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Priming problems?

Old 05-16-2005, 02:00 PM
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Skynyrd Man
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Default Priming problems?

Yep, it's that damn tower hobbies .46 again. I never have gotten this thing to run right but now I am wondering if maybe it is something other than my not knowing how to tune a engine.
I started the thing up to try and tune it so it would not die when I point the plane up. I thought I had it, I was running full throttle and pointed it up twice each time for 15 seconds. No problems. All of a sudden the engine cut down to like half throttle (no, the throttle did not move) This happened while the plane was level. I moved the stick back to half way and gave it full throttle. The engine responded nicely untill all of a sudden it started cutting down to about half throttle. Did the same stuff again but this time it died.
I went to start it again and noticed it needed to be primed. I could not get the thing to prime, I must have spun that prop 40 times before I got fuel to the carb. Also it did not hold the prime worth a darn.
Any ideals guys?
Old 05-16-2005, 02:19 PM
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britbrat
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Default RE: Priming problems?

Sorry Skynard -- sorry that you own one. I have one as well & it is a royal pain. I think that you have a big air-leak in the #$%^&@ thing somewhere. Probably around the base of the carb, or past the throttle barrel, or past the needle-valve o-ring, or past the backplate, or past the joint in the needle valve body where it separates to fit through the !@#$%^& rear support bracket, or past the front bearing. You get the picture?

A good mod is to ditch the carb & replace it with something else that fits & has a similar throttle-bore size. I put a TT .46 Pro carb on mine, & despite the smaller throttle bore it smartened up considerably -- not perfect like the TT, but better than it was. I had a spare carb, but for you it would mean throwing more $ at it. Of course you could have bought something else to start with -- a really good idea. I bought mine because it was cheap & I didn't expect much -- I got what I expected, only more so. I won't buy another one. It doesn't even make entertaining power because you can't keep it peaked. If you tune it so that it stays lit, it is quite mediocre in output. JUNK.

Old 05-16-2005, 02:24 PM
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2slow2matter
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Default RE: Priming problems?

What about fuel tank placement--is it correct? Sounds like your fuel tank might be too low. Just a thought....
Old 05-16-2005, 02:42 PM
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Default RE: Priming problems?

The tank is in a tower hobbies trainer so there is only one place for the tank. Wether or not it is in the right place I don't know.

I do have some more info to work with. The priming problem seems to only happen when the engine gets warm. I went back out to screw around with it some more and it was cool, it primed fine. Ran OK up to half throttle and would then die, no sputtering. It would die like flipping a switch. At this time the engine was warm and it would not prime again.

I will start checking for air leaks. I did not notice any bubbles in the fuel line while running.
Old 05-16-2005, 02:52 PM
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Default RE: Priming problems?

Try this:

Loosen the carb, then push it down firmly and re-tighten it.

Or, as long as you're going to loosen it, just go ahead and take it off. Remove the needle valve and give it all a good cleaning. Blow in the NV seat to make sure there's no blockage, and when you put the carb back on, make sure it seats firmly (And that the "O" Ring is good).
Old 05-16-2005, 03:14 PM
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2slow2matter
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Default RE: Priming problems?

Yes--the O ring may not be any good. As the eingine gets hot, the crankase will begin to expand a little--this could create a tiny airleak where the carb fits into. It wouldn't take much, and with a bad or non-seated O-ring, you could have problems.

Actually, I'm just shooting in the dark--I'm stumped.
Old 05-16-2005, 04:43 PM
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Default RE: Priming problems?

I tried reseating the carb, I thought you might be on to something there Minn. The clamp was not as tight as I would have liked. But I had the same results.
I have now removed the gas tank, it looked like the fuel line may have had a bit of a kink in it so I shortened the brass tubes just a little. One thing I am concerned about is that there is no way to rap foam around the tank. That is how tight a fit it is. The manual does not tell you to wrap it either. I did not see any foaming or bubbles in the fuel. Should I be concerned with this?
Old 05-16-2005, 04:58 PM
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Default RE: Priming problems?

Sure sounds like it is leaning out on you at top end. Take the carb back off, remove the needle valve and force some fuel thru the carb. Make sure it flows well thru the spray bar in the carb. If blocked, clean it carefully. Reassemble all of the above and try to set the needle where it was before. Restart and test. If it still quits open the needle a few clicks and see if there is any improvement. You may just be too lean or picked up some trash in your fuel.
Old 05-16-2005, 05:42 PM
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Default RE: Priming problems?

I give up, as far as I'm concerned Tower can shove this thing where the sun don't shine[:@][:@][:@]
I have blown every thing out, I have reseated the carb twice. The O ring looks fine. I replaced all of the fuel lines. I shortened the brass tubes in case of pinching.
I have waisted to much of my time on this engine. I have had 3 crashes because of it. Luckily only one caused minor damage. I am putting an Evolution in it.
To bad I'm not one of those jerks who sell things "like new" on Ebay.
I don't know, will see what Tower says tomorrow.[>:]
Old 05-16-2005, 05:43 PM
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Default RE: Priming problems?

Oh yeah, it still will not prime when warm.[:@]
Old 05-16-2005, 07:42 PM
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Default RE: Priming problems?

