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Saito 150 keeps locking up

Old 11-26-2015, 09:16 AM
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flyerdave
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Default Saito 150 keeps locking up

Hey guys, I have a saito 150 that I've mounted on a Pica Waco and I know it will be the perfect powerplant for it if I can just figure out how to get it tuned right. I'm running an OS "F" plug and omega 10% fuel. She cranks perfect every time but when I give it some throttle,then it starts knocking and slams to a stop. It loosens the prop every time. I tighten the prop nut and the lock nut, adjust the needle and start her again and she does the same thing. I've leaned the needle to only 1 turn out but even that lean, it's smoking alot I know it just needs the proper needle setting and will be a good running engine. I just need some advice on where to start my needle adjustments.
Thanks
Old 11-26-2015, 10:21 AM
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avinut
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Get a BIG wrench and tighten the prop nut as tight as you can get it. I threw props all over the yard till I figured this out.
Old 11-26-2015, 11:16 AM
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flyerdave
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Was it throwing props because the needles were set too rich?
Old 11-27-2015, 04:27 AM
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Hobbsy
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Daver, get it out of the plane and onto a proper test stand where you can see whuz happenin. Either too rich or too lean will make it kick the prop. Most times if lean it will quit instantly, if too rich it will knock first, smoke heavily and die slowly then quit. Do not exceed 4,000 rpm for the first ten minutes. After that 10 minutes set the HS needle at 3 turns out or wherever it will run without the glow battery.
Old 11-27-2015, 05:36 AM
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flyerdave
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Thanks for the information. The reason I went ahead and mounted the engine in the plane was because I bought it from a friend who had already broken it in. Still your idea is best, I will get it on a test stand and get it right before it goes back in the plane. Isn't it funny how sometimes even when you've been flying for 36 years, you don't think things through. I should have known to do just what you said.
Old 11-27-2015, 06:11 AM
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Hobbsy
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You made one of them "ssumptions" that it was all ready to go. It happens.
Old 11-27-2015, 06:34 AM
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cordell staker
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I've got the same problem with a 150 on an Aeroworks Yak54. The engine was running great and then I had a "lite" crash which damaged the wing. Took the engine off and sent it into Horizon for bearings and a check-up while I was repairing the wing. They serviced the engine and sent it back. Now it does exactly what you are describing in this thread. I run 25% Omega.
Old 11-27-2015, 06:58 AM
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Yeah test running the engines on a test stand is a good way to try the engines out at first. This lets you have access to all of the adjustments easily. Plus it is easy to see things like the fuel tank, etc.

I tend to suspect that the engines have a bit too much compression for higher nitro glow fuels. I typically run 5% nitro glow fuel in all of my engines. I only go with 15% or 20% nitro glow fuel when the engine runs poorly otherwise. My first Saito that was picky with glow fuel is a .80 and it really preferred zero nitro glow fuel. I had to run it for a long time with no nitro glow fuel to get it worn out some before it would use 5%.

I test ran my Saito 1.50 using 5% and it worked OK for me like that. I never tried higher nitro content fuel with it since it ran Ok like that.

I would double check the cam timing on the engines. It is pretty easy to get the cam out of time with the engines. The angle cut gear teeth make it a bit tricky to set the timing. So if someone isn't paying attention it could be off.

