Saito muffler problem

How about a picture of the setup?

Did you clean the threads, both parts, well before using the loctite? Perhaps it's not getting a good grip due to oil. Also, be sure to let the loctite cure before starting the engine.

Once an engine has been run it is almost impossible to get the exhaust threads in the head clean enough to accept a good Loctite bond. Personally, If I have a problem with parts coming loose, I either find the source of the excess vibration, change the resonant frequency of the part, or safety wire it on.

Some of the pattern guys made braces running from the engine mount to their exhaust headers. Think of an inverted V with the two feet spread out at the mount and meeting at the header or the muffler.

This helped keep things from shaking themselves to pieces on soft mounts. It may also help keep your muffler in place.

Marty

Are you using the locking nuts??

John VB

Thanks to all for your suggestions. In reply to some: yes I am using a lock nut and yes, I did clean the threads before using locktight although just how clean they were is open to question. I am a little tired of battling this problem so I have put the model aside temporarily. When I get to it, I'll try some of the offerred solutions with many thanks to all who responded.

Cheers, Lawrence in Toronto.

Seems to me that Loctite shouldn't work there. About the only way to free red Loctite is with heat; the exhaust port gets hot enough to compromise the bond. Car guys use springs to strap the manifold on, rather than bolts. That might work for you too, but I suspect there are other problems. What's on the other end of the neoprene extension? Can it be vibrating the manifold loose? Is the prop well balanced? Metal locknuts, right? not the ones with nylon inserts?

I am now having the same problem with the same engine on a World models Jap Zero (Saito .91), on my third muffler next. Strange that I had NO problems with the Saito .72 and Saito 1.00! My friend sent me this link for a nice aftermarket set up that looks pretty good, hope it holds better.

Have been balancing props with one of those magnetic things. Using a Master Airscrew 13X8 and it runs and sounds great. Have not tacked the RPM but it goes like the dikkens!

And yes we are using the lock nuts.

Have fun, Karl.

I have a SE5A with a Saito 91. Wanting to keep the muffler inside the cowl, I heated the header up red hot and bent it down. I used a 3" extension on the end of the muffler. I use high-temp silicone on the threads where the manifold goes into the head and nothing between the muffler and the manifold on the other end. Everything stays tight and doesn't leak. Since the end of the muffler is only held in with a crimp, the 3" extension causes the end of the muffler to loosen and it eventually comes out. (Happened twice) I re-inserted it and used JB Weld, drilled and tapped the sides for 4-40 screws. I also added a wire tie on the end of the extension to give it a little brace. So far, no problems.

I encountered this problem with the first Saito 1.20 I had. It had the old style (long) muffler, which has a lot of leverage, and the muffler kept loosening. I called the number in the manual and talked to the tech guy. He said that once that has happened the threads are damaged and you can't get it to stay on. I sent it back, they gave me a new (shorter) muffler and fixed the threads on the manifold. That was three years ago and it hasn't come loose, since. I use oil on the threads, as directed, and tighten those nuts as well as I can. My Saito 1.50 came with the shorter muffler and never loosened. I understand that there is an even shorter muffler now, which comes with the new .82 size engine.

I hope so at that price!

Thank you sir for the interest in the matter. If you have anything positive and/or constructive to contribute please do so.

regards, Karl.

Karl, I am not sure, but I am beginning to think that the problem has to do with some sort of harmonic generated by the particular mount in question. I have a 150 that ran great in one application, but in another it shed mufflers like there was no tomorrow.

"Six_O'Clock_High"

This may be the key, but what would one do about it??? Change to a metal engine mount may help?

More backround on the .91 Zero: I am using the black "plastic" mount that was included with the model and engine is most forward due to CG balance needs. I am also using a Saito header pipe with almost 90 degree bend, threads are OK. I am also strapping the battery to a wooden platform on the side of the engine mount for "free" CG nose weight with lots of foam .

Interesting note on the .91 Zero: with a 14X6 Master Air Screw prop the muffler lasted longest but lacked power and vertical and just did not wind up, it even sounded lame which is unacceptable for such a wicked war bird, IMO. When we re-installed the 13X8 Master Air Screw it ran and sounded great but the muffler fell off before one tank of fuel flight. Conclusion -Theory- the higher RPM may be in (or closer to) that harmonic resonance range?

Perhaps I should specify, these engines are in two different models, GP 40 P-51D kit and GP 60 JU-87 BARF. they are both using the straight threaded header pipe, not a curved one. Both are using the included black plastic mounts.

Thanks for the ideas to the whole group you are an asset to the hobby, Have fun, Karl. honda ruehs at cox dot net

Sometimes just a well-placed bit of safety wire will stop the vibrations. Try making a strap from a mount screw to the header pipe.

Also, large MA props have always given me fits with vibration. They just aren't stiff enough and flex all over the place. Try an APC 13X8 and you might find a lot more performance as well as smoother running.

I have been using Permatex High Temperature Thread Sealent (wite tube, orange lettering) quite successfully now for some time. It even seems to work on those arrangememts with worn threads. Clean them up as best you can then then allow a couple of days after application to cure before running. This stuff gets very gummy and fills in those loose threads but still allows removal. It also works well on those wheel pant attachments that use collars on the axles.

Phil AMA609