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PostPosted: Wed Apr 22, 2009 8:55 am
by Shannon
Thanks Tyler ! I can't take credit for much of what I know (or as someone once said "what I think I know") about Lazairs. Much of what I share was learned from other people and not ideas or notions of my creation. It's hard for me to convey how difficult it was for Lazair guys in the past who had to "learn as they went along" or "make it up as they go" using trial and error. Today people are really lucky as they have a wealth of information at their fingertips they can consider and utilize at will. Very lucky indeed !

As for the fuel system on our planes I say keep it as uncomplicated as possible. The way that Ultraflight had the fuel systems set up for 185s proved to be very good. Continuous lines from tank (in-tank filters) to the carbs has proven to work well also. Multiple splices in the lines, in-line filters, primer bulbs, T's, shut-off's ect. all serve to increase the chance for problems. I say be very wary of your fuel system (no matter how it's set up) as often problems with 2-strokes are fuel related. As Tyler mentions always use quality lines and replace them at reasonable intervals. I also can't stress enough the importance of using fresh gas and oil mix. Never let mixed gas sit up in your tank for any long period.

PostPosted: Wed Apr 22, 2009 2:18 pm
by bdiedenhofen
Too true Shannon,
I've got the blue lines on mine, and they're great. Anyone looking to replace fuel lines, go with the blue ones for sure. I have the filters in the tank with the little ball to act as shut off, but find that over time the fuel still drains from the lines. So I added manual shut off's at the engines two years ago. For the first year everything was fine, and last year I started to develop air bubbles at one engine. The bubbles are visible after the valve. So I replaced the valve with a new one, but still getting bubbles.
I wonder if the fuel line is getting porous somehow with age? (They're five years old now). Or, if the valves are actually allowing air in to the system? Not sure. So, I'll replace the fuel lines with new, and may remove the valves altogether.
It's a pain without them as I removed the decompression valves a long time ago. Too many failures. So now my compression is high and I like to start the engine as few times as possible. Without the valves, I'll have to prime - start - draw fuel up - engine quit - reprime - restart.
Ah, what would life be like if we didn't have little problems to challenge us?
Brian D.

PostPosted: Fri Apr 24, 2009 8:14 am
by Shannon
Hi Brian,

How were the shut-off valves secured to the lines ? How were the lines secured to the carb barb turret inlets ?

One method we've long used to secure connections is double looped safety wire on the attachment barbs (filters and carb). I've found that small fuel line clamps of different sorts to be problematic with the blue fuel line. I think most metal clamps were intended to be used with rubber type fuel lines. I personally don't care for the plastic "crimp type" connectors and I never use "zip-ties".

I think it's a good idea to change the fuel lines say every 2-3 years. Much beyond that and I don't trust them anymore. I also think it's a good idea to remove the lines from your tank during short storage periods. We have always used the "lines run through the cap" method so it's no big deal. A handy secondary cap with no holes is then placed on the tank during short storage periods to prevent contamination and evaporation.

On a related note some guys have expressed having good luck with yellow Tygon F4040 fuel line. Here's a few fuel componet links. ... uel%20line

PostPosted: Fri Apr 24, 2009 8:36 am
by xgary
Fuel lines.

Guys Call Bob Robertson 866-418-4164
Fuel line shipped out to Canada overnight ,Rotax 185 parts
He the biggest Rotax Shop in Canada and he is one hell of a nice guy.

Here is a poor quality pic but on double looped safety wire.
Tie wraps can come loose

PostPosted: Fri Apr 24, 2009 9:27 am
by bdiedenhofen
Thanks guys,
I'll try the double wrapped safety wire when I install the new lines. Shorty, thanks for the contact, I ordered mine from LEAF cause I didn't know of anyone local. It's nice to know there's someone around that carries 185 parts.
Brian D.

PostPosted: Fri Apr 24, 2009 12:40 pm
by russell
Brian, your bubbles are most likely not air bubbles but rather gas vapor bubbles. They come from the fuel itself. Things installed in the line triggers the fuel to vaporize and forms bubbles. Vibration is the real culprit. I was running my Pioneers on a test stand and with the rpm's up. The temporary fuel line (with no valves, filters, fittings, etc.) running from the tank on the ground up to the carb touched the stand itself and a steady stream of bubbles developed right at the point of contact.
You can search the archives and find a lenghty discussion about this topic.


PostPosted: Fri Apr 24, 2009 1:16 pm
by lazairiii

One observation I've noticed time and time again (just my own experience here) is that when I have a full tank of fuel (5 gal), and until that fuel gets to about 2 gallons I do not have any vapor bubbles in my blue lines that run directly uninterupted from tank to carb, but when I get below about 2 gallons, I begin to see these vapor bubbles start to appear. I tend to wonder if it isn't a pressure issue due to something with the weigth of fuel and or carb pulse in the lines. I don't really know for sure, it's simply something I've personally noticed on my plane.

I've never had as much as a hick-up with these vapor bubbles, but they are a little bit interesting to look at.


PostPosted: Fri Apr 24, 2009 3:47 pm
by russell
Yeah, I've never lost an engine because of bubbles either. When the series 1 had the primer bulb on it the vapors would build up inside the bulb and then all of a sudden they would come belching out. Really made me sit up and pay attention!

I agree George, pressure or rather the lack of, plays a roll in the bubble issue. Because the gas is pulled rather than pushed, a vacuum is being created which results in less atmospheric pressure. An extreme example is the propane tank on a BBQ grill. As long as it's under pressure the propane will remain a liquid but as soon as the pressure is released it vaporizes. As for having an impact on the Lazair's fuel supply it's probably more theory than practicallity!


PostPosted: Mon Apr 27, 2009 8:43 am
by bdiedenhofen
So my valves being attached to the engine mount would definately produce some vibration. Interesting that I only really see the bubbles on one engine, much more than the other. I too have not had any problems as far as engine performance goes. It's just a bit of a worry when you see so many bubbles running in to the carb.

PostPosted: Mon Apr 27, 2009 9:13 am
by Shannon
One thing I've learned is that if you see or hear something different between the engines STOP right there and do a good investigation. If for example an engine backfires, coughs, makes a funny sound, or generally just does something weird STOP right there and check it out good. The 185's have a great habit of giving a little warning that something is about to go wrong.

Some small bubbles in the lines seem to be entirely normal. Large amounts of big bubbles well... STOP right there !

I've posted this 20 times but here goes again. The in-tank filters part number #FUF02 from Spruce Aircraft were found to cause bubbles in my lines. These filters look exactly like the OEM type in-tank supplied by the factory but have no check ball inside. Stay away from those filters. Manufacturers supply and other places have the OEM type in-tank check ball equipped filters.