Saito 150 Kicks Prop Loose and Dies  
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Saito 150 Kicks Prop Loose and Dies - 7/22/2008 6:10:06 PM   
LESSOR2


 

Posts: 18
Joined: 12/2/2004
From: , IL, USA
Status: offline 		I have a problem I just can't seem to solve and am hoping you may have some guidance. I have a 1/4 scale Cub with a 150 Saito mounted inverted. I have a 24oz tank mounted just behind the fire wall with muffler pressure (no fuel pump or regulator) and I use Powermaster 20% nitro with 20% oil with 2/3s synthetic and 1/3 castor. I also use Widcat 20/20 (full synthetic) YS 2X4. I have a McDanials onboard glow driver set for glow up to 1/4 thottle advance. I use a 16X7 APC prop. I hade to lower the tank to get the tank/plug level with the carb. I have adjusted the valve lash to the correct spec of .003. I am using the stock Saito plug that came with the engine. I use a JR SS 2.4 receiver at 6 volts and the throttle servo is a Futaba 3003. I have the low speed adjustment fairly lean. My experience with my other Saito's (82s and 91s) that they like a lean low end. I have the high end adjusted a bit rich (as this motor is new and has about 1 gallon of fuel through it) and am getting a little over 9000 rpm out of it.

Problem:
When I trottle up from idle she sometimes kicks and breaks the prop nut loose and kills the motor. If I advance the trottle slowly it happens less and if I advance fast it becomes more acute. I was doing a touch and go Sunday and on the climb out (20 feet off the ground) she kicked, spun the nut loose and I almost lost the plane. Fortunately I ditched in the weeds and only sufferd minor damaged to the cowl, and suffered not serious damage. However one of these days I won't be so lucky and the result will likely be catastrophic.

I can't think of any more detail to give. Any advice or guidance would be greatly appreciated.

Dave
       Post #: 1

RE: Saito 150 Kicks Prop Loose and Dies - 7/22/2008 6:21:45 PM   
abacro


 

Posts: 168
Joined: 10/14/2002
From: Gadsden, AL, USA
Status: offline 		From what you described ,i can possably only see 2 things wrong. First is that your low end is set too lean,and Second is that with every Saito i have,when mounted inverted,i have to run a long,idle barred glow plug in them to keep them from back firing and denotating as yours is doing.

Try this simple fix and see if it dosent help you out!

Art

(in reply to LESSOR2)
       Post #: 2

RE: Saito 150 Kicks Prop Loose and Dies - 7/22/2008 6:24:24 PM   
Kruzer


 

Posts: 51
Joined: 11/21/2004
From: Port of Spain, TRINIDAD AND TOBAGO
Status: offline 		LESSOR2 the only time my Saitos backfire is when the low end is too lean. Go rich then start leaning a little at a time (1/16th of a turn). First sign of a backfire go back a little richer and that should be it. I use standard plug and most of mine are inverted with no trouble once I get it right. I run from .65, a couple .82s, 1.00, 1.20S to 1.25. They're wonderful little engines.

< Message edited by Kruzer -- 7/22/2008 7:00:40 PM >

_____________________________

Old Chinese proverb: When your plane meets its shadow you'd better be landing!

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RE: Saito 150 Kicks Prop Loose and Dies - 7/22/2008 6:28:58 PM   
Scar



Posts: 2273
Joined: 10/1/2002
From: Peoria Hts, IL, USA
Status: offline 		Mine's a BUSA ¼ scale Cub with a Saito 100. It's 18° off inverted, to keep the header & muffler inside the left side of the cowl. It spun the prop off a couple times when it was new, I had the low end too lean. Richened it up and never had another problem. I use 10% and fly slow. Ordinary glow plug, no on-board driver.

Good luck,
Dave Olson

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My spelling isn't good enough to post grafitti.

