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Old 01-19-2006, 02:06 PM
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Re: Gas engine tuning for newbies....

I assume that the Xipp method is for a broken in engine?
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Old 01-22-2006, 02:19 AM
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Re: Gas engine tuning for newbies....

Carbs adjust the same on a new engine as they do on a broken in engine...Only difference between the two is a little more compression from the rings being seated and maybe a little looser crank from the seals wearing in....If the carb is adjusted right in the first place (regardless of "factory" settings) it will need very little changing as the engine is run...
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Old 01-28-2006, 06:21 PM
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Re: Gas engine tuning for newbies....

Hi All
I have an old G-38 on my modified Roadrunner. It's not a hovering aerobat, but it is a lot of fun & can do quite a bit. The engine is old & my friend put a carb kit in it last summer and used the setting guage to get it just right. It ran really nice, but after a few flights, it got hard to start. You really had to choke it & then it would die after it ran out of the fuel you just choked in it. If I put my hand over the carb intake while it was running & choke it a few times, it would start running fine and run great through the flight. We just had a nice day here, so I got it out and couldn't get any fuel to choke into the carb. I finally squirted some fuel in the intake and did the hand over the intake quickly a few times after it started to get it running. I tweaked on the needle valves to get a smooth slow idle and a good top end. There was just a tiny bit of hesatation on idle to full speed & if the motor sat idleing for quite awhile, it would lag worse. I'm getting 8640 rpms with a APC 18-8 and no cowl around it.
Any ideas on what to try? About a month ago I had it out, choked it & it started on the first flip - gotta get that back somehow!

Thanks
Terry Peterson
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Old 03-03-2006, 07:50 AM
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Re: Gas engine tuning for newbies....

My MVVS 45IRS four cycles for a few seconds when I back off the throttle, giving me the impresion that she is going to die. Also the idle target RPM is not always the same.
I must say that my MVVS 45 is brand new with only a few taks of gas through her..
You said that four cycling is perfectly normal for carbs NOT equipped with a "check valve" high speed jet.
How can I distinguish a Walbro carb with or without check valve ?
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Old 03-03-2006, 08:16 AM
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Re: Gas engine tuning for newbies....

Quote:
Originally Posted by excelpoint
I havnt tryed this yet but if you were to put a bit of fuel tubing over each needle and left it about 10mm longer then you would be able to slip your screw driver into it and it would hold it there even when the engine was crankin. Might give it a go on the weekend. Anyone else got any ideas?
I've done this and it does work. But with the BING carb, the needles are so bloody close together that you can't do it for both needles. So I did it for the high speed as that's the one that needs the guide when the engine is vibrating.

Peter
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Old 03-03-2006, 09:02 AM
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Re: Gas engine tuning for newbies....

I've heard of guys drilling the cowl and using drinking straws as the guide. I suspect you just push the straw in when the engine is stopped, run it, tune it and then yank the straws afterwards.

Seems like a simple enough method but again guys, if your hand is any place near the prop just dont do it. Stop it, move the needle a 16th of a turn, one flip and test. It may seem slow but its a hang of a lot faster than healing up your smashed up hand.

I personally like rear carbs because you can easily set them up running. Any place else (DA100) no way in heaven am putting my hand in that close.

Kiwi
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Old 03-03-2006, 11:36 AM
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Re: Gas engine tuning for newbies....

For my glow engines, I tune the low end by pinching the fuel line (close to the carb) and listen for the engine to speed up. I keep tightening the needle valve a little at a time until the engine no longer speeds up when the fuel line is pinched. Then I open the needle back up just a little. Just wondering if this method works on gas engines too?
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Old 03-03-2006, 02:16 PM
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Re: Gas engine tuning for newbies....

Nope, takes to long
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Last edited by RTK; 08-14-2007 at 10:36 AM.
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Old 03-28-2006, 08:24 PM
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Re: Gas engine tuning for newbies....

To those that have this method down. I need to run my confusion by you and see if you can help me here.

It says to start the high end by adusting to peak RPM. Does that mean adusting the high end until it holds the RPM without sag? Because then he says to open the low end slightly if it does sag. That's my first point of confusion. Seems like both of the needles are trying to achieve the same result (peak RPM without sag). Is this correct? Or am I reading this wrong? How exactly do I adjust my high needle for peak RPM (micro steps please)?

Excuse my thick headedness but I'd like to get the end result he talks about. I tried this once but I didn't get it right. It's a new DA 50 with less than a gallon through it.
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Old 03-28-2006, 09:56 PM
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haverhill, ma
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Re: Gas engine tuning for newbies....

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
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Old 03-29-2006, 04:38 PM
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Re: Gas engine tuning for newbies....

This is one of the most useful threads here! Thanks to all who contributed! And XIPP...you are the MAN! Thank you!
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Old 03-29-2006, 04:44 PM
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Re: Gas engine tuning for newbies....

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.
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Old 03-30-2006, 05:19 AM
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Re: Gas engine tuning for newbies....

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 .
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Old 04-11-2006, 12:01 PM
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Re: Gas engine tuning for newbies....

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
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Old 04-13-2006, 02:22 PM
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Israel
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Re: Gas engine tuning for newbies....

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.
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