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Mikuni Carb issue?

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jb92563

Joined: 23 Mar 2007
Posts: 314
Location: Southern California

Posted: Mon Nov 12, 2007 10:48 pm Post subject: Mikuni Carb issue?

I tried to run my Cuyuna UL II-02 today.



It fired up and squirted fuel out of its 3 float overflows like a perforated garden hose...quite a mess.



A quick removal of the float bowl revealed stuck floats and a dark goey gunk sticking the floats down.



After some cleaning with paint thinner the goey gunk is gone and the floats and overflows behaved and keep all the fuel inside the carb this time.



However the engine keeps dying of fuel starvation when I take it off the choke and advance the throttle.



The fuel pump is working fine as the fuel is entering the carb under preasure and the floats are doing their job and preventing fuel overflow now but the engine only gets enough fuel at idle to keep running off choke.



Sounds like I need tear down every part of the carb and check for gunk in every orfice.



Anyone have any other ideas or suggestions....I'm new to mikuni carbs.



PS: I Installed a Stratomaster E1 electronic instument that measures my EGT, CHT, RPM and Hobbs Engine time in one instument.



I'm very pleased as you can set the range and an alarm for measurement.



Very cool and I run it off a small 1lb Nicad rechargable battery. 



I also added a Flytec 3005 dual Altimeter and rate of climb instrument and a Dell Axim x50v PDA with the free XC-Soar software and plugin GPS card for a full moving map with airspace, airfields, digital terrain model etc for navigation.



My whole instument pack including battery weights about 4 lbs.



I'll have to put some pics up.

_________________
Ray

Kolb UltraStar (Cuyuna UL-202)
Moni MotorGlider
Schreder HP-11 Glider
Grob 109 Motorglider

Do Not Archive

jindoguy(at)gmail.com
Guest

Posted: Tue Nov 13, 2007 5:36 am Post subject: Mikuni Carb issue?

Ray, If the gunk was in the float bowl, chances are it's in the idle

circuit, the mid range needle jet, and the main jet, too. You don't

want to find that you have a circuit plugged or partially plugged on

climb out. Good old Gunk carb cleaner with the basket so you can soak

the carb body is a good way to go, then blow the passages out in

reverse with compressed air. Mikunis are similar enough to Bings that

you can use a picture of how the passages work to figure out what does

what.

I can send you a Bing drawing if you need it,  but the coffee has to

kick in first. 



Rick



On Nov 13, 2007 12:48 AM, jb92563 <jb92563(at)yahoo.com> wrote:

 	  Quote: 	
		   



 I tried to run my Cuyuna UL II-02 today.



 It fired up and squirted fuel out of its 3 float overflows like a perforated garden hose...quite a mess.



 A quick removal of the float bowl revealed stuck floats and a dark goey gunk sticking the floats down.



 After some cleaning with paint thinner the goey gunk is gone and the floats and overflows behaved and keep all the fuel inside the carb this time.



 However the engine keeps dying of fuel starvation when I take it off the choke and advance the throttle.



 The fuel pump is working fine as the fuel is entering the carb under preasure and the floats are doing their job and preventing fuel overflow now but the engine only gets enough fuel at idle to keep running off choke.



 Sounds like I need tear down every part of the carb and check for gunk in every orfice.



 Anyone have any other ideas or suggestions....I'm new to mikuni carbs.



 PS: I Installed a Stratomaster E1 electronic instument that measures my EGT, CHT, RPM and Hobbs Engine time in one instument.



 I'm very pleased as you can set the range and an alarm for measurement.



 Very cool and I run it off a small 1lb Nicad rechargable battery.



 I also added a Flytec 3005 dual Altimeter and rate of climb instrument and a Dell Axim x50v with the free XC-Soar software and plugin GPS card for a full moving map with airspace, airfields, digital terrain model etc for navigation.



 My whole instument pack including battery weights about 4 lbs.



 I'll have to put some pics up.



 --------

 Ray

 Riverside County, CA



 Do Not Archive





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=145597#145597

jbhart(at)onlyinternet.ne
Guest

Posted: Tue Nov 13, 2007 6:48 am Post subject: Mikuni Carb issue?

At 10:48 PM 11/12/07 -0800, you wrote:

 	  Quote: 	
		  

Anyone have any other ideas or suggestions....I'm new to mikuni carbs.




	


Ray,



Try:



http://www.carbparts.com/mikuni/mikuni_atv.htm



Also, you should be able to find a manual for your particular carburetor on 

the web.



