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Old 07-21-2009, 07:30 AM
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ORIGINAL: nashtm

Hi

I have an inverted 125 and was using an on board glow system but the back fires on start up were so bad and often that I start using a normal glow driver which has helped tremendously (but I still dare not prime it or flip the prop before applying the starter).

Has any one else found an on board glow (with current sensing) to be problematic with an inverted motor ?
Is there anything else one can do prevent/minimise backfires on start up ?

Thanks
Tim
The on board glow is not stricly needed - it just allows the motor idle slower.
I will look at tank height also my fuel line makes a slight loop below the carb ,not above, maybe lifting it will help.
BTW the motor has about a gallon through it - I have leaned the low end till it wants to back fire on throttle up so I dont think that I am too rich on the low end.
Apart from the back fires I much prefere the 4 stroke to 2 strokes !

Thanks
Tim

The high speed needle setting DOES have an effect on the low end. If your high end is too lean, the transition can be bad, but if it's too rich it can affect it as well. If you have a spring-loaded fueler it can do exactly the same thing, popping on throttle up because it sucks air into the fueler dot right into the fuel line. There are a variety of things that can cause your problem. It's not always simple.

But I do agree that the idle is lower and nicer with on-board glow on inverted setups. I can get the Saito to idle fine too when inverted. I can get it to idle BETTER and SLOWER with onboard glow. That's the difference between a plane that sits at idle and a plane that walks across the ground all the time at idle. Personally, I like upright setups, but then, I've always flown a lot of SIG planes for the past few decades....that's pretty much how most of their sport models used to set up.

ALL of my Saitos idle perfectly, transition perfectly, and never, ever stall in the air unless that tank is empty. I'm not lucky. It's a science to tune a Saito just right, but they are worth the effort. Once they're dialed in you have years of carefree flying. It's also fun when my friends and I disect every little glitch and problem and work through each issue. Fun at the field, or at least, it is for ME!

Jim
Old 07-21-2009, 07:34 AM
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ORIGINAL: BChris

Hello everyone. Y'all seem to be a very helpful group, so I am hoping you can help me out. I have an older FA91 that was running pretty good, had a small crash no noticable damage. The first flight after plane repair was great, engine was awesome. Second flight, not so good. The engine runs good up to about 1/3 throttle after that it starts leaning out really bad. I replaced all the fuel lines and checked the tank and everything seems good. I tried to run it again and ended up backing the needle valve all the way out and it was still lean on the high end. Any help would be greatly appreciated. This is my first Saito by the way. It was great up till now.

Brad
The low speed needle is in too far

He said the first flight was fine as adjusted. Unless he fooled with the needles after the first flight (I don't mess with a good running engine), doesn't it sound like something else changed? I piece of dirt in the spray bar could restrict the flow enough to reduce the high end and the fact he can back the high end needle all the way out seems to lead to this. Screwing the low end in won't produce this effect. It just wouldn't run below 3000 or so IMO.
Old 07-21-2009, 07:56 AM
  #15378  
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This is not necessarily true.

The way the carb is made, at a certain point of being screwed "IN" too far, the LSN will restrict the flow of fuel at high speed to where you can screw the HSN almost all the way out and the engine will still be lean at high speed.

However dirt in the spray bar area can create the same symptom. But maybe screw the needle out some will dislodge this dirt.
Old 07-21-2009, 08:02 AM
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Jim and I like to convey the same idea with a slightly different set of words, mine are that the LS needle being leaned too far will render the high speed ineffective. The best idle and transition is usually just slightly rich of where that happens.
Old 07-21-2009, 08:03 AM
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ORIGINAL: w8ye

This is not necessarily true.

The way the carb is made, at a certain point of being screwed ''IN'' too far, the LSN will restrict the flow of fuel at high speed to where you can screw the HSN almost all the way out and the engine will still be lean at high speed.

However dirt in the spray bar area can create the same symptom. But maybe screw the needle out some will dislodge this dirt.
I agree. The main point is, both needles have some effect on each other at almost all times throughout the throttle range. That's why it's so important to find that "sweet spot setting" where you strike the right balance.

