Not24
Posts: 999
Joined: 12/7/2002
From: Gloucester,
VA, USA
Status: offline
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Took the carb to work today and checked it out completely with the flow meter. I have never done this before, so I'm sure I didn't do it exactly right. What I thought I would do is to look for a restriction in the carb assembly. I used 30 psi air pressure and maxed out the meter. I then hooked up just the fuel nipple and compared flow. I then installed the fuel nipple to the spraybar and checked flow with the needle removed, installed, and both ends plugged. All of this showed no appreciable flow losses. I also calibrated the high needle to find its range of adjustment. What I found was that anything open more than 2.5 turns makes no difference in flow rate. However, there is a fairly linear drop off from that point down to closed. This means thatif it won't run rich at 2.5 turns, it will never run rich. The key now is to get enough fuel flow at 2.5 turns to get it to run rich.
I assembled the carb, with the low needle still set where it ran last, and operated the throttle barrel. This was done with the high needle at 2.5 turns open. I registered minimal flow at closed throttle, just enough to hear the hiss. At full throttle, flow was less than with the spraybar alone. Richening the low needle at full throttle will increase the flow to the same level as spraybar alone. The engine won't run well there, because the low end will then be excessively rich. The solution is to modify the slot in the carb barrel to achieve maximum flow at WOT. This was done with a pencil grinder and a carbide burr. Since the spring pushes the barrel to the right, grinding on the left side of the slot will open the hole in the spraybar by effectively richening the mixture. I only ground a small amount away, and only over an area of about 1/4 rotation, or 1/4 the length of the slot in the barrel. I used the flow meter to confirm that I was now getting maximum flow at full throttle, while still having the low needle set at the desired setting. Total material removal was less than .020", but this was enough to open the spraybar to its maximum flow rate with the low end adjusted right.
The next thing I did was to lengthen the slot at the other end to allow for the throttle barrel to close more, cutting off the flow completely, and thus, allowing me to be able to shut the engine down. Mine would never shut down instantly, as I always had to wait 30 seconds for it to quit.
The true test is in the test runs. That'll happen tomorrow evening after work.
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Fly it till you break it!
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Glow Engines >> RE: My 2300 only likes one prop 
RE: My 2300 only likes one prop - 
and I think thats exactly what you need. You can try to reduce the diameter by 1-2mm, 0,04-0,08"inches, and see how you like it. You might lose 300-400rpm at WOT but the engine gets more user friendly 
