corry

I have owned many YS engines and they are great up to about 50 hours. There they begin to loose compression and power. A trip on the UPS truck to repair for a new ring and other replacement parts and they run great for another year and the same thing happens again. I have tried everything to no avail. Does anyone who has good luck with these engines use a different break-in procedure than the factory suggests. Any help would be appreciated.

majortom-RCU

My Feedback: (40)

I've had some of the issues you describe, and seen others with the same problem. Troy Newman had a thread a while back stressing the need for pre-lubing any YS before putting a new engine in service, or returning to service after more than a few weeks of setting idle. This is a good idea for any engine, but YS seems to have more need than others for this kind of attention, maybe because they put out more power for their weight and mass of metal parts as compared to other engines. Another good mentor with a lot of experience told our club he opens up every new engine before he flies it, gives it an alcohol flush to remove whatever junk it picked up in manufacturing, then lubes it liberally before breaking it in. He also practiced pre-lubing any engine that has not flown for a while.

Iflyglow

My Feedback: (79)

First off, do you follow the instructions, are you running the correct fuel 20/20 mininum? 50 hours equates to about 300 flights, that is alot of flying if all you have to do is freshen the engine (New Ring, Bearings and Gaskets). If you look at the specific output per cubic inch, they are way above anything else out there as far as four stroke is concerned by about 25-30%. You have to practace more care for them. Do not run them lean or make them detonate (this will break parts). I also prelube the cam and cylinder when new, and after sitting for a long time. An air filter is very helpfull to keep junk out (only available for the 120 and up sizes though). A scored cylinder from debri or dirt or a lean run is going to effect a YS much more than a normal non asperated engine, since the compression is also used for "Crankcase Supercharging" and to pressurize the tank.

The TBO "Time before overhaul" is going to be shorter. Will a Blown small block chevy last as long as a stock Chevy 350? Never, but is there any comparison either?
A High strung High performance engine is going to have a shorter life before it requires work, but that is the price you have to pay if you want to play with the "BIG BOYS TOYS".
I spent quite a few years racing "Open Modified" Briggs powered GO CARTS, and we rebuilt are engines after 4 nights, and lapped the valves every two nights of racing. That is price we had to pay running them on alcohol and turning them @ 9,500+ RPM while putting out well over 20 HP out of a 5HP block.

RCVFR

My Feedback: (7)

Micky Spilane said it best: "live fast, die young, and have a good looking corpse."