Just got my hands on OS70 Ultimate, but LHS did not have muffler for it.

Guy at the shop told me that muffler for 70 Ultimate is nearly DOUBLE in price of standard OS70/91FS muffler ???

Search on the web did not give any usefull info wheather OS did change something or I can use regular OS 70/90FSII
on Ultimate ?

Good luck with that "trouble maker"

The exhaust parts are used from other existing engines.....

The engine uses the muffler for the OS 91 Surpass II engine

http://www2.towerhobbies.com/cgi-bin...?&I=LXCP62&P=Z

The exhaust pipe is the one for the OS FL 70 four stroke.

http://www2.towerhobbies.com/cgi-bin...?&I=LXKXY9&P=Z

The thread size for the exhaust is M-11 X .75

Four strokes are not as sensitive with respect to the exhaust as two strokes are.

You can use any exhaust/manifold - muffler set up that has the correct 11mm diameter X .75mm pitch on the threads.

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What about the pipe and muffler for the FL-70? The two engines do appear to be related, somewhat.

As long as its threaded 11 X .75 it'll work

The Fl 70 muffler has two pressure outlets?

You might wanna try and run it without the muffler? That engine dont need a muffler pressure as it has a fuel pump so the muffler is only there to make it slightly more quiet. I think if you just clamp a 15cm long silicone tubing over the exhaust header to get rid of the exhaust smoke then the engine also gets quiet enough to be acceptable. You didnt say if you got a header for that engine, but if you dont have it should still be considerably cheaper to buy it alone than the muffler set.

tnx guys,

Seems to be that OS is a little bit overpricing assembly for Ultimate.

I just borrowed header and pipe from OS 91 II pumped and fits nicely.

Now it's time to try to make it work....

Get the Magnum 4-stroke muffler. It costs much less. Just plug the pressure tap.

http://www.hobbypeople.net/gallery/280109.asp