Maintenance & Technical > KX450F / KX250F

Running 200:1 in your 4 stroke

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tharden:
I would like to get a crf450 or a kx450f to go with my 500.  How much better are the 450's on fuel consumption?

gwcrim:

--- Quote from: Kev on May 04, 2008, 05:29:30 PM --- My concern would be the oil on the back side of the valve head. Those titanium valves get very hot and you would have a build up of deposits over time and that causes the valve to retain heat which is not what you want. It would most definitely have no lubricating effect on the exhaust valve as the oil would be burning. I think what you will notice most is a loss of performance due to the slowing of burn of your charge. Overall any results you get from this will most likely not be what you want. My two cents.
Kev

--- End quote ---

Kinda digging up an old thread but here's my experience:

I had a '99 Sportster that routed all of the crankcase vapor straight back into the intake, not the air filter.  I tore the engine down with only 11,000 miles on it and was shocked.  The exhaust valves were gummed up pretty badly and the seats were pitted.  What was shocking was that the exhaust port itself was blocked by about 10%!  All of that oil vapor cooked itself to the port walls and really hurt breathing.

As it was  pointed out earlier, the amount of the stem that is exposed to the intake charge is minimal compared to the risk of damage.

YMMV........

01KX5WOODSRIDER:
  I have been running 100:1 in my RZ-350 and DR-350 with no negative results. I havent torn either engine down since but I have
checked exhaust ports when the pipes are off and there hasn't been
any carbon buildup. 

kawasaki_kev:
Funny I've just ordered a 96 kx450F and was wondering exactly the same question. I have come across this on a diesel van forum and a lot of folk were claiming quieter running from startup along with better fuel consumption. I think they were also running at 200-1 and recommending cheap mineral two stroke oil. One German posted up TUV emmisions results before and after on a well worn engine and it passed when added. Any more trying this out? (Vehicles or X bikes)

redlined_KX500:

I've been mixing my 09KX450F at 200:1 with the Bel-ray MC-1 and C12 fuel.
 

Just over 15 hrs on bike thus far, runs awesome and seems to run cooler than comparable bikes I ride with. Also no changes in valve clearance. Unlike alot of riders I see, I make sure engine is very warm before I start rapping the throttle on make a couple of passes on pit road at partial throttle to cool engine before I shut it down.

As good as this bike runs, it's still anemic compared to my K5. :-D

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