OS 105 HZ-R exhaust mount changed?

[777ER]

I just got my OS 105 HZ-R DRS last week and was installing it in the whiplash 90 today and noticed the muffler bolts are thru design and no threaded muffler bolt holes as the earlier 105 HZ-R were.

So due to this, I would have to get the MP7 for the OS 90 and fit it?
I hope it lines up correctly....


MP7 for 105 has threaded bolts

MP7 for 90 has thru bolt with PSEM inserts in place of nut.

[John Cook]

I'd call the muffler company CYE. I'm pretty sure the 105 and all OS motors are that way your's are, ie the bolt passes through case and secures into muffler.

[Jafa]

Yes - only the YS screw exhaust bolts into the engine case

[whittb]

I have the exact same engine a pipe combo in my T-Rex 700N DFC. The pipe mounting holes in the OS 150HZ-R DRS are threaded. Use the bolts supplied with the MP7105 pipe kit to mount your pipe to the OS105. I used high temp automotive sealant as a gasket. No leaks and the pipe makes great power.

My motor setup is:
Idle = factory (centered)
Middle = 0.80 turns out
High = 1.75 turns out
Rotor rage 15% masters blend with 21% oil
I am using a OS #8 plug and I am still coming down with temps in the 170 to 180 range.
I started out with the Enya #5 plug and it was to cool to run at the rich break-in needle settings, the motor shut off on my after 15 seconds of flight. Once I installed the OS#8, the motor came to life.

I am able to get very consistent power without having to re-tune to motor. Pulled my pipe off to check the piston after 2 gallons and everything looks factory new. So I know she is happy with my setup.

I fly at sea level with 100+ degree temperatures and high humidity.

Be careful when using a crank locking tool wit this motor. The piston will hit the tool on the down stroke.