Howard

My Feedback: (55)

Bax,

I ordered a Great Planes RV-4 from Tower Hobbies and the following day I also ordered an OS 91 II Surpass from Tower on invoice # 13077614. I did the maiden flight this last Monday and flew the plane three times. When I brought the plane home I disassembled the cowl as part of my post flight check and found that the muffler was loose at the muffler end with many of the threads inside the muffler rubbed smooth and no longer functional. The muffler elbow connection to the engine was fine and still tight.

To prepare for the maiden flight I balanced the Topflite prop with my Hobbico magnetic prop balancer and used the aluminum spinner that came with the RV-4 kit. I used blue colored thread lock and tightened both ends of the muffler. I used a Hobbico exhaust deflector to direct the exhaust gas out the back and bottom of the cowl.

As far as I can tell I did everything correctly which leads me to believe that there was a problem with the new muffler threads as it was delivered. I understand that this may be impossible to determine with any certainty but, I cannot think of any other reason for the failure.

I would be glad to send you the muffler for examination if you feel there is some merit to my position.

Howard

Bax

My Feedback: (11)

The threads galled, most likely, due to vibration. The muffler needs to have most of the threads inside the can for best strength and retention. If you believe it to be defective you can send it to us.

Howard

My Feedback: (55)

Bax,

Thanks for the quick reply - I will send the muffler and elbow back to you. Some additional information: I discovered yesterday that the FS 70 Surpass muffler and exhaust elbow are the same part number as for the 90 Surpass. I happen to own two 70's so I borrowed the muffler and elbow, installed it on the 90 Surpass that is on the RV-4, using the same Topflite prop and spinner that came with the RV-4, and flew it this morning four times and spent time adjusting the low speed idle and the muffler did not come loose - the question is why did the original muffler on the 90 come loose and eventually destroy most of the threads? I will get it boxed up and in the mail.

Thanks again for the quick response.

Howard

Thomasp168

I've had the muffler come loose on Surpasses (mostly 40's), it's because I didn't check the tightness of the stop nut on the elbow. now it's part of my preflight.