Fuel Filters for Pioneers

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Postby Stickid » Thu May 25, 2006 10:31 pm

I posted the other day regarding fuel/oil info. but I forgot to log in first...apologies for that but thanks to all who posted info for me.I have assemled my newly acquired series one and have actually been able to start both engines with no trouble at all. I wonder if anyone can tell me what the current best weighted type of filter is for use at the in-tank end of the fuel line. The old ones are all gummed up but appear to be a porous cylimder over a heavy weight of some sort. Is ther an alternative? They appear somewhat like a Radio Control type of clunk tank device btu larger. I appreciate all the info on this site,it has been invaluable. Thanks to all... Bob R
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Postby uscgairdale » Fri May 26, 2006 7:20 pm

Welcome to the site Bob. Here's what I have seen installed on some series II and series III Lazairs. It's the same thing that I am using on my restoration.

http://www.aircraftspruce.com/catalog/appages/fuf02.php

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Postby Chappy » Fri May 26, 2006 11:18 pm

I think there are actually two versions of this filter. The one you would probably be happiest with is the version that includes a check ball valve inside the filter. The check valve helps keep the fuel from draining back down the fuel lines as easily, which makes restarts easier, and is the style that Ultraflight specified (after all the problems with the original felt filters). Unfortunately, both versions of the filter look the same! You can tell which one you have by shaking it; the filter will rattle if it has the check valve. I'm not sure the filter at that link above has the check ball. You might ask before ordering. I think I got the proper replacements from CPS (California Power Systems) or one of the other Ultralight parts suppliers.

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Postby yankeflyer » Sat May 27, 2006 2:32 pm

Hey Bob

Post a pic or two of your plane :ph34r:

Miles
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Postby uscgairdale » Sun May 28, 2006 6:18 am

If you cannot find the in-tank filters with a built in check valve, you can always install the check valves seperately. My brother's series III is set up that way with the check valves just external to the fuel tanks. Another connection increases the risk for a leak, but it has worked well over the years. You definitely want to check the reverse fuel flow for when you refuel as repriming the entire line each time would get old real fast.

Tyler's Lazair site lists a source for check valves under Lazair parts. You may want to check it out. Regardless, there is a lot of neat stuff on there.

http://www.monisys.ca/~tparadis/

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Postby sustainflight » Sat Jun 27, 2009 9:23 am

I'm the new owner of Dave Aldous' Lazair 2EL (OVC/Delloroto carbs). I refueled (may have inadvertently pulled the ends of the lines above the fuel level) and had previously broken the seal for a minute to move the primer bulbs out of the way. Not sure which of the above caused it, but next morning my lines were dry and the bulbs located at wing level couldn't self-prime such a large distance.

What's the recommended procedure to prime the fuel lines? Perhaps I hoist the tank to a level just above the plane, remove the connection at the engine, start a siphon, and reattach to the engine when I'm getting bubble-free fuel?

Will shake the in-tank filters to determine if they have check-valves to make this a less regular event...

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Craig in "windy" Oklahoma City
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Postby sustainflight » Sun Jun 28, 2009 10:05 pm

The Aircraft Spruce filters have the checkball; one of the ones in the left tank of the two seater had its checkball stuck closed. After tapping on it a bit it freed up. New ones on order.

I did the following to prime the dry lines. Seemed to work well, but I'm open to suggestion for better ways.

- took hose off engine, hooked line to a hose that I ran UP over the (cold) exhausts and down to an empty fuel can that was below the level of the gas tanks.

- with the primer bulb down near the tank level, it took only a few pumps before I started moving fuel instead of air. Kept pumping till it filled the system and started a siphon into the empty can.

- jiggled and squished everything, including bulb right side up and upside down to extract bubbles. That took several gallons of fuel flow to be pretty consistently bubble free.

- stopped the flow via a valve at the tank.

- hooked far end back to engine.

Seems like the bulbs do harbor and perhaps even create vapor or air bubbles. They're probably serviceable as long as I follow Shannon's suggestion to keep the discharge down (except when doing the initial prime).

Has anyone used an electric pump, perhaps submerged in the tank? That would give the pressure needed for the OVC carbs with minimum bubbles.
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Postby sustainflight » Fri Jul 03, 2009 8:07 pm

Any Lazair gurus out there? New Lazair owner is confused.

I've tried original and new in-tank filters with brass ball check-valves leading to a primer bulb (discharge down per Shannon's suggestion) and then up to the KFM engines. Seals appear all good. Within 5 minutes I have about a 4" air bubble at the carb inlet.

The check valves are not checking?

I don't see any indication of leakage at the carb or bulb fittings, but it looks like the carb inlet and float on the OVC/Dell'Orto carb may be vented. That might not be the case because pumping the primer bulbs doesn't push the air out, it just compresses it.

Is this normal, to be primed out? Haven't flown yet because this looks unsafe to me.

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Craig
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Postby JPXman » Sat Jul 04, 2009 3:01 am

I think you have the only flying lazair with KFM engines on this forum. There is one other but he has never posted here.

So, you're a bit on your own - but shannon's fuel system advice is sound, but take all of it, not just parts. what I mean by that is, the best fuel system is simply a fuel line from the gas, to the carb inlet.

every single barb and hose connection has a good possibility of introducing air bubbles into the line. without properly sized hose clamps, there is always that little flat spot under the worm screw that doesn't seal the hose tight against the barb. primer bulbs are famous for introducing air bubbles. the two of us lazairing in edmonton found out this same thing over the course of trying to figure things out - so my recommendation is to eliminate the bulbs altogether and find another method of priming, and some really good hose clamps. the best I have found to date are here:

Bevel Heaven - ducati and dell'orto parts

he now sells the spring clips I just noticed but i don't know how big of a fuel line they clamp - they are ideal as they clamp circumferentially completely.

I think the carbs you have are pumper carbs, and one way you can prime them is to cover the velocity stack (trumpet) with your hand, and pull the prop through with the switches off (obviously). a few turns should get the gas sucked up the line. the check valve in the tank should hold the gas in the line for at least the day, but asking for more than that is wishful thinking. some people use shutoff valves, but again - more barbs = more chance for bubbles.

its easy to make things really complex when trying to solve gremlins, but at some point you have to get back to basics.

anyway, just a few thoughts.

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Postby sustainflight » Sat Jul 04, 2009 9:52 am

Thanks Tyler,

I used your link to order some of the 5mm hose clamps from Bevel Heaven; the hardware store clamps do have an annoying flat spot, particularly on the Dellorto fuel intake which fits a 3/16" ID tube. The Bevel Heaven spring clips appear to be sized for the 12 mm (3/16") OD, so they may be too small. I ordered a couple to test anyway. I also appreciate your list of hard to find parts on http://www.monisys.ca/~tparadis/.

The KFMs came with either Mikuni pumper carbs or the OVC/Dellorto float carbs. I have the latter. There is apparently a fuel pump and a float. Will try a few alternate ways of priming that would allow an unbroken fuel line from tank to carb; not sure if pulling the engine through (even with air intake blocked) would move the fuel on this carb.

Anybody know of sources for submersible pumps and/or very effective check-valves (the brass filters are fairly effective, diaphrams may be better) that I could put on the tank end of an otherwise unbroken line?

> the check valve in the tank should hold the gas in the line for at least
> the day, but asking for more than that is wishful thinking.

Sounds like I'm being overcautious. Losing a couple inches of fuel back into the tanks overnight is okay as long as I get bubble free flow while the engine is running?
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