sizam

My Feedback: (6)

My Saito .91 is such a PITA, I can't get a low enough idle for my taste and even at the idle I've gotten it to if I spool it up then drop it back down it takes a couple seconds to get back to the low idle which makes landing a little hot, if I bring it down too low it dies I get the low set with a good 'pinch test' so I pinch it and in 1-2 seconds it spools up, hit the throttle and and runs up prefectly the high is set just right with my Tach then I drop it back down and it idles high for 10-15 seconds then settles back down to a low idle. The guys at the field say its running normally and that that is the idle it should run at, blech. I want a nice low rumbling idle and a 4-stroke that is easy to tune and maintain, this .91 is like a little princess, can anybody suggest an easier to deal with 4-stroke? Weight and performance are 2nd to ease of use and reliability though it should be able to run on its side or upside down without flooding. I don't want to go back to 2-stroke but will if I have to. Time to sell the Saito...

Thanks.

Hobbsy

My Feedback: (102)

The 2 seconds between the pinch test and the engine speed up indicates that the low speed needle is set way to rich. To cure this, set the top rpm at peak and leave it there temporarily and procede to lean the low speed needle 1/8 turn at a time checking the high speed after every other change, on one of the changes the engine will speed up dramatically, you're getting close, now richen the top rpm down about 200 rpm, and then finish setting the low speed the way you want it. Be prepared to sacrifice a little idle rpm for a better transition.

sizam

My Feedback: (6)

Ah, the guy I talked to said the way I had it was good, perhaps 4-strokes aren't his forte Ok, so how long after the 'pinch' should it speed up, immedately? And the plan is (just so I got it straight, this is the first time I've heard the full tuning concept):

-Set my top RPM as high (lean) as it'll go, ie tach it up and up till it drops (because its too lean) then back to top
-Drop back down to idle and lean by 1/8th turn, then pinch, lean by 1/8th then pinch
-Spool back up to top
-Drop back down to idle and lean by 1/8th turn, then pinch, lean by 1/8th then pinch
-Spool back up and repeat until when I spool up to top it goes really high at which point I should richen the top by ~200 rpm then go back and finalize the idle.

Thanks!

bentgear

Forget the pinch test on the low side when you are doing it the way hobbsy explained. Just accelerate the engine with every low speed adjustment to see what you have. The pinch test is a great tool, the bad thing is I think it is something that needs to be experienced from some one that knows what they are doing, not read about and followed.

Ed M.

Maelstrom

I agree with Hobbsy.
Low speed needle set way too rich
Luis

transmission_dr

My Feedback: (1)

I agree with others that low speed is way too rich.

On pinch test if it stays the same for a number of seconds and then speeds up it is too rich.

If it dies immediately it is too lean,

If it stays the same for a second or two and then speeds up SLIGHTLY it is just right.

After each adjustment of low speed, run engine at full throttle to clear it out.

Once low speed is set go back and set high speed a couple of 100 rpm's on the rich side of peak.

Recheck low speed.

HTH

Taildrager-inactive

My Feedback: (11)

You only need a low enough idle that the plane does not move. To lower the idle further is probally going to result in the transition not as crisp as it should be. After using more fuel when the engine is finally broken in completley, then you may idle the engine down to a low rumbling idle.

sizam

My Feedback: (6)

Ok, so the revised plan is:

-lean top end all the way
-throttle down and lean low end by 1/8th
-throttle up to check
-throttle down and lean by 1/8th again
-repeat until when I throttle up it goes even higher then it had in the past (or is it until the low end has a sharp peak?)
--QUESTION-- It wasn't clear, when you are saying 'you'll see a sharp increase in RPM' is that sharp increase on the TOP end or a sharp increase on the low end?

And the goal is to get the idle low enough so it doesn't move, currently at my low idle it still pulls the plane slightly.

Thanks for all the help guys.

Hobbsy

My Feedback: (102)

When you get close one of the 1/8 turns will make a larger difference in the idle speed than the previous changes made, then you know you are close to where you want to end up.

sizam

My Feedback: (6)

Great, got it, maybe I'll run out to the field tonight to try tonight.

Thanks!

William Robison

My Feedback: (3)

Sizam:

Forget it. The engine is junk. Send it to me, I'll send yoo an old Fox with a broken crank to replace it.

Haw.

Seriously, Hobbsy and I have arrived at the same way to set the carb, and it works very well. If your results aren't satisfactory the first time, re-read the instructions and try again. It does work.

Set it, and enjoy a really good engine.

