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Engine basics => Four strokes only => Topic started by: REX1945 on March 23, 2013, 11:15:49 PM
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My first Saito 40 has had about 4-5 gal of fuel through it and
is showing signs of drastically reduced power.
The bearings aren't noisy, but it has very low compression.
What do you use to lap in the valves ?
I presume a new ring makes little difference.
Rex
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Can't help a whole lot as I have never really ran into your problem. Only time I ever had a Saito loose compression was after running it on some junk fuel for break in that contained castor. The fuel was a mix of who only knows what and one run with PowerMaster 20-20 fixed it. I suspect the ring or valves were stuck and running it on 20-20 cleaned it up.
I can't remember how you are running your Saitos, care to enlighten us as to what fuel you are running?
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I have a Saito 40A. Not enough info. Check valves first-could be too tight. Glow plugs actually can blow and leak on any high compression engine-check that. Don't use crap fuel on a Saito 40A-very high quality motor-gotta use good stuff.
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I've been using Wildcat 15% nitro with 18% synthetic oil. I add 5 Oz of Excaibur synthetic oil to each gallon.
That brings it back to 20% synthetic.
I have run 2 other engines on this mix without loosing power, and identical 40 on a different plane and my
Saito .56.
I'm going to take the head off and remove the exhaust valve first. I wish I had a good way to leak check it.
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If it is the exhaust valve leaking, you should hear it in the exhaust pipe when you turn the engine over on compression. If it is the intake valve, you should hear it in the carb. If you don't hear it in either one, it is probably the ring. Add a little oil through the exhaust port. If compression comes back it is most likely the ring. If not, you probably have a glow plug leaking. I have seen bad pushrods on Saito's that would give good compression one time and then hold the valve open slightly on the next time. You can tell this by opening up the valve clearance to maybe .030" and see if you then have compression.
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Is the synthetic oil you are adding the same type as on Wildcat?
I read somewhere that synthetic oil of different kind do not mix very well.
I guess most of us use a 20/20 Y/S Premium Fuel from Byron or PowerMaster.
Martin
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I have a Saito 40A. Not enough info. Check valves first-could be too tight. Glow plugs actually can blow and leak on any high compression engine-check that. Don't use crap fuel on a Saito 40A-very high quality motor-gotta use good stuff.
My first thought also. That would explain lack of compression and poor power.