blackrapids

I have the120 SP mounted in a TF Corsair.Because it is a taildragger I have a lot of trouble keeping fuel to the carb when I am trying to start the engine. Once the engine starts it pulls the fuel just fine on the ground. I have not flown it yet. So I do not know what will happen in flight.It's currently set upwith the uniflow systembut that does not help me much with keeping slight + pressure to the carb before starting besides when I hold my finger over the muffler topush fuel to the carb it pushes fuel to the muffler also and tries to siphon my tank out.If I had known this before I would have mounted the engine so that the carb was muchlower than the engine. Right know it is level which means when on the ground sitting on its tailwheelthe fuel tank is lower than the carb. This 120 likesto haveplenty of fuel available when starting. Theengine does not like the uniflow system (on the ground) as well as the 2 line system.It sputters and is difficult to tune.I do not know whichsystem willperform better at altitude.Right now I am more confident with the 2 line system. Can I use pressure from the crankcase such as use with a regulator. Any suggestions welcome. Thanks, Brian

PeterF

Have you tried the recommended fuel which is 10% nitro and 15% oil, old guidance was oil should have small castor content but now full synthetics seem to have been approved. I was talking to owber of local model shop few days ago and he said the only problems he sees with customers and RVC engines is when the wrong fuel is used. He said they are fairly critical and the recommended fuel should be stuck to.

Another thought, the cylinder has not been rotated on the crankcase has it to alter relative direction of ports and starter as the timing could be slightly off - bet then would not run when it did light.

blackrapids

I will try the 10% nitro and see how that works. Idid discover thatthe engine does not have enough fuel available to start. I have tried several different remediesbut no success. Actually it starts best when the carb is very rich or flooded.The timing is fine, I have not touched that.

trysforscale

I have a 120 sp in a p 6 e hawk , a tail dragger , and I have a small cardbord box that I sit the tail wheel on just to make the fuse level for starting . These engines really do like to be very rich to start and idle the lowest when they are rich . I use muffler pressure into the tank , a line out to the carb and a third to fuel and defuel . I use coolpower 10% and it runs well .

Joe Lott

Brian,

Tryforscale's idea sounds very practical to me. Tell me, is there any way you can get a finger over the carb inlet to try to choke it from there? I made a removeable hatch in the cowl of both my TF Corsair and CMP Zero to get to the RCV's inside. They're big hatches. Basically the top half of each cowl is removeable. Those hatches stay closed via rare earth magnets in each corner. They have never come off in flight. But since your plane is finished, you might not want to start experimenting with big holes in your cowl.

blackrapids

I think the box idea will probably work. I found out as you guys already have that I have to put a finger over the carb to choke it and then lift thetail up so the fuel runs down the carb.Then put the glow starter on andshe starts right up! Man what a learning curve. I will have to cut a hole to reach in or make a hatch as you have, thats pretty slick by the way. I also thought about attaching a tube to the carb and run it through the cowlbut that might introduce to much debris. It would be awsome if they included a choke on those carbs.Got the uniflow system setup. Since I have found the "secret" starting methods (LOL) I have had quite a few successful starts. After all of this trouble I found out that RCV has an onlinestarting guide which outlines these techniques. I am starting to like the engine more now. The muffler quite frankly is a piece of crap. I have it JBwelded now but will probably have to get a new one but I am not buying anoriginal replacement. I have heard that the vibration also wears the carb needles out? Any other helpful pre-warning or preventive maintenance hints would be greatly appreciated. I thought about dropping some mild loctite onto the needle threads. Joe Igrew upin Alabama little town called Clanton.Thanks for your help guys, Brian

Joe Lott

Yeah, I know where Clanton is...a little south of me.

And yes, the mufflers aren't sturdy enough for the engines. On my 120, I made my own exhaust system. I put a 90 deg. bend in a piece 7/16" ss tubing and threaded both ends with an M10x.75 tap. I then tapped a coupling (piece of larger tube) to fit the end my my header and drilled and tapped the side of it for the nipple to charge my fuel tank. I then threaded a straight piece of the 7/16" tubing and screwed it onto the back end of the coupling. On the end of the second piece of tube added a 90 deg. 1/8" street ell (a cast pipe fitting that is larger on one end than the other). I tapped it out to fit the threads of the pipe. I then drilled and tapped the ell fitting for a nipple for the crankcase breather hose. It all fits inside the cowl of the Corsair with only the tip of the exhaust sticking out.

Those steel fittings can be tightened much more than the aluminum muffler and don't expand at such different rates as aluminum connected to steel. Mine doesn't loosen at all.

www.westonuk.co.uk sells a new pitts-type muffler for the SP series, but it is a little pricey. It would work great, though.