1975 T500 Needle Jet Series

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Vintageman
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1975 T500 Needle Jet Series

Post by Vintageman »

Per OEM the Needle Jet and Jet Needle are not available for T500. Mine is a 1975 500M

the Needle Jet is 5FP17 I think I see it availbe at JETRUS for example.

What is the Needle Jet series? It is to be a P4, but not sure what the series is so I can see if available elsewhere. My bike is together so was hoping someone knows what the series is for Needle Jet.

Thanks
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tz375
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Re: 1975 T500 Needle Jet Series

Post by tz375 »

According to my notes, it's a 159 series and uses large hex main jets.

What mains are in yours? If they are large hex, the needle jet is #159. If the mains are Large round, the N/J is #188
Vintageman
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Re: 1975 T500 Needle Jet Series

Post by Vintageman »

Tz

Large round so 188. I'l see if available. Suz said no,t which usually means it is not in general.

But if 188 not available I think 159 will work then... as long as I cross round to hex or make the round fit 159.

Thanks
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tz375
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Re: 1975 T500 Needle Jet Series

Post by tz375 »

188 are still available in a limited number of sizes.

http://www.jetsrus.com/a_jets_by_carbur ... mikuni.htm" onclick="window.open(this.href);return false;
No P 4 unfortunately.

That's interesting that you have large round in your 75-M carbs. I thought they changed to 159 series. I wonder if someone forced round jets in or retrofitted them, or maybe the carb I looked at had been modified.
Vintageman
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Re: 1975 T500 Needle Jet Series

Post by Vintageman »

Tz,

I believe the rounds are stock for the T500M ...97.5 if I remember.

I do remember checking the Needle Jet when I was redoing this bike ... and saw no P4. I forgot. So OEM, agin, is correct when the say NA

I did find info somewhere saying the round will screw in well enough to hold in the 159 series which I think still has the P4. I did try a round and found it to hold real well, just wont go all the way in, but sure holds tightly. Can't go the other way around. If this makes others uncomfortable I understand.... try it for yourself.

Now OEM says jet needle is not available either, 5FP17, I'll check somemore to be sure.
There is a Keyster kit, with needle but think it is for the earlier T500 which is different size,

Thanks
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tz375
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Re: 1975 T500 Needle Jet Series

Post by tz375 »

If you really need to change the needle jets I would recommend changing to 159 and large hex jets. There are conversion charts on the web to get the right sizes. I would not try to jam a round jet into a space a hex was supposed to go.

The best way to check needles is on an optical comparitor if you have access to one. Plot the dimensions from the top down and check taper angles. You can probably find a common needle with the same root diameter and top taper and maybe a richer (steeper) tip taper.
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PippiFyrecracker
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Re: 1975 T500 Needle Jet Series

Post by PippiFyrecracker »

email from sudco, relevant to above conversation for future use!

"The groove on the 159 is 11mm. The groove on the 188 is 19mm.
The 188 has a longer guide pin groove so it sits farther in the carburetor.
The 188 series is out of production. We do have a some size P-2 of the 188 series needle jets left that we can make in P-4 or P-5 if you like. They are $17.00 each. "
Chad Thompson
Sudco International Corporation
2410 South Sequoia Drive
Compton, California 90220
(310)637-8330 x 107 - Phone
(800)998-3529 - Toll Free Order Line
(310)637-8331 - Fax
(800)999-3529 - Toll Free Order Fax
chadt@sudco.com
http://www.sudco.com" onclick="window.open(this.href);return false;
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Follow us on Twitter and Instagram- @sudco68

View our Volume 38 Catalog-
http://www.sudco.com/catalog38.html" onclick="window.open(this.href);return false;
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tz375
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Re: 1975 T500 Needle Jet Series

Post by tz375 »

That's interesting info on the 188 series. Thanks.

The slot/groove in 159 series measures out at 17mm but that could make a difference if a particular carb had the needle jet locating pin further up the carb than usual. There may be some applications where that is an issue so it's good to be aware of that.

So why did Mikuni make a 159 series to take hex jets and an effectively identical 188 series to take Round jets? Probably because different jets flow slightly differently and that's what the OEM needed. Or maybe some prefer round jets. One of life's little mysteries.
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PippiFyrecracker
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Re: 1975 T500 Needle Jet Series

Post by PippiFyrecracker »

the types of mysteries that make fixing the bike a real pain in the ass!! hahaah
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