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Honda Grom (MSX125) Forums
Modifications
Have some questions about oil starvation and a fix
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<blockquote data-quote="69ST" data-source="post: 159291" data-attributes="member: 5"><p>I think that you already know the answer to this one, don't like it,and hope to hear better news. Can't blame you for that. The bottom line is that this would be complicated beyond practicality. </p><p></p><p>Not 100% sure how far the pump can push oil. That said, it is a positive-displacement pump, so that should be a non-issue. The bigger concern would be how well it can <em>draw</em> oil from an extended distance. Unless an extended oil pickup remains filled after engine shutdown, there's going to be lag time...while it refills and that could well be a problem. It's not going to draw air anywhere near as efficiently as oil. The stock setup has the pickup an ~inch away from the pump and oil level, non-running, at oil pump level. </p><p></p><p>With a full crankcase, .8qt, oil level is maybe 2" as measured from the crankcase floor. Doesn't take much of a wheelie to expose the pickup to air and for the pump to go into cavitation...a.k.a. "sucking air". You can get away with several seconds of this and the oil flow is restored almost instantaneously once you're back on two wheels. The tranny will provide more splash lube than normal. The top end and rod bearing will be the most affected by lack of oil flow...and begin to heat up beyond normal. Oil isn't just lubrication in these engines, it's coolant, as well. Fortunately, the oil film tales a while to go away and roller/needle/ball bearings don't need a lot of oil.</p><p></p><p>With automotive road racers, the solution is a dry sump oil system...or an Accusump system. I cannot imagine either as being practical with one of these little bikes, I'll spare everyone the longwinded tech lecture. Further, changing engine operating angle by 45-degrees +/- is a lot more demanding. You're gonna have to deal with that mean old Mr Gravity and that means locating an oil sump that is always at, or near, the lowest point of the engine...such that the oil pickup is always immersed in oil. I'll end this post with the money question: "how important is stunting to you?".</p></blockquote><p></p>
[QUOTE="69ST, post: 159291, member: 5"] I think that you already know the answer to this one, don't like it,and hope to hear better news. Can't blame you for that. The bottom line is that this would be complicated beyond practicality. Not 100% sure how far the pump can push oil. That said, it is a positive-displacement pump, so that should be a non-issue. The bigger concern would be how well it can [I]draw[/I] oil from an extended distance. Unless an extended oil pickup remains filled after engine shutdown, there's going to be lag time...while it refills and that could well be a problem. It's not going to draw air anywhere near as efficiently as oil. The stock setup has the pickup an ~inch away from the pump and oil level, non-running, at oil pump level. With a full crankcase, .8qt, oil level is maybe 2" as measured from the crankcase floor. Doesn't take much of a wheelie to expose the pickup to air and for the pump to go into cavitation...a.k.a. "sucking air". You can get away with several seconds of this and the oil flow is restored almost instantaneously once you're back on two wheels. The tranny will provide more splash lube than normal. The top end and rod bearing will be the most affected by lack of oil flow...and begin to heat up beyond normal. Oil isn't just lubrication in these engines, it's coolant, as well. Fortunately, the oil film tales a while to go away and roller/needle/ball bearings don't need a lot of oil. With automotive road racers, the solution is a dry sump oil system...or an Accusump system. I cannot imagine either as being practical with one of these little bikes, I'll spare everyone the longwinded tech lecture. Further, changing engine operating angle by 45-degrees +/- is a lot more demanding. You're gonna have to deal with that mean old Mr Gravity and that means locating an oil sump that is always at, or near, the lowest point of the engine...such that the oil pickup is always immersed in oil. I'll end this post with the money question: "how important is stunting to you?". [/QUOTE]
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Have some questions about oil starvation and a fix
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