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Die-cast Crank Case on a stunt tank... issue

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Die-cast Crank Case on a stunt tank... issue

Post  WingingIt74 on Sun Jan 20, 2013 3:09 pm

So I built this engine for my wife as a gag gift, and called it Suz's Pink Panther. Well, I've been trying to get it to start. It will run on prime, but it causes backpresure into the tank and the fuel shoots out of the tank like a nice fountain. Any ideas why?

The other thing that surprised me is that the pink paint isn't fuel proof, I just figured it would be.


Last edited by WingingIt74 on Sun Jan 27, 2013 10:55 am; edited 1 time in total

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Re: Die-cast Crank Case on a stunt tank... issue

Post  Cox International on Sun Jan 20, 2013 3:29 pm


Never tried it with a stunt tank but DC engines (non SPI) did run well with a conventional 5cc tank.

The metal tanks are not a good match for the DC crankcases. For one you need to use 2 CC gaskets, one DC and one extruded. The other issue is increased CC volume because the DC reed retainer is not in place. That, together with SPI may cause the issues. It is not a combination we have ever tried.

The powder coating should be fuel-proof, at least to some degree.
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Re: Die-cast Crank Case on a stunt tank... issue

Post  WingingIt74 on Sun Jan 20, 2013 3:45 pm

I have the dual gaskets on this one. Not sure why the crank case has pressure instead of a vacuum. Also not sure why the reed is allowing back pressure into the tank.

My first runs with the Killer Widow was on a 5cc tank and it has SPI. I wonder if it has something to do with the tubes on the stunt tank. Where are the vent holes on them compared to a babe bee back plate?

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Re: Die-cast Crank Case on a stunt tank... issue

Post  Surfer_kris on Sun Jan 20, 2013 3:48 pm

WingingIt74 wrote: It will run on prime, but it causes backpresure into the tank and the fuel shoots out of the tank like a nice fountain. Any ideas why?

I've had that a long time ago, turned out the front of the tank was made too thin. It will then split when tighten up against the case, and the crankcase pressure goes into the tank.
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Re: Die-cast Crank Case on a stunt tank... issue

Post  WingingIt74 on Sun Jan 20, 2013 3:51 pm

I'm going to try that tank on another engine, just curious....

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Re: Die-cast Crank Case on a stunt tank... issue

Post  WingingIt74 on Sun Jan 20, 2013 4:33 pm

I swapped the tank to another engine and it ran. It was a non-SPI engine, ran fine. Looked and Brandon's BW and it's SPI. I don't get it....

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Re: Die-cast Crank Case on a stunt tank... issue

Post  pkrankow on Sun Jan 20, 2013 6:05 pm

Planning on trying this with a cast crankcase (diesel) that I ordered. I would like to know what is up too. One of the 5cc stunt tanks I ordered is going on it with a Tygon pickup.

I wonder if crankcase air is entering the screw holes and pressurizing the tank. The gaskets for the DC cases do not surround the screws.

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Re: Die-cast Crank Case on a stunt tank... issue

Post  WingingIt74 on Sun Jan 20, 2013 6:12 pm

pkrankow wrote:I wonder if crankcase air is entering the screw holes and pressurizing the tank. The gaskets for the DC cases do not surround the screws.

Phil, that is an excellent point. Even with 2 gaskets, it may not be seating/sealing correctly.

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Re: Die-cast Crank Case on a stunt tank... issue

Post  pkrankow on Sun Jan 20, 2013 6:21 pm

I was going to say make a metal shim gasket to go between the two gaskets, but I don't know if that will work.

Can the plastic reed retainer be used with the metal tank?

Guess I'll find out in a week or so when my stuff arrives.

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Re: Die-cast Crank Case on a stunt tank... issue

Post  WingingIt74 on Sun Jan 20, 2013 6:24 pm

Here is a pic of how the gaskets interact.

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Re: Die-cast Crank Case on a stunt tank... issue

Post  WingingIt74 on Sun Jan 20, 2013 6:33 pm

pkrankow wrote:Can the plastic reed retainer be used with the metal tank?

It does and doesn't, as only the tip of the tank venturi will fit. I was thinking the same thing. I think if you trim one down, just for the plastic gasket, it may work.


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Re: Die-cast Crank Case on a stunt tank... issue

Post  pkrankow on Sun Jan 20, 2013 7:10 pm

What does the back of the DC case look like?

