idle speed went up or down.

NOTE: You set your idle speed with the idle adjust screw - which is essentially a "stop screw" to adjust how far down the slide will go. Stopping the slide at a higher location produces a higher idle speed. The pilot air screw is used to find the "sweet spot" when idling (which happens to coincide with the proper setting for general operation), but the idle adjust screw is what you use to set your desired idle speed.

Ed

[go_hercules]

Thanks for that Ed. Just now did another test. I suspended the carb without bowl over a glass container then turned on the gas, to measure the actual fuel level at a particular float setting. When set at 7/8, the actual fuel level was just about 1/8 below the gasket surface. Then with the float arm set to parallel, which gives a float setting of about an inch, that put the actual fuel level just about 1/4 inch below the gasket surface. So the million dollar question is generally speaking, where is the actual fuel level supposed to end up. Some bikes actually spec the fuel level rather than a float setting so maybe I will see what their range is out of curiosity. I know this is going off on a tangent but I enjoy experimenting to understand what's going on. Remember, I am off on this tangent since I got no response at all from the air screw. But Ed, when i put it back together I will try your suggestion of tweaking the air screw SLOWLY. I might not be giving it enough time to catch up and burn what fuel is already in the system.

[Bullfrog]

I love that you want to dig in and understand the detail behind the single number given for guidance! In that, we are on the same sort of wavelength.

Note: You can turn the pilot air screw quickly 1/4 turn or even half a turn . . . but you have to wait to let the engine consume all the mixture which was already on the way toward combustion (thru the intake manifold, thru the transfer ports, etc.) AND you have to let the engine settle in on "how it feels" about the new mixture being supplied after the adjustment. That is the chain of events which call for some wait time to see how things change.
Ed

[squid on a 300]

what kind of shape is your needle in?.if it is worn it may let additional fuel through...had that issue with my 72 husky... could not get the bottom end (up to 1/4 throttle) to be responsive..i dropped the pilot from a 45 to a 40 and it was still too rich...replaced the needle and needle jet (same sizes just new parts) ran the bike and had to put the 45 pilot back in as the 40 was now too lean...the bottom is now much, much more responsive

[go_hercules]

Good point. I actually thought of that and took a good look with a magnifier and it looks like new. No noticeable wear marks or irregularity. BUT, since you mentioned it, I will take a closer look at the needle jet it fits into as well. Thanks for the tip.

[go_hercules]

SOLVED.

I ended up finding the sweet spot adjustment on the air screw today. I was able to do so by following the directions on the Mikuni Round Slide Manual. They said to start by increasing the idle by about 10-20 percent, then adjusting the air screw. I did this and at the higher rpm I could actually hear the difference in the air screw setting. At a lower rpm it was just too subtle. They don't say why to do it this way, but my guess is this: the pilot system feeds into the carb bore through two holes, one under the slide and one in the carb throat just downstream of this. The manual says that at low rpm, the hole under the slide is supplying air and the mixture is feeding the engine through the other hole. As rpm increases, the hole under the slide sees more vacuum and actually starts supplying mixture as well. So I think that by raising rpm the air screw has a more direct effect since air supply from the other hole (which they call the bypass) is sort of taken out of the equation. Anyway, it worked well for me. Thanks for all the help from everyone.

Oh, one more thing. The air screw ended up being out about 1 1/8 turn, so the pilot jet is right on.