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Jetting for RAS Silverstone running Amal GP carb

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  • Jetting for RAS Silverstone running Amal GP carb

    Hi guys,

    Just a quick question regarding the jetting on the RAS silverstones. I purchased RAS109 a couple of months back and only managed to get it out for a bit of a blast yesterday. I have no trouble starting it but it seems to "four stroke" a lot and spit a lot of fuel out of the GP carb. Also when removing the plug it's very wet. I haven't had a chance to remove the carb yet and check the jets but what would be the standard/ recommended jets to start off with (it's the Amal GP carb).

    Cheers Paul

  • #2
    Original main jets were 390-420. Check float bowl level as well. What fuel and oil and ratio are you using? Dogsbody

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    • #3
      Hi dogsbody thanks for the reply! I was going to check the float level too as I had a problem with our Greeves sprint bike and the float bowl gave similar issues. I was told by the last guy he used to run it 40:1 fully synth oil so that's what I ran it on yesterday.

      Cheers Paul

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      • #4
        Personally, and trying to find two Greeves Silverstone owners to agree on type of oil and ratio is like trying to find a Labour voter in this constituency, I run synthetic at 25:1 with Sunoco race fuel as it is guaranteed stable and Ethanol free. I ran Castrol R in the 60s as it was the best THEN, now I believe a synthetic based R, in my case Silkolene KR2, Castrol 747 is another, to be better. It doesn't separate unlike vegetable R and produces less carbon. As I say, just my own preference. Dogsbody.

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        • #5
          Always good to know! I thought that it should be running 25:1 so I will make sure I mix up 25:1 for the next run! The bike hasn't been run "In anger" yet so I will give the carb a strip down and check the jets and float level and 25:1 mix and then give it another blast! Cheers for the help again.

          Paul

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          • #6
            Be aware that ethanol is added to super unleaded in the south west by Esso and BP but not by Texaco. This link below makes interesting reading. I have a Silverstone tank that had been attacked by ethanol, now lined with Caswell.


            Dogsbody

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            • #7
              I thought you racing guys used Avgas aviation fuel which apparently does not (as yet) contain ethanol.
              Avgas is ideal for use in small piston engine powered aircraft, this page summarises the available fuel grades and the history of Avgas.

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              • #8
                John, Avgas burns too slow, most guys run 50/50 with super unleaded but as I am parading I can run Sunoco R6SR 105ll race fuel ( ACU is 102 max ). My new Roger Ennis tank would be ok with Ethanol unleaded but as it goes off in a matter of weeks I will pay the extra to be safe. Dogsbody

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                • #9
                  sunoco fuel

                  Hi , where is the Sunoco fuel available , thanks
                  Pat

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                  • #10
                    Originally posted by bult360 View Post
                    Hi , where is the Sunoco fuel available , thanks
                    Pat
                    Pennsylvania, United States http://www.racegas.com/
                    Last edited by John Wakefield; 13/04/2015, 07:20 PM.

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                    • #11
                      You don't need to go that far John.

                      Colin

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                      • #12
                        found this

                        MTV2t racing fuels
                        http://www.wp-motorsport.co.uk/mtv2t...race_fuel.html

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                        • #13
                          Well over £4 per litre!

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                          • #14
                            Brian, The cost of race fuel ,say £15-20 a meeting , is insignificant compared to cost of getting there, usually £50-100, tyres and maintenance, entry fees etc. Benefit of guaranteed ethanol free and stable fuel.
                            Coupe Motos Legendes entry fee is 200euro,plus cost of getting to Dijon, Spa historic parade laps entry is 400euros so that one is out of the question.
                            The Manx Grand Prix ex riders parade lap ( one lap ) last year was £200, again no way.
                            Gone are the cheap days running a race bike!
                            Colin

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                            • #15
                              Yes, I appreciate the total costs as I'm a member of a Motor Club whose members run Rally Cars on a variety of fuels. One gent did run some World Rally Championship spec Subarus on the specified fuels that cost even more than this stuff. However there seems to be alternatives at a lower price that may well be as good. With the Scoobys, the tyre bill was like buying a house, the maintenance bills were like buying the whole road! To hire, they were about £100 per competitive kilometer.....

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