LargeScale88

Ok, sense I'm still a newbie to 4 stroke engines (I'm a 2 stroke and Gas engine guy), I still need a little help tuning and getting these 4 strokes running good. I fired it up today on my new escapade, it has been run, but for less than an hour, so it doesn't have alot of run time. I followed the manual, opened the high speed 5 turns, and have the low speed flush with the throttle arm. I fired it up, it popped right away. I let it warm up for a bit, then I went full throttle, got my tach, and started leaning it out. The RPM didn't move much (it was around 9100), and then I got confused, because its not supposed to run as high RPM when rich, maybe the 14x6 prop had something to do with it? Anyway, so I just left it fairly rich. I then went for the low speed, and it sounded great. It advanced to full throttle without any problems, and had a pretty good idle. My question is, why is my engine not tuning like the manual or anyone else says? Should I run it rich just to break it in more and get more time on it? I have the valves adjusted properly, and its a good clean engine.

So I took the risk, and flew the airplane with the engine running like that. It flew great, and I didn't run the engine over half throttle. I took 6 laps around, then brought it down and landed. Then I went to rev up the throttle, and it wants to quit about 1/2 throttle, so now I'm confused even more!

Can anyone help me out? Should I just run it very rich for awhile longer to give it more hours of running time?

Thanks

Jason

Gray Beard

My Feedback: (-1)

A four stroke Saito tunes exactly like a two stroke. No difference if it is a gas or glow. High end first then the low end. High end as lean as it will go then fatten it up so the RPM drops about 400. Then the low end until you get a good transition. Saitos seem to like to be on the fat side compared to my other four strokes. Most the high ends land at about 1.5 turns out. + or- a bit. The low end on the saito seems to vary a lot from engine to engine but the ones I have tuned seem to like to be a bit rich. No magic numbers, they tune where they tune.

LargeScale88

Well, I think I have more problems with this engine than I think. Today I fired it up, let it warm up, and now it doesn't even want to go past half throttle, If I try to, it bogs down and quits, even when the needle valve is still rich.

Any suggestions?

I think I'm gonna send it in or ask for a replacement if they'll do that.


Thanks

Jason

Gray Beard

My Feedback: (-1)

Engines talk to you if you learn to listen. It's telling you exactly what it needs. Sit back and think about it, what would a two stroke be saying to you if it did the same thing. It is the same thing. Twist the screws.

LargeScale88

I guess I didn't catch onto that

Tighten what screws?

Thanks Gene

Jason

hyflyer9

Hello Largescale88
it looks like you may have it a little under prop'd i run my saito 100 with a 14x8 apc prop and am getting both high and low end rite on spec. I also run my saito on pro 20 fuel and inverted .

Gray Beard

My Feedback: (-1)

Basics 101. This is what an engine says to you, makes no difference if it a gas engine, glow two stroke or a normal four stroke. If the engine is at idle and you crack open the throttle and it instantly shuts off it is too lean, if you do it and it goes blrubble blurbble and dies it is two fat or rich. You only have two screws to twist, that's it. your engine is starting so this will be easy. High end needle out 2.5 turns from closed. Start it, slowly add some throttle trying to get it to full power. Twist the high end needle IN, this is leaning it. If the engine sags as you are leaning it then open it back up a little and make it fat again then lean it until it goes past it's peak RPM then back off a bit until it is at peak then fatten until it drops about 400 rpm. OK, that takes care of the high end. Now, go back to idle, let it idle for about 20 seconds then crack open the throttle real fast. If the engine dies real fast then the low end is too lean, if it goes blurble blurble and tries to die the low end is too fat. If too lean open the low end screw about 1/2 turn and try it again. Keep doing it until you get a nice smooth transition then open it just a little more.
That's about as basic as I can make it. If the engine is brand new right out of the box then you just get it to run as well as you can and do a several tanks of fuel break in. Some new enginew will not tune worth beans when right out of the box. If you try and it doesn't work this is what we call chaising the needles. The Saito 1.25 I had wouldn't go into any type of tune until it got the first four tanks of fuel through it, about 48 ounces. Anything I did was just chaising the needles. As the ring started to seat I was able to start leaning it out more and more. Once it got to a good spot I just flew it and gave it a little tweak before each flight.
Get yourself a hands on instructor to teach you how to tune an engine. If they are there with you they can hear what the engine is telling you and would know what to do and be able to tell you what it wants.
There is no way anyone is going to take your engine back in a return because you don't know how to tune one. If you try though, maybe someone at the hobby shop would teach you how.
Don't kick the spokes!!!

LargeScale88

Thanks Gene!!

That helps alot! I'm so used to not even tuning because most of my engines are gas, which require minimal carb adjustments.

There was a guy at the field today who had a saito 91, and he was breaking it in. He had it 5 turns out with about 4,000 RPM, and it would not stay running unless he kept the glow heat on, which is normal for a rich setting like that. Its funny becasue when i go 5 turns out on my engine, it acts like its leaned out, and I still get a fairly high RPM (9,000), so I'm not sure why his engine acts that way and mine doesn't.

Hello hyflyer- I switched my prop to a 14x8 zinger prop, which I hear 14x8 is a perfect fit for this engine.

