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Old Sep 11, 2012, 08:44 AM
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United States, MI, Marysville
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Any progress on trying out the Fox carb ? Have you measured the carb bores between the two ?
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Old Sep 11, 2012, 10:53 AM
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USA, TX, Grapevine
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It is on my list of things to do soon. I had misplaced the adapter earlier. I hate it when I put something where I won't lose it, but then can't find it later. I do want to see what happens when using more normal carbs on the engine. Mainly as a sanity check if nothing else.
I might have done it sooner, but I would rather go flying on a nice day than test run engines, sorry.

In any case the engine is running pretty good. I was surprised over the weekend as to how well it ran too.

Knock on wood.
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Old Sep 11, 2012, 04:19 PM
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Oh yea !
Flying comes first this time of year , especially up here in MI . Just eager to hear a bit more of the saga from TX . Good luck amigo .
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Old Sep 11, 2012, 05:07 PM
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Yeah, I usually do my engine tests and stuff on those days when the wind is blowing harder and it isn't any fun to fly when it is that windy.
Thanks
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Old Sep 14, 2012, 03:13 PM
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The Netherlands, NB, Breda
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Walbro regulator parts

Hi everyone,

The Saito FA 80 has a good crankcase pulse now . Flight tests learned that pump perfomance was consistent, but the engine still ran lean on top end, probably due to regulator issues .

I bought a Walbro rebuilt kit (K20-WAT), wich includes gaskets, membranes, needle, fulcrum arm and some other bits. The Walbro fulcrum arm is much better quality than the NGH arm, wich is very easy to bend. After installation of the Walbro needle, pivot and fulcrum arm, I noticed that the arm can be pushed down further than with the NGH parts (both at the same lever height and NGH metering spring). This lifts the needle more above its seat. With the NGH parts the needle lifts less, allowing less fuel flow. I noticed that a poor needle and fork interaction limits the upward movement of the needle. This interaction is much better with the genuine Walbro parts.

The rebuild kit also had a teflon pump membrane , I installed that one in my pump. The regulator membrane and the gaskets are also of much better quality. So I replaced all the internal parts except the metering spring. I also ordered the Walbro 98-3160-7 metering spring. This has not arrived yet. I hope to flight test soon.

Best regards
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Old Sep 15, 2012, 12:17 PM
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Very interesting, I was trying to get a handle on what you did with the Saito engine.
Usually with a four stroke single cylinder engine you need a slight vacuum inside the crankcase so that the air resistance to the piston going down is minimal. So normally the crankcase pressure fitting is setup to provide less resistance to the air being pushed out and some resistance in reverse so the air doesn't come back in. But with our 4 stroke glow engines, they have to have some blow by to allow gasses with oil to get into the bottom end, etc. So maybe it would work then.

So did you run a second fitting off the crankcase for the pump? Or did you do something different.

With single cylinder 4 stroke engines using a pulse pump, that I worked on and saw, they routed a pressure tube from the intake manifold to the pulse pump diaphragm, not off the crankcase. They didn't really have any pressure pulses on these engines there. They usually had some sort of a PCV valve setup that helped maintain a slight vacuum inside the crankcase.

But the problem with using the intake manifold pulses is that as the engine speed increases towards WOT and or under a heavy load (throttle open more at lower speed), the pulses all but disappear and the pulse pump doesn't work. I saw this happen with scooters going up hill or into a stiff headwind at speed. This was similar if not the same as to what I saw happening with the gas Saito engines where the pump got weaker as you approached WOT.

Of course that then led to people like the Perry Pump folks developing the inertia type of vibration operated fuel pump for 4 stroke model engines. I think Enya had a mechanical fuel pump on some of their engines for a while, I wonder how well it worked. I think YS uses something like a mechanical pump too.
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Old Sep 15, 2012, 01:57 PM
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Earl,

I connected the pump to the crankcase vent with a Y-splitter, one end to the engine crankcase, one to pulse nipple on the pump, and the last one hanging down to bottom of the fuselage, leaving the end open.

Its pretty simular to the perry VP-30 installation shown here, they used a T-splitter instead of a Y-splitter, I think that makes no difference:

http://saito-engines.info/pumps.html

I was inspired to do this project by an article written by Pe Reivers:

http://prme.nl/home/regulated_fuelsu...el_supply.html

The NGH fuel delivery system has exactly the parts I need, (pump and regulator), and doesn't have the part I don't need (venturi, jets, high and low needles, throttle and choke). It is much more compact than a Walbro carb.

Best regards
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Old Sep 15, 2012, 07:24 PM
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Thanks for the info, that is certainly interesting.
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Old Sep 16, 2012, 12:53 AM
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Oman, Masqat
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jmaderoy,
thanks for sharing the interesting information about the perry pumps. I have a perry pump on mine and till date i haven't managed to sort out the pressure. its either pumping too much fuel or not at all. but i will defnitly try to vent the crank pressure line and see how it works.
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Old Sep 24, 2012, 07:14 AM
SBP
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United States, PA, Waynesboro
Joined Aug 2011
97 Posts
9cc

I'm going to try a 9cc in a plane as a winter project If I understand what I'm reading, fuel delivery to the carb seems to be a problem. I found a cnc machined electronic fuel pump on Ebay. Pumps 1000cc per min. but didn't give a pressure.Looks to be small enought to put in a plane and is supposed to be shielded to keep interference down. Any advise would be appreciated. Also where is the best place to buy the 9cc engine? I missed the used one in the classified a couple days ago.
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Old Sep 24, 2012, 10:04 AM
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The problem is carb calibration, not fuel delivery.

Greg
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Old Sep 24, 2012, 01:15 PM
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Istanbul, Turkey
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Quote:
Originally Posted by SBP View Post
I'm going to try a 9cc in a plane as a winter project If I understand what I'm reading, fuel delivery to the carb seems to be a problem. I found a cnc machined electronic fuel pump on Ebay. Pumps 1000cc per min. but didn't give a pressure.Looks to be small enought to put in a plane and is supposed to be shielded to keep interference down. Any advise would be appreciated. Also where is the best place to buy the 9cc engine? I missed the used one in the classified a couple days ago.
Quote:
Originally Posted by gkamysz View Post
The problem is carb calibration, not fuel delivery.

Greg
If there shall be a constant delivery pressure, calibration is not a problem at all on a GT9 .So I believe SBP will have great result.
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Old Sep 24, 2012, 01:40 PM
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OK. I give up. I'm unsubscribing.
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Old Sep 24, 2012, 02:09 PM
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It seems at some point there was an indication that delivery was an issue . Maybe Greg sees it differently ?
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Old Sep 24, 2012, 03:43 PM
SBP
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United States, PA, Waynesboro
Joined Aug 2011
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It could be I'm confused. There is an awful lot of info in this thread and maybe I'm not understanding the real problem. Everyone is welcome to their opinion on problems. It seems some folks have good luck getting these engines to run ok and some don't. Maybe a quality control problem with the carbs.I have a little experience with 2 stroke engines . Some of the older chainsaws had tempermental carbs. Oh I better stop, I'll be telling my age.
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