planebow

My Feedback: (1)

I recently ended up with GP Extra 300 with a Moki 1.8. The plane has never been flown but the engine has some use. The compression seems very low to me and was told that this engine is a low compression engine. I have not tried to start this engine yet but would like to know if it is supposed to have a strong compression.

Thanks in advance for any info.
Bob Howard

rcdude7

My Feedback: (264)

Low compression would result in lower power in any engine. My guess would be that if the engine has not seen use for awhile, the most common cause of low compression would be a stuck piston ring.

wcmorrison

My Feedback: (2)

Or it has a Dykes ring. If it is a Dykes ring, it depends on compression and fuel burn to force the ring out to generate a better seal. Thus turning it over by hand is not a good measure of compression.

Cheers.

Chip

hammer 50

My Feedback: (17)

I have two 1.80 Mokis one has great compressionat all time the other after it sets for for a couple of weeks will be much easier to turn. once after it set over bad weather had very little compression. The odd thing is both run equal with same props with good slow idles. Since I traded for them used I don't know how they have been used or abused. I thought the one with weak compression may have been overheated and lost tension in the ring,but it starts just like the other one after priming.
I bought a couple of Frank Bowan rings to try but both run great the way they are. I fly wardirds so I don't expect them to scream. I run castor,thought that might add to a sticky ring never thought about the dykes ring.
If there is no obvious scoring or wear showing in the exhaust port I would run it . Great reliable engines.

planebow

My Feedback: (1)

I will run it the way it then. If I have problems thenI will go deeper. Engine has not been run for many years.

Thanks for the replies,
Bob

Donairplane

My Feedback: (3)

Mokis have standard rings, not Dykes.