hi all - i have a couple questions i was hoping to get some help on:

1) i bought this engine used from someone who claimed it ran great but i haven't been able to establish the low idle at all. the problem is that it gets down to about 3,500 or so and just starts dying. it almost seems like it's skipping or something. the manual and most of the troubleshooting stuff i read talks about whether or not an engine runs at idle for a while then dies (lean) or idles ok then dies at transition (rich), etc. well this thing runs like a top at the mid and high end but just won't run at idle at all. i would normally chalk it up to owner error but i've had my club's two best engine guys (25+ yrs. in the hobby) spend about 10 hours each on it and they can't figure it out either. we've checked the valves, the timing, flushed the carb, changed props, plugs, fuel line, in the plane, on a test stand, etc. etc. etc. currently i'm using 15% nitro with 18% oil i believe.

i'm not an engine expert, but i also own a .91 saito and these two engines couldn't be more different in terms of running smoothness. the .91 was cake to set up and hasn't needed one adjustment in over a year. it ticks off the low idle like a swiss watch. this thing doesn't seem nearly as smooth and adjustments to low and high end seem to have either no or random effect. very wierd.

2) if/when i bail on this engine for my .40 size ultra stick with floats, i'm trying to decide what else to put on the nose. i'm feeling lazy/anxious to get her in the air so i'm wondering what other engines would fit this engine's footprint (i.e engine mount holes and throttle linkages)? i'm also open to non-saito options since i'm sitting on some tower gift certificates so could go with an OS or Magnum etc if they would fit.

As always, any suggestions would be greatly appreciated. The flying season here in VT is short enough - i'm about ready to pull my hair out trying to get into the air this year heh.

Boneman

Did you try a OS 'F' plug? What about some new fuel? What about 15% nitro? Get the engine down a low as it will reliably idle and do the pinch test to see if it is rich or lean. A engine with the valves too tight will not idle well.

Enjoy,

Jim

Is it smoking and dies slowly when it quits or is there no smoke and it is quitting instantly. Where is the low speed needle in relation to the end of the throttle barrel? My guess is that it is too rich, if so set the high speed needle to peak rpm and leave it there temporarily then lower the throttle to lowest speed possible the way it is running now. Now procede to turn the low speed needle cw 1/8 turn at a time rechecking the top end every other time, at some point one of those 1/8 turns is going make a big difference all at once. Now you're close, just keep at it until you get the idle and transition you want. Be willing to sacrifice a little on the lowest idle speed to get a better transition. Don't listen to anybody who says it won't idle right until 18 gallons of fuel has been run through it. You can have a fantastic idle about 25 minutes after the break in is begun. when satisfied, reset the top end a couple of hundred rpm rich.

You must have the older high compression .80. They will not run good with 18% oil and 15%nitro. Try some 10% nitro 4 cycle fuel with no more than 15% oil. The combination of high compression and 18% oil on this 4 cycle engine is causing the plug to cool down and not fire at lower revs. Make sure the glow plug is the one saito says to use with this engine. Oh, and watch out this engine will throw props if run too lean.

Boneman,
check this link: http://www.saito-engines.info/

There is also a thead called "Saito .72 broke in needle setting..." in the glow engines forum
HTH
Luis

Bone:

Something no one has mentioned. You say an"Old" 80, it's possible you have the air bleed carb. With the air bleed, as built by Saito, if the mid range is out if adjustment you can get exactly the symptom you describe.

On the AB carb, the high speed needle is mounted to a disc that can be rotated, you should start adjustment with the disc in its center position, Note the index marks just above the clamp in the first picture.

With the index marks aligned, peak the high speed. Then go to 1/2 throttle and pinch the fuel line. If the rpm immediately falls, turn the disc forward a hair, that is in the same direction as you would turn the main needle to go rich. If the rpm holds momentarily and then falls, leave it alone. If the rpm rises, turn the disc a little bit in the opposite direction.

Then recheck the HS needle, be sure it's still peaked, and finally set the air bleed screw to get good transition from idle to full throttle.

Pictures: First is the HS needle side of the air bleed carb, showing the mixture disc index marks. Second is a TN carb for comparison.

Bill.

thanks guys - i appreciate the responses. let's see - in reverse chronological order:

will rob - no - this engine doesn't have the disc - i guess it's not that "old"

maelstrom - thanks - i reference that site quite a bit and was attempting to follow his directions. the problem is that he assumes you can get to a low idle (2,500 or less) after setting the high end and that is exactly my problem heh.

myway - i hadn't heard about the "high compression" .80's but it's funny, because i was struck initially at how hard it was to turn over by hand and assuming it meant pretty good compression. i've got some 10% nitro kicking around from my trainer days - i can give that a whirl. i'm a little suspicious about the cool plug syndrome as i've tried OS F plugs and the McKoy 4 stroke plugs that came with my .91 as well as leaving the glow plug on while attempting an idle to no avail. i will try using the 10% nitro and let you know how i fare.

hobbsy - i haven't really noticed any difference in the smoke when it dies. i get a pretty healthy amount of white smoke while it's running and then it just starts to shake a little bit and quits. in general i'd say it doesn't run nearly as smoothly as my .91. i've started with the low end screw as rich as even with the barrel and it does seem to come down as i lean it out but i just can't it slow enough. i will get to the point (about 3 or so turns in) where leaning it more actually makes it run worse so i'm really at a loss. a couple of times when adjusting the high end it seemed to bog down the more i opened the throttle but then that went away and i couldn't really replicate it. to be honest i haven't gone back every time i adjust the low end and re-test the high end. i got the high end to about 10,600 or so with a 13x6 prop then backed it off 300-400 or so. i've always thought (erroneously perhaps) that you could run 4 strokes a little on the rich side without too much of an impact on the low end.

w8ye - i've used an F plug as well as a couple others and 15% nitro. we adjusted the valves to be on the wide side of the recommended range (.1 mm). they were kind of a pain to set as the threads on the valve screws seemed real coarse/ not exact - not sure if my .91 is like that as i haven't had to mess with those.


Does anyone have any feedback on part 2 of my question if i decide to bail/send this engine in to horizon? will the saito .72 fit the footprint of this engine (i.e mounting holes and throttle hook-up)? what about other engine brands (OS, Magnum etc.)?

Thanks in advance for all the help - the season here in VT is waaay too short to spend this amount of time messing with an engine!

Boneman

Bone:

Some of your questions. Yes, the 72 will sit in the place of the 80, but the mounting screw holess will not match.

Not the air bleed carb.

Another possibility is a massive intake leak. Get the engine running as slowly as you can, then use a spray can of WD-40 or anything similar, spray around the outside of the carb, and where the intake goes into the cylinder. There will be a reaction if you hit a leak point.

And yet another possibility. Take the carb off and look into the bore from the engine side, holding the throttle full open. You should see a slit in the spray bar, the slit should be centered. If it isn't centered the engine will go lean at part throttle, and you will not be able to adjust for it.

Let us know what you find.

Bill.

Yes! Check the spraybar. I bought a used Saito 120 and had problems with the idle and midrange. Took the carb apart and found something that looked like a piece of thin clear plastic wedged in the sraybar. A little work with a sewing needle got it out. Runs like a top now.