surestart wont stay running!

Either pop the head off and check the glow or go into a dark space (closet) and check the glow through the exhaust, just to make sure.

Pull the needle and push fresh fuel through the needle seat- this WILL flood the engine but will also float out any debris that may have been sucked in and stuck on the reed.  If you remember the needle setting the engine was running at put the needle back in and set it to that setting.  Now turn the engine sideways (plane and all probably) and slowly rotate it through a couple revolutions to push the extra fuel out of the crankcase.  There may be quite a bit in there, so do not force it through compression if it doesn't want to.

Apply a small quantity of fuel to the head/cylinder joint.  It should stay in place due to capillary action.  Flip the engine over and check for bubbles.  If there are no bubbles - good. Try starting now.  It may be "fixed" but it may require flushing every few runs, especially if there is a lot of pollen, floating seeds, or dust around.

For a proper prime of a cleared engine, with the exhaust ports closed prime one exhaust.  When the port opens the proper amount of fuel will enter the cylinder.

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If there are bubbles then the head is leaking.  15% nitro should have 1-2 gaskets.  Retighten the head.  If you still get bubbles remove the head, clean the head and gaskets.  If there are any errant marks in the head use very fine sandpaper on a piece of glass with some oil or fuel to flatten it back out.  Reassemble tight and check for bubbles again.

If the engines still do not run a tear down, inspection and cleaning with reassembly to prevent leaks is recommended.  Replace gaskets and reeds as needed.  A scratched or creased reed is probably junk.
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If you suspect the fuel tank is damaged then use a different fuel tank.  If the tank has crud in it that can cause all kinds of problems too, and flushing as above may eventually solve the problem.  

A party balloon bladder is easy to make, use a short brass tube, put some notches into the tube sides to make perforations consider putting a short piece of fuel line on the inside end of the hard tube.  Rubber band this into a small latex party balloon.  Use your fuel syringe to remove air, then fill (preferably in the same operation) and connect back to the engine.
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Oil content is most important.  These engines like castor oil, minimum 20% total oil with 1/2 of that castor.  If you have a common low oil fuel adding drug store castor is a good solution.  Drug store castor may not be degummed, but since it probably is not all castor that will be fine.  

These engines will run fine without nitromethane, however the difference between lean and rich becomes very small so it is difficult to adjust the needle well.  25% nitromethane is preferred as it does simplify operation and improve power.

I doubt a few tanks of low-oil fuel hurt these engines though as long as there was oil in the fuel.

Phil

Welcome FVO!!
Looks like you're in good hands allready, so
I'll just add......that's why they're called
SureStart and not ShureRun. (and roll eyes....now)
Don't get me wrong, I bought 25 of them when
they were going cheap.
Really, the education in getting one of these gems
to start and run is something to be proud of. Once
you get the ins and outs covered, you can smirk
when you hear someone say,"I can never get those
damn Cox engines to run".
again, Welcome to the forum.
Bob

Welcome to CEF, Viper Owner. I'll let you run with what you've got so far and pitch in later if needed. Bob speaks the truth. Once you get it going, you'll wonder why all the fuss.
Rusty

thanks for all the feedback! i originally posted as a guest under "frustrated viper owner" but i finally signed up as "hyper viper".. still working on it. i've tried everything but a new tank so far. i talked to the former ceo of cox, who now works for estes. he's lookin thru some old stock to see if he can find me a viper tank. i'll keep u posted!  Ron

Cool, nice to have good connections. You might notify Bernie at Cox International and let him know you need one too. He'll keep an eye out for you.
Rusty

RknRusty wrote:Cool, nice to have good connections. You might notify Bernie at  and let him know you need one too. He'll keep an eye out for you.
Rusty

 yeah! i just talked to him b4 i found Mike from estes.. all he has in stock is a couple of 1 oz tanks that we weren't sure would work in that skinny fuselage. still lookin tho. thanks Rusty

I am having a little trouble understanding what is wrong with your current tank. If it's not blocked, doesn't leak and vents then it should work.

You did say it already worked for one flight. Not questioning your reasoning, just want to make sure you are headed in the right direction.

Ron

to the Forum Ron , just reading your post and hope you can get things worked out .. Take your time and try not get too flustered . Eric

Cribbs74 wrote:I am having a little trouble understanding what is wrong with your current tank. If it's not blocked, doesn't leak and vents then it should work.

You did say it already worked for one flight. Not questioning your reasoning, just want to make sure you are headed in the right direction.

