para_racer

My Feedback: (1)

I have an OS 91 V-DF engine without a needle valve adjustment. I was wondering if anyone could tell me if this is normal or not? Do I need to buy a new carb with a needle value?? Thanks, Wade

para_racer

My Feedback: (1)

Picture of my engine carb.

PR38

Yes, that is normal...somewhat. OS knows that you're probably not going to be able to get to the carb once installed in all that ducting, so they block the normal position and give you a remote needle valve assembly. Did you buy the engine new?
There are a couple of really good remote needle valve assemblies out there, and with the help of a servo, you can run the engine lean for takeoff power, then richen once in flight. The JMP remote mixture adjustment ($40) seems to be the popular one.
http://www.jetmodelproducts.com/dynamax.htm
Keep the carb you have, you just need the valve.

para_racer

My Feedback: (1)

I bought a complete (or I thought complete) setup that was partially built. This is my first jet and I'm learning a lot. The person that sold it to me didn't include a remote needle valve. So I just need to buy one of those and add it to the engine? Then tune as usual? Thanks, Wade

PR38

Yup. The needle valve just meters the amount of fuel allowed to pass into the venturi port--it doesn't really matter if its on the carb or set upline somewhere.
There are probably several people out there that have the OS remote needle valve if you don't want to get the one from JMP (I understand BVM has a nice one too), since, when you buy one, the OS valve is not necessary. I would encourage you to get one of the nice ones though, becuase in many setups, you don't have enough travel with the OS valve to properly meter the mixture in flight.
Then again, some people don't even use in-flight misture--just set it and fly. If it works, fine. But if not, is it worth it? Jets glide like rocks.

JimBrown

My Feedback: (2)

From the quote above, I feel that you think you still need to mount the needle valve to the engine. If that is the case, please note that the what you have now is the setup for a "remote" needle valve that is NOT mounted to the engine. The remote needle valve is mounted outside the ducting in a place that is convenient for adjustments, instead of inside the ducting with the engine. Fuel tubing is run from the header tank (if you have one) or the main tanks to the remote needle valve, and then from the remote needle valve to the nipple on the carb. All that is needed is a small hole in the side of the ducting to pass the fuel tubing through. (Use a rubber grommet with in inside diameter that fits the fuel tubing at the point it goes through the ducting.)

Regards,
...jim

Turbulence

My Feedback: (76)

Wade, adjustable in flight or NOT, this will clear things up a bit for you. This is a Dynamax Fan, O.S. 91 and a BVM in-flight mixture control. More pictures can be found on our club FAQ section under engine and fan mounting:

http://www.crcja.org/faq





Turbulence

joeflyer

My Feedback: (48)

Wade,
Not sure which plane this is for, but most DF's use inflight mixture. For that you should get either the BVM or JMP. I have both and prefer the BVM ($42).

If you are not going to use in-flight mixture I have a new OS remote needle valve I'll sell you for $20 shipped. This will allow you to adjust the mixture remotely on the ground, but isn't the best if you need to hook it to a servo for in-flight control.

Joe