.049 needle valve

johnv58 wrote:I want to clean the threads on a .049 engine's needle valve. What size are the threads, measures close to a # 2 screw thread. Thanks for any assistance.

take a Kleenex(R), put a few drops of fuel on it, carefully wrap it around the needle threads,
and turn the needle around a few times. then you should see all the "schmutz" that was stuck in the threads
on the Kleenex
regards,
Beez

The engine is from one of the cars...Baja Bug / Dune Buggy. It does have its own tank, backplate is diecast. I did get all the goop out of it, now it seems the threads are messed up. Not bad, just wanted to see I could save it by running a tap in it. If not I'll replace it.

As to a stuck needle, I'd suggest turning in small increments back and forth before trying a full rotation.

Sounds like you have a Babe Bee style engine with the attached 5cc aluminum fuel tank. In that case the needle thread is a 4-80.

Regards, Matt

SuperDave wrote:As to a stuck needle, I'd suggest turning in small increments back and forth before trying a full rotation.

Yea bit of heat never goes a miss.

OK I will attempt to locate a #4-80 tap and see where it goes, thanks.

4-80 Tap

Before buying a tap, I would be inclined to try thoroughly cleaning the threads on the needle and valve body, then attempting to carefully re-thread the needle into the spraybar. Getting an extremely fine threaded tap restarted correctly can be difficult, especially if the entry threads have been cross-threaded.

johnv58 wrote:OK I will attempt to locate a #4-80 tap and see where it goes, thanks.

To be honest, if the spraybar that is pressed into the backplate is stripped, or no longer useable you are better off getting a new backplate with the spraybar installed. It will be much cheaper than a 4-80 tap/die set.

Regards, Matt

Thought about that, but I did find a tap for $20 and would have it for future problems as well.
I better sleep on this.

Sounds like somebody tightened that sucker down, way too much...

If you are having trouble getting the tap started because the first turn on the threads are damaged then try taking a smaller tap (like a #2 or #3-80) and using it to cut the damaged first threads until you can get the original tap to start. It is like using an internal thread file.

Good luck,

Bob

Just wanted to end this topic with a note. I did purchase the #4-80 tap through a knife builders website. It did the job, I must have messed up a thread when cleaning the spraybar and now it is fine. Thanks all for your help.

GermanBeez wrote:take a Kleenex(R), put a few drops of fuel on it, carefully wrap it around the needle threads,
and turn the needle around a few times. then you should see all the "schmutz" that was stuck in the threads
on the Kleenex
regards,
Beez

I'd like to throw in one last thought, if I may. I spent many years occasionally frustrated that some tanked engines wouldn't needle easily after a fresh rebuild. After reading an article about building a reliable unwavering Texaco endurance engine, I realized my problem may have been fibers from the paper towels I was using to clean the parts. After switching to only lint-free rags, including laying one down as my assembly surface, I have a lot less paper weights when I crank it the first time.

The spraybar and needle orifice is so tiny that an unbelievably small amount of paper fibers can tangle up foul it like hair in a drain. I use a magnifying glass to inspect the components one at a time as it goes back together. It's amazing how much stuff I still find. Anything in the tank area can end up inside the spraybar, so look in all the nooks and crannies. On the reed side and in the venturi it's not nearly as critical. It can usually belch out and burn bits like paper fibers and shredded grass with no problem.

At Lowes, in the paint section, you can buy bags of t-shirt material squares that claim to be lint-free. After a couple of washes WITHOUT a dryer sheet, they can be used as car rags or whatever suits your needs.
Just a suggestion.

My problem is cat hair, my wifes two cats sleep by my little work bench. Cant touch or pick up anything that does not have hair, add a little castor its a problem.
I have to clean two or three times, drives me nuts.

Goodwill sells "goodwipes", which are torn up shirts like Rusty said.

microflitedude wrote:Goodwill sells "goodwipes", which are torn up shirts like Rusty said.

I bought a pack of those. They stunk something awful but they were lint free.