Forgive me for my Newbieness (spelling) to 4 strokes.

Thanks

Jason

hyflyer9

At this point I would start over and reset both high and low set to the original settings and then do a check on the valve clearances your engine should have came with the feeler gauges and the instructions are in the book . after that then open the high end to the 5 turns and leave the low end at factory for now work the high end first and get that set and then work on the low end idle ok. Just remember to take your time .
good luck .
Cheers.

Gray Beard

My Feedback: (-1)

Every engine is a different animal and it sounds like you were watching someone that didn't have a clue how to break in an engine. Once I get one of my glow engines where I want it I don't bother to touch the needles for the season unless I change the prop size. As fall hits us and the temps go from the 100s down into the 70s and mid 60s I will have to start opening up my high end a little. By the time winter hits us and it's in the 40 I will have my high end set about 4 clicks fat. Nothing drives me more crazy then seeing someone twisting the needles after every flight or two. My gas engines I can't recall having to change them even as the temps start to drop.
The best Saito person I know on RCU is John Buckner. If you just can't get it set correctly look him up and shoot him a PM. I'm not a big fan of Saito and don't keep them around very long when I get one, I like my YS and OS a lot better so I trade. John knows a lot more about them then I do. I think there is even a Saito factory support in the glow engine forum. If I was having a problem with a Saito I would be asking John in a hart beat. The last 100 I had that was new in the box I just opened the high end 2.5 and fired it up. Gave the high end a quick tune then broke it in on the ground with a couple of tanks of fuel. It's still running just fineafter 4 years. It's in one of my old students planes right now.

Augie11

Good advice. Put on the 14x8 or 15x6 and go back to square one. Make sure all the engine screws (backplate, head etc. ) are snug. And check your fuel flow from the tank. There is no reason for that Saito to be turning 9000 with the high speed needle open 5 turns. It's either not getting enough fuel or it's getting too much air. I've got a couple of these Saito 1.00's and after break-in and setting the transition they are bulletproof.

LargeScale88

Thanks guys. So i'm just gonna run a completely new break in. 5 turns out on the high speed, and it looks like the low speed is flush with the throttle arm.

Thanks

Jason

LargeScale88

So about how much fuel does it take before saitos really run good and rock solid? I ran the break in process for 2 -1/2 tanks. I went to fine tune today and its still having some problems at high speed. It runs at high speed but it doesn't stay a steady RPM, and from the 5 turns out I leaned it in with the tach until I got max RPM, then brought it down about 300, I did all that, and it stills stutters, so I'm still not sure what to do. I'm thinking if I just keep it rich, fly it, and get more running time on it, it will shape up.


Any suggestions?

Thanks,

Jason

Augie11

For the initial break-in, I usually run 3 tanks....... about 42oz. on a Saito 1.00. But she won't be fully broken in for about 2 gallons. That just means fly her rich for that period.
Now just a couple of questions for clarification. What prop are you running, what % nitro in the fuel, what glow plug and after you back down 300rpm from maximum what rpm are you getting?

Also, your comment about the low speed needle doesn't help me here. How many turns out is it?

Also, when you get your high speed needle set at maximum rpm (minus 300), try this:

Cut the throttle to idle. You should be around 2100 rpm (depending on pro, fuel, etc.). Now let it idle for 20 seconds then QUICKLY apply full throttle. Does it stumble and cough on the way up.......if so your LOW speed needle is set too rich. Does it stop abruptly on the way up......if so your low needle is too lean. Keep doing this test each time you adjust the low speed until the transition from idle to full is smooth. Finally, readjust your high speed to max rpm (-300 or so). You're done.

LargeScale88

Hey Augie11, here are my engine specs:

Fuel- Omega 15% nitro, 18% castor/synthetic blend

Prop- Zinger Wood 14x8

Glow Plug- OS type "F" 4 stroke plug

I was getting around 8300, 8600 RPM for the high speed, it wasn't steady because the engine wasn't running steady, so around8000 RPM when I backed down a bit.I did have about 2300 RPM on the low speed. I had my low speed screw out about flush with the throttle arm, and it seemed to transition good between idle and high speed.

The engine probably has about 1-1/2 gallons through it. I'm still worried that something i actually wrong with the engine because of the way it runs, compared to how everyone says how they run.

The wierd thing is that I got my max RPM with about 3 or 3-1/2 turns out on the high speed, any leaner than that I lost RPM, so I'm almost at the break in setting on the high speed just so the engine runs good, which is kinda funny.

Thanks

Jason

Gray Beard

My Feedback: (-1)

Jason, it sounds like it's in the ball park and getting close. I don't use wood props on the smaller engines and a four strokes likes a little more weight on the props, that's what I discovered anyway. I use all APCs and they seem to smooth the engine out a little at idle. By about the end of the second gallon of fuel the engine should be fully broken in if it isn't already. The surging on the high end has me stumped, if it was me I would be asking John about it about now and see what he has to say. I would look to make sure my valves are correctly adjusted with a cold engine then try to find the sweet spot like Augie said.
Just something to keep in mind. The low end is always operating and it effects the high end, the high end only comes into operation at just under about half throttle. The old adage is: the high end doesn't effect the low end but the low end does effect the high end. That's pretty true but as Augie mentioned, after you get the low end set go ahead and just give the high end a little touch. The old adage isn't 100% fool proof.

