LargeScale88

Hello.

I have an old super tiger 40 engine that is about 20-25 years old. It's always ran great, until last year, I put a new piston in. Now, I have another problem. So I open the needle 2-1/2 turns, and fire it up. I then lean it out to max RPM, and richen a bit, and point the noise up because it leans out a bit. Now, whenever I point the nose up, it always slows down, then dies. I've never had this problem, and I've been tuning the engine the same for all these years with no problems and no deadsticks. I checked all the fuel lines, the fuel, and its all good.

I have no idea what the problem is, but I think its wierd how it all of a sudden starts doing this.

Is this engine ready to bite the dust?

Thanks

Jason

TFF

Have you broken the engine in again? Have you tried to run the engine richer? Why did you have to put a piston in?

aerowoof

if you replaced the piston and the ring is new did you score he liner with sandpaper to remove the glaze so the ring wouls seat?

Gray Beard

My Feedback: (-1)

Sand Paper???????? The Saito reps had be breaking the glaze with 0000 steel wool, they don't want you cross hatching the liner like in a car engine.
Jason, it sounds like your still too lean on the high end is all. Twist the needle to give it what it wants now, not what it used to like.

aerowoof

read the instructions from frank bowman when you buy one of his rings

aerowoof

arent saito liners aluminum as part of the cylinder not steel ?

speedracerntrixie

My Feedback: (29)

Sounds like the front bearing is creating an air leak.

JohnBuckner

My Feedback: (1)

He,he I love this line and its so true yessir Jason enrichen untill it will continue to run after standing up.

Actually I don,t use the pointing the nose up trick but instead tune to a pinch on the high speed and that will also effect a good needle.


John

dbelley

Could be mistaken here. But as far as I know, St-40s, even old ones, are not ringned engines. Changing a piston means breaking-in the engine as if it was new. From my ST-40 experiences, this takes time (a coupe of gallons); tune after that much time/fuel.

I don't know the reason for the piston change so other factors might be invlolved.

Dan

aerowoof

these st .40 use rings
.40 Bullring, S.40 (pin), G21.40 std., G21 .40 Dykes
may be showing my age here

LargeScale88

I can't remember why I had to put a new piston in. I'd say over the years, its probably had 15-20 gallons run through it.

So next time I go out to the field, I'll just turn the needle out more. It was already 3 turns out, and wouldn't run worth crap. I thought standard was like 1 1/2-2 turns out??

Jason

JohnBuckner

My Feedback: (1)

One to one and one half open is a poor starting setting as it will likely be too lean from the get go causing confusion.

If three turns works to start it then use three turns. Four turns is a possibility also After warm up open to full throttle and set your high speed as you would normally. Now if the engine will quite when you raise the nose to near vertical then open the needle a little at a time untill you can actually throttle the engine from near idle to full throttle.

An Alternative is rather than raise the airplane: open throttle to full power and let it run for a few seconds now pinch the carb feed line rapidly (just an instantainious pinch and let go) If you get a slight rise in rpm you are good, if you get stumbling then you are to rich and if you get an almost instant stoppage of the engine then you are too lean. Note this is for setting the high speed needle.

John

kcasser

Not to hijack this thread, but I've SEARCHED and can't find what I'm looking for. A friend has the same engine but no manual. Could someone please tell us which needle is the High End and which is the Low End? We got the engine running on the bench, but as soon as it's lifted from the table, it conks out. We've been turning both needles every which way, but nothing works. Thank you for any help!

cutaway

The G21 .29/.35 were lapped iron, I believe the G21 .40/.46 were ringed. The rear rotor G40 racing engine was lapped.

jester_s1

kcasser- Here's your manual.

http://manuals.hobbico.com/sup/sup-manual-v1_1.pdf

kcasser

Jester - Terrific! Thanks!

Bax

My Feedback: (11)

The older SuperTigre engines had a high-speed needle that looked like a piece of wire that was pointed and threaded on one end and bent to 90-degrees at the other. That needle had to be opened 4-5 turns out from closed because it had very fine threads when compared to other makes.

Here's our normal procedure for the modern engines, but go to about 4-5 turns out on the high-speed needle instead of the 2-1/2 to 3 turns we state below.

bax
*********************
To properly set up your carburetor, there are a few steps...

Make sure the spraybar is set so that the fuel slot is pointed straight down the center of the carburetor. You will have to look through the carb from the bottom, with the venturi opened to full. Loosen the two screws next to the high-speed needle valve to rotate the spraybar so that the slot is centered.

The idle needle can be seen in the slot of the spraybar. It looks like a piece of wire that has the end squarely cutoff. It should be less than one-half way across the slot when the venturi is opened to full.

The high-speed needle should be opened about 2-1/2 to 3 turns out from closed.

All of these settings are very rich. You'll have to start the engine at about 1/4 to1/3 throttle. Once the engine starts, advance the throttle to full. You can then lean the high-speed needle until the engine is running just rich of peak RPM.

Once you have the high-speed needle set, you can retard the throttle a bit and use the idle needle to adjust the engine. Retard a bit, and adjust. Keep doing this until you have reached the desired idle RPM and mixture. Remember, since we started out with an intentionally-rich setting, the idle mixture will have to be leaned.

Finally, the midrange can be adjusted by rotating the spraybar a hair. Just loosen the two screws next to the high-speed needle and rotate the spraybar just a tiny bit. Either direction is OK. This will help you get a good transition and midrange.

kcasser

Thank you "Bax"! Very helpful. We look forward to getting this engine back on its feet.

LargeScale88

Very helpful Bax!


I have yet to run the engine yet, I guess winter is going to stay around a bit longer this year.


I'll let everyone know what happens.

Jason