I sometimes wonder if Saito made their engines for two different markets. The USA market with lower compression for more nitro in the glow fuel. And the rest of the world with higher compression for no nitro glow fuel. Thus if you got a engine not made for the USA market, you would have problems using nitro content glow fuel in it.
Old 11-27-2015, 07:04 AM
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avinut
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Hey fellas, you shouldn't be running nitro in these things !
Old 11-27-2015, 07:30 AM
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I've never had a prop kick loose from being too rich.
Only happens to me when the needle is set too lean.
Check that your fuel tank is at the proper height for where the carb is located.
Make sure that the fuel passages in the carb are not obstructed.
Also make sure the clunk in your tank is not stuck up at the front of the tank..
I've also never run fuel as low as 10%.
Lowest I've ever used is 20% nitro.
I've run Saitos, OS, YS, and Thunder Tiger 4 strokes and not had this type of problem unless the fuel flow was restricted in some way.
Old 11-27-2015, 08:32 AM
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Lvan09
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1 turn out on the high speed needle sounds awfully lean. Back it out to 2.5 or so and try again, forget the amount of exhaust smoke for now. Fuel and plug are probably fine though I don't like the OS F plugs too much.
Old 11-27-2015, 09:15 AM
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JPMacG
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+1 I have thrown props and spinners from being too lean, never too rich. I set my HS needle by finding peak then backing off about 1/8 turn. This is done with about 1/2 tank of fuel. Then hold the model vertical at full throttle to make sure it does not lean out too much.

10% nitro and an OS F plug are perfect for that engine.

Last edited by JPMacG; 11-27-2015 at 09:19 AM.
Old 11-27-2015, 09:23 AM
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flycatch
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I have four Saitos' 1.8 and no two run the same. Go on line and download the instruction manual. Set it up per manufactures instruction and don't over look the valve adjustment section.
Old 11-27-2015, 01:35 PM
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rcmichael
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I am reading a lot of advice that is incomplete. After checking fuel lines and flow on a test stand and making sure glow plug fuel and valve settings are good, and checking for fuel and or air leaks there are a few things you must ask. What altitude do you live at? I live at 5000 ft elevation. The needle adjustments here are much leaner than at sea level. On a normally aspirated engine the carb has a set amount of air flow(air bleed carbs excepted). All we do is reduce or increase fuel flow to obtain proper air fuel mixture. Also at higher elevation more nitro helps with idle and transition when air fuel mix is correct. At sea level 10% nitro may be fine, but at higher elevation you may need 15% or more to run well when properly tuned. So you see you can't make blanket statements about nitro percentage. You didn't say if the engine was mounted inverted. If so fuel tank position and carb adjustments become more sensitive to keep engine running well. If the fuel tank centerline is above the carb fuel inlet you will tend to flood an inverted engine. Make sure your valve clearance is to spec also. You didn't say what size prop you are using and that makes a difference. Just because the manual says your engine will turn a certain size prop doesn't mean it will. I have rarely been able to turn the bigger size props even close to advertised RPM.( Due to power loss at 5000 ft elevation) If you have access to Clarence Lee's engine problem section in the mags try to read them. They are very useful. Good luck!
Old 11-27-2015, 01:58 PM
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He need not concern himself with any of that, just set it for the current conditions, as is, then deal with changes when or if they occur.
Old 11-27-2015, 02:06 PM
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You are basically at sea level so nothing extreme there. My opinion is that your fuel/nitro is fine, the OS-F plug is perfect, but that your issue is too lean. As others have stated when you get too lean you will get that "backfire" and will throw the prop. You also state that you are getting some knocking which also spells lean. I would not worry about what you think may be too much smoking. That will go away as things bed in with time on the engine. I also think that getting on a test stand to work things out is good advice.

Lars
Old 11-27-2015, 02:18 PM
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The same excess richness that can cause an engine to start backwards can also kick the prop off and just as forcefully as too lean can.
Old 11-27-2015, 05:45 PM
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My Saito 1.50 is set at 3 turns out, anything less and it will throw the prop half way across the field lock nut and all. Engine inverted and running 15% nitro.
Old 11-27-2015, 08:44 PM
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Originally Posted by FormerDairyFarmer
The same excess richness that can cause an engine to start backwards can also kick the prop off and just as forcefully as too lean can.
Don't you break in at an overly rich mixture? As in far richer than flight mixture? How come the prop never gets ejected during those rich break-in runs?

Ive only ever lost a prop once. Too lean.

