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Old 09-25-2008, 04:56 PM   #1
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Default Help with Axe Rossi engine

A friend of mine has an Axe Rossi Maranello in his MRX-4, and has been complaining about how ridiculously difficult it is to tune. I've seen mention of this somewhere before, and I figured I would ask on here if the problem can be solved by changing the carb. If so, does anyone know which carbs are direct replacement?

Sorry, wish I had more info for you guys, but I'm more of an off-road nitro person, so I'm not too keen on this one.
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Old 09-25-2008, 06:06 PM   #2
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I have heard others complain, but I thought the Rossi carbs about average on the ease of tune scale. Unfortunately, they use a very large carb neck. I don't think any other carb will fit without machining an adapter.
Many times tuning problems are the result of a poorly sealed tank lid, tiny hole in a fuel line, bad o-ring on a carb needle, etc.
If he can make over to my shop, I'd be glad to give it a shot. (Portage, IN)
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Old 09-26-2008, 04:46 AM   #3
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I run an axe rossi as well in my mrx4-r.its the mamba.yes very hard to tune in the beginning.Ive run this motor all year long and have noticed that after two gallons of fuel it still has tons of pinch.the more fuel you run through it the easier it will be to tune.these motors for some reason take forever to break in.also the % of nitro in relation to head button shimming..very important..mine will only run on 25%.A few other guys in my club run axe as well.A cobra and a marinnello.We all had the same issues that you had.I feel that after the motor is broken in and you have correct nitro % these motors scream.The carbs are just fine.Oh and when i was at the nats a month ago my head button was constantly leaking.Two guys hooked me up with a novarossi long turbo plug.The c7tgc i believe.Its the only plug that has worked in my motor.Why,your guess is as good as mine.It took alot of patiance to get mine where it is now. Two gallons of fuel and it still locks up at TDC.. Hope this info helps
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Old 09-26-2008, 04:56 AM   #4
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I had two these engines. The Pixy 12 and the LS1 Both were imposible to tune. I believe the head clearance on these engine is far too great. I believe that is why these engine will not hold a tune. MY pixy would only run on 30%
the LS1 was the same way.
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Old 09-26-2008, 10:43 AM   #5
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You could rebuild the carb with new orings if the carb has a hassle or see if a new 2 needle carb would fit its much easier to tune.
The biggest hassle i had with teh 3 needle carbs was that you dont touch the mid range needles or you battle to tune the motor.
The compression ratio is also fairly low and more suited to higher nitro % but you would have to check. For 25% its suggested you run .5-.55mm clearance.
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Old 09-29-2008, 04:25 PM   #6
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Quote:
Originally Posted by Fear View Post
A friend of mine has an Axe Rossi Maranello in his MRX-4, and has been complaining about how ridiculously difficult it is to tune. I've seen mention of this somewhere before, and I figured I would ask on here if the problem can be solved by changing the carb. If so, does anyone know which carbs are direct replacement?

Sorry, wish I had more info for you guys, but I'm more of an off-road nitro person, so I'm not too keen on this one.
Fear,

I to have a .21 Axe/Rossi LS1 and had an extreme amount of trouble when it came to tuning. I finally got some help from a buddy and we put a carb from an O. S. 21 and it really lit up the motor and made it a breeze to tune. I will try to find out the exact motor he pulled the O.S. carb from. I think it was an O. S. .21 VZB but I'm not sure.

Regards,
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Old 09-29-2008, 04:34 PM   #7
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All the OS .21 slide carbs are basically the same. Any of them should work great.

If an OS carb fits then a Novarossi carb would also fit.
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