DjGuyG Posted July 3, 2013 Share Posted July 3, 2013 Ive just bought a yamaha dt 125r sm as a little project, its previously had both top and bottom end rebuilds. The previous owner admitted he spanked it everywhere and has cooked the engine. The bore is fine as is the piston, theres alot of oil in the radiator but the thing thats confused me is it seems theres 4 stroke in the head, any ideas? Link to comment Share on other sites More sharing options...
slice Posted July 3, 2013 Share Posted July 3, 2013 Just to clarify, what do you mean by "4 stroke in the head"? It's a 2 stroke and unless someone has fitted valves to it it always will be!! Others may know what you mean but this has confused me (doesn't take much) Link to comment Share on other sites More sharing options...
DjGuyG Posted July 3, 2013 Author Share Posted July 3, 2013 There is engine oil from the gearbox/bottom end in the top end. Ive just been tinkering with it abit more, he seems to have crucified the engine lol Link to comment Share on other sites More sharing options...
Moderator DirtyDT Posted July 3, 2013 Moderator Share Posted July 3, 2013 Are you sure it's 4 stroke oil and not 2 stroke oil? At the moment the only 2 ways i can think of getting 4 stroke oil into the barrel is if it has seeped into the crank area and been sucked up into the top end. That or the right hand crank seal is shot and it is sucking oil from the gearbox into the same crank area. Link to comment Share on other sites More sharing options...
DjGuyG Posted July 3, 2013 Author Share Posted July 3, 2013 Im not 100% but i can smell 4 stroke. Thats what im afraid of if its coming up from the gearbox i'll have to crack open the whole engine and re seal, then its starting to get expensive. Just gone out and bought a new head gasket, hoping if i fit that, clean out the carb and the radiator then if it goes wrong again i'll know i have to crack the block or buy a new engine. What do you think? Thanks btw Link to comment Share on other sites More sharing options...
Moderator DirtyDT Posted July 3, 2013 Moderator Share Posted July 3, 2013 A head gasket won't help. I would determine what oil it is first. 2 stokes must have oil in the bore. If you are going to take the head off you might want to take the barrel off and look into the crank area for case damage or seepage of gearbox oil between the case in that area. Other than that I would say it is a crank seal gone. That all assumes the the oil isn't 2 stoke, which would be fine. Link to comment Share on other sites More sharing options...
DjGuyG Posted July 3, 2013 Author Share Posted July 3, 2013 The head gasket was gone anyway, just once i took the head off i thought i could smell 4 stroke. The crank and piston are both in perfect condition and the top end hasn't warped. If i am wrong a good going over and the gasket should fix the problem, if it goes again then i'll have to split the engine. Thanks for the help Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 3, 2013 Moderator Share Posted July 3, 2013 4stroke mentality tch. The head gasket was fine. Oil in the rad and oily smell when you pull the head will be the water pump seal. Fix it quick before it emulsions the oil, (becomes white sludge like off emulsion). Link to comment Share on other sites More sharing options...
Moderator DirtyDT Posted July 3, 2013 Moderator Share Posted July 3, 2013 I forgot about that in the question. Oil in the water - What Cynic said. Link to comment Share on other sites More sharing options...
DjGuyG Posted July 4, 2013 Author Share Posted July 4, 2013 Cheers guys, replaced the head last night and shes running like a beaut. Im going to keep an eye on the oil in the engine and flush the radiator once a week, so at the first sign of waterr/oil mixing i'll change the water pump seal, thanks Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 4, 2013 Moderator Share Posted July 4, 2013 Dont take this the wrong way but that is stupid. When, not if that seal fails you coolant and oil will mix into a nightmare gloop that can need an engine strip to clean. You going to spend more in coolant flushing that often. Which if your honest you wont. Link to comment Share on other sites More sharing options...
dt502001 Posted July 5, 2013 Share Posted July 5, 2013 Dont take this the wrong way but that is stupid. When, not if that seal fails you coolant and oil will mix into a nightmare gloop that can need an engine strip to clean. You going to spend more in coolant flushing that often. Which if your honest you wont. +1 For a 5er you can replace the W/P seal and it will need doing sooner or later 1 flush and your done or atleast you have narrowed it down to crank seals why wait untill it actualy hurts something? Link to comment Share on other sites More sharing options...
Recommended Posts