Gas engine tuning for newbies....

[ifixairplanes]

I recently rebuilt the walbro crab on my brison 2.4 . I replaced: pump diaphram, pump check valves, fuel screen and gasket. Also diaphram, lever and float needle. The old float needle I noticed had a soft rubber type tip, new one is all metal.

Reason for rebuild was engine would go lean and die after a while of nose up running at WOT. After rebuild, I noticed much better fuel draw and no more running lean at WOT. However I did notice, that no matter how I set the low needle, it would still load up on me. It was fine in the air, never had a lag. but on the ground, during starting I noticed fuel dripping out of the carb. It would get severly flooded to the point all I could do was pinch off the fuel line and flip till she started. Then I would unclip the line and she would stay running fine.

After reading the article and noting my 2 symptoms after the rebuild I took apart the diaphram area and bent the arm down a hair. Hopefully next weekend I will notice the change!

Comments? Suggestions?

Sean

[Texx]

This is one of the most useful threads here! Thanks to all who contributed! And XIPP...you are the MAN! Thank you!

[JoeAirPort]

Yeah I used his method for adjusting the low end it made the engine run WAYYY better. I think I finall'y figured out how to do this.

[Stinger1]

Having run gassies for 15 years I've found a system that seems to work for me and that is : first of all set the needles to the factory recomendations . Then screw in the low speed needle ( the one closest to the engine block ) until the engine won't run , then open an 1/8-1/4 turn, open the throttle and adjust the high speed needle for peak RPM's, then open the high speed around 1/8 turn, you can't burn out an engine running it a bit rich . Adjust for a smooth transition with the low speed by opening it . Two items that help out are an electric starter and a fine screwdriver with a piece of brass tubing on the end that will fit over the needle . The engine must be stopped for adjustments keeping in mind the emergency rooms are full of people that took a shortcut and ended up with a longcut ( on their hands ) . Have fun safely .

[BDSBob]

With Xipps initial needle settings of around 1 - 1.5 turns out for both High and low needles, where do you guys "guess" your needles are on a DA150 when you are finished tuning? The reason I asked is that the DA factory setting is 5/8 on the low and 2 on the high.

Thanks

[i3dm]

Hey guys,

I understand the method, but im not sure im following on how a "four storking" engine sounds, can you try to explain please ?
thanks.

[JoeAirPort]

	Quote: Originally Posted by i3dm
	Hey guys, I understand the method, but im not sure im following on how a "four storking" engine sounds, can you try to explain please ? thanks.

4 cycling is a lower pitch sound. It is not combusting every power stroke so it sounds lower, also can sound like it's missing. After leaning the low end, when running at 1/4 to 1/2 throttle, it will start to fire every power stroke making a higher pitch sound (consistent pops one after another, no missing).

[BAS]

I havent been on here for awhile but thought i would pass on my tuning of my Brison 3.2 yesterday and how happy i am now that i tried Xipps method of tuning gassers. Let me just say i have had all brands of gassers for the last 15 years from Brisons , Taurus , Zenoahs . I have always had problems getting rid of the mid range burble on the motors and was always frustrated with not being able to tune them properly . I used this method yesterday and followed the procedure by the book , and all i can say is that WOW what a difference i can tell now. I tuned my Brison 3.2 by starting all over on the needles as the procedure calls for by having both needles out 1 and 1/2 turns out . After i completed the procedure in the air the motor had absolutely no midrange problems and ran really well , it is like a new motor now . I am running a MSC 22/8 prop on the Stinger 84 span and i am a happer camper now . I will retune all my gassers now including the Taurus 52 and my other Brisons including my 6.4 twin. Thanks for the info on the tuning .

[cforcht]

OK guys I tuned my 3W70 as per instructions found here. it runs flawlessly on the ground with good transition. the idle might be a tad high but otherwise runs great. In the air however its another story. it runs fine for a little while then acts like its choking on fuel and loading up. I have tried to lean out the high side a bit to remedy it but then it runs worse. same goes for richening it. but yet it runs fine on the ground. what am I missing here. fortunatley it hasnt died in flight even though now and then it sounds like it might. but it has died on the ground after landing. any ideas whats wrong?

[Neogenesis]

sounds like a pressure problem inside the cowl. How open is the bottom?



Neo

[cforcht]

the bottom of the cowl is very open. the previous owner hacked the crap out of it for the banjo style muffler. this engine starts easily. usually the 3rd or 4th flip after its popped while choked. runs great on the ground but doesnt work that way in the air. I am using redline oil mixed 50:1. I have discovered today that 3W recommends this particular oil mixed at 40:1 so that may be some of it. what ya think? would this cause it? also the carb is exposed to the air stream around the plane as it flies. there is nothing shielding it or obstructing the intake path of the carb.

[notorious_benny]

I think you are getting turbulent airflow around your carb.

You might need to protect the venturi and the diaphragm vent hole from hostile air.