(in reply to LESSOR2)
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RE: Saito 150 Kicks Prop Loose and Dies - 7/22/2008 7:09:41 PM   
Kruzer


 

Posts: 51
Joined: 11/21/2004
From: Port of Spain, TRINIDAD AND TOBAGO
Status: offline 		Another thing LESSOR2. As you are using 20% you may be tricked into leaning too much as with that much nitro the engine will idle so much better. Check the manual and set the idle RPM around where it should be but that is a balance between throttle and mixture. Throttle should be open about 1/16th of an inch give or take to make the mixture adjustment.

_____________________________

Old Chinese proverb: When your plane meets its shadow you'd better be landing!

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RE: Saito 150 Kicks Prop Loose and Dies - 7/22/2008 9:40:35 PM   
jaka


 

Posts: 4526
Joined: 12/11/2001
From: Upplands Vasby, SWEDEN
Status: offline 		Hi!
Some advise.
First of all you run the engine too lean!
Second you have a too large tank!
You should use a 14-16oz tank. Running a too big tank creates fuel distribution problems as the fuel level changes during flight.
Always use the Uni-Flow system with two clunks in a normal tank for best fuel distribution.
But better yet is to use a Tettra "Bubbleless" tank. These are tanks used by pylon racers world wide.
Use a 17x6 APC prop! 16x7 is a little too much pitch for a CUB. Even a 18x5 wood prop might work if thinned and reduced in area some.
Fuel: 10-15%% nitro! 20% is overkill.
Glow plug: OS F.
Get rid of unnecessary gadgets. No on board glow driver is needed in any engine.



_____________________________

Jan Karlsson Airracing products
MVVS, Motul "Micro" all synthetic oil

(in reply to LESSOR2)
       Post #: 6

RE: Saito 150 Kicks Prop Loose and Dies - 7/23/2008 3:09:03 AM   
JohnMcGowan


 

Posts: 809
Joined: 12/14/2001
From: Birmingham, AL, USA
Status: offline 		And,.... if no one has mentioned this earlier, always try to use 2 prop nuts if possible.This will help as the second nut will act as a jam-nut to the first one.
John

(in reply to jaka)
       Post #: 7

RE: Saito 150 Kicks Prop Loose and Dies - 7/23/2008 10:30:58 AM   
Charley


 

Posts: 986
Joined: 12/5/2001
From: Kerrville, TX, USA
Status: offline 		I have a Saito 1.5 in a Ace 4-120 Bipe. It's mounted upright and uses a 16x8 MA Classic. I run 10% nitro 2-stroke fuel in it. When it was new it spit and threw props every now and then, no matter how I tuned it. I installed a CH ignition and a shim that went under the jug to lower the compression a bit. That worked well; unbelievably low idle speed. For the helluvvit I tried it on gasoline. It ran hotter and the power was down a bit. After a few months of that, I tried it again on glow; finally took out the shim. Now it runs fine, hasn't kicked off a prop in years. CH might still sell the shims but I'm not sure.

My suggestions: richer low end mixture and lower the nitro and oil content. Also, I've had success with Fox Miracle Plugs in my Saitos.

YMMV,

CR



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Charley
ccrobins@ktc.com

(in reply to LESSOR2)
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RE: Saito 150 Kicks Prop Loose and Dies - 7/25/2008 9:55:46 PM   
LESSOR2


 

Posts: 18
Joined: 12/2/2004
From: , IL, USA
Status: offline 		Thanks guys! The low end is riched up has seemed to cure the kicking problem and the idle is very stable. I will be adding a larger prop as recommended. Any preference on the APC vs the Master Air Screw? I have always used APC and have no experience with the Master AS. 17x6? is what I am leaning towards. I actually had several guys at a field in Illinois suggest a 17x10! That seems to be way to much pitch. They said that would keep the Rs down around 8,000. Seems a little low to me. Any thoughts. I will be flying this plane slow and scale. It is a BUSA 1/4 and is about 20 yrs old.