Bill.

mstroh3961

My Feedback: (4)

Never mind Bill, I'll give you $20.00 and shipping for it!
As you get close to the optimum low needle setting the rpm at idle will increase.

Maelstrom

Funny how this "little Princess" engine of yours will suddenly become your finest and preferred!
I learned a lot in this thread
Enjoy it
Luis

blw

My Feedback: (3)

Sizam,

If I'm wrong here then cut me some slack, but you do mean that you are going to peak the high speed RPMs with a tach and then reduce it about 300 RPM, right? The way that I read your message I understood that you are going to peak it and leave it that way. It would be too lean if you do.

Hobbsy

My Feedback: (102)

blw, he's only peaking it until he gets the low speed needle set, then he'll richen it down 200 or 300 rpm.

sizam

My Feedback: (6)

Oh, no, I was going to follow the instructions which are to peak it (as lean as possible) while I'm setting my low end, after I get the low end RPM jump I'll knock off 200-300 RPM from the top so:

-Start up engine, rev up and fully peak the top end (full lean)
-Return to idle, lean low end by 1/8th (listen) rev up to clear carb
-<repeat above step until when I lean by 1/8th I get a large increase in RPM>
-Rev up and richen the top end ~300 RPM below peak
-Return to idle and tweek the low end until I get a nice low idle and a good transition.

Sam

sizam

My Feedback: (6)

Thanks for all the help guys but I'm throwing in the towel, Saito .91 fer sale. Maybe its just the engine and I'll try 4-strokes again some day but for now I just want an engine that's going to fly, I'm tired of playing with the engine.

mstroh3961

My Feedback: (4)

My offer still stands! See post number 12

sizam

My Feedback: (6)

mstroh3961

My Feedback: (4)

Seriously i suggest you take it to the field and have someone who has a 4stroke give you a hand, or send it into saito's service department for a check up. They really are sweet engines! I have two .91 and woulden't trade them for all the tea in China.

sizam

My Feedback: (6)

OK, I haven't seen any of the other guys at the field with a saito but I'll look around. I guess I could mention what I went through at the field yesterday and maybe you'll have a comment. I have it mounted sideways (muff down, high-speed needle up), I started it up, leaned out the engine and shut it down. I flipped the plane over (now the muff is up, low-speed needle is up), started it up and started to work on the low end. I went through a whole full turn (!) on that needle adjustment and finally turned it 1/8th and got a higher RPM boost (what I was looking for) but the engine started to sound funny. I tried throttling up and it stuttered and nearly died, so I tried throttling up really really slowly and it still stuttered and nearly died. So I backed off the needle 1/4th turn, tried throttling up, it stuttered and died. ***? Was this because the muffler was above the engine instead of below (inverted)? Should I unmount the engine and work on it as its kind of hard to get to both needles with it mounted. Really really frustrated, I just want to pitch it out into the field X(

Sport_Pilot

Would you take $30 for it?

William Robison

My Feedback: (3)

Sam:

I'll give you $30 and still send you the broken Fox.

Don't give up yet, you're getting close. When you get the rpm rise with the low speed. reset the throttle to lower the idle speed, work back and forth between the throttle and LS needle to get the lowest idle. Then raise the idle a bit with the throttle, and go a little rich on the LS to get the rpm to fall back.

The high speed is probably lean now after such a major change on the LS - open the HS needle about 1/2 turn, and slowly work the throttle back to full. Probably have to adjust the HS needle a bit more.

With the HS again at peak, richen it until you hear the 200-300 rpm drop. Back to idle, you're ready to finish.

Slam the throttle wide open. Sputters and then accelerates, lean the LS, you're too rich. More likely it will come right up. If it sags before accelerating, or dies, open the LS a small amount.

Phooey. I'll go to $35 and still include the FoxJunk. Haw.

Bill.

Matt Kirsch

My Feedback: (21)

Don't forget that the low speed needle has a tremendous effect on the high speed needle setting. On the typical two-needle carb, the low speed mixture extends into the spraybar and actually covers part of the slot in the spraybar. The sideways movement of the carb barrel moves the low speed needle in and out of the spraybar, exposing more or less slot as you increase or decrease the throttle. As you lean the low end, you close off more and more of the slot throughout the throttle range, and you sometimes need to compensate by opening the high speed needle a bit.

sizam

My Feedback: (6)

Ok, ok, I'll keep trying, I really don't want to have to get a new engine and I do want the 4-stroker to work out as they're clearly the better engine type. Thanks for all the help/tips and keeping my will-to-go-on going cuz this is really really frustrating, but your suggestions make sense, I guess thats why guys have two planes so they can fly one when the other is acting up