Jack B. Hart FF004

Winchester, IN

by0ung(at)brigham.net
Guest

Posted: Tue Nov 13, 2007 6:59 am Post subject: Mikuni Carb issue?

 	  Quote: 	
		   However the engine keeps dying of fuel starvation when I take it off the

choke and advance the throttle.
	


 	  Quote: 	
		  


	


I would check for dirt in the float needle seat.    If it overflowed the

vents on one occasion...  then wont pass enough fuel on the next,,,,  the

common factor is the float needle seat.



Boyd

jb92563

Joined: 23 Mar 2007
Posts: 314
Location: Southern California

Posted: Tue Nov 13, 2007 7:37 am Post subject: Re: Mikuni Carb issue?

Those Diagrams of the carb really makes it easy to check the right parts out.



Will "Gunk" disolve the Tar like crud in my carb?



It was thick like mollases.



I'll tear the thing down and give it a good soaking for a couple days and clear out all the other passages with air and thin wires etc.



The Mikuni is a real simple carb.....can't see much else could be wrong except blokages.

_________________
Ray

Kolb UltraStar (Cuyuna UL-202)
Moni MotorGlider
Schreder HP-11 Glider
Grob 109 Motorglider

Do Not Archive

jimh474(at)embarqmail.com
Guest

Posted: Tue Nov 13, 2007 7:56 am Post subject: Mikuni Carb issue?

Y'all:

  

 Soak the carb in brake fluid, it will disolve all that  goop.

  

 Jim H

  

On 11/13/2007 10:37:48 AM, jb92563 (jb92563(at)yahoo.com (jb92563(at)yahoo.com)) wrote:

[quote] -->  Kolb-List message posted by: "jb92563" <jb92563(at)yahoo.com (jb92563(at)yahoo.com)>

 

 Those  Diagrams of the carb really makes it easy to check the right parts

  out.

 

 Will "Gunk" disolve the Tar like crud in my carb?

  

 It was thick like mollases.

 

 I'll tear the thing down  and give it a good soaking for a couple days and clear out all the other  passages with air and thin wires etc.

 

 The Mikuni is a real  simple carb.....can't

 see much else could be wrong except  blokages.

 

 --------

 Ray

 Riverside County,  CA

 

 Do Not Archive

 

 

 

 

  Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=145716#145716

  

 

 

 

 

 

 

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d-m-hague(at)comcast.net
Guest

Posted: Tue Nov 13, 2007 10:00 am Post subject: Mikuni Carb issue?

At 09:56 AM 11/13/2007, Jack B. Hart wrote:



 	  Quote: 	
		  Also, you should be able to find a manual for your particular carburetor on

the web.


	


Try http://www.mikuni.com/pdf/vmmanual.pdf .



                         -Dana

--

  Inflation is a result of legalized counterfeiting.

jindoguy(at)gmail.com
Guest

Posted: Tue Nov 13, 2007 6:05 pm Post subject: Mikuni Carb issue?

Don't know if Mikuni's have the same needle rotation issues as the

Bing. Shouldn't be very costly to replace the needle and clip. It's

been awhile, but as I remember Mikuni main jets were 1/4 the cost of

those for the Bing. If that holds, It's a sub $5 insurance policy to

replace the needle and clip. Might prevent one of those dasterdly

"Engine out/unlandable terrain" scenarios we've been hearing so much

about of late. 



Rick



On Nov 13, 2007 9:37 AM, jb92563 <jb92563(at)yahoo.com> wrote:

 	  Quote: 	
		   



 Those Diagrams of the carb really makes it easy to check the right parts out.



 Will "Gunk" disolve the Tar like crud in my carb?



 It was thick like mollases.



 I'll tear the thing down and give it a good soaking for a couple days and clear out all the other passages with air and thin wires etc.



 The Mikuni is a real simple carb.....can't see much else could be wrong except blokages.



 --------

 Ray

 Riverside County, CA



 Do Not Archive





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=145716#145716

rowedenny(at)windstream.n
Guest

Posted: Tue Nov 13, 2007 6:07 pm Post subject: Mikuni Carb issue?

Ray,

You have the right idea to remove all the jets and clean em with solvent and 

also the thin wire.

I recently put my Honda Odessy dune buggy back together and had to clean the 

gunk out of the carb with brake cleaner, it was not enough to blow the 

cleaner through the main jet, I had to run a wire through it to get the 

harder stuff out. Not getting all the jets completely cleared is a quick way 

to melt your piston. Don't ask me how I know.



