Pawel Rzedzicki

Hello!!!

I have a Saito 125, its has about 6 liters of fuel thru it. Previously it was in funtana s90 and now in Somenzini Yak 54 69". Its side mounted. During last flights i noticed it dies during idle. If i leaned lsn more it died rapidly, if i richened it died after 10-20 seconds. I was a little confused but once i noticed the throttle barrel has too big about 2 mm axial play (i dont know if this is a correct word- it moved in the carb along the lsn) I removed the little screw which end sits in the groove on the barrel. It apperaed it was too short and its end didnt get into groove deep enough. Because of it the end of the little screw had worn causing the barrel play. I found a similar screw, grinded its end to fit the groove and installed in the carb. I took the plane to a field, started engine, warmed it up and finally got stable perfect idle.
And thats the end of good news. Now i have a huge and first time in my life problem. When i tune the high speed needle with WOT i must turn off the HSN about 4 full turns!!!!!!!! I wouldnt care but it causes dramaticly rich midrange, almost deadly rich.
The only idea coming to my mind is: with defected throttle barrel leading screw i had to turn in the lsn too much to get pretty stable idle and now the needle comes into the sprayer too deep. If you have any other ideas please help me and give me some advices.

My LSN in turned 3 full turns in from flush with the throttle lever. How are yours?

w8ye

My Feedback: (16)

Your Low Speed needle is in too far.

Start over again. Back your LSN out 3 turns - get youe High Speed Needle set - And then set your LSN

octanehuffer

I noticed alot of side barrel play in my carb when I got this engine too. Its supposed to be there. Unfortunatly, it sounds like you messed with a perfectly good carb that was built to factory spec. Just needed a tune Now it wont run right. I would rebuild it back to factory spec WITH THE PROPER SAITO BRAND PARTS! Mine runs great. I have been leaning the low end needle since its just finished breaking in. I think I am 1 turn in now on the bottom end.
Adam

Pawel Rzedzicki

A little play is always. But when i took out this screw i saw it was worn a lot, like 1/2 of it was gone. Factory didnt do it like this. Besides with this huge play i couldnt get stable idle.

mvallyman

My Feedback: (32)

I agree with octanehuffer, also if there was some side force on the barrel caused by misaligned throttle cable/wire, this could have caused the locator bolt to wear in the first place.

youngun

Someone needs to come out with a good aftermarket carb for these engines. One that solves the mixture problems easily, and is affordable. Like the old Perry carbs did for the 2-strokes years ago.

For these middle sized Saito engines, one that included a midrange adjustment might be the ticket. (the old Perry didn't have that, but it still solved a lot of similar problems back then)

However, considering the rather high price of these engines, the additional cost of a good carburetor might be a killer. I remember many of us would not buy certain engines because they were high priced and either lacked a carb, or the one they had wasn't doing the job. So most bought engines that already ran good and were affordable. K&B comes to mind. It was affordable, reliable, ran great and made plenty of prop turning power, for its' day and time.

Just some thoughts about the problems [sm=72_72.gif]

Pawel Rzedzicki

mvallyman you can agree with octanehuffer but that won't change the fact my barrel leading screw was half worn out. I dont think it came out of the factory like this, do you?
But back to the subject. With LSN flush with throttle lever nothing changed. Of course idle was horrible but with WOT nothing changed. I was not able to rich up the high speed. Even with almost all HSN out the high speed wasn't dramaticly rich. With 16x6 APC and 20% nitro fuel i had 8500 rpm with the richest setting.
I took out the engine and removed the carb. Took out the throttle barrel, removed the fuel intake nipple, removed the HSN, looked at everything precisely. First time in my life i saw the little groove in sprayer. I hoped it was plugged with some dirt or what but it wasn't. Everything else is also clean. When i installed throttle barrel, nipple and HSN i put a fuel line on the nipple and blowing into it and moving the throttle and adjusting the HSN i found everything is in prefect condition.
Fuel system is also ok, no leaks, bo air bubbles in lines. The sealing ring in carb is perfect too.

Now i feel like a dog chasing it's own tail!!!! H E L P!!!

Campgems

I'm not sure what your manual calls for the inital settings, but it sure sounds as if your High speed needle and the mix control are way out of sync. W8YE gives you some good starting points. I would start with the High speed needle at maybe three turns.

Start the engine and let it warm up a bit, then go WOT and adjust the high speed for max RPM, then go rich by 500. Set the throttle as slow as you can get it and keep the engine running. At this throttle setting, adjust the mix lean for maximum RPM. Go back and adjust the high speed again. Adjust the mix one more time. This should give you a much slower idle now, That engine should idle around 2000. You may need to do the process three time to get it peaked.

Here are some sketches I did to explain the relationship between the high speed and mix control. The first is at idle, second is mid range and the third is WOT. I showed the barrel throat open fully only to be able to show the mix needle action.

Don

w8ye

My Feedback: (16)

The restriction in your fuel system may be a kinked fuel line or something wrong with your tank?

octanehuffer

Did you put the spray bar in the same way it came out. There is a groove in it that must be "clocked" in relation to the carb. It will lead to poor transition otherwise.