Sorry, I know I said I'd stay out of the Saito threads... But losing a prop due to being too rich sounded fishy. Nothing personal.
Old 11-28-2015, 03:18 AM
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flyerdave
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Thanks for all the help, after reading the responses,I am surely running it too lean. I will get it off the plane this evening and onto a test stand. Just for the record, on the Waco it is mounted upright with a 6 inch muffler extension,working with two different size props, 17x6 and 18x6. Going with a larger diameter prop because of the big fat cowl that the Waco has.
Old 11-28-2015, 04:14 AM
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Excessively rich in my statement means over primed, don't even think about telling me you haven't done that. Running rich won't kick the prop off. You sure do like to fight, why is that? As far as commenting in a Saito thread, engines is engines, the name on them doesn't change much about the way they run or respond to various changes.
Old 11-28-2015, 04:17 AM
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Daver, if you have a plastic throttle arm your LS needle will end about 1/16" deeper than this one.
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Old 11-28-2015, 05:17 AM
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1QwkSport2.5r
 
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Originally Posted by FormerDairyFarmer
Excessively rich in my statement means over primed, don't even think about telling me you haven't done that. Running rich won't kick the prop off. You sure do like to fight, why is that? As far as commenting in a Saito thread, engines is engines, the name on them doesn't change much about the way they run or respond to various changes.
No, I don't like to fight. Just misunderstanding what you said, that's all. You said excessively rich, not over-primed. There is a difference and I just didn't want the OP or any other user encountering the same or similar phenomena to think being (run) too rich will cause the problem this thread is about. As far as me having over-primed an engine and had the prop come loose? I honestly can't recall it happening on a 4-stroke yet, but I haven't been running these engines for that long. It could happen in the future though. I am certainly not immune to anything. I will say that I use an electric starter exclusively on my 4-stroke cycle engines and I use the choke on them too. I probably would encounter more priming problems if I ran them inverted, but I haven't done so yet. The OP's engine locking up certainly tells me it's being set too lean and is being run hot/overheated. Using a tachometer to set the needle would help greatly IMO. I always suggest to guys not familiar to 4-stroke cycle engines to open the main needle a half turn or more on a new to them engine before starting the engine to ensure its rich to begin with. Once the engine is running, I usually run up to WOT after a brief warm-up and open the needle rich further if it's running fast and clean until it slows down. Then I know it's rich and can start working it leaner. Using a tach, work the needle leaner giving a few seconds between adjustments to allow the engine to stabilize. As the engine runs faster and cleaner, the adjustments need to be in smaller increments until to noted drop in rpm, then richen back up a few hundred rpm.

If after an adjustment the rpm sags and the engine slows down, richen the needle quickly a few clicks. 4-strokes do not respond to needle adjustments as quickly as 2-strokes do, so the tell-tale sag doesn't happen immediately and if you go too lean too quickly, a backfire can happen and will indeed chuck a prop. A scary event for a new user as well as a seasoned user.

Dave - engines are engines.. Very true. They all run the same way although the adjustment procedure between various models can differ slightly. Some specific to Saito aren't my specialty, so I try to leave that stuff to the Saito experts.
Old 11-28-2015, 05:30 AM
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You're on the right track Dave and your upright setup is good. Your prop size should be just fine too; the 18" diameter is a bit big but you are going lower on pitch. I think as someone pointed out, the top of your low speed needle screw should be flush with the face of the throttle arm. It is probably set there already. A good starting setting for your high speed needle is 4 turns out from closed. You do that on your test stand and you'll get it dialed in nicely from there. Good luck and let us know how it goes.

Lars
Old 11-28-2015, 07:13 AM
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Another scenario that sets up a too rich condition is on the rare occasion that we over fill the tank and the muffler fills up with fuel, that almost guarantees a backwards start with the engine running backwards for a few scary seconds.

(quote) I always suggest to guys not familiar to 4-stroke cycle engines to open the main needle a half turn or more on a new to them engine before starting the engine to ensure its rich to begin with. (quote)

Sorta like always tuning a guitar from flat upward, never from sharp downward.

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