AllModesR/C

I have a Thunder Tiger trainer with the GP42 engine and it seems everytime I go out to the field I have a very hard time cranking the engine over. Here is what happens: I set the prop away from the compression point, spin the starter, and put the starter cone on the spinner. It will spin it but stop dead right where it becomes hard to turn over. This seems to happen mainly on cold days like below 40 F. I have had much better luck in warmer weather. Once I can actually get the engine spinning it starts no problem. I know it is not flooding which I know would hydro lock an engine. Any advice? The engine is new with less than 1/4 of a gallon of fuel ran through it.

1QwkSport2.5r

The oil residue gets thick inside the engine when it's cold. It will turn over easier when the engine is warmed as you noted in warmer weather. A) have your starter battery fully charged, B) use a (fully charged) rechargeable glow driver; NOT the one in your power panel if equipped, and C) warm the engine with a heat gun, hair dryer, exhaust pipe of your car/truck, etc. this will ensure success if you cannot transport the plane inside of your vehicle where it can be warmed that way.

thailazer

All Modes... What brand of starter and what kind of battery are you using? You might not have enough "oomph" to get it turning. I tried using a fair sized sealed gel cell from a UPS unit and it had very high source resistance and would not power my Sullivan starter well. Ended up going to a motorcycle battery which has very low source resistance and really turns the starter well.

proptop

My Feedback: (8)

My GP-.42 is kind of tight and difficult to start when the outside air temps are low...

One thing that you might want to try is...take the glow plug out, and put the throttle wide open...put a few drops of fuel in the carb and glow plug hole and motor it over w/ the elec. starter WITHOUT the glow plug.

Keep your face away from the plug hole, because fuel mist will come shooting out....

You will hear the engine loosen up as the lube gets worked-in...and it will be well primed too...

Put the plug back in and see iffn it'll start...

After that first time of the flying session, you shouldn't need to do this again...unless it gets really cold in between flights?

JPMacG

My Feedback: (2)

Squirt a little fuel in the carb and turn the prop over by hand a dozen times. The fuel will loosen up the old thick oil and it will turn more easily.

1QwkSport2.5r

Or just heat the engine case up a little bit. A warm engine will start a lot better than a cold one.

aspeed

I vote for heating up the motor a bit. I just tried starting a fairly new Norvel. 074 on a cold day, and the cylinder shrinks more, and sticks in the cold than the piston with the ABC style motors. As soon as I went inside it would not stick. Very nerve wracking day. My starter could not turn it over. It is a very small motor. I heated it a bit and it was better. Even a prime would make it stick.

GREG DOE

For whatever reason the GP-42's are set up very tight by the manufacturer. There is a lot more taper in the liner, then is typical with other ABC or ABN engines. A friend of mine was so certain that there was a problem with his, that he sent it back to the importer, and they returned it with the statement that the condition was normal. This was before Tower took over US distribution, and the engines were still made in Taiwan. All the suggestions of warming the engine, or removing the plug, and spinning it over, will help. Another suggestion that might help, (it worked for me) is just loosen the plug a few turns, and start it that way. After it has started, tighten the plug. Another trick that is for the more advanced "engine tuners" is to "lap" the piston in a lapping tool. Some people will tell you that you can lap the piston to the liner, and that does work, but it is better to lap the piston with a lapping tool to keep the piston from getting a taper like the sleeve. If you have any "true" engine experts in your club, they might have a suitable lapping tool. It's easy to remove too much material, and make your piston and liner useless, so this needs to be done slowly, and if possible by someone who has a good "feel" for what is right. Don't ask me how I know! Good luck, Greg

AllModesR/C

I use a regular hobby battery that is in my field box. I tried using a motorcycle battery and had the same issue. I will try the methods mentioned and see if they help.

Why did Tower discontinue all Thunder Tiger products?

gerryndennis

And it will be nicely primed. Connect your glow driver All modes, give it a back flip for any easy start. No problems with starters or batteries.

Dave H

f16man

One thing I have noticed is the wires that feed the starter are very wimpy, all mine I rewired with #10 wire and gained a lot of power for starting new or larger engines, my Sullivan will start my super tigre 3250 plugged in to my field box........Ever tried to jump a car with wimpy jumper cables???? same deal here....

1QwkSport2.5r

We are talking about a .40 (6.5cc) here, not a 32cc. If a standard field box won't start a .40, then there is something else wrong. Cold engines don't start very well. Pretty simple fix to warm the thing up a little or give it a wet prime and try it though doing both will net better results.

Not dealing with rocket science here.

aspeed

There is some merit in the comments. My starter will not turn over my Surpass .91 or even the tight .074 with a slightly discharged 5 amp gel cell. A real battery is no problem. I even had to upsize the wires on the old Cox glow clip when I lengthened the wires to go to the starter box because of the draw. Oh, rockets use a different science than the toy planes B-) Kind of a lower chemical science.

