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Old 10-17-2010, 06:51 AM
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Wingspam
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Default New Problem

My Jett 50 is chewing up spark plugs like candy corn.

Its been about a month since my last flight on this plane, so today I took out my Patriot(55ax), H9-F22 (Jett 50) and took em for a spin or too. Fired up the Jett 50 on the bench it tached 15,300, thats about 600 less rpm's that the last time I flew it. Using Omega 15%, turning a 10x6 apc prop and using the Mccoy 59 plug. I took to the air 2 minutes into the flight the motor started sputtering, landed it just as the motor died. Glow plug was bad, put in a new plug (same type) and tried it again with the same results 2 minutes into flight motor sputters and I land. This time I was able to keep the motor running for a few seconds and I noticed a large amount of bubbles in the fuel line, then the motor died. Pulled the plug and it was dead as well.
What could cause the plugs to blow like this? I will pull the cowling and check for leaks in the fuel line..

Thanks


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Old 10-17-2010, 08:39 AM
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Default RE: New Problem

Air bubbles in the line cause a lean condition that will cause plugs to quit.
Solve the fuel problem and I bet you don't have a glow plug problem.
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Old 10-17-2010, 10:24 AM
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Default RE: New Problem

That makes sense, pulling the tank and lines today...


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Old 10-17-2010, 10:46 AM
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Default RE: New Problem

yes, as he noted.

90% of blown plug issues trace back to the fuel system.

Let me know how it works out
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Old 10-17-2010, 02:20 PM
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rmenke
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Default RE: New Problem

Hi Wingspam

I had the same problem with the Jett 60 that took some work to sort out with Dub and Bob's help. I ended up using the large Jett "bubbleless" tank and moving the needle valve from the motor to the side of the fuse. I used a small wedge shaped piece of ply to screw into and hold the needle up enough to turn it with ease. I have used bladder type tanks in the past from the old U control days, then formula and quickes. Never liked them. The Jett bladder is made out of plastic and is far superior to the rubber bladder types that start off with lots of pressure and drops during your run causing a lean run if you start out right on the nut. The Jett tank simply converts the normal muffler pressure equally and gives you a good constant run. There is some pressure on the Jett tank when full (overfull) but that will go away if you let a little fuel escape.

On several occasions, I was caught out short of time to the next race. I filled the tank from my electric pump with no problems whatsoever. Would not recommend this as a normal process, but its there after the first run and do or die time. A "tanker" still provides better control. ENJOY
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Old 10-17-2010, 03:06 PM
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Default RE: New Problem


ORIGINAL: rmenke

Hi Wingspam

I had the same problem with the Jett 60 that took some work to sort out with Dub and Bob's help. I ended up using the large Jett ''bubbleless'' tank and moving the needle valve from the motor to the side of the fuse. I used a small wedge shaped piece of ply to screw into and hold the needle up enough to turn it with ease. I have used bladder type tanks in the past from the old U control days, then formula and quickes. Never liked them. The Jett bladder is made out of plastic and is far superior to the rubber bladder types that start off with lots of pressure and drops during your run causing a lean run if you start out right on the nut. The Jett tank simply converts the normal muffler pressure equally and gives you a good constant run. There is some pressure on the Jett tank when full (overfull) but that will go away if you let a little fuel escape.

On several occasions, I was caught out short of time to the next race. I filled the tank from my electric pump with no problems whatsoever. Would not recommend this as a normal process, but its there after the first run and do or die time. A ''tanker'' still provides better control. ENJOY

I second that one on the bubbless tanks, they take fuel system issues out of the equation.[sm=thumbs_up.gif]
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Old 10-17-2010, 06:38 PM
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Default RE: New Problem

Before I went flying today I replumbed the tank and changed out all the other lines, I didn't find any obvious holes in any of the lines but I did notice a few deep abrasions in a couple of the lines. So with that done off i go to the field, once there I fueled up and I would not start (still had bad plug from yesterday in it). Oh crap i was out of the Mccoy plugs, I know the Os plugs have not worked in the past and all I had left was a very old Hobbico 4 cycle super plug. I put it in and fired it up there where no bubbles visible at low throttle and up to medium it still looked good, so I floored it (so to speak) no bubbles and the motor ran strong, it tached at almost 16k. Refueled it and off it, went my timer is set at 6 mins. and it has an 11oz tank. I fly this bird pretty much wide open all the time and when that times sounds I had better be getting close to the runway. 3 flights today and no problems at all..
Old pic but still a pic

Thanks again
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