Kmot

My Feedback: (24)

I need some advice from the experts.

When I first started running this TTR .54 I thought it was all set to go. I got a good idle that stayed consistent and so I presumed all would be well.

Well, now that I am flying it in an airplane all is not well. The engine idles too fast, and the plane moves. I cannot keep it stopped from rolling. When I try to lower the engine speed, it will die.

I have done the following to this engine:

1) Opened the hole for the air bleed carb to 3/32 inch

2) Installed a glow plug heater so that the OS F plug always is heated to improve the idle

3) Adjusted the high speed needle, and then adjusted the air bleed screw along with adjusting the idle to get the lowest consistent idle without the engine dying.

4) Tried three different props of varying pitch and weight

5) Installed another OS F glow plug

While dong the adjustments, when I got a fairly low idle and the engine continued to run, I would blip the throttle and when returning to idle it would die.

The best I have been able to obtain is an idle speed that sounds good, sounds low enough to my ear. But to my surprise it is not, and the airplane rolls forward at a fast pace.

I have tried everything I know. I am out of tricks.

Fuel is Powermaster 15% Sport, new and fresh.

Glow plug is OS F, new and fresh.

Prop is currently a Rev-Up 11.5x6 Four Stroke.

gkamysz

My Feedback: (19)

What is the actual idle RPM?

Kmot

My Feedback: (24)

Last time I checked it was around 3300 when I first ran the engine before making any adjustments but it is lower than that now according to sound and I have not checked it again with a tach.

Kmot

My Feedback: (24)

It needs to slow down just a little. I was wondering if anyone had any 'thinking outside the box' ideas since I have already done all the standard stuff.

I might just add a brake busing to the tail wheel to add some drag, that would probably suffice.

the pope

Howdy Kmot I have just replaced the needle seat arrangement on mine after I found it would still allow fuel through even with the needle fully closed. I dont know whether this is related to your probs but worth checking all the the same. Cheers the pope

NM2K

My Feedback: (14)

I know that you are a very experienced modeler, kmot, but it truly sounds as though the engine just needs a lot of running time in order to break-in. Every Thunder Tiger engine that I have had has needed considerable fuss and attention when new. I suspect that the designer was trying to give the engine line a good reputation for being very powerful. As you know, this can sometimes lead to tractability problems before things settle down. It sure wouldn't hurt to get on the phone and talk with one of the importer's engine men, if the problem persists.


Ed Cregger

Broken Wings

My Feedback: (20)

You could try opening the air bleed hole in the carburetor slightly.

Kmot

My Feedback: (24)

Thanks Pope, I will check that just because.

Thanks Ed. Yes, I was also thinking it may just need more break-in time. Since it is a used engine I bought, I have no idea how much time it actually has on it. When I opened it up it looked nice and clean inside, yet the outside and in particular the muffler made it look like it had at least break-in time on it.

I normally run my engines on a test stand, and get them set to be reliable before I mount them in a model and go fly. However, my big wood test stand chassis has been unusable for months, needing a rebuild and so I just mounted the engine right away in the airplane and tried to make a go of it there.

I am in the middle of refinishing my engine test stand and when completed I am going to yank the engine out of the model and run a gallon or so through it and see if that makes a difference.

Thanks John. I have already enlarged it from stock, to 3/32 which is a significant increase. Do you think I should go even larger?

the pope

Howdy, Not trying to pick a fight with Ed ( I know how grumpy he can get ) but my 54 tt ran pretty much perfect from the get go . So I dont know how much running in they need. I guess every engine can be different. Cheers from the pope

Kmot

My Feedback: (24)

Maybe I'll throw a little Bon Ami up the carb! (old radial engine mechanics trick)

ABORH

Hi
Most posting replies have more experience than I but I shall share my experience. I have 2 of these engines both mounted inverted. One in a little Staudaucher, the other is in a TF Nobler. With my first engine ( in the Staudaucher) I mounted the new engine in the plane and had a similar experience to yours... the engine would not run right and the header would fall off. Well, I futzed with the muffler so much I finally stripped the threads in the head. So I yanked out the engine and out it on a stand. I JB welded the muffler into the head, set the the valve lash, and ran a lot of fuel through it. I did not drill out the air bleed hole, but I did get the engine to idle reliably with the air bleed screw completely opening the air bleed hole. It is a very nice engine. I do not have max and min RPMs or have the prop size at hand although I do use APC props.