Denny Rowe



---

d-m-hague(at)comcast.net
Guest

Posted: Tue Nov 13, 2007 7:31 pm Post subject: Mikuni Carb issue?

At 09:04 PM 11/13/2007, Richard Girard wrote:



 	  Quote: 	
		  Don't know if Mikuni's have the same needle rotation issues as the

Bing. Shouldn't be very costly to replace...


	


What is the "needle rotation issue"?  Something I should be concerned about 

with my Mikuni?



                                 -Dana



--

  CanYouFixTheSpaceBarOnMyKeyboard?

jb92563

Joined: 23 Mar 2007
Posts: 314
Location: Southern California

Posted: Tue Nov 13, 2007 10:24 pm Post subject: Re: Mikuni Carb issue?

Yes Dana,



Apparently at some harmonic the vibration makes the needle and circlip rotate in its hole and around the needle shaft.



Eventually the circlip fails and the needle falls into the jet into the idle position and the engine dies or stays at idle.



Its a good idea to replace the needle and circlip every once in a while as a precaution.



Thats what I read somewhere here or on the Ultrastar forum.

_________________
Ray

Kolb UltraStar (Cuyuna UL-202)
Moni MotorGlider
Schreder HP-11 Glider
Grob 109 Motorglider

Do Not Archive

jb92563

Joined: 23 Mar 2007
Posts: 314
Location: Southern California

Posted: Tue Nov 13, 2007 10:35 pm Post subject: Re: Mikuni Carb issue?

I cleaned the carb out tonight using brake fluid and WD40, and a wire.



After disassembly and cleaning of what I could get to and a repeated cleaning, wiring and blowing out the gunk I finally have a clean carb working right.



I fired up the engine and she runs off choke now.



The engine starts so easy....pull the cord about 6" through the compression and she fires right up......cool!



I fiddled with the idle, idle air and needle position so that I could get a smooth acceleration from idle to half power.



I think I need to read that Mikuni tuning pdf again....make sure I'm doing it the right way.



I'm totally impressed with the thrust of my 2 blade wood Ritz prop.



I'm going to need brakes though as at 1300 rpm idle there's enough thrust to make it roll.

_________________
Ray

Kolb UltraStar (Cuyuna UL-202)
Moni MotorGlider
Schreder HP-11 Glider
Grob 109 Motorglider

Do Not Archive

jindoguy(at)gmail.com
Guest

Posted: Wed Nov 14, 2007 6:09 am Post subject: Mikuni Carb issue?

Dana, It's been seven years since I had an engine equipped with a

Mikuni, which is why I phrased my concern the way I did.

One of the checks done during an annual on Bing carburetors (or any

time, for that matter) is to see if the carb jet needle spins freely

in the clip that sets its height in the needle jet. Bing has three

remedies of which you choose two. One is to squeeze the clip together

to seee if you can tighten up its hold on the needle. If unsuccessful,

replace the needle and clip. Also check the bottom of the spring seat

to see if it has a counterbore on its underside. If it doesn't,

replace it, too.

Now, whether you fixed it or replaced it, after you install the clip

back on the needle, Bing has a tiny O ring that is put on the needle

and up against the top surface of the clip, hence the need for the

counterbore in the spring seat.

If the needle is allowed to rotate in the clip it will eventually saw

through the needle and it will drop into the needle jet amd shut off

the fuel flow from the main jet which, just like the Mikuni, screws

into the bottom of the needle jet housing. I don't know if either carb

has enough fuel flow through the idle circuit to keep the engine

running should the needle fall into the needle jet.

I do know the wear does happen if the needle spins. On a 582 I worked

on at Sun n Fun, one of the needles was almost worn through. Just by

eyeball, I'd estimate the diameter of the needle where the clip was

installed was 1/3 normal.

See also Rotax Service instruction 8-UL 91E. I changed the name for my

personal files, but that is what's attached.

Rick

On Nov 13, 2007 9:26 PM, Dana Hague <d-m-hague(at)comcast.net> wrote:

 	  Quote: 	

 At 09:04 PM 11/13/2007, Richard Girard wrote:

 >Don't know if Mikuni's have the same needle rotation issues as the

 >Bing. Shouldn't be very costly to replace...

 What is the "needle rotation issue"?  Something I should be concerned about

 with my Mikuni?

                                  -Dana

 --

   CanYouFixTheSpaceBarOnMyKeyboard?

