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Wednesday, May 25, 2016

RCGF-USA 10cc Carb Upgrade

The RCGF-USA single needle throttle system didn't work out so well, so they have abandoned it on 10cc engines shipping these days (the website still shows the old carb and detached pump). My second engine came with a standard Walboro style carb. For us early adopters there is a RCGF-USA 10cc carb upgrade kit, its about $50 shipped, and comes with everything you need. I don't like the single needle system either, too sensitive, just putting a driver on the screw could change the RPMS by hundreds, and as it broke in I started getting lags on going from low to full throttle. This was interfering with flight demands, so I pulled the trigger on the upgrade.

I removed the engine from the Sukhoi and made the upgrade the day after it arrived. The easy part was doing the removal and instillation of the carbs. It doesn't come with instructions.


There is a single screw holding the single needle carb on the engine block.



After removing the screw the carb slips easily out with a twist.



The carb mount is different, so the mounting plate has to be removed from the back of the engine. Four screws and a gasket. Toss the old gasket, the kit has a new one.



That is one "butterfly" carb mount, and one helluva sturdy shaft and counterweight.



The new carb "butterfly"/mount uses the same 4 screws. The kit comes with new screws if you want to use them. Remember the gasket.  The two large bolts are the same as on most Walboros, and will be used to mount the carb to the block.



New carb "butterfly"/mount installed. Locktite everything, baby.



Carb installed. You can install it up or down, plan ahead, choose wisely, save time.



The dual needles. I removed the idle needle and unconnected the spring. Not that you can, but don't remove the spring as it helps keep the throttle body in place. It comes with a black tube and screw that you place over the old gas intake to close it off. I trim it and install it in seconds. It too is included. I didn't get a pic, sorry.


This was the easy part. It took ten minutes (five minutes was moving the darn spring), went exactly as planned. 

What would take several hours, and I am still not done, is mounting it in the plane and connecting the linkages, because its arranged different and I put the plane together around the engine, and I want the needle valves on top, so I fitted the carb cylinder down as I did before, and needles up. This puts the choke and throttle levers underneath on the cylinder side. Speaking of the choke, I wish you could reverse its orientation with a screw removal like you can the throttle. It points in, which if I was using a choke servo would be fine, but as it is I will need to jockey a wire around the cylinder to reach up front. 

The motor fits in the mounts with minor adjustments, though I did have to grind away a little plastic on the mount to allow the idle needle arm on the carb to not block the engine going back. I had to change the extension around so many times as I tried different orientations and linkages that the screw is worn out (hard to find a replacement. Joe, if you are reading this, can you throw one in an envelope?). I ended up having to trim off the outer hole end of the throttle arm to allow it to move its full range without stopping against the cylinder head. I am using the inner hole on the arm. I have tried a couple different throttle control linkage ideas, trying not to move the throttle servo.They all had issues of one sort or another. I finally stopped for the evening last night, worn out. I knew I would have to change the linkages, I just thought it would be more straight-forward. This is a me problem, not an engine problem. I have a plan, but will need to remove the throttle servo and figure out how to lay it on its side, and run the throttle arm fore and aft, like a a hanging leg, without too much drama. I had to change to a longer servo arm, which screwed the resolution all up but may be able to go back to the shorter original one. I will work on this tonight if I'm not dead after work, and tomorrow. Hope to run it tomorrow. More to come!

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