Mrdrink Posted July 29, 2013 Report Share Posted July 29, 2013 for years I've been using Magnetec semi synth car oil in my bikes without a whiff of an issue (probably 6-7 bikes in as many years). they are race bikes and its changed regularly. Lately ive not found the stuff i usually used so brought some of the Castrol P1 racing motorcycle oil. Its working lovely in the zx6r so no issues there. A friend has a steely and he has run the magnetec car oil on mine and the engine guys advice. its been faultless. Yesterday we were fitting a new clutch to said steely and cos the oil we normally use wasnt available i said pick up some of the P1 racing as it seems pretty good for me. finished the job and struck her up. once it gets a bit of warmth in there it starts smoking like the piston rings arent sealing. Could this be because of the change from semi to 100% synthetic oil? is it because the bike is best part of 20 years old and not really comparable with an oil like that? theres no other mechanical reason why it would start smoking as all we did was put a new clutch in and oil/filter change. I think we are going to swap it back to semi to be sure but am a bit confused. Link to comment Share on other sites More sharing options...
Guest Posted July 29, 2013 Report Share Posted July 29, 2013 It'll be more likely down to the grade of oil rather than the fact it's synthetic, the numbers refer to the viscosity when hot, thinner oil can certainly find its way more places it shouldn't than thicker. If you try and run early air cooled Potsches on modern thin oil, then you get plenty of smoke due to the original tolerances being wide (as air cooled motors run hot and had more take up) and wear from age. Link to comment Share on other sites More sharing options...
boris Posted July 31, 2013 Report Share Posted July 31, 2013 I would use semi on a bike that old. may even cause the clutch to slip. I had issues with clutches slipping in the past when ive gone from semi to fully even using the same grade. check online and see what grade it should use and get semi and see if the prob still happens. also what barry j says the older motors aren't nowhere near as tight and efficient as newer motors that run on thinner more slippery oil. its all in the viscosity lol Link to comment Share on other sites More sharing options...
lorenzo Posted July 31, 2013 Report Share Posted July 31, 2013 The viscosity, how slippery it is and how thick it is, has nothing to do with how it's made and therefore if it's getting past the rings & seals more easily. A synthetic will just be more stable when exposed to heat, damaged less by your gearbox and generally designed to last longer. Slipperiness is all about the rating of the oil, 10W40 etc, and the same numbers on one oil mean it's the same as another oil with those numbers, irrespective of how it's made. Link to comment Share on other sites More sharing options...
boris Posted July 31, 2013 Report Share Posted July 31, 2013 true true Lorenzo I just wanted to use a big word lol. im sure that bike should take 10w40 semi synth oil though? like I said before ive changed from semi to fully and had clutch slip so thought maybe this could be causing probs where hes changed from one oil to another. still id never use car oil in a bike as its not designed to work with a wet clutch. Link to comment Share on other sites More sharing options...
Mrdrink Posted August 12, 2013 Author Report Share Posted August 12, 2013 Quick update on this, swapped back to regular magnetec semi and after 2-3 laps the smoke cleared and she runs clean as a whistle. You live and learn Link to comment Share on other sites More sharing options...
Mrdrink Posted August 12, 2013 Author Report Share Posted August 12, 2013 I should add that it we didnt change grade, we stuck with 10w40. only change was semi to fully and back again. Link to comment Share on other sites More sharing options...
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