gazzaecowarrior Posted August 6, 2012 Report Share Posted August 6, 2012 Just got a Montesa mh123. The guy before me had been using Castrol R40 in it. I would like to change to a modern premix such as comp 2 or mx5. He said if I do this I must remove head and barrell and clean small end, rings and piston etc as a non castor based oil will not adhere to the residue of the R40. Is this the case or is this a bit of over kill ? Can I just switch to the new oil ? Quote Link to comment Share on other sites More sharing options...
big john Posted August 6, 2012 Report Share Posted August 6, 2012 He has a fair point, in "days of yore" even switching to a mineral based oil from Castrol R was a painful decision and usually only after a rebuild. If you don't believe me speak to an old motocross hand as they tended to race CZ and Hukys with vegetable based oil such as Castrol R. Switching to a modern synthetic isn't that good an idea for an old design of motor and an air cooled one at that. I did ride the 1977 SSDT on a Bultaco lubed by Bel-Ray 1 at 60:1 ratio and had no problems, but that was after a complete engine strip down and rebore so everything was new inside before I switched from Shell 2T mineral. You could go over to Castrol A747 which can be safely mixed up to 50:1 ratio which is also a vegetable based blended lubricant like R40 and still easily available in litre bottles, not as expensive as R40 either. Hope this helps. Big John Quote Link to comment Share on other sites More sharing options...
gazzaecowarrior Posted August 6, 2012 Author Report Share Posted August 6, 2012 He has a fair point, in "days of yore" even switching to a mineral based oil from Castrol R was a painful decision and usually only after a rebuild. If you don't believe me speak to an old motocross hand as they tended to race CZ and Hukys with vegetable based oil such as Castrol R. Switching to a modern synthetic isn't that good an idea for an old design of motor and an air cooled one at that. I did ride the 1977 SSDT on a Bultaco lubed by Bel-Ray 1 at 60:1 ratio and had no problems, but that was after a complete engine strip down and rebore so everything was new inside before I switched from Shell 2T mineral. You could go over to Castrol A747 which can be safely mixed up to 50:1 ratio which is also a vegetable based blended lubricant like R40 and still easily available in litre bottles, not as expensive as R40 either. Hope this helps. Big John Thanks for that Big John. That is good advice. I will stick with it then. The guy I bought it off kindly gave me about 2 litres of the R40 so that will keep me going for years. I sadly am recovering from knee surgery so there is no riding for me anyway. The Mont is just a little project to appease the sadness of me having to sell my Evo. Just couldn't bear not having a bike. Apparently this oil smells great when it's running. Once I've sorted the amal carb Ill be able to comment on it. Gareth Quote Link to comment Share on other sites More sharing options...
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