Clunk VS Non-Clunk tanks

Old 09-08-2014, 02:13 AM
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Default Clunk VS Non-Clunk tanks

Hi all,

I've always wondered what the benefits and caveats of a clunk tank were and why some manufacturers (including Mugen for the MBX7T) still use traditional tank systems without a clunk. Can someone explain why you might want to use a non-clunk tank?

Thanks,
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Old 09-08-2014, 07:55 AM
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In my experience, the only advantage to a non clunk system is you don't have to worry about the clunk getting stuck and thus not letting it float in the fuel and not letting it pick up fuel. Occasionally that will happen, depending on the tank and setup of the clunk.

But having said that, I'd pick a clunk every time. Knock on wood, I've never had a flame out while running a clunk and it seems like I have had easier and more consistent tuning.
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Old 09-08-2014, 08:04 AM
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Thanks for the reply! I guess that raises the question: why do some manufacturers opt to use a non-clunk tank, like in the MBX7T?
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Old 09-08-2014, 05:19 PM
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That was the only thing I didnt like about the RC8.2. I havent had a failure from running a clunk but my 8.2 has died a number of times from being upside down too long; thankfully never during a race as the marshals have always righted it in time. That being said, the clunk in my Tekno is in a really odd position after the last race I ran... should be facing 90 clockwise.
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Old 09-08-2014, 06:19 PM
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Clunks need to be checked periodically because they do move from chassis flex sometimes and from tipping so much. They need to be about 2mm from the front wall of the tank in that little well. Some fuel tanks need to have the slosh guards trimmed at an angle also to prevent the clunk from getting stuck on top of the guard.
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Old 09-08-2014, 09:54 PM
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Originally Posted by madweazl View Post
That was the only thing I didnt like about the RC8.2. I havent had a failure from running a clunk but my 8.2 has died a number of times from being upside down too long; thankfully never during a race as the marshals have always righted it in time. That being said, the clunk in my Tekno is in a really odd position after the last race I ran... should be facing 90 clockwise.
yeh it should be done the middle buddy you might need to check as mentioned they do move a bit i think you need to push a bit more fuel liine back in and it would be less the 1/4 inch or so and that should stop that from happening to the clunk section on that fuel tank
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Old 09-09-2014, 10:27 AM
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The reason a lot of manufacturers don't make there tank clunk style is because ifmar and possibly roar have a rule against using a clunk style tank in there races! It's beyond me why this even matters but I know ifmar races you have to use the special gas tank part losi gives you in there kit to make it legal.
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Old 09-09-2014, 11:09 AM
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Originally Posted by Matt Piva View Post
The reason a lot of manufacturers don't make there tank clunk style is because ifmar and possibly roar have a rule against using a clunk style tank in there races! It's beyond me why this even matters but I know ifmar races you have to use the special gas tank part losi gives you in there kit to make it legal.
I think you are confused with the 125cc maximum capacity regulation, which some manufacturers have a tank which can be on the large side, and you have to fit a small insert into the tank bottom in order to make sure your tank will not be too large.
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Old 09-09-2014, 11:28 AM
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Originally Posted by Eivind E View Post
I think you are confused with the 125cc maximum capacity regulation, which some manufacturers have a tank which can be on the large side, and you have to fit a small insert into the tank bottom in order to make sure your tank will not be too large.
Like the ae tank inserts, I've seen those..

A few years ago I read the losi building manual and remember seeing that the kit comes with a little extra part for the tank to change something with the function of the clunk (I believe to keep it from being able to move) I read that it's because ifmar doesn't allow clunk style tanks. Inall my racing I've never had to do an ifmar event so it didn't really cross my path to worry about it but I do know I read somewhere here that the losi tank stock is not legal in ifmar events.
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Old 09-09-2014, 01:07 PM
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Originally Posted by Matt Piva View Post
Like the ae tank inserts, I've seen those..

A few years ago I read the losi building manual and remember seeing that the kit comes with a little extra part for the tank to change something with the function of the clunk (I believe to keep it from being able to move) I read that it's because ifmar doesn't allow clunk style tanks. Inall my racing I've never had to do an ifmar event so it didn't really cross my path to worry about it but I do know I read somewhere here that the losi tank stock is not legal in ifmar events.
Just went through the manual, the little part you are talking about is the 90 degree fitting coming out of the tank. It's function is to meet EFRA Rules by not allowing the clunk to move or come out. There is nothing that says clunks are illegal for IFMAR events.

Page 42
http://www.tlracing.com/ProdInfo/Fil...4%20Manual.pdf
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Old 09-09-2014, 02:05 PM
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Originally Posted by Sean Dickinson View Post
Just went through the manual, the little part you are talking about is the 90 degree fitting coming out of the tank. It's function is to meet EFRA Rules by not allowing the clunk to move or come out. There is nothing that says clunks are illegal for IFMAR events.

Page 42
http://www.tlracing.com/ProdInfo/Fil...4%20Manual.pdf
Ok so your saying I was correct in my statement other then the exception of efra instead of ifmar!
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Old 09-09-2014, 02:16 PM
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No, it keeps the clunk from moving forward or backwards. The clunk still does its function of going to the top of the tank when flipped over, and the bottom when on its wheels. So, like I already said clunks are legal at all events.
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Old 09-09-2014, 02:19 PM
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Originally Posted by Sean Dickinson View Post
No, it keeps the clunk from moving forward or backwards. The clunk still does its function of going to the top of the tank when flipped over, and the bottom when on its wheels. So, like I already said clunks are legal at all events.
This is because you could alter the fuel tank capacity by pushing/pulling the fuel line forward/back.
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Old 09-09-2014, 03:03 PM
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Originally Posted by sickboy View Post
This is because you could alter the fuel tank capacity by pushing/pulling the fuel line forward/back.
That is the correct answer, the fitting is used to prevent the clunk and tubing being pulled as far back as possible leaving more capacity for fuel.
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Old 09-09-2014, 06:07 PM
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Originally Posted by DBL15 View Post
yeh it should be done the middle buddy you might need to check as mentioned they do move a bit i think you need to push a bit more fuel liine back in and it would be less the 1/4 inch or so and that should stop that from happening to the clunk section on that fuel tank
I know how it should be, as indicated in the comments My point was that it moved to a crazy position.
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