Fuel coming from Needle Valve

[darrzemp]

Have 2 .20 Sporsters & 2 .28 Sportsters. When trying to set the needles, at higher RPMs, Fuel is visibly flowing out of the needle valve. What do I look at to correct the problem. .20s & .28s are of early vintage. None have many hours on them, but have been in storage for about 12 years.

[astrahog45]

Have 2 .20 Sporsters & 2 .28 Sportsters. When trying to set the needles, at higher RPMs, Fuel is visibly flowing out of the needle valve. What do I look at to correct the problem. .20s & .28s are of early vintage. None have many hours on them, but have been in storage for about 12 years.

Hi
Presume you have Tried the obvious
a. Put a Spring over the threaded part prior to inserting and turning needle to fully closed .
b . Putting tubing over the threeded part of NVA and the actual hedke itself
Are the Sportster 20 and 28 needles interchangeable ?
If not it could be possibility of putting 20 needle jet into a 28 NVA.


Is there any o-ring seal either side of the Crankcase aperture to seat the NVA ? Look for any rubber seal which may have become perished
or partly perished so that when high rpm achieved fuel pressure may 'blow '

[darrzemp]

Have tried the fuel tubing with small success. Also replaced the 2 O-rings in the carburetor. Small success here also. Thanks - Keep all the suggestions coming. Just can't fly with any confidence with this problem continuing. Wish for a Factory tech would try to intervene. All 4 engines used to run very well. 2 of the .28s are on a twin Engine Bird.- Darryl Zempel :roll:

[astrahog45]

[quote="darrzemp"]Have tried the fuel tubing with small success. Also replaced the 2 O-rings in the carburetor. Small success here also. Thanks - Keep all the suggestions coming. Just can't fly with any

Darryl
Are you in situ plane running if so re-check following
(Assuming you have a Sullivan/Dubro config tank )
a. Position of the Tank ( carb tubing exitting tank /cab tubing entering NVA)
b. Positioning of all Tank hardware from bung end / inside tank
Are both filler and Muffler approx one eigth inches away from repective
tank walls . Also clunk position on main carb feed.

c. Have you tried an in-line carb filter as this may calm down the
apparent omnipresent fuel surge at nva end . ( obviously putting it
nearer the nva than the tank .

[MECOA]

Try running without any muffler pressure. The very first Sportsters didn't even come woth a muffler pressure tap. That was added later. An o-ring was added to the main needle in the 90's.