i have a super tiger 61, the newer model.
and i had it on a cub for a while, ran great, i put it on a cap, let it sit for a while, all of a sudden its running like crap, i can get it tuned nice on the ground, but once its in the air, i keep the throttle at the same spot, the engine rpm gos up and down, the engine starts to studder and eventually conks, every time,
when im on the ground cranking the throttle, i dont see any airbubles at all enter the lines, it idles perfect, runs great on the ground, just not in the air.

any ideas?

It could be overheating in the air, and quitting on you.

Set the main needle 4 clicks richer than you normally would
and try it. Give the motor 2 minutes at full throttle in the
air (allow it to get hot) before you pass judgement on it.

If it's not leaving a slight smoke trail, bring it down, and give
about three more clicks. Sometimes a motor has to be set
really rich on the ground, to prevent it from overheating in
flight.

Remember that the mixture is the only thing that will keep
the engine from overheating, and quitting on you. Hopefully
you are running a castor blend fuel in that motor.

Dave.

ill try setting it much richer, one thing i ment to do was put another plug in, but before i could do that i crashed, minor crash, ripped off the landing gear and thanks to nylon bolts, nothing else. sanded my wing a little, and sanded down a control horn on my wing. other than that it all looks good.

im running 30% in it, same fule i used in it before when it was on my cub,
it ran great on my cub, the same guy helped me tune it before and it ran like a champ, he helped me again today because it was conking on me, he thought it was perfect, and it still did it.
so ill try going richer and another plug,

one other thing i did is i have the engine inverted, on my cap i had the holls drilled as planned for the latteral engine, i just turned the mount upside down and went with it like that, so if anything the carb is a quarter inch or so lower than it would be per plan, im hoping thats not my problem because i like it that way.

another thing, in the air, if i cut the throttle way back, it would run smooth just over idle in for a landing when i could bring it in without conking.
and ran nice just a few clicks over.

its also the same prop i was using before on my cub, 13X5.

should i try a colder plug because of the higher nitro ?

sounds like it may be overheating. how much area do you have cut out behind the cylinder head to let air get out of the cowl? you need plenty of cooling air, and you need to have lots of area behind the engine for the hot air to get out of the cowl.

also- tigers need ti run rich so they leave bit of a smoke trail in the air. whenyou set the engine point the plane straight up to make sure it doesn't slow down.

ed

ive been running it without the cowling,
i havent even finshed the cowling.
ill try richer by a few clicks. see what happenes. i dont think there was much smoke inthe air, i cant rember.

When you get it started and tuned to your satisfaction on the ground, have two other people pick the model up by its wingtips with the engine running. Check for air bubbles in the fuel line with the engine running at various speeds. This is how you check for fuel foaming.

The resonant nature of the model changes when the main landing gear are off of the ground and the fuselage is allowed to vibrate as it pleases.

Good luck.

I think there's nothing wrong with the engine...since it runs fine in one model (Cub) and poorly in the Cap....????

First off: The high tank position with the inverted engine. These two things in combination make for lousy bedfellows!

You likely don't see the problem on the ground, because the nose high attitude of the Cap when sitting...masks the tank position error.

You must correct the tank position or nothing will ever work.

Lastly...30% nitro seems to be absolute overkill in this engine.


'Race

i use 30% because i run it in my 25% extra, so its out of convenice, i ran 30% in it for a while, while it was on the cub to,

so even though the carb is only a tad lower, would it realy make that much of a difference ?

what about using a c-line regulator

A "tad" lower carb centerline becomes ENORMOUSLY lower during Pos G maneuvering flight. Head pressure is multiplied by the force of gravity.

A regulator might work, but why mickey mouse up the fuel system when you could reach in and re-position the tank? Take the easy way out! Reposition the tank. Cost: $0.00

30% nitro out of convenience? Ok.

'Race

i would rather try a cline that lower the tank, looking at the design, lowering the tank is not realy much of a possability without alot of work,


true, a tad lower carb would be a large difference in high g manover flight, but if im flying stright and level, with no positive g forces, then the engine should run normally to a extent, when i flew the last couple times, i was flying very easy trying to see how my engine reacted to the changes i made on the ground. it didnt take positive Gforces to make my engine run like its been running.

if it were the case, the example your giving says that it well push more fule into the engine than it can burn, this should be a rich condition, where as most people are saying the symptoms of my engine in the air are of a lean engine.

i think mickey mousing is overexargating for adding a simple little cline. thats kinda like saying your mickeymoused your setup by adding a fule filter. aside from the fact, one the cowlings on, your not gonna see it, and ifs its 100% functional, then its more than worth the trouble.

This IS a hobby...and there is much to be gained by experimentation.

We simply have different philosophies where corrective actions are concerned. I prefer to fix the source of the problem rather than compensate for it elsewhere.

However, I can see in your first posts a stack up of issues (incorrect tank position AND and inverted installation) that can cause problems which are hair-tearing to resolve. And often made worse by the addition of complexities and other unknowns. It needs to be understood that the high tank position relative to the carb centerline necessitates a leaner-than-normal initial NV setting to get proper engine operation. As the fuel level diminishes...the mixture runs the risk of being TOO lean. Yes....a pump/regulator will bandage this nicely. And almost without a doubt...you will discover new problems to replace the old.

(and PS: Fuel filters are a HUGE source of air leaks....)

Have at it. Put in a pump. I hope it all works out well.

Best regards...

'Race

I have a ST 75 with a tuned pipe that eventually developed possibly similar problems. Originally I was running 15% in it and it would idle great but would surge at anything above 1/2 throttle. I changed to 5% and the problem went away. The other day I had my Ultra Stick 60 out (with the piped 75) and forgot my 5%. Put 15% in it again and the surging returned. Would run well enough to get it in the air and then start surging and finally deadsticking and HOT!

Have you tried MUCH lower nitro?

i have not tryed lower nitro yet.
a plug and going a few clicks richer are my next trys.

Your fuel tank is probably the majority of your problem. Unless you lower it, your going to have problems. I have a couple of inverted engines (OS 1.08s) I lowered the tank significantly and not problems at all.
Fuel is siphoning into the carb making it darn near impossible to tune or run right. It is also easy to detect with the plane just sitting around not running and see if fuel is dripping out of the carb.

ok i figuered out how to lower it, lotsa foam needed, but i think i can do it.

how is it supposed to match out,
in a stright line down the fuse, mine is towards the bottom, 3/4th of the way down.

In a straight line down the fuse...

I would suggest that the tank centerline be slightly BELOW (perhaps 1/4" to 3/8") below the NV assembly on the engine.

It's a pain in the ***** but you are doing the right thing in addressing the tank issue.

Good luck!

'Race

Tigres aren't designed for that much Nitro. 30% will cause it to run much hotter.

If you wan't to keep feeding it 30% , then you will have to lower the compression ratio by knocking up some shims to insert under the head.

if its inverted you want to run an idlebar glowplug as the fuel will puddle up in it and put the fire out if you have a regular non bar plug in it


john

Just a thought. How old is your fuel. Every time my engines start to run differently or quit in flight, I think I did something wrong. A new jug of fuel solves a lot of problems.

Keith

my fule is actually only about a month old, used it a few times, it should be fine, normaly is around this time.
what kind of bar glow plug should i get?
the bar well keep it running a better idle?
does sound good.
i think i have a plan now.
thanks guys

yes i believe an "idle bar" plug is what u need for inverted installations. keeps the fuel from cooling the element off when idleing



john