Warm regards,
Dave


(in reply to LESSOR2)
       Post #: 9

RE: Saito 150 Kicks Prop Loose and Dies - 7/26/2008 5:27:54 AM   
Charley


 

Posts: 986
Joined: 12/5/2001
From: Kerrville, TX, USA
Status: offline
quote:

ORIGINAL: LESSOR2

Thanks guys! The low end is riched up has seemed to cure the kicking problem and the idle is very stable. I will be adding a larger prop as recommended. Any preference on the APC vs the Master Air Screw? I have always used APC and have no experience with the Master AS. 17x6? is what I am leaning towards. I actually had several guys at a field in Illinois suggest a 17x10! That seems to be way to much pitch. They said that would keep the Rs down around 8,000. Seems a little low to me. Any thoughts. I will be flying this plane slow and scale. It is a BUSA 1/4 and is about 20 yrs old.

Warm regards,
Dave





I always propped my Saitos to around 8500 to 8900 RPM on the ground. That has always worked for me, and I'm talking 20 yrs.
Guys seem to want to run 2-stroke RPM when propping a 4-stroke. It's a mistake, IMHO. You want to keep the engine in the middle of the power curve. Unlike a 2-stroke, a 4-strokes power is at lower RPM.

Good Gosh, Guy, RTFM.

CR

_____________________________

Charley
ccrobins@ktc.com

(in reply to LESSOR2)
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RE: Saito 150 Kicks Prop Loose and Dies - 7/26/2008 11:15:33 AM   
jaka


 

Posts: 4526
Joined: 12/11/2001
From: Upplands Vasby, SWEDEN
Status: offline 		Hi!
Just forget a 17x10 prop it is way , way too big! Aim for a rpm around 8500-10000 , No more! APC props naturally!
Black Master A with white tips and those with rounded tips are no good!! Their Scimitar series is better though.

_____________________________

Jan Karlsson Airracing products
MVVS, Motul "Micro" all synthetic oil

(in reply to LESSOR2)
       Post #: 11

RE: Saito 150 Kicks Prop Loose and Dies - 7/27/2008 12:11:49 AM   
LESSOR2


 

Posts: 18
Joined: 12/2/2004
From: , IL, USA
Status: offline
quote:

ORIGINAL: jaka
Always use the Uni-Flow system with two clunks in a normal tank for best fuel distribution.



Could explain this type of fuel arrangment. I am not familliar with it.
Thanks
Dave

(in reply to jaka)
       Post #: 12

RE: Saito 150 Kicks Prop Loose and Dies - 7/28/2008 7:13:02 AM   
LESSOR2


 

Posts: 18
Joined: 12/2/2004
From: , IL, USA
Status: offline 		Just want to say thanks for the guidence. I went to the field today with a new 17x6 (balanced) APC prop and armed with the knowledge I learned here. I richend the low end (it took several adjustments to find the right spot) and now she runs great with no prop kick. The 17x6 prop spins about 8700 to 8900 with a nice smoke trail and plenty of power. I flew her and at 1/3 to 1/2 throttle she flies very scale. I ran 6 tanks through it (in the air) and the engine runs like a champ.
Thanks
Dave

< Message edited by LESSOR2 -- 7/28/2008 7:14:21 AM >

(in reply to LESSOR2)
       Post #: 13

RE: Saito 150 Kicks Prop Loose and Dies - 7/28/2008 10:50:15 PM   
jaka


 

Posts: 4526
Joined: 12/11/2001
From: Upplands Vasby, SWEDEN
Status: offline 		Hi!
Problems with ordinary tanks is that fuel pressure varies from start to landing due to the fuel head level in the tank.
Uni-Flow tanks works like a water bin in a bird cage. The water will maintain its level (in our case: fuel pressure will remain constant in the tank from start to landing).

It's just a ordinary clunk-tank but with to clunks. One clunk line goes to the carb (as usual) the other goes to the silencer pressure nipple.
This principle has been used for decades by CL-control fliers but seems to be forgotten by R/C fliers.
A lot has been said about the Uni-Flow principle on several other sides on R/C Universe.

_____________________________

Jan Karlsson Airracing products
MVVS, Motul "Micro" all synthetic oil

(in reply to LESSOR2)
       Post #: 14

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