I have had two OS .91's, and on each of them I have a issue with them running lean on the top and rich in the middel. Is that a carb modification for this? And does any one know who make a ported cylinder for them.

I have now build a 42" span 78" length F 104 that weights 14 lbs. I am going to need all that I can get form engine to get it to fly well. Plus I have a f-8 that weights in at 15 lbs that just needs more power. Its a great flyer but it has zero vertical.

I know 99% of you will say go with a turbine or edf. But I dont want too. I love two stroke engines and goo.

I also know that are alot of guys here that know alot more about df than I do from years ago, so if you can try to remember a few tricks form 15 years ago I would be a great help.

Thanks

Josh

Josh,

Are you using an in-flight mixture control ?

Mike

Hi Josh!

Sounds like you have too thin fuel lines. No carb mods needed.

Inner diameter must be 3 mm minimum. 2,5mm or 3/32 inches is not enough, ask me how I know .

If the fuel system is made well, you don't need inflight mixture control. It's the easiest glow engine I've ever used.

My setup is following

OS 91 VRDF
Bolly DF91B pipe
McCoy MC9 plug
Ramtec fan
pitot pressure
Sullivan saddle tanks plumbed in parallel
normal hopper tank 100 ml
fuel and pressure lines inside diameter 3mm
Fuel: 80% methanol 20% Aerosave, no nitro.

Reply one, Yes and no. On the JDE F-8 with the os 91 yes. I have a BVM mixture. On my Byron Mig 15 with a os 91 no. And on my Byron Bullet with a k&b .82, no.

Reply two, I think your right. I am using the small fuel tubing. I dont know the size but its the standard stuff for .20 and .40 c.i. I will step up to the larger size.

The k&b has a much smaller bore carb and this has not been an issue with the engine. But, the O.S. has a huge carb and it is.

Thanks,

Josh K

Yep, you gotta have at least the "medium" sized fuel tubing. The Prather medium pink stuff is the weapon of choice but it's becoming hard to find. [link=http://www.quicktechhobby.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=QTH&Product_Co de=Pra7080]Check this source[/link]