Like you, I also do the calculations that way to see my miles per gallon, if you will.

Well, I just tried to do an engine test. First, the car battery I use for the starter motor was weak. So I bought a new one. Then I realized that when I went to the store, I had left the glow starter on the engine so when I got back that was dead. What I hate most about RC? Starter batteries, glow batteries, Tx batteries, Rx batteries...why on EARTH would I move to electric RC models?!?!?!?

Gas engines I love. If only they came with starter cranks.

Charged the glow starter and tried the 82 again. This time I leaned out the throttle setting by a half turn or so and at the same 6,200 (or so) rpms got a runtime of just over 8 minutes. So figuring the larger tank in the Snipe and assuming that with this larger engine I'd be flying below 1/2 throttle much of the time, I think I might be able to get 10 minutes flights. Of course, I'd start with 5 minutes on the countdown clock on the Tx and then see how much is left after a flight and from there slowly work towards longer times. At this leaner setting there was still a healthy amount of exhaust but not nearly as much pooling oil (though it was still pretty messy).

That's the good news.

The not so encouraging news is that leaning it out didn't seem to give any higher top end. It still maxed out at about 9,200 and in fact it wouldn't even hold that consistently. It would be at 9,200 and then drop down to 8,800 then maybe rev up to 9,000 then back to 8,700. And further leaning it out just lowered the rpm and then killed the engine. At idle I was able to get a very irregular sounding 2,400-2,700 but it wouldn't hold that. It kept creeping back up over 3,000. I'm wonder whether this isn't in part an issue with the linkage on the stand. There may be some flex in the linkage that is allowing the throttle arm to move.

I feel like I'm making progress but this engine is nowhere near ready to put into a good scale model. Unless I can get it purring gently on the stand I won't use it in the model. Also it's a bit of a PITA to start. It starts easily enough but it won't start at all with the throttle more than half open (which I suppose is a good thing) but I think this means it's prone to flooding and since the engine is mounted inverted on the Snipe this could be a problem. Also there is just so much compression that it's a really strain on the model to get it to turn over. The 72 is much better in all of these ways.

(Oh, and it turns out that my glow starter wasn't just discharged; it was busted. Now I need to buy a new one.)

I don't know, I still feel like a hotter plug is worth trying. I had similar problems with one of my saitos, ( don't remember which one) and a hotter plug resolved it. Just a thought.

To be honest, I don't know what you mean by 'hotter plug." I know there are long 4-stroke plugs (like the OS F plugs) and shorter 2-stroke plugs. But are there really difference between on 4 stroke plug brand and another?

http://saito-engines.info/throttle_setup.html

Tuning engines isn't my strong suit. I think I need to go back to square one: Low speed screw flush and high speed needle about three turns out. Then 1) start and allow to run for about a minute then 2) go to full throttle and tweak the needle value until I get to maximum rpms then 3) back off 200-300rpms then 4) drop down to the idle position and step by step screw the low speed set screw INWARD to lean the low speed mixture.

Real OS 4 stroke plugs seem to work the best. Generic usually dont work as well for the average person. A real OS plug can solve problems. Full tuning is iterative. Tune high needle then tune low, then tune high then tune low. Tune low in 1/4 turn increments. Besides obtaining a target rpm, when adjusting the needles, especially the high, is how sensitive it is. If you are making adjustments and response seems not responsive, the prop is too big or the engine is not broken in. As an engine breaks in the needles can go leaner. New engine run great out of the box but they still need running to pull the biggest prop. That is why it is best to put it in an airplane and fly a gallon or 2 through it instead of boring 5 min bench runs that you cant wait to stop.

They do, sort of, at least some of them, many Zenoah engines can be fitted with recoil (reverse wind up) starter springs that make starting pretty darned easy. I have a G38 and a Quadra Q42 both so equipped.

Tff is right spend the bucks and get a genuine OS typr F plug before making ans harsh judgments, they really are better.
Doc

If I had a junk model to put it in I would.

