This is an old small 2 stroke mower engine with a worn out float chamber needle. A mfg. replacement is not available. I turned one up out of nylon which works but obviously allows leakage as the fuel tank level is critical! and floods when stationary for any length of time. The original (silver alloy? ) needle had what looks like a neoprene tip 60 deg included angle that gave way a bit as it entered the fuel supply hole and made a proper seal with the float pressure available. I am trying to bodge up a precision tip from a bit of O ring but getting a fixing to the body of the needle is a problem as any glue will be in a really melty envionment (fuel/oil mix). Any one else been down this path with a solution?! The widest part of the tip is 2.5mm to give some idea of scale. My nylon body works well for the larger part and doesnt wear out the barrel it slides in. Oh and of course all this lives in a very vibrating chamber! Charlie+
Making a float chamber fuel level needle
Mar 17, 2009
8 Replies
Perhaps you might try a different approach; there are auto carburettor needle valves on some older model vehicles which may be able to be modified for your purpose. Some Bendix - GM models of the 70's come to mind, complete wirh neoprene tip.
Why make something that can be easily adapted from another vehicle? Carburetor needle valves are cheap, find one close and fit your carb to it.
Any chance you could use a metal needle part and counterbore the fuel inlet to hold a tiny o-ring or maybe just a piece of neoprene with a small hole through it?
Jeff
Charlie, Don't reinvent the wheel...........go to a carb shop and they will probably give you one. If it doesn't exactly fit, make it fit. Steve
Many carburetors use a soft tipped needle. Some small engine carburetors use a hard needle with a soft seat insert. Someone at a small engine or carburetor shop should be able to find something that will work with little or no modification.
Don Young
On Tue, 17 Mar 2009 16:22:24 -0400, Jeff Wisnia :
Now that is an interesting workaround! Thanks Jeff . Thanks to others who replied also. Yesterday evening I made the tip out of a bit of O ring as planned and mounted it mechanically on a 1mm dia. brass panel pin head and ground to shape, and that has the engine working perfectly, however longevity is another matter - I wait and see - ! Charlie+
There are zillions of automotive carb needles, many of which you prolly could adapt. Trouble is, there are not many carbed cars around, and most repair shops, which would have lots of carb parts 20 years ago, prolly don't even know how to rebuild one anymore.. Napa might have a selection of needles only by application. Or a speed shop. JR Dweller in the cellar
Charlie+ wrote:
Brass is your friend. Viton tipped needles are a recent phenomenon. Brass and aluminum were used for years - or steel with a fiber or nylon or rubber seat. Look at a Tecumseh or Briggs float valve to see what I mean. Might be able to convert the carb to use one of them.
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required