Carb_needle_wear.pdf

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jbhart(at)onlyinternet.ne
Guest

Posted: Wed Nov 14, 2007 7:10 am Post subject: Mikuni Carb issue?

At 10:26 PM 11/13/07 -0500, you wrote:

 	  Quote: 	

At 09:04 PM 11/13/2007, Richard Girard wrote:

>Don't know if Mikuni's have the same needle rotation issues as the

>Bing. Shouldn't be very costly to replace...

What is the "needle rotation issue"?  Something I should be concerned about 

with my Mikuni?

Dana,

The only reason it could be an issue is if the clip has a burr on it that 

will shave the brass needle as it rotates and the clip is held fast.  Check 

the clips for burrs and if they exist remove them with a jewelers file.  

If Bing had been careful about the clips they would not have to have added 

an "O" ring to the needle clip assembly to keep the needle from rotating.  

If the needle cannot rotate the burr can not shave the slot.

It might be a good thing to call Mikuni and ask if there has ever been a 

problem of the clips cutting the needles into two pieces.

Jack B. Hart FF004

Winchester, IN

d-m-hague(at)comcast.net
Guest

Posted: Wed Nov 14, 2007 7:42 am Post subject: Mikuni Carb issue?

Thanks Rick and Jack,



 When I had it apart the other day (moving the needle clip for colder weather) it looked tight, but I'll check it again.  According to ultralightnews.com (referring specifically to the Mikuni):  "The first and most widely reported was the failure of the retaining clip of the jet needle, due to vibration and fatigue located in the carb slide. This failure allows the jet needle to fall down into the main jet cutting of the supply of fuel to the engine. 



  "The engine still runs but at an idle. This should be an area of regular inspection. An update kit was available at one time which replaced the slide and jet needle, and allowed for the placement of a small plastic spacer between the slide and clip helping to eliminate wear and fatigue on the clip."



 



                                  -Dana

 --

  This is a test of the emergency tagline system.  Were this an actual tagline, you would see amusing mottos, disclaimers, a zillion net addresses, or edifying philisophical statements.  This is only a test.    [quote][b]

gaman(at)att.net
Guest

Posted: Wed Nov 14, 2007 3:53 pm Post subject: Mikuni Carb issue?

The carb update just uses an O ring around the needle just above the clip.The pressure of that O ring being squeezed between the plastic spring seat and the base of the slide prevents the needle from spinning in the clip.



Dana Hague <d-m-hague(at)comcast.net> wrote:[quote]  Thanks Rick and Jack,



 When I had it apart the other day (moving the needle clip for colder weather) it looked tight, but I'll check it again.  According to ultralightnews.com (referring specifically to the Mikuni):  "The first and most widely reported was the failure of the retaining clip of the jet needle, due to vibration and fatigue located in the carb slide. This failure allows the jet needle to fall down into the main jet cutting of the supply of fuel to the engine. 



  "The engine still runs but at an idle. This should be an area of [quote][b]

d-m-hague(at)comcast.net
Guest

Posted: Wed Nov 14, 2007 5:09 pm Post subject: Mikuni Carb issue?

At 06:52 PM 11/14/2007, gary aman wrote:

 	  Quote: 	
		  The carb update just uses an O ring around the needle just above the 

clip.The pressure of that O ring being squeezed between the plastic spring 

seat and the base of the slide prevents the needle from spinning in the clip.


	


I don't have a plastic spring seat in my carb, just the metal needle 

retainer plate.  Presumably it would work the same, but then the plate 

wouldn't sit down flat against the slide?



                                 -Dana

--

  It feels great to wake up and not know what day it is, doesn't it?

gaman(at)att.net
Guest

Posted: Wed Nov 14, 2007 6:37 pm Post subject: Mikuni Carb issue?

Sorry, thought the inquiry was about the update on the bing 54 series.You don't want to  change the location of the needle in relation to the slide  no matter how you secure the needle. 



Dana Hague <d-m-hague(at)comcast.net> wrote:[quote] --> Kolb-List message posted by: Dana Hague 



At 06:52 PM 11/14/2007, gary aman wrote:

 	  Quote: 	
		  The carb update just uses an O ring around the needle just above the 

clip.The pressure of that O ring being squeezed between the plastic spring 

seat and the base of the slide prevents the needle from spinning in the clip.


	


I don't have a plastic spring seat in my carb, just the metal needle 

retainer plate.  Presumably it would work the same, but then the plate 

wouldn't sit down flat against the slide?



                                 [quote][b]

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