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Re: Die-cast Crank Case on a stunt tank... issue

Post  WingingIt74 on Sun Jan 20, 2013 9:09 pm

the same shape as the top gasket shown below.


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Re: Die-cast Crank Case on a stunt tank... issue

Post  RknRusty on Sun Jan 20, 2013 9:14 pm

I think Pkrankow is right, that it's blowing through the screw holes. Silicone sealer will fix that if that's what is happening.

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Re: Die-cast Crank Case on a stunt tank... issue

Post  Surfer_kris on Mon Jan 21, 2013 12:29 am

Yes those gaskets are no good. Can't you use a regular one?

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Re: Die-cast Crank Case on a stunt tank... issue

Post  WingingIt74 on Mon Jan 21, 2013 7:39 am

They won't work by themselves, no.

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Re: Die-cast Crank Case on a stunt tank... issue

Post  pkrankow on Mon Jan 21, 2013 8:41 am

Wild and crazy idea, cut a gasket that is the combination of both.

I have had an extruded case engine that a tiny crumb of an old gasket made the engine not run well, and vibrate like nothing else.

I would LOVE it if you got this working before my engine shows up.

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Re: Die-cast Crank Case on a stunt tank... issue

Post  tru168 on Mon Jan 21, 2013 8:52 am

Hi,

Normally when I have gasket problem, I will use high temperature RTV silicon rubber gasket, don't tighten the screws too tight, wait until silicon cured and tighten the screws , it works for me.

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Re: Die-cast Crank Case on a stunt tank... issue

Post  Surfer_kris on Mon Jan 21, 2013 11:04 am

I must be thick, but I still cannot see why one couldn't use the regular gasket with the regular tanks...
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Re: Die-cast Crank Case on a stunt tank... issue

Post  WingingIt74 on Mon Jan 21, 2013 11:21 am

The DC case is about 3/4 of the wall thickness of the extruded case larger. You can see how much different the diameters are of the gaskets in the pic above.

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Re: Die-cast Crank Case on a stunt tank... issue

Post  Surfer_kris on Mon Jan 21, 2013 12:02 pm

I had to have a look for myself, and yes the regular gasket is a little too small around the outer rim (it might still seal though if perfectly centered). One can easily cut a new gasket, the outer size and shape doesn't matter. I cut the right-hand one below some 30 years ago, and meant to trim off the edges once I disassemble the engine the next time...

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Re: Die-cast Crank Case on a stunt tank... issue

Post  WingingIt74 on Mon Jan 21, 2013 12:09 pm

I'll have to see if the depths are different between the tank and the backplate also.

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Re: Die-cast Crank Case on a stunt tank... issue

Post  pkrankow on Wed Jan 23, 2013 4:17 pm

My diesel bomber is here. The plan is to put it on a bee tank, just haven't decided which tank to use!

Actually the plan is to put a glow head on it, run about 2 oz of glow through it, then try it on diesel the way it is. Bad mojo might be caused by making too many changes at once ( lol ).

The plan is to make a square gasket that the round corners match the existing gasket designs, the inside hole will be to fit the tank. I and not going to consider crankcase stuffing, or lack of stuffing, at this time.

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Re: Die-cast Crank Case on a stunt tank... issue

Post  WingingIt74 on Sat Jan 26, 2013 12:50 pm

I cut a reed retainer and I don't have the pumping issue any more. Now I just can't get the stupid thing to run...... I give up. Last nigh I could get it to oscillate with maybe a brief run then it would die. I think I'm just going to swear off of DC cases, it's not worth my time.

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Re: Die-cast Crank Case on a stunt tank... issue

Post  Cox International on Sat Jan 26, 2013 12:56 pm

WingingIt74 wrote:I cut a reed retainer and I don't have the pumping issue any more. Now I just can't get the stupid thing to run...... I give up. Last nigh I could get it to oscillate with maybe a brief run then it would die. I think I'm just going to swear off of DC cases, it's not worth my time.

The DC case is not the issue - we sell loads of them every month and our Pink Panther placed close to top in a previous tach race.

Try taking the tank bowl, with reed and retainer installed, attach a piece of fuel tubing to the veturi side and do the blow/suck test. If the reed does not seal on the suction part, carefully grind around the hole where the reed sits.



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