Hyper 50 Blown Piston again!!
06-08-2008, 10:33 AM
#1
Junior Member
Thread Starter
Join Date: Feb 2007
Location: Melbourne, AUSTRALIA
Posts: 29
Likes: 0
Received 0 Likes
on
0 Posts
Hyper 50 Blown Piston again!!
HI all,
I must say this is the first time I have had so much trouble with an OS engine! I have a brand new Hyper 50 in a T-Rex 600 and it has had less than 5 ltrs of fuel through it.
It killed 4 glow plugs in the running in period, did a ring after 2.5 ltrs (changed the piston and ring) and today blew a hole through the new piston. I don't get it!!
I've been flying glow helis for 4 years so I have half an idea on what I'm doing. I changed all fuel lines so there are no splits or kinks etc and cleaned the carby.
The engine behaved the way it should during the break in.
Started with 2 turns on the high end needle and left the factory low end. Heaps of smoke, very rich! cool to touch after 2 or 3 flights then all of a sudden she goes bang!!
Considering the rubbish bin for this one and a Thunder Tiger PRO H 53 instead
Any tips or suggestions?
Cheers
CJ
I must say this is the first time I have had so much trouble with an OS engine! I have a brand new Hyper 50 in a T-Rex 600 and it has had less than 5 ltrs of fuel through it.
It killed 4 glow plugs in the running in period, did a ring after 2.5 ltrs (changed the piston and ring) and today blew a hole through the new piston. I don't get it!!
I've been flying glow helis for 4 years so I have half an idea on what I'm doing. I changed all fuel lines so there are no splits or kinks etc and cleaned the carby.
The engine behaved the way it should during the break in.
Started with 2 turns on the high end needle and left the factory low end. Heaps of smoke, very rich! cool to touch after 2 or 3 flights then all of a sudden she goes bang!!
Considering the rubbish bin for this one and a Thunder Tiger PRO H 53 instead
Any tips or suggestions?
Cheers
CJ
06-09-2008, 10:04 AM
#2
My Feedback: (11)
RE: Hyper 50 Blown Piston again!!
Without seeing the engine, we'd have no way to know what the difficulty might be.
If you find a hole in the piston, you'll need to investigate the reason. Did you use a piston lock when the flywheel was tightened onto the engine? That's a primary source right there. It will stress the piston enough that if it doesn't break when you tighten the flywheel, it will soon.
If you examine the piston, do you see an area of discoloration that matches the squish band of the cylinder head? Does the hole in the piston match the location of the glow plug, and does the hole have beveled edges? Is the top of the piston rough, like it's been stippled with metal particles? All of these indicate too-lean running with detonation. Detonation causes a very localized hot spot that causes the piston to vaporize at that location. The metal gets re-deposited onto cooler parts of the piston's top.
If you see a broken, caved-in hole, it's possible that the piston was just too long for the engine, and made contact with the top of the piston.
As you can see, there can be several reasons for a hole in the piston. The exact cause can only be determined by examination of the disassembled parts by someone with model engine experience. You may wish to contact your regional O.S. service center for assistance.
If you find a hole in the piston, you'll need to investigate the reason. Did you use a piston lock when the flywheel was tightened onto the engine? That's a primary source right there. It will stress the piston enough that if it doesn't break when you tighten the flywheel, it will soon.
If you examine the piston, do you see an area of discoloration that matches the squish band of the cylinder head? Does the hole in the piston match the location of the glow plug, and does the hole have beveled edges? Is the top of the piston rough, like it's been stippled with metal particles? All of these indicate too-lean running with detonation. Detonation causes a very localized hot spot that causes the piston to vaporize at that location. The metal gets re-deposited onto cooler parts of the piston's top.
If you see a broken, caved-in hole, it's possible that the piston was just too long for the engine, and made contact with the top of the piston.
As you can see, there can be several reasons for a hole in the piston. The exact cause can only be determined by examination of the disassembled parts by someone with model engine experience. You may wish to contact your regional O.S. service center for assistance.
06-10-2008, 04:38 AM
#3
Junior Member
Thread Starter
Join Date: Feb 2007
Location: Melbourne, AUSTRALIA
Posts: 29
Likes: 0
Received 0 Likes
on
0 Posts
RE: Hyper 50 Blown Piston again!!
HI Bax,
Thanks for the reply.
The hole is dead bang in the middle of the piston. It is light grey and looks like welding platter. Sounds like it was too lean.. I just don't get why it was fine for 3 or 4 tanks. The engine was cool after each flight but the last one killed it.
It was hot and smoking. Something changed. It is rich on low end and 2 turns open on high end. Plenty of smoke and fuel pouring out of the exhaust. What would cause it to lean out mid flight?
I have a header tank sitting a little higher than the carb.
Cheers
CJ
Thanks for the reply.
The hole is dead bang in the middle of the piston. It is light grey and looks like welding platter. Sounds like it was too lean.. I just don't get why it was fine for 3 or 4 tanks. The engine was cool after each flight but the last one killed it.
It was hot and smoking. Something changed. It is rich on low end and 2 turns open on high end. Plenty of smoke and fuel pouring out of the exhaust. What would cause it to lean out mid flight?
I have a header tank sitting a little higher than the carb.
Cheers
CJ
06-10-2008, 09:32 AM
#5
My Feedback: (11)
RE: Hyper 50 Blown Piston again!!
Leaning in mid-flight can be caused by a few things: vibration-induced fuel foaming which agitates air into the fuel, leaning the mixture; an leak/crack in the fuel pickup line that is exposed once the fuel level in the tank goes down a bit, a loose needle that vibrates lean, and possibly a bad piston/ring/liner fit that causes compression loss when the engine warms up. Head bolts can become loose if the engine's been overheated. If you tighten them while the engine's still warm/hot, they will continue to get loose. You need to tighten the cylinder head bolts when the engine is cold...or at "room" temperature.