Augie11

As Graybeard says, you're getting close. Run that throttle test (idle, then full open) and let's see what happens. I'm thinking your low speed needle is rich but I can't tell from here

Oh, using that setup (prop, fuel, glowplug) I get a very steady 8500rpm. But I prefer the way she handles a 14X7 so I switched to that and get just about 8900. But I am at a much higher altitude than you are (5300 feet). Get that transition set using the low speed needle, get another gallon through and you should be ok (assuming that surge at full throttle goes away).

LargeScale88

Ok thanks Augie and Gray Beard.

Augie, how many turns out from closed is your idle screw? How many turns out is your high speed with your 14x8? I figure they would be the same setting because they are the same engine?


Thanks

Jason

Gray Beard

My Feedback: (-1)

They are not the same engine!!! Engines vary way too much to think someone Else's settings will be the same as yours. Too many things come into play. I have had engines of the same brand and size have the high end closed down to 1.5 turns and the other one opened 2.5 turns. When you tune an engine it is what it is. I can't recall the last time I counted turns to see where I had a low end or high end set. Are you adjusting while the engine is running?? I do, I can hear what the engine is doing that way. I have one gas engine with the needles pointed at the prop so I have to tune with the engine off and use a tach. Too many things come into play that will change the settings a lot. Augie is at 5300 feet, I think I'm at 1700 feet so just that would move us both way out of the ball park. I live in a very dry place with about 7% humidity, that makes a difference. It will be about 100 degrees today, a big difference. Prop, fuel, age of the glow plug, valve adjustment.
I bring this up just so you get an idea of different things, just the brand of the prop can change things even if they are the same size. It's time you learned engine tuning so you know how to do it. The only way to learn is to twist the needles and see what they do. Your so close, just fire that puppy up and do it. How far in or out someone else has there carb set doesn't mater.
You say you know how to tune a two stroke, same thing only this engine has valves. No difference.

LargeScale88

Hey Gray Beard,

You're right. Why did I think that?? I think I'm about 860 ft, so we are way different. I'll just tune according to sound and tachometer, not someone elses settings. Thanks! Jason

TedMo

I can not understand why your engine runs at 9000 with HS needle 6 turns out. That should be slobbering rich. Never ever had any engine run that much open.You must have air leak someplace

Augie11

Large- You have to tune the engine that's right in front of you. My high speed needle on that engine is set about 1 3/4 turns out. I've never checked the lowspeed for where it's set. It's probably a hair leaner than 'factory' but I don't know or really care. If you don't have air leaking in anywhere effecting fuel flow just tune them together using the transition test and you'll be ok.

LargeScale88

Thanks Augie and TedMo.

In that case, anyone know the best way to check for air leaks or the most obvious places to have air leaks? I'm not sure howI can have air leaks with an engine this new.

Thanks

Jason

Gray Beard

My Feedback: (-1)

I GIVE UP!!!!
Augie, it's all up to you!!

Augie11

Large-
Air leaks can come from the fuel system or the engine itself. Any air bubbles that get in will change the air/fuel mixture and that will overwhelm any attempt to 'tune' the engine since the tuning process is really just getting the air/fuel mixture properly 'balanced'. If you think about it, that fine balance is why talking about needle settings from one location (Mile High) to another (Sea Level or Death Valley) is almost useless because we're really talking about oxygen content and air density. And full scale pilots bet their lives on getting temperature, humidity and altitude data before flying. We make it simple and just tweak the needles, but first we need to control the amount of air getting into the engine. It's a start.
OK, that being said, air can come from the tank. If the stopper isn't sealed properly or the fuel line has a hole in it air can seep in and get mixed with your fuel. So check your tank for leaks by putting in pressure to see if it holds the pressure. I usually assemble the tank, put on the lines and then blow into it while it's submerged. Crude but it works. Also, if your tank is not properly padded, the vibration from the airframe will take any air in the tank (it's never 100% full) and turn your fuel to foam. Now I assume your tank is mounted in the right position with the center of the tank about even or 1/4" above the spray bar in your carburetor.
Now if that's all working, check your engine screws and glow plug for snugness as air can be sucked in if these are at all loose. I always check before I first run an engine and again AFTER A RUN OR TWO as sometimes they loosen up. There are screws on the backplate and in the head and around the manifold connections. DO NOT USE IMMENSE FORCE especially on the glowplug- just snug is fine. And do it while the engine is cold. Some engines have head shims or backplate gaskets and if they are worn they can leak but your new Saito won't have this problem.

Now go ahead and run your breakin paying great attention to the transition test. I haven't heard you talk about it but it is THE key to tuning. And while your'e at it, check your fuel line while the engine is running to see if there is any air in the line. Once the engine is running there should not be any bubbles in the line or you have a leak in the fuel system.

Keep us posted because I know Gray Beard is sitting on the edge of his chair waiting for this to be resolved.