Hello, it's me trying to get my "problem engine" to run again
I apologize for the long post.
A few years ago I bought an ASP FS61 for my Flyin' King. No matter how I tuned it, the midrange was way too rich, even with the top and bottom leaned out as much as possible. I got a new carb from the shop, and the problems were still there. After a couple of gallons I finally gave up and decided not to use the engine. Earlier this week I decided to try again. Top and bottom are great, but if I leave it at half throttle, rpms gradually decrease, and it smokes and vibrates a lot.
What I have tried so far:
- A new carb (same type)
- Several glow plugs (all OS F)
- Different types of fuel (Byron 4T 15%, Rapicon 15% HLS, JeRo 5%)
- Different APC props (12x6, 12x8, 13x6, 13x4W)
- Checking the valves
- Moving the camshaft one tooth either way
- Using RTV on the intake to prevent leaks
- Fuel tubing on the needle valve
- I even tried the carb from my FS30. The mounting pattern is the same. With this carb the midrange is clean, but the engine won't idle, and the top end RPM is lower (for obvious reasons).
- If I turn the needle valve appr. half a turn in, the midrange is clean, but I can't go past 2/3 throttle without running too lean. This leads me to thinking that the carb is the problem.
Next on my list is:
What if I bought a 40N (OS FS-52S) or a 40NA (OS FS-56a) carb? Correct me if I'm wrong, but I have understood that they are interchangeable. I have only had good experience with OS carbs myself, and my OS FS-52S (sold) was smooth regardless of rpm.
What do you think? Should I buy an OS carb and give it a go? It is less than half the price of a new ASP engine.