Mikuni fuel pump

Timchick

Tim Chick
Joined
Sep 15, 2004
Messages
10,894
Location
Panama City, Florida
Aircraft
Sport Copter Vortex, 582 Greyhead
Total Flight Time
~30
My gyro has a Mikuni dual fuel pump with the 2 outputs tied together before the lines get to the single carb. I was planning on adding a second fuel pump for redundancy like several people have recomended. Mikuni makes a single fuel pump with one outlet. Should I switch over and use 2 single pumps or add another dual pump?
 
Hey Tim ! Back in the mid 80's when we bought 2 gyros from Bill Parsons, one thing he told me was that I'd want to get rid of the little Mikuni & replace it with the round one. So I got one from him.....it's still in the box, never used.

He said to install it the way yours is. He told me that the small one would fail & that the round 2 outlet would be better.

I always worry about my rectangular one, but I havn't even installed a rebuild kit in it yet. Bill said that it wouldn't just quit but that it would give you some warning.

Also people say that they should be mounted away from heat & vibration, but keep the pulse line short.

Well mine is mounted to the side of the motor with plastic washers(447) & I am yet to have trouble.

Every time I consider installing the round one, I get a little frustrated trying to come up with the perfect way to mount it. It will not match the 2 holes I use for the other one. So I use the theory ....If it ain't broke, don't fix it !

But this is one issue I am always thinking about. Also the electic backup would be nice.

Maybe we could get others to post actual pictures of good mounting & plumbing for different types of engines.

I will try to remember to get some pics of my fuel systems today!

Oh, & Tim ...you'd better get to bed because if you are like me lately, you'd be waking up in 3 & 1/2 hrs !!!!
 
I have mine mounted to the engine with rubber isolators, did the same thing on Phil's Air Command. And I looked at Greg Spicola's and his is mounted to the mast on a piece of 1"x1" sq tubing.
 
On the Mikuni dual pump is there 2 diaphrams, one for each fuel outlet? If that's the case wouldn't one diaphram keep pumping if the other one failed? If the 2 outlets are tee'd together wouldn't that add a redundancy already without adding a second fuel pump? How many of you are only using one fuel pump and how many use 2? I'm just asking before I redo all my fuel lines, etc.
 
The round pump only uses one diaphragm. It has two outlets coming from the same chamber. No redundancy.
Alan
 
Tim. The round Mikuni pump is the correct pump to use. They come with 2 & 3 outlets designed for snowmobiles. I use the 2 outlet pump but plug one of the outlets with a 1/6 x 27 plug.You can see from the photo that the two pumps are tied together before they reach the carb. (Do not run one pump thru the other)
 

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Tim,
For redundancy, I would use a 3-7 psi electric fuel pump mounted in parallel to your Mikuni pump. If you install the Mikuni by the book, it has to be mounted horizontally and away from vibrations and heat. I mounted mine to the mast, as you can see in the picture.
Udi
p.s. Rick - your pump is installed upside down - the vent hole should be pointed down for drainage.
 

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Udi, I hadn't heard that they had to be horizontal. Thanks. I don't have a battery so an electric pump isn't an option.
 
The reason they should be mounted horizontally, Tim, is that the pulse chamber has a pinhole at the bottom for draining condensate. Gasoline vapors can get back from the crank case thru the pulse line and condense in the pulse chamber. If the pulse chamber filled with liquid the pump will stop.

You can use a small 12V motorcycle battery to run a fuel pump. Your engine will recharge it.

Your engine operating manual has much of this information.

Udi
 
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