TNRabbit

I've attached a pic of the needle valve from my Rossi .45 w/mini pipe. I've had a he** of a time getting it to run and transition properly and the HS needle doesn't seem to have much effect. It won't run unless it's over 3 turns out and there is no discernable difference when you take it out to 4 or 5 turns. Transition sucks; I've fooled withe LS needle but unless the HS is right, what's the point? I pulled the HS needle out today and notice these "imperfections" or scratches on it--take a look at the pics and tell me if you guys think this is the problem. BTW, all new tank, clunk/line, fuel line, etc. Also cleared out the carb. No Joy.

Set up is 10 oz. Dubro w/check valve on vent side and filter on the fuel side. It did run right once! Tached 13,700 on an APC 12x4, and over 15,000 on a 10x6.

Keefer

My Feedback: (2)

A picture is worth a thousand words!!
I'm not a pro, but I submit this evaluation:
If you imagine how far that needle moves in and out of it's seat per revolution (let's say for argument that there are two threads per millimeter), you can see how much the diameter changes in that distance based on the taper. I would submit that the change due to the taper is quite a bit more than any change those small imperfections would cause. Hence, the imperfections would not significantly affect your mixture.

Sorry - this won't help solve your problem, but it might get someone else to respond. I also have a Rossi 45 (and a 40) that both give me fits when I try to run a 12x4. Of course, I was laughed out of the forum for using a Rossi with a 12x4.... go figure. I guess they're only good for high revving applications. They just won't swing that 12x4 prop and maintain any respectable power level or needle setting.

TNRabbit

I would think the low pitch would keep the rpm's up...?

Keefer

My Feedback: (2)

Mine would only run once a day with a 12x4 - than junk after that. The rest of my 45s or 46s handle a 12x4 just fine.

TNRabbit

Well, I ordered a new needle/o-ring just in case. The old one wobbles around in the carb like it's the wrong size! Hmmm....bought it off ebay; it COULD BE the wrong one!

Keefer

My Feedback: (2)

A wobbling needle presents quite a different problem - you may be sucking in air around the threads, in which case you'll never get a good setting. A new one sounds like the best choice.

Keefer

bugsiegel

My Feedback: (2)

I have had several rossi engines. when they were on sale for 99.00 I bought them up. I have also had the 53 and the 60. I tinkered with the 45 the most because they were my first engines. they were just too rich on the low end and that lead the terrible transition and an idle that would only last 15-25 seconds before it stalled.
so I put the low end needle in all the way and it was still rich. accidently I tried to lean the low end some more while the carb was open a little and found that with the carb slightly opened it would allow me to lean the low end even more. that lead to good transition and an great idle.
BUT that lead to a different problem.. now with the low end needle in so far the carb wouldn't close all the way... after taking the carb apart I found that filing the spray bar down just a little I was able to get the carb to close all the way again.

TNRabbit

Thanks bugsiegel! That sounds like it might be the problem. Any hints on an effective way to mill down the spray bar? Dremel tool?

RossiRay

The spray bar is soft brass. You can use a drill bit that is slightly larger than the spray bar and twist it with your fingers to remove the material. 060-.090'' should be enough.

TNRabbit

Did the above mod and PROBLEM SOLVED. I also switch back to a 10x6 APC; Jeezus! This thing sounds like an extremely irritated bumble bee. It just doesnt' fit the character of a Four * 40...but man, will it move like stink! I never thought I'd be able to pull this plane straight up 400 ft with a 10x6 prop, but by golly, it does it. The best way to describe standing behind it for a engine check is "furious."

...thinkin' 'bout cutting a little off each wingtip and converting this thing to a speed demon....[>:]

bugsiegel

My Feedback: (2)

they are good engines and they take abuse..
but they are heavy...
IMO they are good to make a heavy plane go fast if that's the kind of speed you're after...
enjoy....

DarZeelon

Paul, Gary, Keith,

The Rossi .45 is a very strong engine.
It is very robust and yes it is heavy.

To allow this engine to express itself (pun intended), it must be allowed to rev, especially with its stock carburettor.

If loaded down by a heavy prop, the RPM will not be there and the needle will act dead, not responding to opening it further.

You could, as Ray wrote, modify the brass spray-bar, but this will solve only a part of the problem, improving fuel control at part throttle settings. The carburettor made by MVVS for Rossi engines is a drop-in replacement, into the 16 mm spigot hole.
It costs much less too.

It improves the idle, transition and mid-range performance and allows the engine linear fuel control with larger props. It may also add 200-300 RPM to the top end, with the recommended prop sizes.

Forcing the engine to get on-the-pipe, or on the un-adjustable tuned mini-pipe is a different story.

It is best to stay with the recommended 10x6 size for the .45 and the 10x7 for the .53.
Props of equal load are also suitable; 9x8, 9.5x7, 10.5x5, 11x4 and 11.5x3 for the .45. One inch more pitch for the .53.

borneoflyer

Dar,

Where can one get hold of the MVVS carb to fit the Rossi45 as you mentioned?

I am having a terrible time tuning mine. As you already know, she needs more than 3.5 turns on the high end needle. Is this a norm on all R45s or what am I missing here?

Any ideas if fitting a Perry pump and carb will make my life easier? My engine is mounted invert.

Thanks.

arikflorida

I am haveing the same issue with my rossi. I finally was able to make sure the low end was ok, but the gap of the carb stay open now.

What 0art exactly have to be shorthand insite the carb?

Thanks