Pawel Rzedzicki

I inspected everything. Fuel lines are clean, pressure nipple in muffler too. When i gently blow the muffler pressure line the fuel goes thru the line going to the carb.
Campgems, i dont know if you did it accidently but at your drawings the longitudinal holes are at both sides of the spray bar. In my carb this hole is one and it faces to the intake collector (dont know if its correct word). I couldnt see it before removing the carb from engine. With HSN at three turns off i cant get a rich mixture. In fact i cant at all. Of course only at WOT. MIdrange and idle is no problem to be overrichened.
octanehuffer i didnt remove the spray bar.

octanehuffer

Okay, lets see if I am on track here. The engine had a bottom end issue, with a good top end. Now it has a good bottom end with a poor top end.

Either the carb wasnt correctly rebuilt or the homebrewed part is to blame. My 1.25 has about 2mm of barrel play and rockets the QQ 69" out of a hover. Cant you buy the barrel screw?

Pawel Rzedzicki

I cant buy- i live in Poland, i can barely buy an engine Here's no service, only 2 shops sell Saitos and noone has any spare parts.
I'm not completly sure now but it seems i had to turn the HSN more than 3 turns from fully closed from the begining. I remember I started a therad here asking people about their final HSN settings in Saitos 125. And i was a little confused when apperaed everyone has about 1,5 turns off.
And i must say i dont grumble about my engine's performance- it runs great. Pulls my Yak from hover like a dream. But i am afraid to ruin it with too lean mixture

octanehuffer

I know that I still see a smoke trail from under half throttle, and still need to lean the bottom end some more. After half throttle I cant see any smoke and the engine likes it there. I would prefer a smoke trail indicating a rich setting but it wants to burble before that setting can be achieved. I dont get any crackling from the pipe either-indicating too hot. I have to lean out the bottom end about another 1/4 turn and I think it will be fine. Your base settings= 1 turn below the throttle arm for the low end. 3 turns out for the HS needle. Give it a try

Pawel Rzedzicki

Ok, so i flied today a couple of times. Mmmm, i love my QQ69" Yak As for the engine let's say i'm not completely happy. HSN doesnt affect the top end as much as it affectes the midrange. With WOT I can turn HSN from 5 turns out till 2 turns out with very minimal influence for the top end. I think these 2 last sentences describe my problem best. Today i flied with HSN 2 and 1/4 turns off. Turning HSN more caused choking while WOT in vertical. Top end wonderful 9000 rpm with 16x6 APC. Idle perfect. But midrange a lot too rich. There is a very rapid transistion between midrange and almost WOT. Engine loads up with fuel during midrange. Transition from midrange to almost WOT is uncontrolable by radio stick :/

Now i have one more question. I have connected to the breather nipple a 40 cm long tube to prevent the fuse from all the oil coming tru this nipple. Can it make any problem for the engine?
And the fuel lines. I use 0,08 inch of inner diameter fuel lines. Maybe its too thin to give enough pressure to the tank? I dont know. Everything can be possible.

Today i looked at brand new Saito 125's carb and didnt see any differences between mine and this one. The sprayer groove is the same as mine and the LSN slides on the spray bar just like mine increasing and decreasing the groove the same way.

Flyer95

My Feedback: (1)

Midrange has never been a problem on a Saito. If midrange is rough on your 125 then maybe its time for a new glowplug and OS-F works very nice on all my Saitos. I did not like the stock Saito glowplug very much but hear they are made better now? A smaller prop like the APC15x6 wouldnt hurt and let the engine run cooler. I would say worth to try a smaller prop as it makes the needles more responsive and throttle response superinstant and gives you more rpm and speed for some aerobatics.
My Saito 125 been inverted runs great and very stable. Superlow idle, nice midrange and good topend.

RCWI

Any body have RPM readings for 125 with a 16x4 or 17x4? What should be the max rpms with any prop on the ground??

Flyer95

My Feedback: (1)

About 9800 on the 16x4w and 8800 on the 17x4w. I liked the 16x4w a whole lot better on my UCD60. I think 10000 is a safe ground rpm.

Hobbsy

My Feedback: (102)

There is no problem with Saito carbs, only with with the human adjusters.

Pawel Rzedzicki

OMG Hobbsy what a magnificient statement. I think this solved my problem i no time!!! Thanks a lot, you are my idol forever!!!


For all the rest good people trying to help me two pictures of this original screw:

Biggles2

can someone advise me as to what size three blade prop would suit the saito 125? Its going on 12lb warbird ( hellcat) .....[8D]

Flyer95

My Feedback: (1)

Pawel,
Do you use any castor oil in the fuel? Castor oil is superior to syntetic for lubrication. If you use 100% syntetic fuel then just add 5% castor oil and the engine will run better and cooler and the parts will last longer.

Biggles2,
My best guess would be a 14x6 three blade or maybe a 14x8.

Pawel Rzedzicki

I use fuel with 19% castor/synth mixed 1:1.

Hobbsy

My Feedback: (102)

I would suggest a Graupner 14x7, MasterAirscrew also makes a 14x7 3b but the Graupner has the nod for good looks.

Hobbsy

My Feedback: (102)

Sorry, perhaps this is more helpful, the LS screw is almost the thickness of the plastic arm down inside the barrel.