I would appreciate any suggestions regarding my difficulity getting my Saito 150 to run consistently. Here's the story.

Engine is about two years old and put it on a Ultra Stick. Broke it in as per the directions. Using 16 X 8 prop and 15/18 Wildcat 2/4 cycle fuel. Engine broke in fine and ran perfectly for the first gallon of gas. All of a sudden it started throwing the prop. Lost several and a couple of tru turn spinners. This was happening at different needle settings. The "experts" at the field were stumped and suggested that I send it in to Horizon. Did that and they returned it stating that it tested fine on their bench. Mounted it on the plane again and got several good flights. On the last flight the engine quit at a very bad spot. I tried to save the airplane but ran out of altitude and airspeed and wrecked the stick.

Just got another stick completed and went out tonight to test the engine. Engine started fine, good idle and transition but at max power the engine would run for several seconds then quit. Someone with more experience than had took a look and he tried the engine at various high end needle settings. Started at 1 turn and did various increments up to 4 with no difference in performance. At richer setting, engine did seem to sustain a higher rpm before it quit. This other club member is now also stumped. Does anyone have any ideas? I am using a OS F glow plug. I am using a larger fuel supply line to the carb but remembered that I did not change the fuel line to the clunk to a larger diamater. I don't know if this would make a difference. Tomorrow I plan on changing the clunk line and putting the engine on the test stand at the field to see if it runs any better.
Since I am new to 4 strokes, this has me stumped and disappointed with my Saito. Since I have been in he hobby, this engine is the first one to give me headaches. I sure would appreciate any suggestions. Thanks in advance.

Your engine system is not worth taking a chance on flying untill you can get the engine to run slobbery rich with the needle. Something is restricting your fuel supply or letting it suck air. It may even be around your needle valve?

The engine is running lean up in the air is the reason it backfires and/or quits.

Jim

w8ye is right.
If it backfires it is too lean. Maybe leaking air, or restrictions in fuel line, clogged filter, etc.

Thanks for the input guys. Regarding my run tonight, the engine did not backfire. That was the problem last year and I learned that is usually the result from a lean mixture setting. the main problem tonight was that it would not sustain a high rpm setting. It would run for several seconds then quit. Was just down checking the engine and the needle valve was out 4 turns. That should be rich enough. I did pull the tank apart and checked the fuel lines. I did discover that the line to the carb was cut where it attaches to the copper tube that goes into the stopper. I am now thinking that might be the problem. I will test it again at the field tomorrow night and let you know.

On a Saito, the low needle affects the ability of the high needle to regulate....Adjust the low end a bit richer than normal, and you'll have plenty of fuel at the high end...

However, having a slightly lean low end will prove to be bad at the high end.

I'd richen up the low end a bit to see if you can get the high end richer.

I think that you have found the problem with the fuel line. the f plug is the best one and if you are not running a fuel filter put one before the carb 4 cycles are prone to get dirt in the carb wich will cause irregular runs and don't mess with the low speed neadle unless you know what you are doing !!!!!!!!if you have played with it let me know and I will send you a description of how to tell if it set right and how to adjust it if it is not
I have 2 150 saitos and they are good runners but I like the os better and if they had a 150 to 180 range single cylinder I would have one or two!



Ron mcgarth

Ron,

Thanks for the info. One of the senior guys who helped me last night did play with the low speed idle. Can you please let me know how to set that properly in the event his tinkering causes a problem. How many needle turns out (high end) would you saw is about right for this engine. I seem to recall about 2 1/2 to 3. Do you think that is about right? Appreciate your help.

OOps almost forgot. Pinching the fuel line is a common way of checking for proper mixture in 2 strokes. Can you do this with the 4 strokes? The person who helped me last night was checking the low speed idle using that method which I thought you couldn't do with the 4 stroke engines.