Does it feel like it's loosing compression when it gets warm? Maybe the cylinder isn't quite right, and it's expanding too much when hot. Just another shot in the dark.....
Old 05-16-2005, 08:00 PM
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Default RE: Priming problems?


ORIGINAL: 2slow2matter

Does it feel like it's loosing compression when it gets warm? Maybe the cylinder isn't quite right, and it's expanding too much when hot. Just another shot in the dark.....
Yes, I noticed it did spin easier when hot, also no prime and it wont stay running when hot.
I put my Evolution in it, at least I finally got a flight in. It's been a couple weeks.
Old 05-16-2005, 08:16 PM
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Default RE: Priming problems?

Not priming when hot suggests loss of crankcase compression. That could be from a loose backplate, or leaking front bearing.
Old 05-16-2005, 08:18 PM
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Default RE: Priming problems?

Good that you got a flight in. For the gas tank, If you need to, you can put foam in there. On my superstar(same thing as yours. I made a hatch on that part over the firewall and sutff as much foam as possible. It is great now...
Old 05-16-2005, 08:24 PM
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Default RE: Priming problems?

Skynard,
If you have Tower Trainer you are right, there isn't any room to put foam in. I learned on the same trainer (still have it today, 9 years after I learned) and I thought the same thing, that it needed foam in there. While it would be better to have it surrounded with foam, it will be just fine in this plane. Don't worry about the foam here.

It does sound like you are having motor problems. I have had one Tower engine and I found a great use of it. I cleaned it up and it makes a great paper weight on my desk. I would replace the motor and try again.

Hope this helps
Old 05-16-2005, 08:36 PM
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Default RE: Priming problems?

Ken,

Other than the covering on the plane I am happy with it. In fact that is the plane I just re-covered. Thanks for the tip on covering with the controls in place. I liked it so well that I am going to do the Rapture that way. I really took my time on it and it turned out nice. I'll try to get you some pic's tomorrow.

As for the engine, I bought this a month and a half ago from Tower. What are my chances of getting an exchange for a different model if this is bad. I think they have a 2 year warranty. I would prefer an Evolution but I don't think they stock them.
Old 05-16-2005, 09:00 PM
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Default RE: Priming problems?

All they can say is no, but I doubt they will. When you call them make sure you get a supervisor and tell them that you want a new motor. I'm sure you'll be able to do something with it.
Old 05-16-2005, 09:02 PM
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Default RE: Priming problems?

Skynard, one last trick to try. Put the Evo muffler on the Tower & see if that does the trick. The extra backpressure could keep the tank pressurized a bit more & ---who knows--
Old 05-16-2005, 09:04 PM
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Default RE: Priming problems?

I have read where others have had problems with their Tower engines. It sounds like TH was decent and took the moter back or replaced it. Lots of flyers that were sent replacement engines said the replacement engine worked great. The factory quality seems to be all over the place on the smaller engines. It seems like the larger engines are better. I have a TH 75 that runs great with tons of power. I have an Evolution 60 engine that ran crappy from the start and gets worse with each run so I am not all that impressed with Evolution. I haven't given up on it yet but I am getting close to it. [8D]
Old 05-17-2005, 02:23 AM
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Default RE: Priming problems?

I procured a THobbit 40 with a plane I picked up at a swapmeet. I fired it up after checking that the throws and such were correct. It ran fine...at half throttle, even though the barrel was at idle. then it ran fine at half throttle, even though the barrel was wide open! Now that my friends is a sign of an air leak, if I ever saw one. Nice little paperweight though!
Old 05-17-2005, 07:22 PM
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Default RE: Priming problems?

did you call tower?
Old 05-17-2005, 08:45 PM
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Default RE: Priming problems?

I have a tower .46 also, came stock with trainer... when i go to fire it up it will prime good, run good until i start moving it around, i can sit there and transition high to low no problem, but when i taxi around it seems to die... ive tried switching fuel lines making sure i had the correct one where it needed to go and all that... ive adjusted it to the only place where it will run. It just dies on me when it moves, also if i point it upwards it revs real high and quits like its leaned out? but thats the only place on the carb settings where it will run high and low...
Old 05-17-2005, 09:05 PM
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Default RE: Priming problems?

ORIGINAL: Pilot Chad

did you call tower?
Nope, had chemo today. Will call tomorrow after I get worked up dealing with my health insurance, for some reason they are not paying all of a sudden. A word of advice, don't ever piss off somebody that has a terminal illness. They can snap at any time. Especially when dealing with all the crooks in the insurance industry, harsh words but true. It is there job not to pay.[:@] A person should not have to deal with this crap when they are told they are dieing.
Old 05-18-2005, 09:39 AM
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Default RE: Priming problems?

Just got off the phone with tower, they said they would replace or repair it.
I mentioned that the engine is not talked about kindly here at RCU and asked for a credit for a different one and they said it was possible. Put it all down in a letter when returning the engine.
I took the polite route and called them before I called the insurance scammers.
Let you know what happens.
Old 05-18-2005, 09:52 AM
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Default RE: Priming problems?

Probably a good idea to talk to them first, [>:]

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