Anything that eliminates a battery sounds good to me.

I'll see what's available.

Cub

Seems way overkill to put a 82 in a 2.6kg model. At this point though, with the way it's running I wouldn't even put it in the Cub.

One of my field habits is to start an engine then shut it down, then start it again. If everything is perfect, I'll fly. If not, I pack it up and go home. Once I've flown a model with a given engine many times, I'll eliminate this. But I always do it with a new model.

In short, never setup an engine and fly it on the same day.

BTW, this is my idea of a junk model:

From the way your 82 is varying in RPM I think it may still be a bit tight. I don't know if 2 gallons through your engine is the magic number, but do know that the looser they get the happier and more tolerant they seem to be.

I've found that I just can't judge the needle setting of a four stroke by sound. I have to use a tach to see where I am. On a fairly new Saito, I find that a good running setting can be had by peaking the RPM and then backing down about 500. As the engine loosens up, it can be run at more like 300 below peak, and when really, really loose, can be run essentially at peak. Once thoroughly broken in, the engines seem to be far more tolerant of needle setting and prop size. The quality of the idle seems to follow with looseness as well. I have an old Saito 45 that has perhaps 250 hours of run time and it now idles reliably at 1600 RPM. But it took a really long time to get there.

The other thing to consider on your Saito is valve adjustment. When new or nearly new, the valve clearances seem to change. Once thoroughly broken in it seems like they never need to be touched. On the subject of valve adjustment, the feeler gauge that came with one of my Saitos was far thicker than the instructions called for. You may need to check the feeler gauge with a micrometer to make sure it's the prescribed thickness.

How do you know if your glow plug is "hot" enough ? Watch the RPM when you disconnect the glow plug battery. If the RPM (we're talking full throttle here) drops significantly when you disconnect the battery, you may need a hotter plug. If the plug is hot enough, you will notice very little RPM drop with the battery disconnected.

Dick

You haven't mentioned how much Nitro you are using in your fuel...I would not hesitate to increase it to 15% if you are not already there.
This will probably help smooth out the transition from idle to full speed and help stabilize low idle.
There is definitely a noticeable increase in power with higher Nitro %.
I only have one Saito engine ...the 220 Single cylinder beast...I kept having deadsticks until I really leaned out the HS needle...it still leaves a good smoke trail.
I couldn't believe running fat this was the cause of my problems being so counterintuitive from years of OS engines .

What I meant by a hotter plug, and I'm sure a bunch of guys will chime in on it, was this. I used to have an old saito, I think it was a 56 that ran like yours. I couldn't get it to run reliably for nothing. At wits end with it, I figured I would try what an old guy at the field kept telling me which was to try a hot two stroke plug. It helped immensely. I flew it like that for a number of years. It turned out to be a descent little engine. Weird, huh? It was the only four stroke that I ever did that with. Have you asked around in the glow forums?

I think I'm just going to put the 72 back in the Snipe. That's already one engine size larger than the 56/62 I had flying the equivalent size and weight Puppeteer. And that engine seems a lot more reliable. Also I'm wondering whether torque from the larger engine with larger prop might not be a problem on take-offs. The gear on the Snipe is both tall and narrow (in other words "scale") and the rudder is relatively small (also scale).

And the fact is that the model has already flown with the 72 and if there was any problem it was that I was flying it too fast. Also the 72 will allow longer flight times. I'll keep playing around with the 82. Maybe I can eventually get it running well enough to use in some future model.

Sounds like a reasonable plan to me. I'd rather have reliable over a little more power any day. I hate dead stick landings.

Don, here's some food for thought.......I learned to fly on a Falcon 56 & OS40 with a 10x6 prop. I couldn't slow it down for landing - by the time it did slow down I was already past the cut grass and over the tall grass - power up and go around. Time and time again this happened, then my flying buddy said I need to try a different prop. He suggested a 10 x 3 1/2 pitch. The plane didn't go very fast, but it went almost straight up with ease and the best thing - it slowed down for landing. The 3 1/2 inch pitch did the trick. It might be worth the effort to experiment with prop sizes.