I had a .65 Saito that wouldn't run at high throttle either. I was having idle problems, so I spent some time w/ the low-end adjust. Well, it idled great - what I (others) didn't realize was that I had blocked the spray bar with the low end needle at full throttle. Saito recommends starting w/ about a 1mm clearance between the spray bar and idle needle (this puts the screw adjust about even with the throttle horn cap). Anyway, I backed it out, adjust the high-end, then brought the idle needle in to where it was starting to lean at full throttle, then backed it out a bit (to make sure it was still at the right full throttle mixture). The engine still has trouble idling, but problem do to other factors. I suspect it'll get better when I start running the high-end a little leaner. (using a os-f plug)

Just got back from the field. It seems that my problem with this engine the previous night was as simple as a cut fuel supply line to the carb. Once replaced, I started it and it ran really well. Got several flights in and is a nice match for the Ultra Stick. I just assumed the problem was a continuation of what happened last year. Thanks to all who took the time to respond to this thread.

This is how you set the low speed first always ck the manual to get a starting place for the low and high speed needle then run the engine up to operating temp and then bring it back to a idle let it run for 5or 10 sec then pinch off the fuel line (you do not have to let it Quit just unpinch the fuel line and it should keep running). The rpm should increase a little and then quit if the rpm increases alot you are too rich and the low speed needle needs to be screwed in I use 1/8 of a turn increment. If the engine just quits with no noticeable increase then you are too lean and you need to screw the low speed needle out When you are adjusting the needle sometimes you have to increase the throttle so that the engine does not quit when you turn the low speed needle. The other thing that I have not mentioned about idle is that it is very important to have a rock solid linkage If you need a consistent low speed idle. if you would like to know how I set up a throttle linkage let me know and I will take a pick or two and send them to you.
when you are done with the low speed needle reset the high speed and go flying!!!!


if you are using a composite prop it should idle for minutes without quiting

Ron,

Thanks for the tip. My linkeage is fine. I did have a question about the "pinch test" to check needle settings. I wasn't sure if you could do that on 4 stroke engines. Since the senior guy helping me the other night did it for the low end and you described the same test, I guess that question is answered.

Since you have two 150's can you tell me about where your high end needle valve is set? I had mine running fine but rich at 4 turns. When the engine runs, I like it. Plenty of power and it pulls the Ultra Stick around just fine. Thanks for you advice.

Chuck B.

My 150's needle is set at 1 1/2 turns.

Are you using a tach to set ?

I find it is best to set the idle a bit rich then peak the high speed and back off a few hundred rpm,
then check and adjust the idle if necessary, then do over the high speed.

Not sure what engines are included, but Saito has two designs for high-needles. One ends up in quite a bit further then the other. I think the initial position is 2-1/2 for one and 5 for the other. Again, not sure if that applies to the larger engines.

I do not generally use a tachometer to check the rpm when setting the high speed needle I just peak it and then back it off till I hear a change in rpm that takes away the temptation to get the most that you can out of a engine !

i have two 150 saitos one is 4 years old and one new. the high speed needle is about 4 turns open on the old one and 2 1/2 turns on the new one. both smoking like hell! that is where you should end up with a good smoke trail . no matter what the needle setting. if you can't richen it up to smoke alot better look at your fuel system. saitos like to {must be} run on the rich side or you will back fire and throw props. the smaller ones aren't so picky but the large ones are. good luck

Appreciate the advice. One thing I know, I am getting a good smoke trail and have from the beginning from this engine. I am always a little paranoid about running my engines lean especially the bigger $$$$$ ones. Out to the field later today for another light. I will try and tweak the engine a little bit and put my tach to it. Let you know how it goes. Thanks again.


P.S. I know about the back fire and prop throwing thing. That
was my problem last year and lost several props and tru
turn spinners. Pretty exciting when it happens in the air it's
always nice to give the spectators a little something
different :-)

Breeze, I have nine Saito's and one thing they all have in common is that the idle needle is even or very nearly even with the end of the throttle barrel when set for a good and slightly rich idle. The high speed needle is not the same for any of them. I see lots of guys who try to count the turns on the main needle and it is just is not the same from one engine to the next.