Gauch

I've had to replace my muffler manifold (pipe between engine and muffler) twice in the past 4 weeks. Each time the break was at the section of the threads next to the header end of the pipe. Both prop and spinner are balanced. Very little engine vibration observed. Horizon Hobbys solution is to replace the pipe free of charge but they have no idea of what's causing it or how to prevent it from happening again. Any thoughts.....

w8ye

My Feedback: (16)

There are three different designs of these.

Straight all threaded

15 degree bend

30 degree bend

pumbadog

I have a Saito 100 and the original pipe broke at the thread as you described. My LHS had one that was bent at an angle instead of curved, it fit so I bought it. So far this ones ok. The wall thickness on these is really thin and then when it's threaded, it's worse. If yours is like mine, it would get loose and have to be retightened regularly. I think when these are torqued down it stretches the thread and creats a crack then just breakes off. Luckily mine was held to the aircraft by the pressure line so I didn't lose the muffler.

Broken Wings

My Feedback: (20)

My guess would be a manufacturing defect. If you had a thread micrometer you could measure the minor diameter of the thread and see just how much material is left holding the muffler/header pipe on the engine.

It's probably getting thin right at that joint. The header gets hot, cold, hot, cold and work hardens until it gets brittle and breaks or cracks. Maybe you could fabricate a small aluminum stay or bracket to help keep the muffler from moving. Kind of like a motorcycle "P" clamp.

Just a thought.

blw

My Feedback: (3)

The straight, all threaded manifold is meant to be a breakaway type.

chuck993

I have a Saito 100 sitting in a box, third time the muffler broke and it broke the cylinder and Horizon will not fix it, they claim they never heard of this before and I posted this info in another thread and some Saito ***** reamed me, they believe it can't be true and that it must be my fault, the Saito ***** always claim they have never heard of a problem with Saito or mufflers even though I've run into several people with the same problem as mine...$300 piece of junk...O.S. is a much better engine and much better quality, go to O.S.

Hobbsy

My Feedback: (102)

How about a picture there Chuck, I have 17 Saitos, I've never broken a muffler nor ever had one come loose. I don't buy it.

chuck993

yeah right...none of the Saito nuts ever believe that something could be wrong with Saito...search the forum, open your eyes, that's how I found this one...LOL

drink the Saito Cool Aide!

wcmorrison

My Feedback: (2)

Thats not a bad thing, better to break a pipe than a head. I had have Clarence Lee fix my head, albeit it was a OS four stroke, but same issue.

Cheers,

Chip

scott17

I posted pics of 2 broken in a row on my saito 56. I ended up going with a flex pipe. It happens....[&o]

Hobbsy

My Feedback: (102)

Chuck, I'm not only a Saito nut but also an Enya, Fox, Webra, SuperTigre, Irvine, LASER and OS nut.

Gauch

Meanwhile, back at the ranch.....#3 broke today.......

bingo field

I was just looking to see if someone had found a method to secure the pipe. The original on my 91 split off after about 50 flights, Horizon sent me a new one, no questions asked. But this one keeps loosening up on me. I love the way it runs, but hate having to keep tightening the manifold.

bingo field

#2 just broke. Exactly like the first. The pipe breaks where it exits the head. Does anyone have any suggestions?

Gauch

I had the same problem. I sent my engine back to Horizon Hobby and they found "The rear bearing and crankshaft are badly rusted and the resulting wear is allowing enough play to allow the con rod to rub the inside of the crankcase. There is also a build up of dried fuel residue coating all of the internal parts. This build up causes excess friction and premature wear. The cam lobes are severely worn. I am confident that these factors have created excessive vibrations which have caused the failure of the exhaust manifolds." Where did the rust come from? With the exception of the 1st gallon of Omega 15%, I've used nothing but Cool Power 15%. I've religiously ran the engine dry with the glow plug attached after each days flying. I was extremely confident I did everything possible to keep the engine in good shape. After run oil was not used because Morgan Fuels website specifically states "No need for after run oil." This is a bogus claim. The technician at Horizon Hobby said you should always use after run oil regardless of what the manufacturer states. The rebuild appears to have fixed my problem. I've also switched fuels and now use after run oil.

Hobbsy

My Feedback: (102)

Gauch, running the tank dry on a fourstroke does nothing for the stuff that is left in the crankcase. I religiously use this stuff by injecting it into the crankcase after a day of flying or any time I run an engine. I have pulled the backplate from an engine stored for 5 and even 10 years and the CX looks exactly like it did when injected and the engines are prestine inside.

bingo field

So far, I have managed to keep mine on for 2 flights since I ran it up on the ground and got it warmed up for about 5 minutes, then, when it was still hot, just firmly seating the nut against the head. I had enough threads left on the pipe to thread it into the head after I fished out the piece that was fractured off. I still like the way this thing runs, so I am going to work on keeping it.

Where do you get that CX at?

Hobbsy

My Feedback: (102)

I used to get it from Sheldon's Hobbies in XCalif. but they have changed owners and the new owners are car oriented.