Hobbsy, we're still on the same page!
Jim
Old 07-21-2009, 08:25 AM
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That's the reason I like to set the HS needle at absolute peak before setting the LS needle, the HS needle seat is fixed and will not be effected by the barrel movement. If the HS needle is set rich while setting the LS needle, then that richness may cause you to over lean the LS needle.
Old 07-21-2009, 10:36 AM
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You can easily see how both needles interact if you set one of them too rich. You can watch the smoke throughout the throttle range. Setting the low speed very rich is the most interesting to watch.
Old 07-21-2009, 11:41 AM
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ORIGINAL: w8ye


The low speed needle is in too far

Ditto.
I had an OS 70 that wouldn't richen up on the high speed needle no matter how far I wound it out. Could have the needle held in by the o-rings only and it still wouldnt richen up enough.

Reset both needles and when setting the LSN I realised it was set way too lean. After I reset it it ran fine.

I have also had a semi blocked fuel line on another engine which had similar symptoms.

Old 07-21-2009, 03:36 PM
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This is all well and good, and very nice to know if one is staring from scratch with the tuning process on a rebuilt or otherwise tinkered with engine. But, he said he had a good flight the way it was. It seems to me that it wouldn't be a needle adjustment issue that being the case.

However, I do agree with the thought of screwing the needle all the way in to clear the passage. This has a chance to work. I prefer however to disassemble it and actually find the culprit for my own satisfaction, rather that driving it through the system.

Also, personally, I guess I have never gotten the low end needle so lean the high end couldn't feed the engine. If it is so lean it won't idle, but will run high, it has been obvious to me it was too lean and I never went farther in from there. Thanks for the warning. I don't like getting these engines too lean and overly hot.

Of the OS, ASP, Enya, Saito, and YS 4-strokes I have owned over the years, my Saitos have proven to be the workhorses. My Saitos with out pumps run as dependably as the Pumped OS ones. They run all summer long with little or no adjustments as well. I just don't find them to be in need of the constant tinkering others may require. Get it clean and properly adjusted with the help you find in this thread and it will do you right.
Old 07-21-2009, 04:06 PM
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a chance to put a nice scar on you needle valve Im with you take it apart and clean it.
Old 07-21-2009, 04:47 PM
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Thanks for the advice everyone. I think I'm going to go ahead and start with cleaning the needle valve assembly. I made about 2 clicks of an adjustment to the high speed prior to the first flight. Went back to the original setting after the first flight. No other adjustments until after the third very short flight. Low end transition seems good. I haven't made any adjustments to the low end since spring time. I will let you know how it turns out. Thanks for the help.
Old 07-21-2009, 05:03 PM
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Watch for those tiny O rinds. Looking forward to your findings. They will surely be helpful to others. Thanks.
Old 07-22-2009, 04:10 PM
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Okay. More questions. I pulled everything apart and didn't really find any orings?? It looks like the slot on the spray bar was partially blocked. I cleaned it with the tip of a needle and will flush it with alcohol prior to install. The big question is which way does the slot in the spray bar go, or does it matter. Thanks
Old 07-22-2009, 04:13 PM
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The slot has to be inline with the airflow.

If you look into the carb from the intake manifold side, you should see the slot pointing directly towards you
Old 07-22-2009, 07:40 PM
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Everything is back together and the back yard runs were pretty good. I am now out about 5 turns on the low speed and 3 on the high. Transition seems pretty good and I actually got a whole tank of fuel out of it with out it dieing, although it did seem a little warm. I think for tomorrow I am going to leave the cowl off and see how it does. Any good tips for tuning the low end?

Brad
Old 07-22-2009, 08:13 PM
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You already mentioned one good tip. Leave your cowl off on the ground. When you're sitting still you're missing 70 MPH forced-through cooling air. The propeller helps, but you need the extra flow of the cowl off to run whole tanks through..

I'm sure you'll get a bunch of tips on the actual tuning here pretty soon. If not let me know.

Jim
Old 07-22-2009, 09:22 PM
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ORIGINAL: BChris

Everything is back together and the back yard runs were pretty good. I am now out about 5 turns on the low speed and 3 on the high. Transition seems pretty good and I actually got a whole tank of fuel out of it with out it dieing, although it did seem a little warm. I think for tomorrow I am going to leave the cowl off and see how it does. Any good tips for tuning the low end?

Brad
The relative measure of the low speed screw position on a saito is its turns in from being flush with the outside face of the throttle arm

On a old Saito with the metal throttle arm the perfect setting for the low speed screw was flush with the outer face of the metal throttle arm.

