Gas engine tuning for newbies....

[pe reivers]

	Quote: Originally Posted by rcign
	Any gasser engine will run with the high speed needle completely closed, just not as well.. If you want to set the low needle first be sure the high needle is open at least 1 1/2 turns, or 4 turns on the new EPA spec carbs with superfine threads...Somewhere on the Walbro website it explains this 4 turn thing, do a search...

True.
Starting point always is with both needles 1,5 - 2 turns open. Except of course with the very fine thread needles.
I had one carb without knowing this, but soon found out how much I could adjest the needle for just a little mixture change. Removing the needle to check the taper then revealed the very fine thread pitch. of about 0.4mm

[RTK]

	Quote: Originally Posted by rcign
	Any gasser engine will run with the high speed needle completely closed,

A long time ago I tried just that, and adjusted the low needle for very smooth running on the low end. Then I started opening the high, as I did this I discovered how soon the high starts feeding and richening the low/mid range. Not all carbs are the same, but the high kicks in really soon on some.

[flynz4me]

Symptoms of a diaphragm carb having a float valve leak:

(1) Rough idle, and engine loading up.
(2) Fuel dripping from the carb when its not running
(3) Lowend needle does not tune well.
SOLUTION:
Replace the float valve and adjust the lever to its flush position OR use a "W" gauge to set it.



Mark - What is the "Float valve??" Is it the needle valve?

[mfuess]

	Quote: Originally Posted by flynz4me
	Symptoms of a diaphragm carb having a float valve leak: (1) Rough idle, and engine loading up. (2) Fuel dripping from the carb when its not running (3) Lowend needle does not tune well. SOLUTION: Replace the float valve and adjust the lever to its flush position OR use a "W" gauge to set it. Mark - What is the "Float valve??" Is it the needle valve?

Yes.

[flynz4me]

OK thanks... Where do I order a rebuild kit for my HDA 48??

[RTK]

Go to your local mower/saw shop and pic one up there.

[rcflyer]

	Quote: Originally Posted by mfuess
	Before you begin your tuneup, reset your needles to factory settings to start from gouund zero. It's best to set the topend first. Start your engine, let it warm up. Transition to full throttle. Adjust the HIGHEND NEEDLE to peak RPM. Then, SLOWLY throttle back until the engine begins to FOUR STROKE. At the point, adjust the LOWEND needle until the FOUR STROKING stops. Pull the throttle down more until it FOUR STROKES again and repeat this until you reach full IDLE. NOW, transition up rapidly. IF it sags or bogs, open the LOWEND needle SLIGHTLY until the sagging is gone... YOU"RE DONE! One big MISTAKE people make (when they tune up a gasser) is to peak the engine then back off the needle to richen it up slightly just like a glow fuel engine. DO NOT DO THAT! Once your carb is properly tuned to peak it will maintain the CORRECT air to fuel balance. Richening it up only causes the engine to run wet and inefficient. IF you are not sure if you have a good tune, look inside your muffler or pull your spark plug. It'll tell you real quick. If it's black & wet its time to re-do your tune.

I would like to request that someone makes a youtube video on mfuess tuning method. I am still not sure what "four stroking" sounds like and a video will definitely be helpful. Thanks

[krayzc]

a well tune gas engine with a throttle curve sure is very nice to run with make the low very rich and u will quickly know what 4 stroking sounds like is how i learned.

[Al Lewis]

Make it sound like this and you'll be very close.

http://media.putfile.com/DL-50-Tunin...-Vess-23A-Prop

[mogley]

what should a properly tuned da50 turn with a 22x8 menz on a slim line mufffler?

same question with a Mejlik 23x8

all at sealevel?

thanks

[rcign]

Asking wwwhat a DA50 will turn is like asking what oil is best Now......A little problem with semantics....
First off, gasser carbs don't have a float valve or even a float, it wouldn't work unless the carb was never rotated from moslty level, where it can float on the fuel..In a float bowl..
The float connects to a lever that lifts the inlet needle off the seat to admit more fuel to the carb when the fuel level in the float bowl lowers ...A gasser carb has the same inlet needle and lever but it's controlled by a diaphragm with a metal center, opened by atmospheric pressure coming through the hole in the steel carb top...
A "needle" valve is in a glow carb, a tapered needle that admits fuel drawn into the carb from the tank by suction when the piston goes up...Some have a low needle and a high needle, some have a high speed needle and a screw with a flat end...This is an air bleed carb, screwing the flat ended needle in RICHENS the low speed...Screwing it out LEANS the low speed by admitting more air, less fuel...
There is no needle valve as such in a gasser carb...There are 2 needles, a high speed and a low speed..
The low speed needle progressively admits fuel at low speed through 3 little holes in the venturi up to the point where the high speed needle adds to the fuel flow....
And the low speed needle DOES control fuel flow, contrary to what is posted in a forum elsewhere...

[nesikachad]

This is the greatest thread I've read yet on this site.

PROPS to you!!