Hi, I`m having trouble with two 1.08 engines. They are 6 years old and I have changed the piston, ring, sleeves, low needles and all O-rings and gasquets. They worked fine for about a year, one in a world models extra 300 and the other in a C.G. Sukhoi. Now, the problem with both is that they do not hold their peak rpms, they are easy to start and maintain idle all day if you want all the way up to about half throttle, but as soon as I take them to full they heat up and die without warning of any kind. Any comments are welcome.

Just for information purpuses, the engines are running on 15%nitro two stroke fuel, when they were running good they gave me about 8000rpms on a master airscrew 15x8K prop. I have used them as I said for 6 years and did not have any problems with them. When the problems started I tried everything and ended up changing the parts mentioned above, and they worked for another year and the problems started again. BTW it is fitted with a slimline pitts muffler the one that has a fitting for smoke.

i don`t want to buy more engines and these 1.08 are incredible powerhouses, easy to use and safe. but.....
Any help please?!?

When engines are running well and then start having problems, it means something has changed. The inability to sustain full-throttle RPM without overheating usually means that something's worn out or is bent. One thing we noticed is that the bearings were not replaced when you replaced the piston, ring, and liner. That may be a source of difficulty. Corrosion products could also have caused excessive wear to the piston, ring, and liner, too.

Also, please check your fuel. If it has accumulated moisture in it, it will tend to make the engines run hot. Idle will also be problematic. If you have these problems with known, fresh fuel, then you'll have to disassemble the engines and inspect very carefully.

Thanks Bill, I will check the bearings again, I forgot to mention that i did change those too. The fuel is fresh Tower Hobbies fuel.
I will take a look at the engines. If the bearings are OK, do you think I should overhaul them again?