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Carb challenge for all you gurus and number freaks

  • Thread starter Thread starter Smokinapankake
  • Start date Start date
S

Smokinapankake

Guest
So I got a set of Carbs off eBay. Seller claimed they came off an 85 700E. I have no reason to doubt this.

Some of you might have seen my previous post about how a manufacturer would detune a motor. That was an indirect reference to this question I'm about to post.

I've dug into the eBay carbs and have got the numbers off the jets and such, and have compared what the Ebay carbs have vs. what the Alpha Sports fiche lists for an 85 700E.

Ebay carbs Part Alpha Sports fiche

Unmarked, stainless. DJ? JET NEEDLE 5C28

37.5 PILOT JET 37.5

118 MAIN JET 122.5

Y-5 NEEDLE JET Y-5

135 THROTTLE VALVE 135

160 PILOT AIR JET 160


It appears the only 2 things changed on the Ebay carbs vs. stock (according to Alpha Sports) is the jet needle and the main jet. Assuming it is a DJ jet needle, would the main jet be reduced in size because the jet needle, with its smaller diameter and more gradual taper, allow more fuel to flow?

Next question:

Comparing the Alpha Sports GS700E fiche to the CMSNL.com GSX 750SE (Pop up Katana fiche), we can see these differences:

GS 700E Part description GSX 750SE

5C28 JET NEEDLE 5C32-3

37.5 PILOT JET 45

122.5 MAIN JET 117.5

Y-5 NEEDLE JET Y-7

135 THROTTLE VALVE 135

160 PILOT AIR JET 190

----- PILOT SCREW 1 5/8


I assume the pilot screw at 1-5/8 is the number of turns out from bottom. These were accessible in the Japanese market the pop up was originally sold in.

Can anyone deduce from these figures how the Jap market bikes were detuned from their American market counterparts.
It may be of note that the pop up Katana's displace 747 cc's as cast on the side of the cylinders.

Any thoughts you carb pros?
 
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