Model Forum / Radio Controlled / Air Models / July 2004

Good suggestion and a lot of info on your past thread, but most of it
pertains to running too large a prop.  I did learn a lot about fuel mixes
though.  I think your suggestion about disassembling the Walbro carb and
cleaning is the possible solution.  Do I need a rebuild kit just to clean
it?

Check with the LHS for a stopper made for Gas  and also line for gas  The
gas will dissolve the lines used for glow fuel as well

Thanks for all the good suggestions from DR and BC.  As suspected it was a
fuel problem.  I took off the cover to the Walbro carb and discovered that
the fuel screen had a lot of crap in it.  I cleaned it out and then blew air
through the lines and the needle valve port.  I then went to my tank and
found the rubber stopper was dissolving from the gas environment!  What kind
of tanks are you suppose to use for gas?  I then hastily built a tank from a
small plastic water bottle and within minutes I had the Ryobi purring like a
kitten.  Top RPM 6,300 and idle 2,500 RPM on an 18x10 prop.  Back to its old
sweet self.

In addition to my question about tank type, what about an inline fuel
filter?  I have one for my glow engine and I will check if it is metal with
no internal rubber.  And how about the sintered clunk?  Oh little
grasshopper, there is so much to learn.
====================================
Some tanks come with a stopper that's supposed to be compatible with glow
fuel or gas; others require you to buy a gas stopper.
Here's a link to tanks on Tower's site
http://www2.towerhobbies.com/cgi-bin/wti0093p?&C=QCA&P=0

Find the brand/size/shape you're interested in.  The part notes will tell
you if a special stopper is needed.

Fuel tank stoppers
http://www.towerhobbies.com/listings/cat-cat-p2.html

You need a standard tank with a "gas" neoprene stopper.  This is black rubber,
not grey or brown like glow stoppers.
Dr.1 Driver
"There's a Hun in the sun!"

       You may have your problem come back to haunt you: When you
blew air into carb to clean it its possible that some trapped dirt may
have worked its way up into a chamber just below a welch plug. This
dirt will lay there and depending if the passage is for metering
fuel/air the dirt can work its way back into that passage. You would
not want this to happen when your plane is in the air. I would say you
have a 50/50 chance of nothing or something bad happening. When you
give a carb a thorough rebuild; you remove the welch plugs and replace
them with new ones. Now you have 100% in your favor of nothing bad
happening. I replied on your other post explaining about welch plugs.
 I dont want to scare you, but just trying to help you. I have been
in the small engine service feild for 15 yrs and I am wroking at
cemetery maintaining there equipment....also digging graves, trmming,
cutting, ect, ect ,ect....
Out of those 15 yrs 4 yrs I raced go-karts (yamaha kt100s/ yamaha
heavy class).....I learned from the best and did my own engine
work......have a nice trophy collection and among those trophies I
have my championship points trophy ( stroking the ego alittle  :-)
).....so i know what I am doing. Please feel free to email if you need
any further help.

   Good luck
       Mike

A grasshopper????  Are you teathering that plane down at the feild
like the fullsize at the airport???        :-)

Mike thanks for the info, but you lost me on some of the terminology.  Welch
plugs and pop off are parts I'm not familiar with.  We have our monthly R/C
club meeting this Friday and we have some members who are gas knowledgeable,
so I will be asking them many questions.  If you see my earlier reply, you
will note that I did a quick and dirty (bad choice of words) carb and fuel
system cleanup and now its humming.  I do want to be more gas savvy so that
I can overhaul the Walbro carb in the future.

My next project is building a PIC based electronic CDI ignition.  I've got
all the hardware together and tonight I start on the software.