Evolution 26GT quitting....

[Ramz]

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?

[GremlinX]

Man... This story sounds all to familiar. A friend bought one and before he ran it at all... He noticed a guy at his field had one and it leaked out this ink black tar/gunk all inside the cowling... I wonder if it is the piston coating coming off??? His runs ok now but is a bear to start sometimes when hot.

[cloudshaker]

As far as I know the Evolution is supposed to be broken in on synthetic oil from the start. I spoke to Horizon about it and they told me not to use petroleum based oil at all. They tell me that the engine is too small to process the petroleum oil.

[Ramz]

Well that's good to know...I don't remember hearing the manual say that although they do recommend mobil 1 oil. I checked the 2 crankcase pressure fittings and one of them was a bit loose, so i took both of them out, put a bit of loctite on them and put them back in. I also replaced the clear plastic line. I'm gonna richen it up a bit and run it with the cowl off and see it if makes a difference. Any ideas where else i could look?

[0llie]

Do you have a Kill switch fitted?...I ask because we had a simple rc switch fitted as a kill switch and had intermittent engine cuts where it would restart straight away,without any choke indicating that it was'nt a fuel problem.... I rang the guy who makes the switches and when I told him mvvs 26 he said the ign and the switch was'nt compatible, so we are now looking for an opto isolated one....We are using a choke servo as a temp measure and since had no trouble...

We had the dreaded black stuff but now on our 5th gal of fuel it does get better...We started on a 18x6 and now we are on 18x8 menz and theres much more pull - although the revs are down a little

Cheers Shaun

Ps we are running fully synthetic oil

[Ramz]

I am running a kill switch but i can't see how that wouldn't be compatible with the ignition....it just doesn't make any sense. I could swap it out for a JR HD switch and i may do that just to be sure. I'm gonna try it with the cowl off for a few fligths and see if it quits. The last time it quit, it couldn't have quit in a worse spot...i'll keep it up high and see what happens. I do plan on switching to synthetic very soon.

[0llie]

Its just a simple relay type switch, and he claims the mvvs ignition is the only one he has problems with, it must cause the relay to operate??? The only other problems are extreme G's and this was cured by repositioning, this wasnt the cause for because ours happened straight and level.
Just bypass your killswitch to prove it.
Thanks
0llie

[jumah]

Ok guys, I want buy an Evolution 26GT for my zen 120 WM; is it good for that or buy glow engine better?

Thanks.......

[cloudshaker]

Jumah, I'd go for a gas powerplant any day over glow. The cost of the fuel alone is immense with glow. But that's just my opinion.

[GremlinX]

I am still nervous about this GT26... have you ever seen the endplay on one? I have not sen one start reliable by hand...

[dick hanson]

the 26 Evolution is a piece of cake to hand start -
I would never even consider an other method

[GremlinX]

Dick, does your GT26 have .300" end play? I swear I think there is a bad batch out there... That can't be good if a motor has that kind of tolerance. I am considering it for a 74" plane soon to come out... (EF Yak 54 ) Do you have the MVVS or the GT 26 ? I know about soldering up the idle hole in the choke buterfly, but what other tricks? How do you start it(proceedure, amount of flips/choke) when cold and how do you restart the motor when hot? Its definately got my attention, but I am scared of the quality.