Engine basics > Four strokes only
Upon request
RC Storick:
This is a place to discuss four stroke set ups.
Walter Hicks:
Thanks Robert,
I have Saito .40 with stock C/L venturi modified per Bob Reeves articles with larger spray bar hole and nylon screw.
I adjust it on the bench and it runs fine for a period of time then starts running very ragged like it is lean, I richen the Needle valve and same thing occurs shortly thereafter. I am running Powermaster 20/20 fuel and a rev up 11x7
prop at around 8000 rpm. Any suggestions as it did the same thing in the air.
Dennis Adamisin:
--- Quote from: Walter Hicks on June 24, 2009, 05:39:28 PM ---Thanks Robert,
I have Saito .40 with stock C/L venturi modified per Bob Reeves articles with larger spray bar hole and nylon screw.
I adjust it on the bench and it runs fine for a period of time then starts running very ragged like it is lean, I richen the Needle valve and same thing occurs shortly thereafter. I am running Powermaster 20/20 fuel and a rev up 11x7
prop at around 8000 rpm. Any suggestions as it did the same thing in the air.
--- End quote ---
Hmmm, sounds like overheating (?)
Plan A - try again with a lighter prop - maybe an 11x6 and see if it will hold.
Plan B - and this might be more likely: are you using Uniflow? if not then consdier this: a standard vent tank always tends to lean out as the fuel burns off and fuel pressure-head decreases. Instead of 8000 RPM start it off around 7400. It should speed up some, but mabe will not reach the point of going lean and running rough...
Plan C - a Personal Message to Bob Reeves requesting help, as his Saitos run like watches!
Bob Reeves:
Thank you Robert..
Walter, That's a new one on me, out of 7 or 8 40's I've been involved with never had one that wouldn't turn an 11-7 at over 9 grand (RC carb wide open) and hold it. Am assuming you have checked the valve clearance and all the normal basic stuff.
I'm tending toward something too tight or changing in the engine, how much time is on it and are you seeing any black discharge from the breather?
Willis Swindell:
Walter
A few weeks ago I took my SA40 out to fly with a 11x5 zinger 15 % 18%oil at 9,000 RPM The engine easily turned 9,500. the plane flew great. My buddy Jim Welch uses 20 20 in his Saito 62 and wanted me to try some of his 20 20. I tried it on the next flight . The engine would not turn over 8,600 RPM . I let it go at 8,400 and had a flight of 10 min. on 2 1/2 oz of fuel. Landed and put my fuel back in the tank and the engine was back to normal. Who knows maybe it needs some castor. I got my old log book out and with a 11 x 7 on 10 % Nitro and 50 50 oil the engine turned 9,500 RPM
Willis H^^
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