Hello everyone, I have a new, but three year old Rossi 45. I am using 10% nitro Omega fuel and using a APC 10x6 prop and an O.S. #8 glow plug. The engine is running great on top end.
However, it is loading up on the bottom end. The engine hesitates when I give it full throttle from idle speed, to the point it almost stalls. I have the low end needle valve screwed in almost all the way in. Does anyone out there know how to get this engine running right? I know that Rossi engines are suppose to run on fuel without nitro, but this type of fuel is not available in my area. Thanks for your help.

Check the plug... put in a new one and try again...

And make sure your not actually too lean at the bottom... try making it richer and see how that does...

Robert,

Your Rossi needs the included extra head shim just to run 5% nitro. You need another extra head shim to safely run 10%.

The Rossi carburettor has an inherent midrange problem, that cannot be cured by changing the glow plug.
There are other replacement solutions out there, though.

Cub: Go in the direction of DarZeelon, I have a lot of Rossi for years and from different manufacturing date and all of them have same problem. Mine runs max 5%nitro and one shim. Rossi carbs are smaller venturi making transition problem due porting configuration.You have tro options :

1-Go to http://shop.vendio.com/rossienginesusa and contact Sahak, they have Perry carb and will help you a lot if you don't know how to deal with Rossi engines.Just swap carb.
2-Bore your stock carb at least 1mm. Ideal will be 2mm. This is the difficult way and also need some special tools.

Before doing any mods, please add shims or lower your nitro to no nitro but remember, transition never will be same as an OS but they develop a lot of power.

David P.

Replacement of the carb is not necessary.

The Rossi carbs installed on many .40, .45, and.53 had too long of a spray bar. This would not allow proper adjustment of the low speed mixture screw. The problem you described is typical of these carbs.

To fix it is simple. Pull the carb from the engine. Remove the high speed needle and throttle barrel. Using a drill bit that is slightly larger than the spray bar, mill the end of the spray bar until you have removed 1/8"-3/16" of length. The brass is so soft that you can twist the bit with your fingers and prevent accidental excess material removal. Clean it all up, reassemble, and remount it on the engine, remembering to press the carb firmly into the bore while tightening the pinch bar.

You will find that you can now tune your engine to idle as normal.

Have Fun!

Ray,

I have the same problem with Rossi 45, loading up at idle. You are milling the end of the spraybar from the carb barrel side? There is slot in the bottom of my spray bar, about 3/32 long, in the middle of the carb barrel, pointing down into the engine. When I open and close the throttle, rotating the barrel, the low speed needle opens and closes that slot. What does milling the end of spray bar do? Thanks. I just want to understand before I start removing brass.

Paul

Edited....if the spraybar would not allow the low speed needle to close in
enough to lean the mixture, it would indeed cause an over-rich condition.

Dave.

Robert, MVVS makes a replacement for the Rossi, a far superior carb. I think Dar has the info. on this as I recall. I only use 5%with Castor...no more is necessary.

I have a rossi 45 "2000" model and had the exact same problem, great top end, loads on idle and dies or stumbles. rossi ray is correct, milled down the spray bar and problem went away immediately.. just be careful to clean out any of the shavings.... this is the fix that the morris hobbies guys told me about 2 years ago... worked great....