Carburetor study with microscope plus Smarter Every Day video

Joe Kuhn

Joe Kuhn

Active Member
I once got a mower to run by spraying out the carb with cleaner. It ran, but it surged some, so my son said to give him the jet. He put it under a microscope and we saw all kinds of fuzz around the hole. We had to change the focus some to see the extent of it, but it was clearly dirty still. Here's what it looked like with red arrows pointing at the dirt in one I happen to have laying around today. This one is not bad compared to the one causing the surging.

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I cleared the dirt with a jet cleaning tool so that it was nice and smooth looking under the microscope. The surging stopped. Here's the tool:

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Here's the setup I had to use to take the picture above.

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The white thing is a piece of tape.

And here's the video. Darn good video. Have fun.

 
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You are right about the surface of the jets which is why jets are sized with end mills or 4 flute jet drills to give a smooth bore.
However the blue pack are tip cleaners which are files and should never be used for jet cleaning as you can easily make a round hole into an oval or funnel the ends .
Always better to use actual drills between your fingers as the flutes do not cut under finger pressure
 
bertsmobile1 said:
You are right about the surface of the jets which is why jets are sized with end mills or 4 flute jet drills to give a smooth bore.
However the blue pack are tip cleaners which are files and should never be used for jet cleaning as you can easily make a round hole into an oval or funnel the ends .
Always better to use actual drills between your fingers as the flutes do not cut under finger pressure
Click to expand...
Drills like these? I like that concept and I happen to have a set of these. Will use them, but the spun wires bend easily, so not a lot of pressure can be applied. And the wires are round, not with sharp edges. Plus I'm careful when I use them. The purpose is to remove debris, not increase an inside diameter. Will change that photo above to just the spun wires.

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I actually use the micro bit for resizing jets here but most I use them just clean up a jet that corrosion. If it is a new jet that I haven't already size check they are for that purpose too. With jets being size in .001 mm there will times that a bit will not work as well. Sizes like 115.5 (1.155mm) are out there.
 
You are ALL crazy ! The jets on tiny carbs found on small engines are so finely tuned that any metal object will gouge the soft brass and make the engine run richer. Just because you get away with it doesn't mean it's not happening. Just because you can't see it doesn't mean it's not happening.

If you must stick something in there, then use a soft wooden object, like a fat wooden toothpick designed for serving Hors d'Oeuvres. Like These.
 
Born2Mow said:
You are ALL crazy ! The jets on tiny carbs found on small engines are so finely tuned that any metal object will gouge the soft brass and make the engine run richer. Just because you get away with it doesn't mean it's not happening. Just because you can't see it doesn't mean it's not happening.

If you must stick something in there, then use a soft wooden object, like a fat wooden toothpick designed for serving Hors d'Oeuvres. Like These.
Click to expand...
You tell them B2M.

I use monofilament fishing line. No chance on screwing up my brass jets. 2-4lb on pilot jets and 10-30 on mains.

slomo
 
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