OS 50 hyper blow out

[Gunner]

I'm new to the hobby. I purchased a Tiger 50 and an OS 50 Hyper engine. I burned in the engine on a bench jig at the local club president's hangar with 2 tanks of 15%. I know he knew what he was doing. We ran it rich and it ran beautifully. I put the engine in my Tiger 50 and hovered almost a tank. Did nothing fancy since I'm just learning. Never really got it higher than 5 feet off the ground and never came close to WOT. My pitch curve is -3 to +9 degrees and I'm hovering at about 3/4 stick. My throttle curve is close to linear. Hovered in normal mode, never went to idle-up. On my second tank on the heli, hovered a little higher but always tail-in until I get more comfortable. After about 5 minutes, I heard a pop, like a cap gun going off. The engine died and since I was only a few feet off the ground, I easily landed the heli. Removed the glow plug and checked if it was dead. No problem, it heated up fine. But no compression on the engine. Took it to my bench and removed the engine. When I looked down through the glow plug hole, I could see that a small round hole had been blown through the piston. I took off the back of the engine and of course there were lots of metal shavings. I know that I was running the engine rich. Plenty of smoke, needle about 2 1/2 turns out. Anybody have any idea as to why this happened? I used a crankshaft locking tool to attach the clutch. I never inserted anything into the cylinder to lock the piston. I would be curious to know if anyone else had this happen so I can avoid it in the future. It will take at least 2-3 weeks to get another engine and I'm dying to get back out to the field.

[Gixxer]

Look a little something like this ???

[Gixxer]

Send it back to hobby services and they will ship you a new one in a week. I would break-in the motor on the heli next time too for proper loading on the motor. Richen it way out till it will barley leave the ground for a few tanks then lean her on out. Use a temp gun to like 160-180degF. Done forget the Hatori Pipe!!!

[BarracudaHockey]

Or this?

This one we think the likely cause was a loose head bolt producing a lean run.

[slow]

Yep, same thing happened to mine. Loose headbolt. Unfortunately, OS Service isn't as good in sweden as in the US, so in their infitite wisdom, they decided that them not tightening the head bolts were my fault...
I now buy my OS engines abroad..

/James

[Gunner]

Gixxer,
Yep. Looks just yours and Barra's. So you think it was running lean, huh? I'm positive that the needle was over 2 turns out. Everything is new so I'm sure that the fuel flow was good. I'm using the high priced muffler from Audacity. When I get the new engine back, I'll make sure I run it real rich. Since you live in Richmond and I'm on the west end, maybe I'll get with you and Debiandog to look over my settings and my setup before I try flying it again. Thanks.

[Gixxer]

Lol i didnt even look to see where you were from... yea man come on out and fly with me and Dan one day! Itll be fun I got to get this new Evo 50 in the air first

[BarracudaHockey]

Just for the record, thats not my engine, it happened to someone at our field and I had my camera handy. :glasses2:

[Mark J]

hehehe I just popped a pic of mine that did exactly the same thing in another thread!

Now reading this, I thought it was because I hadnt richened the needle when I changed to a higher nitro fuel! but with you saying about loose head screws, mine were seriously loose when I removed the head on my engine! didnt have to put any effort into removing them at all!

Seems to be a common problem then (great! spend a load on an engine and it cant keep hold of the screws in its head lol) Better let my mate know about the prob so he can keep a good check on his new hyper he got yesterday!.

[Gunner]

MarkJ,
Sent my engine to Hobby Services here in the US. Got it back in 2 weeks with everything replaced. I haven't had time to dial it in and fly again, been too busy. But I'm hoping that once I tighten the head bolts, they won't come loose. I truly believe that they were never tightened in the first place from the factory. I tightened the carb because the instructions said to. But I didn't think about checking the head bolts. If you have yours flying again, let me know if the bolts loosen up after each flight or every couple of flights.

[DavidH]

3mm bolts are torqued to 13 inch ozs. You would be surprised how very little effort it takes to obtain 13 inch ozs. I use a torque wrench when assembling engines. You really don't want to use a gorilla grip in tightening the bolts in the engine. All the engines I have took apart that were NIB. The bolts were probably torqued more that 13 inch ozs.

David

[Mark J]

Gunner, unfortunately, in the UK our service for RC stuff is more than likely as bad as anything else over here when it gets sent back, so ive ordered a new piston for mine, so hopefully will be back in the air asap!

Will report on how it fares on the bolts coming loose etc, but I know i'll be checking them every flight thats for sure!