fit90

Last weekend I took out a NIB .061 AP and broke it in. Everything was pretty good except the idle/transition. After going through many back posts I decided to try an adjustable air bleed mod. I got a #0-84 drill and tap kit and a 0-84 bolt. I decided on the size due to the small amount of material between the front of the carb body and the barrel. All went well and the two holes lined up. Unfortunately I did not purchase a stop nut to keep the bolt from moving due to engine vibration. I hope to pick one up before the end of the week and try it out. I just wanted to thank everybody for sharing your wonderful ideas, knowledge and insights. Without them I would probably not have tried this simple mod. I will keep you posted.

Jaspur_x

My Feedback: (1)

Did you try a spring instead of the stop nut? Thats the way I might have went with it.

fit90

Jaspur x,

Great idea.  The spring should be far more convenient than the screw.  I will try to find a spring small enough and try that and the stop nut.

Thanks,

Bob

fit90

Good news, I used the throttle stop screw's spring to tension the airbleed adjustment screw.  I ran the engine today.  At first idle would not settle down below 6000 RPM.  I opened the airbleed hole with a #53 bit and tried again.  Using an APC 5.7x3, Sig Champion 25% with one ounce of castor added per quart and the original head and plug I was able to get an extended and steady idle of 5300 to 6000 RPM with a good transition to full power of 18000 RPM.  This is just a little rich (about 500 RPM below peak).  I might get the idle a little lower with a bigger airbleed hole-the adjustment screw is in a position where the hole is wide open.  I have stayed with the original 0-84 adjustment screw that I started with.

Andy W., I want to especially thank you for your ideas and pictures of the adjustable airbleed on your VA.  My highly unqualified and unrepeatable experimentation shows that you have been right on all the way-thank you!

AndyW

My Feedback: (1)

fit90,

You're certainly most welcome and thank you, I do so much appreciate your comments and congratulate you on your success. Good throttling has been a passion of mine for a long time. I would love to see the plane you're going to put this engine into. [8D]

juanjulian

My Feedback: (9)

Andy:

In wat post do you haver your mod pictures. Have a norvel 0.061 with the same problem. Will like to do the same mod.

Cheers,

Juan Vadillo

AndyW

My Feedback: (1)

Hi Juan,

I never did do a post on how to do that. Just some random pics, here and there, mostly showing how I modified the first VA carb to take an adjustable screw for the airbleed and then how VA came up with a redesigned throttle that had the feature.

Norvel had the barrel close in the reverse direction from normal. When the throttle was bolted in, it was relatively easy to make the modification. Then they went to that cast body throttle and used a *&^%$#* slot for an airbleed. Your engine is one of the VERY early Norvels and has the throttle glued in. In that case, there's a way to install an adjustable airbleed that, intuitively, looks wrong but works. I haven't tried that on your type of throttle, though. Normaly I would apply heat to the body of the engine to burn off the glue to take the carb out and do the mod and then glue in the carb in the normal orientation.

I would love to bring you back into the fold of REAL engines. I'll try and take some detailed pictures as to how it's done on your design throttle and post that in a new thread. Right now though,I have some family issues but I'll try and do that within the following week.

The following pics may help.

fit90

Andy,

On the first two pictures how is the airbleed screw assembly attached to the carb body?  Is it welded or glued?  That set up looks like it could be far more forgiving and more flexible.

I plan on putting the mdified  AP .061 on a Sktdrill that I hope to start building in the next two or three months.  Unfortunately, I am an incredibly slow builder; but with a little luck it should be flying by Thanksgiving.  In the mean time I plan on trying to put the adjustable airbleed on some Norvel carbs.

Thank you again for being so generous with your ideas and knowledge and the best of luck with your family issue.

Bob M

fit90

Juan Julian,

Norvel FAQ pages 16 and 17 were my starting point for learning what I needed to do.  If I remember properly there are a few links to youtube videos also.  If not just try typing in the names of 1/2A engines and throttle and you should find some helpful videos.  I have not tried this mod on a Norvel carb yet but I hope to in the next few weeks.  I will put the results on this post when I complete the mod.  In the mean time good luck and keep us all posted.

Bob M

AndyW

My Feedback: (1)

Bob,

Both, sort of. The first two pics show an idle screw carrier that was JB Welded to the carb body. No other way to do that considering how the stock carb was made. And, of course, the second two pics show VA's final version.

Juan,

Here http://www.youtube.com/user/hopeso#p/a/u/2/oj7EqwLqXLs are my videos dealing with tinkering with engines.