Mikuni Carburetors for Rotax 912ULS ?

For general discussion of the Just Aircraft family of aircraft.
Includes: Highlander, Escapade, Summit and SuperSTOL.
Post Reply
User avatar
marl59
Seasoned Member
Posts: 84
Joined: Thu Oct 22, 2015 5:59 pm
Location: Oakland, CA

Mikuni Carburetors for Rotax 912ULS ?

Post by marl59 »

I wanted to ask my fellow Rotax owners if they or anyone they know have ever explored the possibility of substituting a pair of new Mikuni carburetors for the problematic Bing 64s on the Rotax 912 engine. I was looking at a Mikuni TM36-68 pumper carb on a guys 500cc motorcycle yesterday and it looked like a great set up. I took some rough dimensions and it looked like it could be made to work with some innovative massaging. The first question that comes to mind would be high altitude operation. I have used Mikuni's over the years in motorcycle operations and they have always been solid performers. I haven't checked hard dimensions yet to see if the 36mm would be the right one for the Rotax intake boot but Mikuni has many models in various sizes, so I'm pretty sure one that would fit and have the proper CFM flow for the Rotax. The Mukuni's sell for about $280. Here are some adaptability items that would have to be addressed:
Crossover tube adapability
Throttle cable adaptability
Choke cable adaptability
Intake & air filter boot adaptability etc.
Proper jetting.
Any thoughts from the community would be appreciated!
User avatar
Av8r3400
Seasoned Member
Posts: 57
Joined: Mon Aug 04, 2008 6:50 am
Location: North Central Wisconsin
Contact:

Re: Mikuni Carburetors for Rotax 912ULS ?

Post by Av8r3400 »

What's problematic about the Bings?

There are tens of thousands of them operating just perfectly. They are simple, easy to work on and matched perfectly to the engine.
Av8r3400
User avatar
marl59
Seasoned Member
Posts: 84
Joined: Thu Oct 22, 2015 5:59 pm
Location: Oakland, CA

Re: Mikuni Carburetors for Rotax 912ULS ?

Post by marl59 »

Carburetors are pretty simple. I have been trying to get mine to stop leaking for several months now. The floats I replaced were around $100 for the pair and there are 4 of them, still leaks. The float needles I replaced were around $40+ each, still leaks. The seats will be replaced next which I will have to take to my Rotax mechanic to do so it will end up costing more, hopefully no more leaks. So I have to leave the gas off when the plane is not running. I can do that. When the is throttle closed too hard against the light metal stops, they go out of sync. My tail wheel instructor did this so hard on one of our training flights that the engine wouldn't idle after we landed. Had to re-sync the carbs. The replacement cost is around $1,200 for each of the carbs and there are two of them. And I agree, there are lots of them in service and they are simple to work on. And I like the altitude compensation feature. I just hate the overpriced parts. So that's the reason I wanted to put the question out there to see if anyone had explored the Mikuni option. Thanks for replying!
User avatar
FlyerChief
Veteran Member
Posts: 290
Joined: Tue Nov 03, 2009 9:53 pm
Location: Ontario, Canada

Re: Mikuni Carburetors for Rotax 912ULS ?

Post by FlyerChief »

Have you installed carb cable stops to prevent them from being pulled too hard?
Carb Cable Stop.jpg
They tighten in position with an Allen screw ... simple but effective.
Dan
You do not have the required permissions to view the files attached to this post.
When everything seems to be going against you, remember that the airplane takes off against the wind, not with it. ~Henry Ford
User avatar
marl59
Seasoned Member
Posts: 84
Joined: Thu Oct 22, 2015 5:59 pm
Location: Oakland, CA

Re: Mikuni Carburetors for Rotax 912ULS ?

Post by marl59 »

No I haven't. I didn't know they existed. Great idea! Where can I get them? Thanks!
User avatar
gkremers
Veteran Member
Posts: 495
Joined: Sun Aug 08, 2010 8:06 am
Location: Michigan

Re: Mikuni Carburetors for Rotax 912ULS ?

Post by gkremers »

Lockwood or McFarlane has them
jak
Veteran Member
Posts: 445
Joined: Mon Mar 17, 2008 9:40 pm
Location: toccoa Ga

Re: Mikuni Carburetors for Rotax 912ULS ?

Post by jak »

The ones in the pictures come with the McFarline cables but any cable stop will do. Jak
Pick up a rifle and you instantly change from a subject to a citizen.
User avatar
SheepdogRD
Proprietor
Posts: 930
Joined: Tue Nov 30, 2010 5:41 pm
Location: West of Atlanta, GA

Re: Mikuni Carburetors for Rotax 912ULS ?

Post by SheepdogRD »

You can find them in the aviation section of your local auto parts store. Dorman 03336 is an assortment of six stops in three sizes for $3.
Cable Stop - Dorman 03336.jpg
Summit has them (http://www.summitracing.com/parts/rnb-03336) for $2.69.
You do not have the required permissions to view the files attached to this post.
Richard Holtz
Highlander N570L -- Ms. Tonka -- in gestation

If just enough is really good, then too much ought to be perfect.
User avatar
marl59
Seasoned Member
Posts: 84
Joined: Thu Oct 22, 2015 5:59 pm
Location: Oakland, CA

Re: Mikuni Carburetors for Rotax 912ULS ?

Post by marl59 »

Thanks guys for the feedback. I will order some cable stops and if I decide to experiment with the Mikuni carbs I'll post my results.
Post Reply

Return to “Just Aircraft”