I have read through many threads on the EF yak 74,which i just purchased,but im torn between OS 160 or a brilleli 46gt,everything new prices are pretty close within25-30 dollars,the OS is light ,but to put the tank on the CG will i have to use a pump,im hearing yes and no s, so that got me to thinking about gas which ive never done, but weight dosent seem to be a factor there from what ive read.First plane larger than a 90 for me and i havent a clue as to which motor to use,gas -more expensive up front ,but burns less fuel,what other reason should or would u go with the os over the brilleli?,can anyone help me out,have a plane just sittin here ready for a powerplant,if i can decide!!!!!!

Dont worry about putting the tank on the cg....I fly 3D and there is not big "have to" advantage to doing that...I have used an OS160 and I sold it....would never sell my gas engine....This Yak 74" is my first gas too.....luvn it.... Just go with your gut.....or buy both eventually..lol

So u didnt use a pump with ur OS right,are you usuing the 46GT on your yak74?

I just got the yak with the 46 and it was my first gas engine, one of the guys at the field showed me in about 2 minutes everything I needed to know.

I figure I could buy a new yak about every 6 months for the cost of running my 30 percent heli fuel in the 1.60 but keep in mind I got an outstanding deal on my Yak and engine.

Heli fuel in an OS 160?
It runs top with 5%,anything over 10% is a waste for that motor,and probably damages it.
He is talking about the 2 stroke.

I get it in bulk and only haul one jug to the field so if its a waste is immeaterial. It hasnt hurt my 108 which has I can't even tell you how many flights in my Funtana, I do use a pump on that btw. It makes it look like I'm running a smoke system

An extra head shim lowers the compression and keeps it from pre-ignition with the higher nitro.

do u have any pics of your yak with that setup? did u have to add any weight to balance the plane,also what kinda battery r u usinf for ignition?

I don't have any detailed pics but here she is.

There's a 2000mah battery up front for the ignition and a 2900mah rx pack right behind the cg, the fuel tank was moved back to the cg, weight is 12lbs 6oz zfw

As a former glider pilot, I detest adding weight to anything if I can at all avoid it.

Balance is at 6 1/2" though I probably need to move it up a bit till I get used to it.

I had a 160 in my ultrarc Katana extreme. It was plenty of power for that plane at 10lbs even and should be plenty on the EF yak as well. You will not be able to use 30% fuel in it however. Before my 160 I was running 30% in my 120ax and my 55ax with no problems. I tried it once in my 160 and it sounded as if it was going to tear itself apart. I don't know if it is because of a high compression ratio but the 160 detonates terribly with high nitro. Also you have to run it so rich with the 30% the mid range is terrible. If you set the low end properly the mid range will be very rich on high nitro. Even on 15% it's a little rich. Adding a cline regulator helped but this engine really just seemed to like 10% much better. It won't lose hardly any rpm with lower nitro but the transition is better because the mid-range is not so rich. Hard to believe but true.

With all that being said from what I have read aout the plane you are buying I would go with the brillelli. I you get the combp brillelli sells you aren't paying much more than you would for that plane with a 160 and pitts muffler. Plus shipping is free with the combo, or was last time I looked at it. You will make up the initial investment in 20 or so flights I would think. Just my 2 cents.

Does detonation sound like a rattle or knocking in the motor? My 160 sounds like that at mid-range and I am running 15%..