Ron

Hi Cribs! yeah, 1st flight resulted in a ''hard landing'', aka CRASH! blew the wheels off, killed the motor & bent the overflow tube on the tank. after that the original motor wouldnt restart. replaced the motor, fuel line, & upgraded my nitro content. i've done all the reed flushing & glowhead testing, all that crap. only thing i havent done is change the tank. my best guess is theres a pinhole somewhere letting the motor suck air. new motor runs just above half throttle for 10 to15 seconds & dies. especially if u try to adjust the needle valve. i'm waiting to find a tank b4 i take the plane apart again. its held together with screws in plastic, so every time u take it apart the holes are closer to stripping out. already had to replace 1 screw with a slightly thicker one. well, thats where i stand right now. thanks! Ron

Run it on an external test tank?
Phil

pkrankow wrote:Run it on an external test tank?
Phil

good idea Phil. probly do that next, all though it will involve unscrewing that bellypan again to get to the fuel intake on the motor. if i get desperate enough i might just mount an external tank on it.. i hate to sacrifice the slick look of the plane tho. thanks!  Ron

Mount the spare engine to a 2x4 and run that one on an separate tank then. I have benched a lot of engines this way. This way you can learn the correct operation without taking apart the model again since you are worried about the screw holes.

Phil

Hey Hype. Since I don't know your mechanical skill level, I want to drop a piece of mechanics 101 advice on you, but don't want you to feel insulted if you're way ahead of me.
So, regarding re-threading the screws into plastic, I understand your concern about wearing the threads out. But when you insert the tip of the screw, best with a perfect fitting magnetic screwdriver, be sure to first turn it backwards slowly and feel for it to drop into the leader thread, and then gently screw it in, That should be pretty stress free on your fragile beauty. Bracing for a ballistic tomato now.

Bye the way, I'be been in love with the Hyper Viper since I first saw one. I've been talking about building a balsa imitation for over a year now and have drawn up plans basically disguising a Flite Streak at the Viper. One of these days I'll actually do it. The biggest difference in my design is that the nose has to be shorter, but the set back canopy gives the illusion of a long snout. Here's my drawing that everyone else here is probably sick of seeing.
Rusty

Click to enlarge
https://i.servimg.com/u/f71/16/76/00/59/viper_10.jpg

That there is a sweet design Rusty. U gonna go profile with it or build a fuselage?

Profile. I want it to be a rugged fun flyer, nothing fancy, but still pretty.

Rusty; Shoot man U need to put that at the top/or at least closer that Looks GOOD and with the BIG MIG Toooooo!!ERic

Well, my dad brought over a butter tub full of old .049's. i figured with all the parts of 6 motors i could make one run. didnt take long! i found a complete one with a red backplate on it. looks like an old pt19 motor, so i put it on the test bench and the thing screamed to life in less than a minute! so my ol viper is ready 4 the sky again.. thanks again for all the help! Ron (i hope to get a short video of it soon.)

Well, I was wrong yall! thing still aint fixed.. I ran TWO tanks thru the latest motor! one on the test block, one mounted to the bottom half of the fuselage! both drawing fuel from the viper's own tank, ran great! reassembled the plane, back to the same crap! runs a couple seconds & quits. I did notice this time that when I would turn the prop backwards to engage the spring starter it would spurt fuel out the top of the tank. don't think that's normal.. I did the flush thing thru the needle valve, even tried another needle valve & new glow head. I give up. gotta be something to do with the tank. works uninstalled, doesn't flow right installed.. any ideas? thanks! Ron

Ron , I have never seen one of these but could it be that when you put the other half of the body on it is pinching the fuel hose ?  And bee sure the vent is open/clear . That's all I can think of trying to help you smoke this thing over , I know it can put you in a tail spin when it runs and now it don't. About the fuel back pressuring out of the tank ???? Eric

1 the engine is fine
2 you have a fuel feed problem

Fuel spitting out of the tank while flipping is not too unusual, although it probably indicates there is a plugged vent.

Take a fine wire and check all openings in the tank.  A single strand piece from inside a network or telephone cable is about the right size to pass easily.  The wire should enter and bottom with no resistance.  The wire should come out clean.  Take your fuel syringe and forcefully fill and empty the tank through the problem opening(s) several times.  Waste out this fuel, and clean/flush the syringe.  Consider doing this to all three openings.

Make sure the fuel line is intact, in good condition, has no pinches, and is clean.  Replace if there is any doubt.

Back flushing the needle is to remove free trash from the reed and NVA.  The needle should be gently wiped and reinstalled unless damaged.

Make sure there is sufficient air passage to the engine.

Phil

Turning backwards or forward is all the same to the reed. Either way the reed shouldn't let pressure pass back through it into the tank. So my question is, how else could pressure get from the crankcase into the tank to blow fuel back out of the vent? Is the engine's backplate the same in the plane as on the bench? Is there some way that the air intake behind the engine is being blocked? Can you show us a picture of the engine and tank in place with one side of the fuselage removed? I'm puzzled at the moment.
Rusty

It sounds to me like a blocked vent. It could also be set too lean on lauch and it's sagging and shutting down.