With that experience, I ran the second engine on a stand until it performed well. The air bleed screw is all of the way out. Checked the valve lash and mounted it in the Nobler. I have no complaints about either engine. I just needed to be patient. (no problems yet with the header on this engine)

I hope that you find that yours runs nicely as well.

Kmot

My Feedback: (24)

Thank you ABORH for your post, I appreciate it. All levels of experience are worthwhile and yours is no exception!

I think you and Ed are both right. I am going to need to put more time on this engine, on a test stand. In fact I just completed the refinishing of my test stand chassis today. Tomorrow I will remount my PSP engine stand and be good to go.

jimmyjames213

My Feedback: (2)

i would say it just needs more breakin, i have a magnum 52 fs that had that same issue but i just flew it and after a gallon or two or so it tuned much much better. magnum engines seem to take a while to break in, i could not comment on tt as i only have one that is well used.

Kmot

My Feedback: (24)

Thanks Jimmy. BTW, love your avatar!!

Kmot

My Feedback: (24)

I put about an hour on the engine today. It really is a fuel miser, it just sips it. I burned 15 oz. of fuel. After about 5 oz. the engine was able to idle down to 2500 RPM. It shouldn't take much longer for it to be fully broken in. I think it was close already.


[youtube]http://www.youtube.com/watch?v=tThYL_OxuIM[/youtube]

mike109

G'day

I was given two Thunder Tiger four strokes (54 and 75) which the previous owner just could not get to run right. He had leaned the low speed needles too far AND they just were not run enough.

He was using all synthetic fuel and I used some with some castor in the mix and almost immediately I had them running fairly well but both still needed more running to be their best.

I had an earlier 54 some time ago. I think it had an air bleed carby (the recent ones were twin needle). Mine ran well (on castor mix) after about 20 minutes of bench running. I guess engines just vary a bit despite all the CNC gear around.

Mike in Oz

NM2K

My Feedback: (14)

It used to be, as you may remember, that engines that broke-in quickly did not last long. I can't help but hold it against some engine manufacturers that their engines break-in a little too quickly.


Ed Cregger

TedMo

By you opening the air bleed hole you allowed more air to enter which increases speed. Re adjust your low speed needle, if there is one.

Kmot

My Feedback: (24)

Thanks for your comment TedMo!

The air bleed screw is the 'low speed needle' and the screw can still completely close off the air. Enlarging the air bleed port was the recommended (by many) solution to an engine that would not idle, period.

Kmot

My Feedback: (24)

Just put another hour on the engine today. Got it to idle at 2100 with glow heat on.

Jazzy

Kmot,

I had a heck of a time with mine when I first got it. I could have either good idle to low mid or low mid to high speed but not both. Adjusted for a good low end speed it would starve and die at half throttle. At a good high speed setting it would load up down past half throttle and die. I sent it back and they said it ran fine.
I tried opening up the air bleed hole but that didn't work. (Years later I thought about it and I don't think I drilled all the way into the carb throat...)
I took a fine dremmel stone and ground a tiny lobe on one side of the throttle barrel. This allowed more air to enter the engine at lower throttle settings. Worked like a charm.

The 54 needs around a gallon through it to run well while the 91 needs two or more to be happy.

Sounds like you're on the right track. Be patient, you're almost there!

Kmot

My Feedback: (24)

Thanks Jazzy.

Jazzy

Tom,
I looked back and saw that you are using an 11.5 x 6 in prop. My engine does not like props over 11 inches so I compromised with an 11x7 APC. A 12 x 6 would not run well at all. I never tried an 11.5 in prop...
I don't have my prop loading program on this computer so I don't know how much difference there is between the two but it seemed the 11" let it rev easier during break-in.
It might be worth a shot at a slightly smaller diameter.

Kmot

My Feedback: (24)

Actually, I first ran it and flew it on a Zinger 11x5.

I switched to a Royal 11x7 composite prop but even though I thought I balanced it, it made the engine shake violently. So then I switched to the Rev-Up 11.5x6, in the hopes the slight added weight will give a little better flywheel action.

Well, another wrench may have been thrown in the works. I have been using a spinner hub that adds weight, as well as scale looks. But it has come loose a few times when the engine kicked. I know it's going to do it in flight one day, so I ordered the double locking nut set from Thunder Tiger and have installed it. It weighs less than the spinner hub, so who knows?

Sport_Pilot

If it is like the TT .91 four stroke, it needs a cooler plug for the larger props. But it will prefer the smaller props unless the pitch is very low.