Needle Valve johnson RD-18

[fry-cook]

I want to replace the Idle needle valve on my 1956 Johnson RD-18, the part number is 303966. The issue is when I search for that part number it shows threads only at the end, near the needle, the needle valve I pulled out of my carb has two sets of threads. One set of threads at the needle end and a second set of threads mid way up that the bushing actually screws onto. I can’t locate a needle value that has the two sets of threads. Has anyone ever come across this?

Thanks, Tom

[olcah]

I removed a slow speed needle from a parts 1956 Johnson RD18 carb.. The needle has threads at the needle end. There are no other external threads. The packing is tightened by 303982 needle valve nut. It threads into the carb body. The only other threads on the needle are internal at the far end to hold the indicator in place. RD18 is a 30 HP motor. Is that what you have for sure?

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[fry-cook]

I have p/n 303982 Nut as shown in your picture, and a needle valve, however, as mentioned my needle valve has another set od threads that actually thread onto the bushing. I’ll post a picture when I return home this afternoon.

Thanks, Tom

[frankr]

What olcah shows is all they ever made

[fry-cook]

Here is a photo of it, now the threads at the needle end wore off taking it back off. Keep in mind it has(had) two set of threads.

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[opposedtwin]

Those weren’t threads, those are wear marks. That needle is toast!!

[fry-cook]

So I’ll order the P/N according to my parts catalog. So, the bushing doesn’t thread onto the needle valve then?
Thanks, Tom

[olcah]

The aluminum bushing is part 303939. Normally it is retained in place in the carb body and prevented from turning by the 303982 nut. If you unscrew the aluminum bushing off the needle, your needle will look like the one in the parts list. Here is a factory parts list in case you do not have one.
Interestingly the one in my photo does not look much like the parts list, bet they interchange. I would put your needle in a lathe and try to recut the damaged tip. It’s worth a shot.

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Attachments:

Johnson 1956 30HP RD18 RD18E RD18C Parts.pdf

[chris-p]

What you think are 2 sets of threads are just 1, you just have the bushing mid way on them.

[Buccaneer]

I tore apart a carburetor on a RD-17 yesterday.
The "high speed" needle is blunt on the end,
not pointed like the low speed. Has low speed
needle been altered, or is that the way they are?
Hard to tell from the parts diagram.
Thanks.

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Prepare to be boarded!

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