Evolution 58 problem

[Greyhoundman]

I have less than 5 gallons of fuel through mine and until yesterday it has ran like a champ. On my first flight saturday about 3 minutes in to my flight it dead sticked got it back on the ground safely and I had almost no compression. I took off the muffler and from what I can see the cylinder looks good and the plug is tight, but still no compression. Then today I pulled off the jug to find out the ring had broken. My question is what could cause this?

[Greyhoundman]

Bump...

no ideas? spontanious ring combustion?

[Chris Puckett]

Could be a couple things. Does the piston still have locator for the ring to keep it from spinning? Did the motor ever have a hot run that might have damaged the ring?

[Greyhoundman]

Yes the locator is still in place and It never ran hot to my knowledge I temped it a few times and it was never over 180 after flight usually 170-175 and it was a cooler day than normal when it happened.

[loan4utoo]

Too hot or bad oil...only two things I can think of. Any other indications of it getting too hot? What oil and ratio were you at?

[Greyhoundman]

Running 40:1 mobil 1 2XT ? synthetic, same oil I have been running for a couple gallons, and when I got it down after it died it was very hot to the touch but when I got it back to the pits and temped the engine only a few minutes after landing it was only 115 deg.

[loan4utoo]

I don't think the oil was an issue. I think it overheated. Even though you took temp...it was after a dead stick...which can pull off a lot of the heat, and then it took a few minutes to get back to actually read the temps. Send it in to Horizon...let them try and figure it out. If you had five gals thru it, I would think you would have noticed an overheat prob before now. Even if they charge you some $$, if the same people that worked on my dirt nap lawn darted Saitos work on these, they'll get it back really quick. Let me know what the outcome is. Good luck.

[KrisW]

Rings are cast, then machined to final shape. This makes them pretty brittle.

I'd look for a small mark in the cylinder to see if a flaw in the ring had made a mark before the ring finally broke. Any lines inthe bore in the same location of the ring's break would indicate that there was a stress riser or crack starting in the ring. You may see something. . then again you probably will not. Best to check though.

After the ring broke you would have no compression, which is probably what caused the Deadstick situation. My thinking is that either a flaw in the ring itself, possibly a stress crack or weak area from when it was manufactured or during installation (most likely scenario. . during installation) caused the ring to fail after a a few heat cycles and a bit of pounding from the engine running. Overheating would have caused a problem with scoring, but probably not with ring failure, since the ring and piston would have gouged into the cylinder wall due to excessive expansion, instead of the ring merely breaking, and you would have piston damage as well as a damaged ring.

Best bet is to send it in for repair, and give them all the information on running conditions, oil, and fuel quality and octane rating.

Hope this helps.

[Greyhoundman]

Thanks for the info guys Its off to horizon tomorrow

[toprudder]

I had the exact same thing happen to me, with a 45GX. Less than 4 gallons of fuel through the engine.

Pulled the cylinder -- broken ring. I noticed what looked like blisters in the cylinder wall also, looks like the plating on the cylinder wall had started to delaminate. It had not broken off anywhere. This happened in the same area where the small portion of the broken ring was riding.

After looking at the engine some more, I noticed that two of the three ports (one intake port and the exhaust port) appeared to have no plating on the vertical web dividing the ports, and there was a noticable bump when going from the web up to the cylinder wall. The whole reason for having a web in the port like that is to support the ring, so it will not expand and catch the top of the port as the piston moves up. Perhaps this is what caused my ring to break.

I'm really bummed about this. I thought about getting a DA50, and sorta wished I had. I can't share props with anyone, parts like headers and mufflers are harder to find, etc. The engine ran VERY reliably up to this point, but I always felt like it was a little down on power compared to a DA50.

I will be sending my engine in, and hopefully Horizon will take care of it. I've heard really great things about Horizon service, so I am optimistic. However, my son and I were looking forward to competing in our first IMAC contest, and we will miss two contests because of this.

BTW, if anyone has ANY doubt that this engine is made by MVVS, the MVVS logo is on the side of the connecting rod.

Bob R.

[adrian]

well - many issues at stake here - the running in of these engines are crucial - and needle setting likewise - the engine is a gem and they make tons more power than any of the other 50's - i have a Da and zdz and sold my 3w so i know - i hope its just a normal component issue as can happen and has happened with all - you can be shure of good service from Horizon atleast - keep us posted - was wondering if your engine barrel was nickosill like mine - i have a 58 prosport?

[Greyhoundman]

Got the 58 back from horizon today VERY fast service! 4 business days total.

I looked at the cylinder and I could not see any bumps or defects before i sent it off. It seemed that it was just a broken ring. They replaced the ring, piston, base gasket, and carb all under warranty. Only time will tell now, It always ran like a champ before and if anything I ran it a little rich.