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32a Premix Ratio

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  • 32a Premix Ratio

    I'm wondering what ratio I should be using in my 1960 Scottish - currently using 30:1 but perhaps could run a little leaner?

  • #2
    Oil ratio

    I would not recommend going as low as 30:1 unless with synthetic on makers recomended ratio. For 'normal' mineral 2 stroke oil I use 25:1.
    Remember oil is cheaper than engine rebuilds, & carbon build up with modern oils is minimal.
    Last edited by Brian Thompson; 07/05/2010, 05:23 PM. Reason: Clarity.


    • #3
      Hi rightsideup, and welcome aboard the forum. Thanks for the post.

      I guess it all depends on what type of oil you're using. 30:1 sounds about right from what I've been told, on a run-in engine and using a good quality mineral oil. However, some manufacturers of mineral oils claim their products can be run safely at leaner ratios than this, but I would consult their techical dept. first to be sure. If you're using Castrol products, speak to Martin at Castrol Classic Oils on 01954 231688. He will also be able to advise you of a stockist in your area.

      Some members report good results from using fully synthetic oils, which can be run at leaner ratios and reportedly burn cleaner with reduced carbon build-up etc. However, I can't comment on synthetic as I run my TCS Scottish (32A) on Castrol TTS (now called Actevo) mineral oil at 30:1.

      There is much debate on the pros and cons of mineral vs. synthetic oils in classic two-stroke engines, with some saying 'take advantage of the technology' and others reporting premature wear from the use of synthetic. Colin Sparrow once told me his roadster 'thrives' on a diet of synthetic (what brand and ratio do you use Colin?) and I must admit I'm tempted to change if there is an advantage (less smoke, cleaner running, etc) albeit at slightly greater expense.

      What do the members think?

      While I'm on I thought I'd add this reference table for premix ratios, in cc's per litre (for those of us more used to gallons!) ;

      16:1 = 63cc per litre
      20:1 = 50cc per litre
      25:1 = 40cc per litre
      30:1 = 33cc per litre
      32:1 = 31cc per litre
      40:1 = 25cc per litre
      50:1 = 20cc per litre



      • #4
        Thanks John, you beat me to it (and headed me off at the pass!)

        What I didn't say in my previous post is that I'd been advised to carry on with running in at 20:1 (new piston and rings), then gradually lean it off to 25/30:1 on Castrol TTS mineral.

        Cheers for putting me right mate, and what type of oil do you personally favour, i.e. mineral or synthetic (and at what ratio?)

        Mineral oil, 25:1 it is then. Besides, a bit of smoke at least let's you know somethings happening!

        Last edited by Brian Thompson; 07/05/2010, 05:26 PM.


        • #5
          Chaps, I've always worked on the basis of 50:1 with fully synthetic for trials use (30:1 for scrambles) and 30:1 with semi-synthetic. Rob


          • #6
            Wow - very helpful replies, thanks all!


            • #7
              All part of the service!


              • #8
                Putolene fully synthetic competition premix at 30:1 in all the two-strokes.

                Pretty expensive though and not really necessary for a roadster or a trials bike. That was when I was running a racer and a scrambler in competition, and it just meant the same fuel could be used in any of the bikes.

                30:1 is ok with any modern two-stroke premix oil.

                Don't forget to check your main jet size if you change oil ratio; adding more oil makes the fuel:air mix weaker, less makes it richer.
                Last edited by Colin Sparrow; 07/05/2010, 08:12 PM.
                Colin Sparrow


                • #9
                  Thanks Colin, great tip.

                  In your experience chaps, is there any problem with 'mixing' synthetic and mineral oils if 'converting' from one to the other, or is this best done after an engine rebuild?


                  • #10
                    Never mix synthetic and mineral oils. As for change over I would not think there is a problem as long as you drain the tank & start afresh. I certainly dont think you need an engine rebuild. The brand I use is Comma 2 stroke which I buy in 5 litre bottles from a local agricultural dealer.
                    Its always a bit cheaper than motor shops. (Farmers are a bit on the tight side) Its about £14for 5 litres.
                    As Colin says synthetic is not required in road bikes (nor trials) I would have thought.
                    Last edited by John Wakefield; 08/05/2010, 10:36 AM.


                    • #11

                      I have run my East Coaster on fully synthetic at 30:1 goes really well with minimum smoke.As for the cost how many miles do we do.


                      • #12
                        Bet it smells nice too merlin!

                        Thanks for the clarification John. I'd heard it's not a good idea to mix oil types as they can react badly, but as you say, with a tank flush and a good run to burn off anything left over in the crankcases I thought it'd be ok.


                        • #13
                          I have run my 32 A with a greeves barrel on silkolene synthetic at 30 to 1 for 3 years now 3500 miles aprox. I have been told a few times that I could run leaner but choose to play safe. That said has anyone tried castorene R 40 ??


                          • #14
                            oil/petroleum mixture

                            castorene R 40 I wondered about putting a drop in for the smell what do others think?.


                            • #15
                              A definite No No, it will damage your engine as caster based oil will definitely not mix with any other oil. I have heard of people putting a drop of R into 4 stroke petrol tanks to give the smell, but not two strokes. I would not even advise running R in a road going two stroke, it will just gum things up. I doubt these days if anyone uses R in strokers as there are now much better oils available.
                              Last edited by John Wakefield; 08/05/2010, 10:42 PM.