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Rainman
Joined: 17 Feb 2011
Posts: 76
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 Posted: Thu Apr 19, 2012 11:54 am Post subject: Rotax Carb Question! |
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 I run Rotax Max at Non MSA and weigh between 13/14 stone.
I have both float set ups and have tried both but with no signifigant results.
Which float and needle would be more ideal for my given weight, and the track i race on is classed as tight and twisty.
I understand the heavier floats is richer across the range and the lighter floats is leaner, what i am trying to establish is because i am a heavier driver would i require the richer floats and the same with the needle, i believe the k98 to be slightly leaner than k27. Any thoughts would be appreciated  |
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John Savage
Joined: 27 Sep 2006
Posts: 893
Location: UK
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| Posted: Thu Apr 19, 2012 12:35 pm Post subject: Re: Rotax Carb Question! |
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| Rainman wrote: | I run Rotax Max at Non MSA and weigh between 13/14 stone.
I have both float set ups and have tried both but with no signifigant results.
Which float and needle would be more ideal for my given weight, and the track i race on is classed as tight and twisty.
I understand the heavier floats is richer across the range and the lighter floats is leaner, what i am trying to establish is because i am a heavier driver would i require the richer floats and the same with the needle, i believe the k98 to be slightly leaner than k27. Any thoughts would be appreciated |
You can setup both float combinations to give the same fuel height in the float bowl by adjusting the float heights and therefore the same static head of fuel.
So question you are really asking is what combination of floats and idle jets would you recommend for a senior driver?
My answer to that one would be the 5.2g floats and the 30/30 idlejets.
Having setup your carb float height then select the correct mainjet and needle/needle clip combination to match the current air density and away you go with maximum engine performance 
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Dellorto, Mikuni and Keihin Jetting & Kart Setup Software
www.rotaxjetting.com |
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Rainman
Joined: 17 Feb 2011
Posts: 76
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| Posted: Fri Apr 20, 2012 4:09 pm Post subject: |
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My question was which floats which you have answered, which needle would suit a smaller tight and twisty track K27which i believe to be slightly thinner ie richer, or k98 which is slightly leaner.
I am trying to determine whether a heavier driver would require a richer or leaner set up.
I know it is very involved and there is alot of science behind it, but i am just trying to get a good basic set up without expensive software as i am only racing non msa but do obviously want to aquire as much knowledge as i can to be competitve . I know a good starting point is 3mm on the float arms i think mine maybe 4mm but i see in your carb pdf you probably recommend 6mm is this correct. |
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hirsty
Joined: 06 Nov 2009
Posts: 597
Location: Doncaster
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| Posted: Fri Apr 20, 2012 4:20 pm Post subject: |
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Needle settings depend on
Driver,
Track,
Carb body,
Carb parts
Motor,
Who and when the motor was rebuilt by,
airbox,
Exhaust,
humidty,
and temp probably more on top of that.
You can just say 27 p3. 3mm is a really good starting point, if your running non msa stick to 3mm.
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John Savage
Joined: 27 Sep 2006
Posts: 893
Location: UK
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| Posted: Sat Apr 21, 2012 1:22 am Post subject: |
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| Rainman wrote: | | I am trying to determine whether a heavier driver would require a richer or leaner set up. |
And I am trying to tell you that regardless of how heavy you are all drivers want a setup that makes the most power and having found that setup you then need to maintain it by adjusting your jetting to match the current air density.
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Dellorto, Mikuni and Keihin Jetting & Kart Setup Software
www.rotaxjetting.com |
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Rainman
Joined: 17 Feb 2011
Posts: 76
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| Posted: Sat Apr 21, 2012 8:01 am Post subject: |
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| Thanks for the replies you have been a little helpful. |
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ireman
Joined: 08 Jan 2008
Posts: 357
Location: east sussex
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| Posted: Sat Apr 21, 2012 11:16 am Post subject: |
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I think that you will find that John has told you exactly what you need to do but not in the way that you want to hear it. Without the software there is no quick and easy way to a 'base' one size fits all solution. If you don't want to use the software then you have to put in some work yourself. Test, make notes, test again - and repeat. After a while you will have a reasonable set of data - but, considering the amount of time and cost spent testing you might well find that investing in the software isn't that expensive after all  |
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