[size=2][font="Arial"]I'd like to know if anyone out there can tell me if the 91fx is mounted on it's side on a U can Do 60 How do I get the muffler to clear the fuselage? If I Buy a tuned pipe system or a pitts style muffler which will fit best in the cowl If either will fit at all. I'd like to keep from invering a two stroke as mine is new and according to the OS rep you need to run two gallons of fuel through a two stroke before inverting it. As it sits a 91fx muffler will not fit on this plane without leaving the cowl off completely. I think if running a two stroke inverted is difficult they should not reccommend two stroke engines for such a narrow plane especially on a plane for beginners at 3D. Sorry to be long winded but any help in resolving this is greatly appreciated

dnb55, I'm running a 91FX on mine but only its inverted, I would almost be willing to bet you would be fine inverted but instead of installing a pitts you instead install a perry pump as I am doing, I have never had a lick of trouble running my 91 upside down with a perry on it. I also don't think you need two gallons through it, one should be just fine on a test stand.

You can grab one of the cheaper brands of fuel for break in as performance would not be an issue.

Also by using the perry pump, it will allow you to place the fuel tank on the CG, again as I have.

As far as mounting the engine inverted I had to drill two small holes on the opposite side of the muffler in the cowl to allow the allen wrench for tightning the muffler screws.

Blackie

Thanks for responding! Where can I buy a perry pump? Are they difficult to install?

I mounted my .91 upright. Sure the head sticks through the cowl but it works and it was free Tank in stock location, no problem hovering.

dnb55 here is the link for purchase.

http://www2.towerhobbies.com/cgi-bin...?&I=LXDG59&P=7

You will have to tap the crank case of the engine but its no biggie. What I did was to, and make sure you do this remove the rear crank case cover by removing the four allen head screws holding it in. Since the cover is thin metal I laid a thin layer of JB weld first, let it dry then I taped with the recommend tap set through both the JB weld and the plate, inserted the nipple provided and then added just a tab bit more JB weld around the nipple only.

The pump I mounted just behind the engine on the fuse just where the slop starts with a wood screw. To keep the pump from moving around in the plastic hold sleeve (also provided) I used RTV (silicone) to keep it in place.

One other thing I did was to replace the stock muffler with one from an older model Magnum in which gave me 400 more RPM, What I have seen others do with the stock muffler that comes with the 91FX is to remove the extending spacer which seems to help also.

With the pump setup this will also give you better throttle response when in a hover or 3D in general. Keeps a constant flow of fuel to the carb, hence engine inverted and at idle on the ground. One last thing I did for my configuration was to add a remote glow igniter, "NOT ONBOARD glow system" but a remote which allows you to apply a starter stick from another location on the plane.

http://www2.towerhobbies.com/cgi-bin...&I=LXBC35&P=ML

I wouldn't bother with the pump if I were you, I haven't found that one is necessary. I have mounted my 91FX inverted in my U-can-do 60, it runs fine. When I was breaking in the engine I did find it was easier to start it with the plane inverted, but after the first dozen or so flights I haven't done this - the plane has over 40 hours on it now. I do lots of hovering, up to a minute or so at a time. I am using the stock muffler, if you used a Pitts muffler it might not give the same back pressure, and I believe the power is somewhat less. The big OS muffler sure is ugly, and it weighs alot, but I believe it works a bit like a small tuned pipe.

The only time I would use a pump was if I wanted to mount the fuel tank around the CG, which I haven't done. My approach is to try the engine without a pump first. Only if I am having problems that I can't solve any other way would I consider a pump.

I believe some people had problems with fuel dripping out of the carb. The worst I have had is a drop or two, no big deal.

Malcolm

Good advise.

Malcolmm you are correct but only if the person is proficient in knowing how to tune an engine. The pump helps make up for this lack but also gives a bonus by allowing you to mount the tank on the CG and making sure there is a steady flow of fuel to the carb when in high alpha maneuvers and when the nose is pointed up.

In my case I had no choice as I was one of the ones that got a lemon, the pump solved my problems.

do like i did ronnie put on and amp down the muffler it will work i've got the 61fx on my 46 size and it works good they are the same case so it will work fine are you can bring it to me and i'll put it on for you



until next contact happy landings