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Old 09-03-2008, 05:57 AM   #1
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Angry EK4 - Piston and Ring

Hey All,

I am hoping someone can help me.

I've had an EK4 since they first came out. I drove it 2 or 3 times and then put it away for 3 years. I got it out last week and installed the "improvement" kit that I got free from Thunder Tiger that I never installed in hopes that I could take it out for a spin. I tried starting it for 1/2 hour with no luck so I pulled the head off and discovered that the piston had a big chip out of the side and the ring was damaged.

I have been trying to find one with no luck. I found a ring and ordered it, ehobbies showed a piston in stock but they just cancelled my order saying they did not have any.

Anyone have a piston source for the Pro70 engine? The part # is AN0914.

If I can't find one, I might just get a 5th scale with a Zenoah engine.
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Old 09-03-2008, 06:32 AM   #2
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Try Ace Hobby directly, they're the distributor for Thunder Chicken.
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Old 09-03-2008, 06:39 AM   #3
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You should be able to get the parts from Thunder Tiger. the engine came from their helicopter line, which is still available.

http://www.tiger.com.tw/product/9607.html

It's very important that the ring be installed properly, and that the piston be installed in the right direction. There's a gap in the ring that indexes with a pin in the ring groove. This prevents the ring from spinning when the engine is running. This is important because, if the ring were allowed to spin freely, the gap in the ring would eventually enter one of the many ports in the sleeve, and it will catch the edge of the port and damage the piston. It appears that is what caused your current problem. Also, the piston has a relief in the skirt that must face the crankshaft. If the piston is installed facing the other direction, the same bad result will happen. Basically, if the gap in the piston ring even aligns with one of the ports, BOOM! So, be sure to check that the ring stays aligned with the pin in the groove (it's easy for it to slip out of alignment before the piston is fully installed in the sleeve), and be sure that the piston is facing the proper direction so the ring gap runs on a solid part of the sleeve where there is no port, and you should be good to go.

Last edited by SteveP; 09-03-2008 at 06:53 AM.
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Old 09-03-2008, 07:26 AM   #4
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Quote:
Originally Posted by SteveP View Post
You should be able to get the parts from Thunder Tiger. the engine came from their helicopter line, which is still available.

http://www.tiger.com.tw/product/9607.html

It's very important that the ring be installed properly, and that the piston be installed in the right direction. There's a gap in the ring that indexes with a pin in the ring groove. This prevents the ring from spinning when the engine is running. This is important because, if the ring were allowed to spin freely, the gap in the ring would eventually enter one of the many ports in the sleeve, and it will catch the edge of the port and damage the piston. It appears that is what caused your current problem. Also, the piston has a relief in the skirt that must face the crankshaft. If the piston is installed facing the other direction, the same bad result will happen. Basically, if the gap in the piston ring even aligns with one of the ports, BOOM! So, be sure to check that the ring stays aligned with the pin in the groove (it's easy for it to slip out of alignment before the piston is fully installed in the sleeve), and be sure that the piston is facing the proper direction so the ring gap runs on a solid part of the sleeve where there is no port, and you should be good to go.
Thanks Steve!

Thunder Tiger probably has the worst site ever but I did find one that let me order at thundertiger4u.com. Hopefully they actually have it!

I'd rather get this beast running again rather than sell it.
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Old 09-03-2008, 05:53 PM   #5
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Well I just got an email from thundertiger4u saying they are out of stock and will send it when it is back in stock. Since this engine is discontinued I guess I will be waiting a pretty f'ing long time huh?

I will never purchase another Thunder Tiger product as long as I live. In fact, I think Mr Tommy would love to meet my EK4. I'll try to video it. That would give me SO much more satisfaction that selling it for $100 for scrap.

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Old 09-04-2008, 05:46 AM   #6
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If you want to sell it for $100 LMK, I'll get it running again.
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