Home › Forum › Ask A Member › 1966 JW-21 3hp fixed carb orifice
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ede.
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July 23, 2016 at 6:17 pm #4820
Does anyone know the ID of the fixed high speed orifice in a 1966 Johnson JW 3hp? I’m working on one I recently picked up. The carb was really dirty and the high speed orifice is stuck and feels like the slot to remove it is wallowed since it is a loose fit on the tool to remove it. When I try to turn it out it just kind of cams the tool out of the slot. I got a small twist tie through the hole and the engine will run now but I’d like to run the correct size small drill through it to make sure it is clean. I don’t want to enlarge the orifice though. I’m going through the ignition now. It should be a good runner again with the carb repaired. Any info would be appreciated.
-BenOldJohnnyRude on YouTube
July 23, 2016 at 6:34 pm #40758Interesting that ME would chose to out that data on the ’66 model. The ’65 & ’67 models both show a 29D orifice show I believe we can be confident that it is a .029 diameter. Now these jets were not drilled rather reamed & flowed, but I think you would be safe to use a .029 or .030 drill. Just don’t spend any time wallowing the brass! Your problem may not be the hole rather the area behind the hole. If it is gummed up the jet will not flow properly. Have you let the bowl seat with Engine Tuner over night? That stuff is very effective at removing the most stubborn gum & varnish. I have all of the orifices new for replacement if you could just get it out? If you get desperate enough, clamp the bowl to a 2X4 & hold it in your drill press. Drill the orifice out (it is 1/4 X 20 threads). Leave enough for a small ease out to remove the hull of the orifice. I can send you a new jet. I have done this many times on both aluminum & plastic bowl carbs!
Dan in TN
July 23, 2016 at 7:10 pm #40765Thanks Dan! I’ll try to get it with a .029 drill. It’s probably gummed a but behind it too. I’ll give it a shot of engine tuner and see how it does. I can definitely get the old one out. I’ll clamp it up in my mill and drill it for an ez out.
-BenOldJohnnyRude on YouTube
July 23, 2016 at 8:24 pm #40770Left hand thread drill bits work great on brass the few times I had to drill something out. Usually it screws itself out before you get all the way through. I have not tried them on anything as small as the jets so maybe it wouldn’t work for those but they work great on needle valve seats.
July 23, 2016 at 9:20 pm #40771Chart says it could be a #28 or 29. I guess they dinked around with it a bit.
July 24, 2016 at 1:21 am #40782I have been meaning to get a set of left hand twist drills. With all the other stuff I do have its a wonder I don’t already have them. 🙄 That is very true, things often start to unscrew before you get all the way through.
If they’d left the silly thing adjustable they wouldn’t have had to dink with it at all. 😎 I guess I could get a kit a convert it but I don’t actually mind the fixed ones that much.
Thank you all for the replies and the help. I’ll probably end up replacing the orifice but I am going to keep trying to get this one cleaned out first and see how it does.
-BenOldJohnnyRude on YouTube
July 24, 2016 at 2:59 pm #40810The p/n for the orifice is 330142
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