Say for instance, if an engine is really happy with a 14 x 8 (add the numbers 14+8=22).........then almost any prop, as long as the diameter and pitch add up to 22 will be happy on the engine........you might have to detune the engine (richen it up) to handle the larger diameters, but the engine will be fine.

Remember, 4 strokes put out nearly 90% of their power even when running very rich.

Just my 2 cents worth. And by the way, you will need to learn the rudder to handle torque on take offs, no matter which engine you use......so start burning more fuel.....I guess you got an extra 2 cents thrown in there, eh!?

I'm pretty sure (through the haze of maiden flight nerves) that the problem with "going to fast" was simply that I didn't trust going to idle. I do remember that the model dropped quickly when I cut power so landings have to be power-on then cut just before touchdown. I'll do a little more stand testing of the 72 then put it back in. It's impossible to fine tune an engine until it's in a model connected to a throttle servo and Tx.

I hadn't heard the idle of adding diameter and pitch for equivalent props. That's a pretty nifty rule of thumb.

One good bit of news is the mounting holes for the Saito 56 (that I have in my Cub ARF) and the ones on both the Saito 72 and 82 are EXACTLY the same. The larger engines weight about 50g more but that's not a major problem.

Maybe it was going back to square one on the tuning; maybe it was the "threat" of putting the 72 back in. Whatever it was, I got the 82 to idle reliably at just over 2,000rpm today. Mostly this was due to repeatedly turning the idle set screw inwards. It was at least four full turns. (Recall that the tuning instructions suggests starting with the screw flush and then adjusting it inward in 1/8 turn increments so that would be 32 adjustments!!!) Also it was clear that my test stand throttle linkage wasn't rigid enough because when I held the throttle arm in place it idled nicely.

The top end is still only 9,400. Of course I set that first, and that's the highest it would go before starting to lose rpms.

Once again, I was unable to fly because of wind. No one flew. I think I'm just going to have to write off the rest of March and probably much of April as well.

For this reason, I hate spring. It's finally warm enough to fly, but if it's not raining, it's blowing 20 + MPH. seems to be absolutely perfect while I'm at work, but as soon as I have a day off, forget it. I'm glad your making progress with the 82.

Progress, yes. But here's what my Japanese friend and our local Saito guru has to say about the 82a:

"According to experience of me and other experts ; Dynamic balance of FA-82a is not so good, there is much vibration. I cannot recommend that engine to your Snipe. The maker (Saito) also knew it, so they was released advanced FA-82b now. I recommended to you still using FA-72, or purchasing FA-82b (if you need more power ). I replaced FA-82 (two sets) to FA-72 and FA-62a."

Anyway, I can say absolutely that I won't be buying a new 82b!

While looking for info on the 82b I found this RCU discussion:

http://www.rcuniverse.com/forum/glow-engines-114/9008700-comparison-saito-82a-new-saito-82b.html

So what was the reason for you not wanting to use the 72 in the first place? More power?

Recommendations here. And larger prop = a bit more weight as far forward as possible. I'm sure the 72 will be fine. Besides, I don't think I've ever had a flight problem where "more power" was the solution.

Best case scenario is that I get to fly maybe 10 days between now and the end of June. And that's being unrealistically optimistic. During the working week it's pretty much impossible to make the hour and a half drive to the field. If I could make it, there certainly wouldn't be anyone else at the field. Then from the end of June to the middle of August, I'll be teaching up in Tokyo each weekend and it's exceedingly unlikely that I would be able to get to the flying field on a day that it's not raining (since this also is the rainy season in Japan). Then for the rest of August and into September I'll be visiting family in the US. Then...well, you get the picture. Truth be told, between the weather and absences most years I don't manage to fly more than 20 days.