1QwkSport2.5r

I rewired my field box with larger wires behind the panel as well, but it still won't turn a 1.20 twin 2-stroke over, but it turns a 1.20 single 4-stroke okay though. If the 1.20 4-stroke is at 40F, it won't turn it over.

ocrcdude

My Feedback: (179)

Wow, some of the things you read about that happens in other parts of the States. To cold for the engine to turn over. Man that must be cold to gum up the oil. But, it seems like a lot of get advice from a bunch of cold weather flyers. Keep it up guys, and stay warm. The ocrcdude in a little warmer part of the States. Happy New Years guys!

aspeed

Ya, we hardly fly for 6 months here. It is building season. I run up motors on nicer days to check things out for better days. I never ran into the tight motor thing in the winter before. I guess the last ones I tried were not ABC. We used to use the old style lighter fluid for the cold weather primes when we were younger, but fly indoor electric in the winter now. I'd like to have Cali weather here, but suffer. Usually go to Fla. for a month, but not this year. (health insurance) Electrics aren't too bad in the winter if the batteries are kept warm.

AllModesR/C

How do you warm the engine up? I thought about connecting a hair dryer into the 12v in my vehicle but I'm scared it would draw too many amps and start blowing fuses. I once turned my vehicle on and blasted the heat with the airplane inside but it took 30 minutes to warm the glow motor up enough for an easy start.

You're so lucky to live in So-Cal. Someday..... Florida is too humid and rainy in the summer time for me. Southern Cali is perfect year round.

GREG DOE

Folks, unless you have owned one of these GP-42's you don't understand how tight they can be, even in warm weather! If you turn one over cold without a glo-plug it will squeak.
Gerryndennis, You would think that the back flip method would work, but it won't with a cold GP-42. I had two GP-42's, which I gave away to some 14 year olds. Maybe if you run about 10 gallons of fuel through them, the might loosen up? They are just an inexpensive plain bearing sport motor. It's TRUE that there is no substitute for a healthy starter. My starter will spin Nelson 40 racing engines, but didn't want to spin a cold Thunder Tiger GP-42. Another problem is that if you have a starter that will spin it over cold, that puts a huge amount of punishment on the connecting rod. If the engine lasts long enough to get broken in, the con rod will probably be shot. This suggestion will bring back memories. In the winter, we used to hold our engines in the exhaust from a running car to warm them up. Maybe the best suggestion is to find a 12 volt hair drier to warm it up. Let us know if you find a workable solution.

aspeed

I used a paint stripper gun to heat mine up, but had 120 volts in the garage. I would think "careful" heating from a distance with a propane soldering torch would help. It is hot and humid enough here in southern Canada in the summer. I would not want to be in Fla. in the summer. Just maybe 3 months max in the winter would be fine. We were going to buy a place a couple years ago. Cali. maybe but I don't think I can live there. Just noticed Greg Doe snuck in. I lapped my little Norvel a bit, and it stuck while doing that too. I twisted the rod and had to straighten it out. It was nasty tight as well. (kind of a weak***** rod)

AllModesR/C

Thank you. I thought all this time I was doing something wrong. But it's just the nature of this engine. I am almost thinking of buying an OS or something to put in the plane for winter flying.

1QwkSport2.5r

Ever had your hands on a Jett Engineering engine that has never ran before? If you haven't, you have no idea what tight is. These ABN GP-42 engines are not anywhere near as tight as a Jett is setup and my poor old Hobbico Torqmaster 90 started my Jett .35 in 40F temps. How? Bring a thermos full of HOT water to pour over the cylinder. You can't hand flip start a Jett unless you're incredibly talented (when it's brand new).

ocrcdude

My Feedback: (179)

Well guys if it's not the cold weather that makes the GP-42 hard to turn over, maybe a O.S. might be a good choice. I did have a Thunder Tiger 91 4 stroke that was hard to get to run right. Sold it. A buddy in our Club bought it. He reworked the carb, and it ran a lot better. To much trouble for me, so off it went.

1QwkSport2.5r

Some engines are just tight. Replacing a Thunder a Tiger with an OS is like replacing a Chrysler with a Geo in my book. The GP might be a snug engine - running it in will help with that. Starting a snug engine requires heat to expand the cylinder some. Imagine wedging a Soup can into a bell.

aspeed

I have had better luck with my Geo Tracker than with most of my Chryslers over the years.

1QwkSport2.5r

Okay, bad comparison. The geo is really a Toyota in disguise. I've put over 250,000 miles on Chryslers over the last 15 years.

The uninformed make irrational decisions like replacing a TT with an OS because it's hard to start when it's cold.