JohnRC

I have a Jett bse 35. After flying less then a minute it begins to lose power. I have a 9x6 prop on it. It is most likely over heating.
I land it right away and it does fell hot enough to burn your finger on the engine bottom.
We have been taching it up and first bring it down 300rpms then the next flight 500rpms.

How rich is it suggested that we make it?

Thanks
John

bob27s

My Feedback: (19)

Hi John....

Thanks for writing.

Tell me a little bit more please .....
1) Is the engine new ? Have you completed the break-in process? What prop did you use for break-in?
2) What fuel are you using ? (reference only)
3) What plug are you using ? (reference only)
4) You noted a 9x6 prop. Is this an APC 9x6? Other brand ?
5) Have you measured ground peak rpm? If so, what is the engine turning ?
6) What aircraft is it installed in? Possible to post a photo of the installation ?
7) Fuel tank -- conventinal installation ? Or bubble-free tank ?

The engine should get warm/hot at normal operating temperatures... just like any engine ... but should not get THAT hot....

First... if it got that hot... make sure you check and re-tighten the head bolts.

You want to back the engine off at least 500-600 rpm for flight. I prefer to back these engines down closer to 800 rpm.

If i recall, the instructions Dub provides with the engine recommends 700-1000 rpm down for the first flights, and then work from there.

Always error on the rich side. Then sneak up on it as the engine gets more time on it.

With the tuned exhaust... the engine will unload quite a bit in the air. As it does, it requires more fuel. Thus you have to set it just a bit richer on the ground prior to launch.

You noted here that it starts to lose power after it is in the air.....
Aside from setting the high end needle appropriately,
if it runs well on the ground (just slightly rich), but leans out a great deal in the air to the point the engine gets hot, blows a plug, or otherwise shuts down, that often indicates a fuel system issue.

When you are working with the rpm and energy output of the Jett engines, fuel foam becomes a risk if the fuel system is not properly padded and isolated from the airframe. You may not even see foam or bubbles occur on the ground - but as the engine unloads in flight... it occurs.

Try just richening-up the engine first.... that may solve all of your issues.
Ensure the fuel feed and pressure lines are clear, no kinks
If need be, drop down to a 9x4 or 9x5 prop for a flight or two ..... let the engine run at higher rpm while just a bit rich.

Let me know how you make out
Bob

rmenke

My Feedback: (13)

John:

I am blessed with superior experience, haveing done everything stupid a person can do to a plane and/or engine. Double check your prop stud to be sure it is not bottoming out on the crank. Take a piece of your fuel line and double it back on itself. Can you still blow through air with no problem. If not, you are suffering from cheap tubing sindrome. Appears some of the suppliers came across some high margin stuff they passed on to everyone. It will coollapse into itself with a simple right angle bend, and puncture like crazy. If you did not see it come off a DuBro reel, and its a bright color, better get rid of the stuff, quick. Apparently Prather went out of business, the best tubilng ever. DuBro stuff is also good. Don't use anything else, unless it comes from Jett, Nelson or Darol Cady, trust me here. If you see annnnnnnnnnnnnnnnnnnnny bubbles in the front line at any time, order a Jett bubbless tank asap. They seem to hold up fine, and are easier to use than the tetra tanks with their rubber bladders. Still need the big syringe (Tanker). Yes, the tetra tanks are quality tanks. I pull the bladders out and use them for hard use locations that wil kill anything else. ENJOY and good luck.