ninefingers

My Feedback: (18)

I recently acquired two of these Rossi engines that appear to be in great condition. They both use same carb. When I took the back off the .40 and gazed inside I was reminded of my younger moto days when I first seen a CZ (or Husky) engine disassembled after rebuilding Kaws and Yamahas. They are "very European" the quality is evident. That said however unlike my OS's and TT's I cannot get either one of these to run longer than a minute. There either blowing smoke out the exaust like a mosquito fogger or theres that dreaded ringing sound - awfull smell - then abrupt stop that comes from starving the engine from fuel. I think the problem is the low end is way out of wack. Both carbs were taken completely apart and reassembled by someone who knows nada about the basic function of a two stroke model engine carburetor (that would be ME). The high end is well documented at being good around 1 1/2 turns out. My problem is the low end needle. It turns about seven or eight times before it stops in either direction. Were is the default setting? Is it about two turns out from all the way in or two turns in from all the way out or neither. Maybe flush with the casing? (like some car glow engines). I think I have a good handle on the correct prop and fuel. I'm using a 10 x 6 MAS and Omega 10%. I pushed aside the temptation to use 30% heli after reading all the threads about "Europeans dont use nitro". I'm just using an OS #8 plug. I have hotter or colder plugs if required. I'm using the stock silver pipe that used to come with these models. I've noticed that they supply different pipes now. Either a Jett Manufacturing "tuned" pipe or a Rossi version black "stinger" looking pipe. I want to get these engines spitten fire soon. I've got a Weston UK Velocity 50 on the way from Dumfries and I got a bad jones on for "riding into the danger zone". I know the knowledge compiled into the RCU is limitless! Seriously any help on this matter would be greatly appreciated! ...nine

C185Pilot

My Feedback: (25)

Two issues with the Rossi's. First the fuel must be absolutely fresh...fuel open more that a week or two absorbs water which will kill its ability to idle reliably. I notice that you live in FL...humid air will kill fuel quickly. Second, the Rossi's when new come with head shims to lower the compression. Hopefully you got them with the engines...if not get some and install them. Lastly, no more than 5% nitro...these engines were designed to run with European fuel...basically FAI fuel with no nitro. Put the shims in and lower the nitro and you have two great powerhouse engine which run great.

Mike

YUKONFLYR

Ninefingers, as C185Pilot said, the Rossi's run very well with zero nitro, and with one head shim, max of 5% or you could have all sorts of tuning issues. I run two head shims and a max of 10% Nitro. One of the unique things about Rossi's are no default settings on the needles. If you read the manual which is a list of parts it has a segment about running the engine in, again, no default settings. This is what I do to run a Rossi, either a .40 or .45. On the main needle, screw it out 4-5 turns, then open the throttle wide, start the engine then tune to be on the richer side of max rpm, bring it up to max rpm, then screw the needle out to make it a little richer. As for the idle needle, they usually come from the factory so rich that they will not idle when new, after break in, I would attempt an idle and simply see how long it will idle. sometimes it will die rich after only 5 seconds or less. screw it in and see if you get a change, if it idles longer before it dies you are on the right path. eventually it will idle for at least 30 seconds.... then return the throttle to full again. if it studders and is very rich, keep screwing the needle in. eventually you should be able to idle the engine for at least a minute and have a very clean full throttle response. It is normal to screw the needle in quite a ways prior to getting the right setting. You want to approach the correct setting from the rich side instead of the lean side, which is more difficult in my opinion. When the Rossi's are properly tuned, they will not want to stop when you cut the throttle. They also like a colder plug, I use K&B HP plugs and have had good luck with them. Good luck with your engines.

Gizmo-RCU

My Feedback: (27)

Keep the high end a little rich as they will like the extra fuel when they come up on the pipe.

maxtenet

Yukon is on the money. Start with the main needle 4 or 5 turns out. Get it to at least run rich, then lean it out. Otherwise you could ruin the thing. Many times older engines need to run at a rich setting until the congealed crap in the carb gets cleaned out just by having fuel run through it. As a former motorcycle racer and tuner, I can tell you that these things are more finicky in the aspect that you may need to adjust before every flight. Motorcycles, on the other hand, once you get em right leave em alone as long as you don't move to a different elevation.

Used to race motocross, CZ, Dalesman and Puch. Flat track Kawasaki Greenstreak 100. Shows my age!

Max

ninefingers

My Feedback: (18)

Max I do remember the price to pay for the extra power and reliablity was extra initial cost more tuning and care. Guess these little engines are no different or even more so. WOW fellas thanks for all the input. I should have expected it from RCU! Enough to make my head spin at this point but I got the basics and just need time for it to soak in. The key is patients and experimentation. What I'm having the hardest time with is imagining how an engine runs better with 0 nitro. I've seen with my own eyes an engine just about jump off a plane after treating it to 30% Heli mix. I guess its about compression ratios and timing and all that. Got plenty to try now and I will update this thread when I see some progress for future R/C'ers to enjoy. Thanks again for the input...nine

1QwkSport2.5r

Most engines destined for the US (designed for us Nitroheads) have lower compression ratios since Nitro is cheaper and easily obtainable. As said, European designed engines are highly compressed because Nitro is very expensive there. Engines that run on alcohol cant take full advantage of the power potential of the fuel if the compression isnt raised. The Italian Super Tigre's, Picco's, Rossi's, Enya's, and many many others all run well on 0-5% nitro.

Try 80/20 FAI fuel in an engine designed for the USA and it will not run nearly as well as it would on 10-20% nitro.

Someday I'll pick up a Rossi .40 or .45 to play with. I wouldn't mind an old Picco either.

turbo.gst

My Feedback: (8)

Here is a review of the Rossi .40 by Clarence Lee in RCM archives.

http://www.rcmplans.com/issues/reque...061988-1-1.pdf

Wonderful engine!

ninefingers

My Feedback: (18)

Thanks for that Turbo what a treat! ...nine