Eagler's Nest

Engines => 2 Cylinder => 1/2 vw => Topic started by: leshoman on December 02, 2013, 07:46:03 PM

Title: Mikuni Float Level setting 1/2VW
Post by: leshoman on December 02, 2013, 07:46:03 PM

I am getting fuel from vents on one carb and not the other.  I make the assumption one float is set slightly higher than other.  Any thoughts what they should be set at on our Eagles.

Title: Re: Mikuni Float Level setting 1/2VW
Post by: Steve on December 03, 2013, 08:04:08 AM

Les:

If you are getting fuel spits at low rev's that's in the nature of the Mikuni's... If they are vibrating work on  changing that... I have written a number of Mikuni gas or fuel spitting messages over in the group conversations - I don't know if the search function is working over there but you find the string slot at the top of the screen slightly to the right side and click the [Search Groups] button to launch the search...

Steve

Title: Re: Mikuni Float Level setting 1/2VW
Post by: rockiedog2 on December 03, 2013, 05:59:24 PM

mine spit a lot at idle. I ckd the float levels and OK. So I just let em spit now. Gets on the pilot at idle airborne.
For a while mine were dumping fuel at high power settings. Rigged some arms back and strapped em to that cause they were shaking. That stopped it and also the power/smoothness improved. Like Steve said...shaking
Spencer

Title: Re: Mikuni Float Level setting 1/2VW
Post by: Bob Wood on December 10, 2013, 09:08:51 AM

Steve, I read your post someplace that the Mikuni's can come with a fuel pump or gravity pump inlet valve ,how can  I tell what I have on my 28mm. It just looks like a brass inlet with hose barbs on it.....
thanks,
Bob

Title: Re: Mikuni Float Level setting 1/2VW
Post by: leshoman on December 10, 2013, 10:17:04 AM

I believe the size of float valve opening is what it is about and if you open the carb. Remove float and needle valve and the brass seat the hole is in brass seat. I forget the sizes but steve had sent me something and i found more on internet. Mine is gravity feed an hole is larger than 1/8"

Title: Re: Mikuni Float Level setting 1/2VW
Post by: Steve on December 10, 2013, 10:57:55 AM

Go here to see the answer to questions in the photo Comments...

http://www.eaglersnest.com/forum/index.php?action=gallery;su=user;u=3 (http://www.eaglersnest.com/forum/index.php?action=gallery;su=user;u=3)

Title: Re: Mikuni Float Level setting 1/2VW
Post by: Dan_ on December 10, 2013, 11:33:24 AM

The vent tubes serve 2 purposes, allowing the float bowl to be at atmospheric pressure, and provide a place for fuel to go (instead of your oil pan) if the float or needle and seat malfunction.  They can be affected by slipstream and prop blast.  


Consider this post I ran across on the net:
 The reason many people connect the two vent nipples together with a single tube, is to minimize the effect of the wind that is created by the prop.   An open tube can act as a venturi, creating negative pressure inside the bowl.  The bowl has to be at atmospheric pressure in order to have a consistent level of fuel in the bowls. To minimize the wind effect, connect the two nipples with one tube and make a few small (1mm) holes along this tube for venting and draining.   Make the holes symmetrical on the upwind and the downwind sides on the tube to cancel out the wind effect.

Could be an answer, and could be a lot of tinkering to get right...:o

Addendum:  Make certain any changes you make to the vent tubes does not adversely affect your mixture.  Modifying the pressure in the float bowl chamber is used by a commercial mixture control product...  

Title: Re: Mikuni Float Level setting 1/2VW
Post by: leshoman on December 10, 2013, 05:48:45 PM

That spunds good BUT. I know an eagle driver that put his in the bay because those tubes were teed and run down gear leg turned out to be a low pressure area and after about 10 minutes flying power went away. Not a good first flight

Title: Re: Mikuni Float Level setting 1/2VW
Post by: Dan_ on December 10, 2013, 06:12:59 PM

Quote from: leshoman on December 10, 2013, 05:48:45 PM

those tubes were teed and run down gear leg

Right,  I'd say it would not be a good idea to run them anywhere very far.  Perhaps just enough to get them out of the slipstream and prop blast.  Definetly don't want the bowl to have a pressure differential... 

Would definitely stay over the field until absolutely sure when monkeying with it...

Title: Re: Mikuni Float Level setting 1/2VW
Post by: Dan_ on December 10, 2013, 06:37:20 PM

Les,
I'd say the best way forward is to let Spencer figure it out...  See attached...  His vent tubes are definitely out in the breeze...  Looks like prop blast and slipstream...

Title: Re: Mikuni Float Level setting 1/2VW
Post by: leshoman on December 10, 2013, 06:59:56 PM

Mine are just like his.

Title: Re: Mikuni Float Level setting 1/2VW
Post by: Dan_ on December 10, 2013, 08:15:38 PM

I'd say it is going to take a short piece of 1/2 inch aluminum tube about six inches long, drilled top and bottom in 8 or 10 places, much like the static for a pitot.   It may need the ends plugged.


Strap the sucker under the carb and run the 2 vent tubes into it.  Orient the holes 90 degrees to the slipstream.  This will conveniently align 2 of the holes to accept the vents...


We have it solved, all we need is for Spencer to try it out.8)

Title: Re: Mikuni Float Level setting 1/2VW
Post by: rockiedog2 on December 11, 2013, 06:54:10 PM

Good idea...sounds like will work
I put it on my list
am heads down right now in this new thang
besides, the temp is kinda low nowadays

Title: Re: Mikuni Float Level setting 1/2VW
Post by: Dan_ on December 11, 2013, 07:03:40 PM

Awight tin (http://wavcentral.com/sounds/movies/slingblade/allright.wav)

Title: Re: Mikuni Float Level setting 1/2VW
Post by: leshoman on January 01, 2014, 08:42:48 PM

We'll I have checked float levels. Both the same. Added carb stabilizers to keep then as one with the engine. After one hr flying today it appears EGT is down 50 to 75 degrees. Forgot to check overflows.  Nice to not see the carbs shaking

Title: Re: Mikuni Float Level setting 1/2VW
Post by: Steve on March 01, 2014, 07:43:32 PM

Quote from: leshoman on January 01, 2014, 08:42:48 PM

We'll I have checked float levels. Both the same. Added carb stabilizers to keep then as one with the engine. After one hr flying today it appears EGT is down 50 to 75 degrees. Forgot to check overflows.  Nice to not see the carbs shaking

How are the Mikuni's behaving?

Getting 1400 F static EGT?

Both carbs showing about what EGT temps?

Are those VM-32's and what main jets?

Title: Re: Mikuni Float Level setting 1/2VW
Post by: leshoman on March 01, 2014, 08:01:20 PM

The stablizers and changing float level on on side where it was spitting and learning how to adjust the needles and playing with jet sizes i cam put theme where i want then   I am running just below 1400 at low altitede. Carbs are 34's