.049 runs good for 50% of the time then coughs and dies

While this gets brought up frequently and I do know you are knowledgable, but I have to ask how the engines are mounted, upright or sideways, as well as where the fuel pick-up is located? In the bottom for standard flying, and to the 9'oclock position for control line. I have caught myself with the pickup being in the wrong orientation before....

Hi The engines all mounted vertical.
I am using the aluminum tub bent as Gibeault describes. It is in the 8 pm position away from center of flying circle.

Thanks
Ice

Screw the needle valve down until it seats. Pressurize the tank with a large syringe and watch and listen for leaks. Put oil on the screw heads, tank connection, case to tank, needle valve body and needle. Double check the reed, I have seen brand new reeds fail. Flip them over and re try. If you put a 5 oz. syringe with tubing onto the venturi and your able to pull the plunger back even the slightest, the reed isn't sealing. I have even had the need to true up the reed seat in the lathe. I just took a faint pass on the center.

Hi Darren, There's always the possibility that the tank screws are leaking where they seat. If so; it could be because of a couple different scenarios.
The "best case scenario" would be that your crankcase(s) weren't tapped deep enough for the screw's fillister-head to tighten against the backplate. This was not uncommon.. and can be checked by measuring the thread-depth using a tank-screw.. and then the depth of the bore. You may find that there's enough difference to cut a couple additional threads; using a 2-56 (American Standard Machine-Screw size) bottoming-type tap.
Another scenario would be that the backplate has issues where these tank-screw heads seat. If any of the screws were ever over-tightened.. they could have opened-up (enlarged) the seat-area of the soft/pot-metal. Look for leaks around all four screw-heads.. and be aware of how-well or "if" all four screws are seating/sealing. You "can" make seals.. if the backplate holes aren't damaged too badly. I've made some from kitchen-gloves (Playtex rubber-type) I used a paper hole-punch to make these..

swap back plate bet u disasemble clean 2 engine at same time and change back plate golden bee us its own desing back plate wit its extra part inside ventury look for its golden look inside if some color remain

Thanks Roddie
Excellent suggestions. I'll put them into affect hopefully will fix the issues!

Thank you!

roddie wrote:Hi Darren, There's always the possibility that the tank screws are leaking where they seat. If so; it could be because of a couple different scenarios.
    The "best case scenario" would be that your crankcase(s) weren't tapped deep enough for the screw's fillister-head to tighten against the backplate. This was not uncommon.. and can be checked by measuring the thread-depth using a tank-screw.. and then the depth of the bore. You may find that there's enough difference to cut a couple additional threads; using a 2-56 (American Standard Machine-Screw size) bottoming-type tap.
    Another scenario would be that the backplate has issues where these tank-screw heads seat. If any of the screws were ever over-tightened.. they could have opened-up (enlarged) the seat-area of the soft/pot-metal. Look for leaks around all four screw-heads.. and be aware of how-well or "if" all four screws are seating/sealing. You "can" make seals.. if the backplate holes aren't damaged too badly. I've made some from kitchen-gloves (Playtex rubber-type) I used a paper hole-punch to make these..

Roddie,

I think the plastic washers put under the backplate screw heads will be good to prevent fuel losses there. Otherwise no matter if the screw head seats are air-tight or not, because the tank communicates with the outside atmosphere through the tank vents, anyway. Sorry if I misunderstood you message.

Don't forget the most common ailment of the reedies, the crank to case seal. It does not take long for play to lose the seal. Pull the crank forward and try to rock the crank up and down using the prop. If you can see the piston moving up and down, that will be the culprit. Also check all the other normal leaks and the reed etc. A new case would be the fix for the case leak. Sometimes I make a bushing up, but that is too fiddly for most people, and the cases are quite cheap.

Darren, I forgot to ask. After these cut-short flights; have you tried measuring the amount of fuel needed to refill the tank? If it requires an entire 7-8cc's re-fill.. then you're losing it all somewhere. aspeed (Alan) mentioned the "crank to case" fit.. and if worn; maybe there's what I'd call blow-by.. of raw-fuel out-through the front-end? You wouldn't notice this in the pit.. or maybe not-even during static testing.

EDIT: If the reed is sealing properly.. then on the down-stroke of the piston; the crankcase has positive-pressure which might blow some unburned/raw-fuel out of a worn crank-journal.

Just a bit more to think about bro.

Hi Roddie
Only burns half tank so not all disappeared. I keep looking and little by little knocking out possibilities.
Thanks very much!
Darren

roddie wrote:...somewhere. aspeed (Alan) mentioned the "crank to case" fit.. and if worn; maybe there's what I'd call blow-by.. of raw-fuel out-through the front-end? You wouldn't notice this in the pit.. or maybe not-even during static testing.

EDIT: If the reed is sealing properly.. then on the down-stroke of the piston; the crankcase has positive-pressure which might blow some unburned/raw-fuel out of a worn crank-journal.

Just a bit more to think about bro.

That's what took out my Golden Bee block...lots of hours over lots of years. I could see it pump raw fuel and bubbles on the test stand. I never did take the time to try other, newer cranks.

I have a few anodized crankcases that are all slightly loose fit with the shaft and I always wonder if this loose fit is an advantage because of lower friction as Paul Gibault advises in his Mouse race paper, or disadvantage for weaker seal. True that their surface hardness better resists abrasion if the prop is unbalanced but somehow I still favour the oldschool old stock 049 crankcases with exact fit and no anodization. I make sure my props are always balanced though. The crankcases last a helluva long time then.

On my leaky cases I could see a wear spot on the bottom back of the crank hole, like when it would push the crank down when firing. I could see it and even measure to see something was oval. They are faster when loose, but at a certain point they leak, and rev up and down and generally make you mad. Of course it can be some other thing too. Maybe the nipple has a crack or some other tubing or gasket/O ring. I pressed in some bushings on the worst ones but never tested them since, as I got away from the reedies, and also I would have to press them apart to know which ones are which. Probably have a dozen, and two were rebushed IIRC.