4 stroke spool down???
 

Today I took my edge to the field for a possible maiden. Well I never got to take off due to my concerns with my idle and spool down on saito 100. My transition from idle to full is amazing. no issue what so ever. However, my when bringing throttle back to idle...It takes about 5 seconds for the engine to reach the original idle rpm range - So stick comes all the way down, and engine stays at an elevated "idle" - then comes down to where it should be. What does this mean? Running saito 100 w/ APC 15x6.

Also at about 2300 rpm or so, the idle seems way too high. it pulls the plane across the runway fast. Re-tune I guess?

I have some video, will try to post later tonight.

RE: 4 stroke spool down???
 

any chance the linkage is binding a bit at the low end on the return with the engine running.?

RE: 4 stroke spool down???
 

Consider that there is a lot of fuel in the fuel flow from the carb down into the engine.  Most engines throttle down pretty well to within a few hundred RPM of the initial idle set.  Then they settle down to the original idle point.  That's residual fuel and takes a few moments to consume.  Don't worry about it.  Fly the thing.

CGr.

RE: 4 stroke spool down???
 

Hmmmm...CG that make perfect sense. Well the only reason I am worried is because the idle, even though reading at about 2300 rpm....is to high. It pulls my plane along the runway too fast. So worried about having to rush my take-offs and possible fast landings. Working on posting videos now.

RE: 4 stroke spool down???
 

Are you on pavement or grass?

If pavement, well, the best solution is toangle the main gear in toward each other.. offering some resistance to the forward movement.Another solution, if on pavement, is to put some tubing between the wheel hubs and the wheel to offer some braking resistance to the wheel.

If you are flying on grass.. well, are you sure of your RPM? Mine idle at or around 2500 RPM and don't move at all until I throttle up.

CGr.

RE: 4 stroke spool down???
 

Actually, when a four stroke behaves like that I've found that's it's a sure sign that the low-end is a just little lean. Which also explains why you can't get the idle much lower without the thing cutting out. I think you'll find if you open the low end mixture adjustment a quarter turn or so, she'll behave a little more predictably for you.

Hope this helps,

-Joe

RE: 4 stroke spool down???
 

If you listen closely, you can here it after bringing it down.

http://www.youtube.com/watch?v=2Qb6j_lebqY

RE: 4 stroke spool down???
 

And here it is taxiing on pavement at idle. I should have dubbed it with Benny Hill theme song and ran after it!!!!

Anyhow on the 3rd pass, I lowered the trim to a more manageable speed...but then it cut off right when it went off camera.

http://www.youtube.com/watch?v=InzEIhCZNJc

RE: 4 stroke spool down???
 

I am a newbie, so take this with a grain of salt..but..wouldn't a less aggressive prop pitch help slow it down?..  i.e.       14 x4  instead of

14 x 7  .. or whatever is proper.... for a 100 engine?  Rich

RE: 4 stroke spool down???
 

I've run into a couple situations where my linkage caused similar issues. Often, I'd could give a quick blip of throttle and it woud be back to idle.

As for it rolling around, that seems to happening when you turn bigger props. They seem to make thrust at lower RPM. You can keep tuning the engine to get a lower idle. If it is still a problem, try adding some resistance to your wheels. Maybe with some toe-in as suggested or placing something like fuel tubing between the wheel and collar. Just don't get them too tight, you don't want a wheel to hang up, especially on landing.

RE: 4 stroke spool down???
 

Just remembered....It wasnt doing this when I had it on the test stand a few weeks back. Hmmmmm....

RE: 4 stroke spool down???
 

I had a Magnum 52 four stroke that did exactly as you describe. Iended up switching over to an O.S52 four stroke and the issue went away. Mine would drop to around 3500 rpm and then slowly settle down to around 2300. Very slowly. Hobby People tech suppport replaced the carb and It solved the problem for a day or so. Then the old behavior came back. My guess is that their is an air lean in the carb, either High speed needle, mix control needle, or the carb to intake manifold. I never got the problem resolved and I now have an O.S52 carb on the Magnum and all is well.

The recomendation to Fly it like it is, is OK as long as the engine will idle down by approach end of the runway and hold a good idle and be able to respond to an emergency application fo full power. If it won't do this, fix it before you fly. Mine wouldn't,

Don

RE: 4 stroke spool down???
 

<p style="MARGIN: 0in 0in 0pt" class="MsoNormal"><font size="3" face="Times New Roman">How much time is on the motor? It sounds like it isn’t quit <span style="mso-spacerun: yes"> </span>broke in yet.
 What are you using for fuel? My Saito’s like Powermaster YS/Saito 20/20 fuel. Your idle will probably settle down after 3or 4 more tanks of fuel. Then you should be able to lean out the idle as described in the instructions. </font></p><p style="MARGIN: 0in 0in 0pt" class="MsoNormal">Saito motors are shipped with a rich idle mixture for brake in. </p><p style="MARGIN: 0in 0in 0pt" class="MsoNormal">Is the motor inverted? </p>

RE: 4 stroke spool down???
 

