wessco

My Feedback: (7)

After being put up for the winter, I've put an older .63FZ on a plane. This engine has less compression than my .63FZ-S. Just looking at the FZ, it looks to not have been run much. I got this engine used. If it's not broken in, will the compression build the more fuel that is run through it? Last fall when I ran it, it ran fine and had the same amount of compression.

Fuel: Cooper's 30%
Plug: OS F plug
Prop: MAS 13x6 Scimitar

wessco

My Feedback: (7)

Anybody, anybody at all??????

Can you hear me? Can you hear me now????

After I got home from work, I ran this engine for about 6 or 7 minutes. Compression is fine. Adjusted valve clearance and started the engine. Idled for about 5 minutes. Ran throttle to full open and it runs like a champ. No problems with the running. Just checked compression and it's good. Why would it be low after sitting for a while and then build up after it's ran?

Wess

Troy Newman

Wess,

I responded last night or this morning tho this thread. RCU must have had a problem and lost some posts...I've seen this happen from time to time.

Basically what I told you was put a little oil in to lube it. When they are dry and or have been sitting for long periods the compression will sometimes get really low. The oil that was in them either migrates or gels up and then its nearly metal on metal inside.

Once you run it and get it up to temp all the oil will move around and it will burn off the old nasty stuff and compression should return to normal.

Compression is a sign of how healthy a motor is...but in the case of YS engine I find that it really means nothing in the end. I have had very well worn out motor that have a large ring end gap and don't run properly due to it...but they feel like they have great compression. And then I have had real stump pullers that sit for a week and when I turn them over it feel line there is little to nothing there. Once some fuel gets in it and some oil it will come back.


Glad you didn't have a problem...sorry about the missing post thats one on RCU

Troy Newman
Team YS Performance

wessco

My Feedback: (7)

Thanks for replying. I appreciate the help. I've been stuck on 2 strokes for the past 6 months, so this was a great surprise when it ran flawlessly!