Well, i've got 5 flights on my Evolution 26GT and on my 5th flight it quit 3 mins into the flight. I'm running the stock evolution pipe and header on premium fuel and lawnboy ashless oil for break in and a Top Flite 18x6 prop. My DA50 and DA100 both run great and my Evolution did run great up until this point. It quit 3 mins into the flight so it didn't run out of fuel. The battery pack is brand new with 5.6V and the ignition seems to be working properly as I just pulled the plug and turned the motor over with lots of spark. I noticed that the top of the piston is coated in a black like tar substance which, as far as i know, shouldn't be there. I haven't taken the head off yet becuase i'm thinking of sending it back to evolution. The plug appears to be fine. I haven't looked at the carb yet though. Anybody have any ideas of where to look?

why the Lawn Boy ashless - The instructions as I recall say just run 32-1 Mobil1 -
also be sure you have set needles for ever so slightly rich on the ground (there is no factory setting)
Mine has run only mobil 1 since day 1 -at 32 -1 terrific compression and 9000-10000----rpm all the time on the 18x6
Has it quit due too being hot?
good possibility ?

I ran the lawnboy becuase that's what i had and it has worked fine in my DA's. As for being too hot, I really don't know. Is their a way toi be able to tell if it did?

I would say your lawnboy ashless did the motor some harm. Everything you read on the MVVS/ Evolution motors tells you to use full synthetic for break-in and running. Different motor builds at work between DA and MVVS.

How would running lawnboy do harm to the engine? I don't understand how that would happen.

The lawnboy is not synthetic (comes from nature) and my understanding is that the coated piston / these motors do not like the "organic" oils. All brochures from MVVS always says to use fully synthetic high-end racing type of oil. That's one of the reasons that this small of a motor produces as much power as it does.

I'm with Ramz, somebody tell my why Lawnboy can possibly harm an engine in the space of 5 flights mixed at ANY ratio......Scientific facts please, no hearsay or manuyfacturer's hype.....Any 2 stroke engineers out there ? A G26 has no coating on the piston and makes at least as much power as any other 26 out there..Maybe I should try some piston coating ?

Running too hot? Making the pistion rings run to thight? Maybe the Nikasil coating doesn't like it? BMW had Nikasil engines that was destroyed by some types of pumpgas in the mid 90ies due to high sulfur contents (do a google seache for "BMW nikasil issue" or read here: http://www.bmwworld.com/engines/nikasil.htm

Post in the MVVS direct support forum and you might get a better answer from Pe / Dar / David.

Where do you get Moibil 1 full synthetic 2 stroke oil ??? I would use the stuff in all my engines but I have never seen it sold anywhere.

OK...does anybody know if Amsoil 100:1 would work ok? I've got some but it isn't mixed up yet. I appreciated all the responses i've received so far guys. I haven't had a chance to run the engine again...waiting for some props to arrive from DA.

Stay away from Amsoil !!! If you use any oil at 100 to 1 you can expect to ruin more engines [:@] Use a good quality synthetic such as Mobil 1 or Pennsoil Full Synthetic etc. etc. Amsoil is bad oil that makes wild claims.

I have some mobil 1 and have found it on the internet but since I've not used the first quart it didn't stick out in my mind to me at the time where I found it. I think www.mvvs-nl.com carries it and shipping is pretty reasonable if you buy several quarts at a time.

Autozone!!!

The design of the engine with a cantilever crankpin is more prone to flex than a double crankweb design. The advent of synthetics made it possible to extract a serious amount of power from this design, which is taken to the limit in the 26cc engine. These engines will not, I repeat will not, tolerate anything less than the best quality two stroke all synthetic racing oil.
Bearing failure will occur if the lubricity of the oil is reduced by either running the engine too hot, or using inferior oil.
Pistons are not that sensitive as long as a fair amount of slippery stuff is present. The MVVS graphite coating makes it even more durable.

Pe -I don't think these flex-
the weed whackers /blower commercial engines have no need for a propshaft layout - so the samefront rear bearing and a stub crank setup is ideal
the std ol cantilever with a big rear radial load bearing and a small fron thrust bearing - can take a hell of a lot of load with no flex
the smallcase on the 26 --requires very small needle bearings -so tolerances for size and heat and load all get pretty critical -relative to a weed eater.
I have been flogging the 26 I have for a few months now on 32-1 Mobil 1- the clearances I felt when new and never run, still feel the same and the piston looks perfect
You can't treat a Porsche like a Trablant.

That quote will go down in history. Best one to date I've seen!

:-) so true
You certainly take good care of yours, and it serves you well because of that.

Everything flexes Dick. You should have seen those huge 20 meter long ships diesels flex like a snake when watching along the engine with eye lined up with the explosion doors. It always filled me with awe seeing that. It often made me wonder why we had to align everything within 0.02mm.

Yes -
I had a another engineering associate get mad at me years back -when I tried to explain to him that the new machine frame he designed , flexed too easily
He said "flex?"
that that thing is made from steel!"

Is this the correct Mobil 1 stuff? http://www.mobiloil.com/USA-English/...Racing_2T.aspx

yes

thanks guys. I'll go pick up some of that oil and give it a whirl. Much appreciated.

What is the operating temperature range on the cylinder head? My MVVS 26 gasser gets considerably hotter than glow and other gassers (BME 50, converted OPS 30, Zenoah 23) I have.

Even when run without a cowl, the head on the MVVS vaporizes spit on my finger in a fraction of a second. I mix 5 oz of Mobil 1 Racing 2T to a gallon of premium gas. That's a little more oil than the 30:1 in the instruction (4 oz makes 32:1). Thank you for an answer.

Have you properly set your high speed needle?

I set the HI needle to get 8.3krpm with APC 18X6. The instruction says to achieve max power at 8.5k with the right prop size.