flyday58 Posted December 28, 2012 Share Posted December 28, 2012 Got to thinking while reading a thread in another part of the forum. BLACkHAT250 posted the following comment about DT400E jetting: Aha " thats what mine used to do, after it sits for a night, I think you should pull the head & barrel , then spin the crank, an see if thers gear oil on the bottom of crank, i suspect R/h crank seal sucking thru , i know it will burn it off , but if its as bad as mine was, it will be half up the crank, talking up swept volume in the case, resulting in that kangaroo effect, see how smooth that DT in video is, So now I'm thinking (yup, Danger! American thinking! ), where do the main bearings get their oil? The two drilled passages in the case direct oil to the bearings, but whither the oil? I've had oil on the crank in the past, it just never occurred to me that this was bad. So it must be the injector oil mix? Or are there internal passages leading from within the case to the bearing cavities? If there are, I couldn't find them. It's raining again so I've got time to come up with nutball questions like this. Link to comment Share on other sites More sharing options...
flyday58 Posted December 28, 2012 Author Share Posted December 28, 2012 Link to comment Share on other sites More sharing options...
Moderator Cynic Posted December 29, 2012 Moderator Share Posted December 29, 2012 Condensation. Yep annoyingly simple. When the engine is cold the oil doesent burn because the engine isnt hot enough. Once up to temperature the oil. If everything is set right will not quite make it to the combustion chamber. Ultimately some of it will. Thing is some will stick to the piston and more. Due to the temp to the side of the cases. Will collect on said cases. This will collect in the gullies and feed the bearings. Suzuki do it differently. The mag bearing is pump fed. The other is open to the gearbox. Thats why suzuki boxes are even tougher than dt's. But the wont run without an autolube. 1 Link to comment Share on other sites More sharing options...
Preload Posted December 29, 2012 Share Posted December 29, 2012 Flyday. Here's how the oil get to the main bearings. When the piston is on the upward stroke it sucks in a petrol & oil mix into the bottom of the cases, then as the piston is on the down stroke the fuel mix is compressed/pumped by the piston which pushes the mix up the transfer ports to get to the top of the piston ready for burning, however while its being compressed some of the mix get pushed into the bearings so to lubricate them. Its simple but effective system. 1 Link to comment Share on other sites More sharing options...
Moderator Cynic Posted December 29, 2012 Moderator Share Posted December 29, 2012 If that was the case why the gullies? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted December 29, 2012 Moderator Share Posted December 29, 2012 If that was the case why the gullies? Maybe the gullies are there for the reasons you said earlier Jason, but are not playing a part when the motor is running...what i'm trying to suggest here is that when the engine is stopped, the oil that is all over the sides of the transfer ports will run back down to the bearings, and the engine running condition will be as preload said..ie some of the mix is pushed through the bearing into the transfer port...never really gave it a thought myself but I can appreciate that it's a great system and even greater for it's simplicity Link to comment Share on other sites More sharing options...
flyday58 Posted December 30, 2012 Author Share Posted December 30, 2012 Thanks, you guys are the absolute shit! In a good way of course!! I guess the is enough oil in the mix to prevent piston lock-up and lube the bearings. Guess I'll quit filling the crank gallery with oil every time I remove the cylinder. (Haven't, really. Well, not FULL, anyway...) Link to comment Share on other sites More sharing options...
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