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Author Topic: Upon request  (Read 4085 times)

Online RC Storick

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Upon request
« on: June 24, 2009, 05:01:31 PM »
This is a place to discuss four stroke set ups.
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Walter Hicks

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Re: Upon request
« Reply #1 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.

Offline Dennis Adamisin

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Re: Upon request
« Reply #2 on: June 24, 2009, 08:55:32 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.

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!
Denny Adamisin
Fort Wayne, IN

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Offline Bob Reeves

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Re: Upon request
« Reply #3 on: June 25, 2009, 03:23:34 AM »
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

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Re: Upon request
« Reply #4 on: June 25, 2009, 06:18:54 PM »
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^^

Offline Ralph Wenzel (d)

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Re: Upon request
« Reply #5 on: June 25, 2009, 09:54:07 PM »
Saito is pretty explicit about not using Castor oil in their engines; something about varnishing up those little valve-thingies, I believe. My Saito .40 is very reliable with Pat Johnston's C/L mods. 1-flip starts, and turns an 11-7 APC at 9800. I launch at 9000, and it's like a tractor engine.

Edit: I should have added that I use only Powermaster YS 20/20 fuel, and the tank uses standard venting, not uniflow.

« Last Edit: June 26, 2009, 11:00:45 AM by Ralph Wenzel »
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Online jim welch

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Re: Upon request
« Reply #6 on: June 26, 2009, 06:30:48 AM »
Just wondering if that 40 was run on uniflow or muffler pressure?My 62's run great on muffler pressure but act the same as that 40 on uniflow.I don't think the fuel draw is the same all the way through a tank on uniflow as is the pressure set up.At the end there's no speed up or warning it just cuts off as if you flipped a switch.That takes a little getting used to but it's ok.   Jim
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Walter Hicks

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Re: Upon request
« Reply #7 on: June 26, 2009, 08:35:31 PM »
Thanks for all the replies,

   I was using  Powermaster 20/20 fuel with  OS  F plug.  It will rev over 8000, however I adjusted the screw after

getting the rich lean setting for rpm, then setting the rich lean again etc. I am wondering if I have the venturi

chocked down too much  with the adjuster screw. I have not checked the valves I will do that. I have another


Saito .40  I will also try with the same carb set up. What are the  indicators of valves not properly adjusted???

Offline Bob Reeves

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Re: Upon request
« Reply #8 on: June 27, 2009, 02:19:56 PM »
Thanks for all the replies,

   I was using  Powermaster 20/20 fuel with  OS  F plug.  It will rev over 8000, however I adjusted the screw after

getting the rich lean setting for rpm, then setting the rich lean again etc. I am wondering if I have the venturi

chocked down too much  with the adjuster screw. I have not checked the valves I will do that. I have another


Saito .40  I will also try with the same carb set up. What are the  indicators of valves not properly adjusted???

Hi Walter, might check out the other threads started in this section.. Not sure if it will help but might give you a little more insight on how I'm running my 40's and if you follow the links you will see some of how I got where I am now. Can't answer your question about mis-adjusted valves as I've been pretty prudent about checking mine and have never had them far enough out to cause any problems.

Your problem is one I've never seen with a 4 stroke so just grabbing at straws. Doubt it can be caused by having the intake choked down too much, when I've don it the engine still ran fine just at lower power/rpm. This is leading me to believe something may be wrong internally with your engine. Bob Z tells about one guy that received a new 72 with the cam gear off by one tooth so stuff happens even with the best. Break in the other engine and if it does the same, think we need to start looking at your fuel and/or tank setup.


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