O.s. 2.10
 

I was wondering what kind of set up other guys are using on your O.S. 2.10. I am running a Zinger 20 x 8 prop, and 15% Wildcat fuel. No fuel pump.

The reason I am posting this is because the engine leans out as my flight progresses. Moving the fuel tank is not an option, ( it is level with the carb).

O.s. 2.10
 

You might need a fuel pump.

What size fuel lines are you running? With no pump, the pickup tube should be the next size larger than normal.

BTW, what's an OS 2.10? 2-stroke? 4-stroke? Twin? I didn't know OS made an engine that size.

O.s. 2.10
 

Its the BGX 3500.

O.s. 2.10
 

My BGX runs great without a pump. The tank is about 3" behind the firewall and I run only large fuel tubing. Medium will not pass enough fuel. I opened up the holes in my tank to accept large brass tubing as well. It turns an APC 20X8 2-blade at 9K RPM on the ground. Fuel is Magnum #1 2-stroke. It must be set richer on the ground than you would expect as the engine unloads quite a bit in the air and will lean out if you do not allow for the extra revs. The only time I've had a problem with this engine was when I first tried to run a tuned pipe on it. The compression is high enough that it detonates and overheats unless you install 2-3 head shims. It should also be noted that the factory muffler is junk. It is VERY restrictive and will cut down on power considerably while creating a lot of back pressure which could cause the engine to run too hot in some conditions. I'm currently running a Slim Line large volume Pitts muffler and the engine is very happy.

John

O.s. 2.10
 

Large fuel lines don't make much sence when almost all the large motors come with .40 - .60 size nipples. You can have 1/4 i.d. fuel line but it is only going to let the amount of the nipples i.d. so the only way to solve that is to drill out the nipples.

O.s. 2.10
 

Small diameter tubing will restrict the fuel flow over a distance. Using large tubing does in fact make a difference. And, in the case of the BGX, while it has only a slightly larger than normal nipple on the carb, the hole is in fact larger than you would find on a .60 sized engine.

John

O.s. 2.10
 

The big 2-strokes (OS, Moki, others) need larger diameter fuel tubing. It's not just the size of the nipple on the carb. The smaller diameter fuel tubing creates more restriction than the carb fuel draw can overcome. Don't just replace the fuel tubing either. You need larger brass tubing in the fuel tank stopper, larger tubing in the tank, and a large diameter clunk.

I'm running a 24 oz. tank on my Moki 2.10 set up with everything in the fuel system large diameter. I can set the needle where I want and it will hold that setting from full tank to empty (or as close as I care to get). It shows no signs of needing a pump or regulator, either.

O.s. 2.10
 

I am using medium size fuel tubing, with a 24 ounce tank.

Also, I am using whatever tubing came with the tank on the inside of the fuel tank.

This O.S. sure runs quite compared to the Moki's at my field. I am thinking that the Slim Line Pitt's style muffler may be too restrictive?

O.s. 2.10
 

Medium is working just fine on my Moki 2.10: 2-2.5 ounces a minute is not a huge flow rate.

If you can richen it way up, don't bother changing your tubing out.

O.s. 2.10
 

I seriously doubt it's too restrictive as it has twice the outlet area of the stock muffler. Mine is pretty quiet all things considered, but I attribute that to a decently designed muffler and prop.

John

RE: O.s. 2.10
 

JWM, am considering a BGX 3500 for a Dave Patrick Extra. See where you like a tuned exhaust pipe versus OS's stock muffler. Can you tell me what tuned pipe works well and where I could obtain it? Thanks. RDRC Willy.

RE: O.s. 2.10
 

The pipe I run is the Macs Quiet Pipe #1096 for 35cc engines. It's available through Macs directly at http://www.macspro.com . Tower does not list this pipe online any longer, but they may be able to special order one for you for less than full retail. Of course, just about any hobby shop should be able to do the same.

John