wild foamy Posted March 13, 2009 Share Posted March 13, 2009 Hi everyone. ive jsut changed from using mineral oil to using Semi Synthetic in the autolube on my DT50MX as it seemed to be running hot and occasionally cut out if i was really hammering it along the backroads. is there really any reason to use one oil over the other and will using semi synth be better for my DT? Link to comment Share on other sites More sharing options...
JimR Posted March 13, 2009 Share Posted March 13, 2009 Hi everyone. ive jsut changed from using mineral oil to using Semi Synthetic in the autolube on my DT50MX as it seemed to be running hot and occasionally cut out if i was really hammering it along the backroads. is there really any reason to use one oil over the other and will using semi synth be better for my DT? Hi Wild, you could be in the poo here, did you clean the tank,pump & lines ? if not there is a chance that where the two oils meet you could end up with a substance that resembles mint jelly, back a few years Belray (semi) used to have this effect with any mineral oil, but I would guess the oils over the last 30 years have got better. I would suggest you drain the tank & lines then reattach them refil with the oil of choice then undo the blead on the pump and allow a good half pint (234ml) to bleed through the system and should insure you dont have any oil reaction problems. The bike will not run any different on either oil so the choice may be down to availability & cost. Regards Jim Link to comment Share on other sites More sharing options...
wild foamy Posted March 13, 2009 Author Share Posted March 13, 2009 yes i did fully drain the tank and lines and bled the oil pump according to my haynes manual... ... im getting good at this engineering lark , maybe if i keep practicing i wont break it so much... Link to comment Share on other sites More sharing options...
JimR Posted March 13, 2009 Share Posted March 13, 2009 yes i did fully drain the tank and lines and bled the oil pump according to my haynes manual... ... im getting good at this engineering lark , maybe if i keep practicing i wont break it so much... Just wondering why the motor is getting hot ? perhaps the mint jelly has blocked the small pipe to the carb or in fact the brass feed. Oh did the H manual tell you to bleed a half pint out or until the bubbles stop comming out of the bleed hole ? Regards Jim Link to comment Share on other sites More sharing options...
wild foamy Posted March 13, 2009 Author Share Posted March 13, 2009 erm, just bled it until the oil was a pinkish colour (semi snyth) and not green (mineral). the mixture is fine so that can't be the problem, and as far as im aware there is no mint jelly in the oil pump, will take the oil feed pipe off tomorrow and give it a few revs to make sure the oil is getting through (will mix some oil into the fuel first though... running without lube is fail... Link to comment Share on other sites More sharing options...
Moderator drewpy Posted March 13, 2009 Moderator Share Posted March 13, 2009 put some pre mix in just to be sure. if it don't smoke too much you have a blockage!! Link to comment Share on other sites More sharing options...
Moderator mervin Posted March 13, 2009 Moderator Share Posted March 13, 2009 Dont panic mr manwaring we have has this out many times on the RD forum semi synth contains mineral how else would it be semi synth? if it was going to gel it would do it in the bottle and you would not be able to use or even buy the stuff now when you get a problem is if you mix vegetable oil I:E castol R with a mineral oil, semi synth is great i have not oiled or whiskered a plug since using it, in the days of my fizzy i used to carry a pocket full of plugs and was able to change the plug in the dark, used to have a fag while the engine cooled too avoid burnt fingers, then change the plug, the engine is running hot. have you changed the exhaust , jets or anything? if not make sure the pump is working properly, running premix in the tank is a temp measure which may cause a weak mixture because the oil in the fuel will reduce the amount of petrol getting in and weaken the mixture, if you go down that road permanently and remove the oil injection system it would be wise to go up a jet size or two merv Link to comment Share on other sites More sharing options...
steve m Posted March 13, 2009 Share Posted March 13, 2009 On the nose Merv I prefer mint sauce to jelly on me roast beef n yorkshire pud Link to comment Share on other sites More sharing options...
wild foamy Posted March 13, 2009 Author Share Posted March 13, 2009 its got a bgione expansion chamber and slip-on, K&N air filter and 60cc big bore kit, but i have jetted up to a #115 main jet and did a plug chop, the electrode is a chocolatey brown but is starting to turn black because i am still running it a bit on the rich side. so fuel mixture seems to be fine. i was told semi synth holds its properties better through the temperature range than standard mineral oil, and it only really seem to be when i am batting along at 50mph (flatout) that occasionally it will cut out, so maybe the semi synth will cope better with the high temperatures and maybe help it run cooler by providing more lubrication Link to comment Share on other sites More sharing options...
blackhat250 Posted March 13, 2009 Share Posted March 13, 2009 mineral oil / vegitable/ synthetic; Willd one [foamy] A wee trick -- take a little of each oil [ ur old & the new stuff] put them together in a glass . mix them up leave for a couple of days. Inspect results ; i always do this before add ing to the bikes in question . Now have u not smelt Castrol R [40] Yet ? if not ur still a virgin of the two-stoke faternity Link to comment Share on other sites More sharing options...
steve m Posted March 13, 2009 Share Posted March 13, 2009 mineral oil / vegitable/ synthetic; Willd one [foamy] Now have u not smelt Castrol R [40] Yet ? if not ur still a virgin of the two-stoke faternity AHRrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr, will be smelling that at Mallory tomorow Mind you ,,,,, you can`t go wrong with the smell of real Gunk on an hot engine........... Link to comment Share on other sites More sharing options...
Moderator mervin Posted March 14, 2009 Moderator Share Posted March 14, 2009 A little shot of r in the tank of an injected bike will give ya that smell and not affect the bike, paul off the rd club in newton abbot does this and has done for years just to get the smell merv Link to comment Share on other sites More sharing options...
JUST ME! Posted March 15, 2009 Share Posted March 15, 2009 Just wondering why the motor is getting hot ? perhaps the mint jelly has blocked the small pipe to the carb or in fact the brass feed. Oh did the H manual tell you to bleed a half pint out or until the bubbles stop comming out of the bleed hole ? Regards Jim The motor is getting hot because that style of 2 stroke donk was never designed to be held at peak revs. Short bursts of peak revs wont worry it but holding it at peak revs will destroy in quite quickly. Air cooled, old school 2 strokes run quite large bore clearance and they simply full apart if you don't get on and of the throttle regularly. Add to that the new changes to the balance and possible port timing changes as a result of the big bore kit and it should be easy to see how revs may undo all your tinkering efforts. I stand by a reply to you some weeks ago where I suggested that if you are going to fang it then premix it! If you have gained some noticable power go back down 2 or 3 teeth on the rear sprocket!Remember when we gave you the heads up re jetting your new big bore arrangement. Well this is the heads up re holding 2 strokes at peak revs! For what it is worth, I would suggest that you continue to premix the Jawa as well. HAVE A BLAST! Paul. Link to comment Share on other sites More sharing options...
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