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May 7th, 2007, 01:28 PM   #21
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Thanks for the info, it looks like KTM simply likes the scavenge type system better than the reed valves. Can't argue with that, dry sump motors from Norton and Harley have been designed that way for eons on their roller bearing bottom ends.
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May 7th, 2007, 03:33 PM   #22
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gday there again fellas.
my bike had the the ball bearing set up on either end of the crank,it lasted close to 5 years before the clutch side one failed.these bearings have a load max load factor of 19kn.to me the nj206 rollers with a load rating of 42kn should easily be able to handle the crank loads.
dale says he sets his crank end float to .21mm and doesn't have any problems,if i were you guys i would be doing the same. .5 or .6mm whatever it says in the manual seems to be excessive and as we all know doesn't work.

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May 7th, 2007, 04:51 PM   #23
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The point I was attempting to make is simply that the down stroke of the piston is the scavenge pump on the berg engine.Since all three engine capacities rely on the same size and shape reed valve the different engine strokes may have an effect on the bottom end lubrication.
For instance at 9000 rpm the 450 engine has a pump capacity of 4 cubic meters per minute of air.The 650 engine at 6800rpm, 4.3 cubic meters of air and the 550 at 8500 almost 4.7 cubic meters.
Since the oil supply to the engine via the pump is simply a pump volume x rpm formula it occurred to me that each engine capacity acts differently as a scavenge pump because of its different swept capacity.
Since the 550 engine seems to be best balance between bore/stroke ratios and has a reputation for high RPM this engine may be a more effective scavenge pump than the others.
Since the size and shape of the reed cage and valve are the same for all engine capacity's could it not be possible that the relationship between air mass flow and reed cage flow on the 550 engine create a situation where it simply is too efficient with the result that the bearings are starved of oil.
As the reed cage closes on the pistons upstroke limiting the theoretical air volumes to a fraction the the above stated the mathematical relationships remain constant.
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May 8th, 2007, 03:23 PM   #24
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just thought i,d set the record straight.it doesn't matter how much crank case compression there is on the downwards stroke .only a fraction of the air gets blown through the reed valve.most of the air gets blown into the left casing through the 1/4 inch hole next to the counterbalance shaft.
the crankcase will never run short of oil because the reed valve only expels oil that is over the 8mm overflow rib.
the crankcase has to have a minium of 8mm in the bottom at all times ,doesn't matter how many rpm.
have a look in my gallery to see what i,m getting at

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May 8th, 2007, 04:00 PM   #25
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With an oil pump pressure feeding the bearings, they should have oil supply regardless of crank pressure. On the flip side, Dale once commented to me as to how small the oil feed on the crank end was. With the old suction system, Husqvarna found through high speed photography that the crankcase pressure didn't relieve enough at sustained high RPM resulting in a lack of oil in the bottom end. They added a supplemental oil pump in 2000. This and the better filtration of the oil pump systems is probably why we have the newer oiling system today. When KTM went to roller bearings on the cranks of their 2 cycle engines in the later 80's to increase the load capacity, I swore I'd never own another. The rollers didn't care for the high RPM's and I had to constantly service the mains. With a small 2 cycle, you don't have much choice but to rap the snot out of the thing. On my Berg, I tend to short shift it respecting the RPM limits of rollers and the speed that the counterbalancer bearings are seeing due to counter rotating on the crankshaft, and (knock on wood) my bearings have been trouble free.
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June 27th, 2007, 06:24 AM   #26
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oil connection nipple

Does the oil connection nipple on the left (parts manual 2001 pg 28 #210-168-01) side of the crank supply oil to the connecting rod only, maybe it is the only why oil is entering the lower end.

Is this nipple a pressed in or thearded into the crank in?

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June 27th, 2007, 07:39 AM   #27
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oil in crankshaft area

There is a small outlet just above the counter shaft bearing in the left side case, so I can see 2 inlets of oil to the crank area. Is it possible that we would provide more oil into the crank area by opening these outlets to reduce main, counterbalance and connecting rod bearing failures? I think then we would reduce oil to the cam area, but with the new rocker arms and correct adjustment of the valves we have seen fewer top end failures.

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