Running 200:1 in your 4 stroke

[KXcam22]

I am toying with the idea of running a 200:1 or 300:1 fuel mix in my new 4-stroke.  The goal would be to provide additional valve guide and valve seat lubrication to extend top end life.  I have no worries about carbon since my KX power valve was clean after 400 hours.  I have heard about this before in race engines. What does everyone think??  Cam.

[Arigato]

Good question.  I've always run a bit of leaded race fuel in my four-strokes, which is also supposed to prolong valve life.  What do all you smart people out there think?

[Kev]

I have run car engines without stem seals to allow more oil to lube the shafts of the valves. I have only done this on engines that I was going for max rpm and was planning on tearing the engine down frequently, but I don't think you are going to gain any lubrication on the valve stem with oil in the fuel. The minimal amount of stem that is exposed during intake will probably be inconsequential. 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

[maddoggy]

i think arigato is on the right track with the leaded race fuel. probably mixing leaded fuel with your normal fuel would get you the benefits that you are after. however the extremely light 200 or 300:1 mix that you're proposing would be so light that i highly doubt that you would have any adverse affects on the firing. you just might achieve your goal with the lubrication properties. i guess you'll never know till you try it. if the bike was mine i'd try it. i really don't think there would be any risks involved. just my thoughts on the subject. MADDOGGY

[maddoggy]

the company i work for recently did some testing of a product called DFC made by envirofuels the same company that makes the "rev r up" 2 and 4 stroke race fuel additive. it is a product made for diesel fuel intended to restructure the steel and impregnate the surface of the cylinder walls with a permanent lubricant. well long story short, about a million dollars worth of hailed out engines and hundreds of stuck injectors later we finally convinced our company to stop using the additive in the fuel. as soon as we stopped the additive our engine problems dissapeared David Copperfield style. i guess the moral of the story is don't use an unproven chemical product in your engine trying to improve it. Maddoggy

[KXcam22]

All interresting points of view.  What I am considering is running my belray MC-1 at 200:1.  That is a 0.5% mix.  At 400 hrs at 60:1 in my K5 there was no carbon buildup and what suprised me was no powervalve wear, a beautiful oil film everywhere and never any plug fouling.  It I could translate those properties to the wear areas of a 4-stroke head it could add some wear reduction without detriment.  Intake valve would be easy as the mix would lube the stem/guid and seat, exhaust valve might be hot enough to burn it away - but is it hotter that the exhaust port of a K5 where the MC-1 lasted pretty good?  I'm not sure.  Also there would be some additonal cylinder lubrication above the top ring.  I am going to try this out next ride and see how it works.  Heck at least I get to smell that nice smell again. Cam.

[Hillclimb#42]

What about the Marvel Mystery Oil? I believe sprint cars run it for the same reasons. It helps counteract the corrosive fuel that they run, i think.

[rrguy]

I have added Marvel Mystery Oil, especially when messing with different fuels like E85 just to add a little lube. It never hurt, don't know how much it helped?

[KXcam22]

First ride at 200:1 and the bike ran great.  It even ran a bit cooler on the racetemp strip, but that could be due to other conditions. Smells nice.  The biggest issue was having a 4th type of gas in the shop to keep track of.  Don't want to put the 200:1 in the weedwacker. cam.

[Hillclimb#42]

  The biggest issue was having a 4th type of gas in the shop to keep track of.  Don't want to put the 200:1 in the weedwacker. cam.

  Heck no, the weedwacker only gets U2 VP @ 50:1

[tharden]

I am curious as what happened to pro-longed running with the 200-1 mix.

[KXcam22]

Not really a prolonged test yet but I have 14.6 hrs runtime (meter) since new with no valve clearance changes.  Runs excellent and starts first kick hot or cold.  Haven't checked the plug yet but I am not worried as my KX500 would go all season on a plug.  I plan to keep doing this for the life of the bike unless I find out something different. Smells nice......ahh......Cam.

[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]

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

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........

[KXcam22]

I appreciate the point of view.  The excess carbonization could be an issue but here is my reasoning why I think this will work well for me. 
    General engine oil is non-synthetic and is not intended to be burned while in the engine.  It has a high ash (carbon) content that is inherent to engine oil. Two stroke oils are a completely different animal and are specifically designed to be burned at combustion temperatures.  They are formulated with a low ash (or no ash) content to avoid carbonization. Some like Torco are even smokeless (I ran some in my outboard and it was disconcerting to see NO smoke from a 2-stroke).  One of my engineering philosophies is that "One good test is worth a thousand expert opinions", so my main reason for trying this is the phenominal results I got with my KX500. I ran my KX500 at 60:1 with Belray MC-1 for 14 years, approx 300-400 hours before I took the top end apart. Carbon - zilch, wear - not much.  I didn't even have to clean the powervalve or exhaust port.  Long ago when I was racing I had identical results with my 400 Maico using the original MC-1 at 85:1.  So based on that, I am confident that at 200:1 there should be no carbon buildup and enough film strength in the oil to make a significant reduction in top end wear.  I could be completely wrong.  I'll let you know in a couple of years. Cam.

PS fuel consuption is about the same.  Plan on getting a larger tank.  I can reliably go 60km between fills, but that is lower speed single track riding.