The .61 engine I purchased has a remote needle valve, but the engine
does not fit into the plane with the remote valve attached. Can I just
attach the remote needle valve somewhere else in the engine
compartment? Is there a maximum length for the fuel tube between the
needle valve and the carb?
As advised by K & B when they were first to introduce remote needle valves,
maximum length away from outlet of spraybar into throat of carb of a typical
.61 - 1.00 ci (outlet into carb) is 4 inches [10mm]. The length of fuel tube
between the needle valve and outlet will act as a "header" or " holding"
tank. Response time to throttle input is severely compromised and will also
lead to "unexplained" motor cut out in mid air - K&B advice has been well
tested, even on pumped motors. (Pump pressure is on the other side of the
Smaller motors require shorter lengths of standard diameter Du Bro tube or
use tube with a smaller internal diameter but 4" still appears to be the
limit with a .25 and different sized tubing.
Alan's Hobby, Model & RC Web Links
Though the 4" distance is probably good, response time has nothing to
do with it. Once a water hose is full of water the flow stops as soon
as the valve is shut no matter how long it is. However some water may
spill out of it after it is shut down. The fuel in you line may also
spill out into the engine when it is shut down, possibly flooding it
for the next start.
I first used a remote needle on a Merco 29 because I kept breaking the
normal needle. On one occasion I couldn't get a proper replacement so
mounted a needle from a different make engine on a small aluminium bracket
mounted on the firewall. I soldered over the broken end of the original
needle and connected the fuel tube from the "remote" to the original
connection. It worked well and it was some years before I returned to the
"proper" arrangement by which time I was able to land the model without
breaking the needle assembly - we had a very rough field at that time.
In some cases, the farther the needle is from the carb, the less precise the
throttling becomes. Using a smaller diameter tube can help this. If you
are only talking about a one inch change, you might not even notice the
If you want to sink the money into a Jet engine from DubJet...They state
you can put the needle valve up to 2 ft from the carb,as long as it's
somewhat in line.
Mine is bout 8 inches from the engine and have had no problems at all.