Ok all, I have read numerous numerous threads, and I am now at my wits end with my Saito 91 inverted. Have spent a couple hours trying to get it to run at low end. Replaced stock plug with an OS type F. Tank is in line with carb. I have adjusted the low needle all the way till it was closed. And everywhere in between. It runs fine with plug attached. Once removed, depending on where I have the LSN adjusted, it will idle fine for between 5 and 30 seconds and then all of a sudden, it will just die. Not speed up, not gurgle just DEAD! This is the second Saito 91 engine for this plane,the old one ran perfectly till the bearings went out. I needed another engine quicker than the rebuild would have been. Any tips on the newer engine will be appreciated. Thanks in advance!

Set the HS needle at full peak and leave it there for now, then in small increments as in 1/8th turn at a time lean the LS needle and test the idle and top rpm after every other change. This is much easier on a test stand. One of the 1/8th turn changes will suddenly make more difference than the previous ones. Now you're close, shoot for a 2,000 rpm idle but fly at about 2,200. I like to use a repeatable system to do things and this works every time. Do you have 40 minutes or more on the engine? If not, put about 40 minutes on it at 4,000 to full throttle in 1,000 rpm steps. Don't do this part at full peak, richen the top rpm down about 400 rpm.

I tried to do as you suggested. I never could get even a good top end. It died there too once the glow was removed. I kept it on and ended up burning out two glow plugs. Frustrated I took the motor off with the full intention of buying a new motor. Once home, I decided to check gap. I was easily able to slide the .010" feeler in each valve. I re-adjusted them to .004. Do you think that could have made chasing my issues impossible to catch?

Hi!
No!

What typ of fuel do you use? Use at least 5% nitro!

The tank placement is very important! The center of the tank should be in line with the fuel intake orifice in the carb when plane sits horizontal.That very, very important!
Also use the Uni-flow tank set up for best running characteristics. That means using two clunk lines one 1-2cm shorter than the other, the longer is the fuel feed line to the carb, the shorter is the pressure line!

Prop size should be a 14x6, 15x4, 15x6, 16x4W APC or RAM . Those are the best props.

Glow plug should be OS F!

Power Master 20/20. Tank is inline with carb. Nothing has changed other than the worn out engine that WAS on it. Replaced with same size Saito. The old Saito was running fine other than the grinding of the bearings. So I don't think it is tank set-up. I haven't heard of the uni-flow, but I will look into it.

Also, not sure if this is a player in the equation, but this is the fuel valve I have on it. Glow version
http://shop.dubro.com/products/produ...1.1.0.0.0.0.0?

Hi!
Get rid of all such things!!!!
They sooner or later leak!
Have you bubbles in the fuel lines?? If so it could be the fuel valve.

I haven't seen any bubbles yet, but I will look closer next time. Also, the fuel is a month old and it runs in another Saito. 170R3. But then again, I have in-board glow on the 3 cyl.

Thanks for taking the time to offer suggestions...it IS appreciated.

If this was purchased second hand the original owner may have taken the cam carrier/cover off and failed to get the cam back in time correctly. It can be a bit tricky to do. I took my Saito 91 apart once and got the cam off by one tooth and it had issues very similar to yours. After correcting the problem it has since run very good.

I thought about that. It still looked pretty new when I got it. No oily residue, no burn marks etc... Are these engines marked already or did you mark it when you took it apart. IF I have to go that far.

I had a similar problem with a Magnum 91 4 stroke. However my tank was a little higher than the center line of the carb. When the engine was at idle it would load up and quit. I tried adjusting the low end and had no success. What I did was run the fuel line above the height of the tank then came down to the inlet on the carburetor. That solved the low end idle. However when I am fueling up the tank I have to make sure the carburetor is closed or the fuel will leak out of the carburetor.

Jaka, Saitos like 10% or 15% nitro.

Try a different bottle of fuel. Very common problem here in Florida. red

It sounds as though the engine hasn't been broken-in as yet. No engine will idle perfectly out of the box from sample to sample. The fact that the engine quits at high speed when the glow driver is disconnected is another hint that all is not as it should be. Not being broken-in could be the problem, as long as the previous owner did not take it apart and then reassemble it improperly.

Your fuel and glow plug should be fine. Check the glow plug in another engine, just to be sure.


Ed Cregger

Okay, the winners of the what's wrong with my engine sweepstakes is all those that suggested fuel. At the field today I was going through the process eliminating things, one at a time. Finally I pumped my fuel out and pumped 4 or 5 ounces of fuel from another flyer at the field. WALLA!!! It ran a like a top. Transitioned fine, up and down. Then I let it idle all the way till the tank ran dry. Hopefully this will help someone else down the road. Thanks to all that contributed. I guess I got a bad batch of fuel or something, because it aint that old, and there has NOT been much humidity this year here.

Don't reuse the jug as it will probably recontaminate fuel again. You may already know this.