If you have a plastic throttle arm the LSN is going to be recessed somewhat.
Old 07-23-2009, 12:15 AM
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Sounds like you are back in business with your engine. Just some fine tuning now. Lots of help already posted on that. Consider running a filter for awhile. That dirt came from somewhere. Could still be some in the fuel system. Might need a new plug as well, if you didn't already change that out after the accident.
Old 07-23-2009, 06:40 AM
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FILTERS...YES! Good point, Ram!

Many of the Saitos have spray bars and fine orifices, I always run a filter. I used to run those clear ones with the two screens in them(Goldberg? Can't remember) on all my Saitos, and then toss them once a year. Now I get the pretty colored metal ones that you can open up and check for gunk and clean out.

I also try to run filters on my fuelers too.
Jim
Old 07-23-2009, 07:50 AM
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Sullivan. I used to use inline filters but now only filter the fuel using PSP fuel jug caps which have a filter at the filler end.
Old 07-23-2009, 08:31 AM
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ORIGINAL: Hobbsy

Sullivan. I used to use inline filters but now only filter the fuel using PSP fuel jug caps which have a filter at the filler end.
I prefer this method as well. I have had more problems with the filters themselves, then without. The ones that open are another place to leak air as well. You will get a lot of pros and cons on the subject, and you'll find guys swearing by both ways, but I do think,in this case, where dirt is known have been present, filtering the system for a few flights is prudent. I would also recommend filtering your fuel as it is dispensed, if you don't already. An engine that go's lean gets hotter, and excess heat is bad for any engine.
Old 07-23-2009, 10:06 AM
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SAITO FG-14
[link=http://cgi.ebay.com/SAITO-FG-14-82-Gasoline-Four-Stroke-Aircraft-Engine_W0QQitemZ350228998691QQcmdZViewItemQQptZRad io_Control_Parts_Accessories?hash=item518b466a23&_ trksid=p3286.c0.m14&_trkparms=65:12|66:2|39:1|72:1 205|293:1|294:50#ht_4486wt_924]dirt cheap![/link]


Counting the price of the mount, and the ignition system, it's not too badly priced, I don't reckon.
Of course, we Saito owners don't mind spending big nickles for quality engines...

I'd be interested in your evaluations, gentlemen!
Old 07-23-2009, 10:37 AM
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ORIGINAL: mike early

SAITO FG-14
[link=http://cgi.ebay.com/SAITO-FG-14-82-Gasoline-Four-Stroke-Aircraft-Engine_W0QQitemZ350228998691QQcmdZViewItemQQptZRad io_Control_Parts_Accessories?hash=item518b466a23&a mp;_trksid=p3286.c0.m14&_trkparms=65:12|66:2|3 9:1|72:1205|293:1|294:50#ht_4486wt_924]dirt cheap![/link]


Counting the price of the mount, and the ignition system, it's not too badly priced, I don't reckon.
Of course, we Saito owners don't mind spending big nickles for quality engines...

I'd be interested in your evaluations, gentlemen!
He's advertised that off and on for a month and hasn't sold any

You would have a hard time getting support from Horizon?

Old 07-23-2009, 12:33 PM
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ORIGINAL: Hobbsy

Sullivan. I used to use inline filters but now only filter the fuel using PSP fuel jug caps which have a filter at the filler end.
That is right!Same here, i'm using only two filters -one in the fuel botle,another in the fueling line.But none of them in the engine system(to much troble).
Old 07-23-2009, 12:41 PM
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ORIGINAL: w8ye


ORIGINAL: mike early

SAITO FG-14
[link=http://cgi.ebay.com/SAITO-FG-14-82-Gasoline-Four-Stroke-Aircraft-Engine_W0QQitemZ350228998691QQcmdZViewItemQQptZRad io_Control_Parts_Accessories?hash=item518b466a23&_ trksid=p3286.c0.m14&_trkparms=65:12|66:2|39:1|72:1 205|293:1|294:50#ht_4486wt_924]dirt cheap![/link]


Counting the price of the mount, and the ignition system, it's not too badly priced, I don't reckon.
Of course, we Saito owners don't mind spending big nickles for quality engines...

I'd be interested in your evaluations, gentlemen!
He's advertised that off and on for a month and hasn't sold any

You would have a hard time getting support from Horizon?


True, the customer support from Horizon is always a good thing to have on your side.






I was just looking at my Align in-line filter next to my carb and was surprised to see quite a lot of gritty-looking stuff. It was not gritty to the touch but I am still glad it never made it to my 125...



I also have a crap-trap in my fueling line. I guess it's some sort of residue from the exhaust pressure line....

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