Engine sits on its side at about 8 o'clock. There is over 2 hours of run time on the engine now(on ground break in). Use wildcat 2&amp;4 stroke, 15%/18%.

RE: 4 stroke spool down???
 

<font size="3" face="Times New Roman"><p style="MARGIN: 0in 0in 0pt" class="MsoNormal">Idle should be starting to settle down soon. Is the prop an Apc 15-6 wide or slandered? If it is a wide you will be swinging a little extra mass. You should expect idle around 2000 rpm or a little lower when the motor gets broke in.</p><p style="MARGIN: 0in 0in 0pt" class="MsoNormal"> 

</p></p><p style="MARGIN: 0in 0in 0pt" class="MsoNormal">It’s my experience that the Saito’s like higher nitro fuels to run well and the manufacture recommends a 20% minimum oil ratio and they also recommend not using fuels that are entirely caster oil.</p><p style="MARGIN: 0in 0in 0pt" class="MsoNormal"> 

</p></p><p style="MARGIN: 0in 0in 0pt" class="MsoNormal"><span style="mso-spacerun: yes">   </span>What was the idle on the test stand?

 Double check the linkage you may be having slippage or binding issues.</p><p style="MARGIN: 0in 0in 0pt" class="MsoNormal"></p></font>

RE: 4 stroke spool down???
 

Oh ohhhh!!! Running 18% as advised by my LHS! But ive been running this on my Saito 91 without issue. Using fully synthetic. Am I really hurting the engines deviating by 2 %?

RE: 4 stroke spool down???
 

Question: After doing some reading im seeing that many recommend the OS F plug for saitos. Whats the difference between F plug and what the saito comes with?

RE: 4 stroke spool down???
 

sounds like your low end might be lean...my saito 100 ran like a champ right after break-in and would not hang the RPMs like yours does. Try richening up the low end just a bit. Mine will also idle all day at about 1500 rpm...

but like the other said, check your linkage as well..

RE: 4 stroke spool down???
 

Actually, it sounds like the low end is rich.

If an engine's low end is rich, you go to idel, and has the fuel builds, the RPM go down.

RE: 4 stroke spool down???
 

Hey Minn...the idle is actually hanging on the higher side for a few seconds, then coming back down.

RE: 4 stroke spool down???
 

<p style="MARGIN: 0in 0in 0pt" class="MsoNormal"><font size="3" face="Times New Roman">I would agree with Minny about being to rich.</font></p><p style="MARGIN: 0in 0in 0pt" class="MsoNormal"><font size="3"><font face="Times New Roman"> 

</p></font></font></p><p style="MARGIN: 0in 0in 0pt" class="MsoNormal"><font size="3"><font face="Times New Roman">One thing that bothers me is you didn’t have the problem until you mounted it in the airplane and it ran good on the test stand.<span style="mso-spacerun: yes">  </span>This sounds like a key. Is the tank mounted above the carb?<span style="mso-spacerun: yes"> </span></font></font></p><p style="MARGIN: 0in 0in 0pt" class="MsoNormal"><font size="3"><font face="Times New Roman"> 

</p></font></font></p><p style="MARGIN: 0in 0in 0pt" class="MsoNormal"><font size="3" face="Times New Roman">What the LHS suggested is probably as close to Saito’s specs as they sell. No you are probably not hearting the motor by shorting it 2% of the oil. </font></p><p style="MARGIN: 0in 0in 0pt" class="MsoNormal"><font size="3"><font face="Times New Roman"> 

</p></font></font></p><p style="MARGIN: 0in 0in 0pt" class="MsoNormal"><font size="3" face="Times New Roman">As to the OS type F being better I’m considering going the other direction in a OS fS.91PII I’m having problems with. </font></p>

RE: 4 stroke spool down???
 

Exactly... You have a combination of two problems

1 - The idle is set too high
2 - The low end is rich

What's happening is, you go to idle, you should almost immediately get the low RPM that you want, but the idle is set too high so you're not.

But now, as the engine idles, it's getting too much fuel, so the RPM slowly drops. If you turn the LE adjustment needle in, you will hear the RPM rise. Then, you'll need to lower it with your trim, AND you'll probably need to richen the High-Speed needle too.

RE: 4 stroke spool down???
 

My saito 82 has a gallon thru it. Running a 14x4w apc..Idle is 1900 all day and no problem. The prop works like an air brake. I do a long dive then pull level at the ground and land.On one of my cubs with a saito 80 I did have to change pitch on the prop to make it stop flying..

RE: 4 stroke spool down???
 

I'm with Minn on this one too. If you set the throttle to idle and the RPM drops, the idle setting is rich. If the RPM increases, then the low end mixture is lean.

Lean out the low end and lower your throttle trim. Do it in small increments, and stop when you can give the engine some juice, drop to idle, and it maintains a consistent idle for 15-20 seconds.

I have read all over this thread that Saitos come with a low end setting that is very, very rich and needs to be leaned out quite a bit.

RE: 4 stroke spool down???
 

I second the very very rich low end from the factory