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    Jetting help

    I have a GS 750E (1979) and have real K&N, a 4-1 exhaust (brand unknown, badge is gone) with the Dyna coil kit. I have already dipped and detailed the carbs. I've beadblasted them and have already painted one. I bought a carb rebuild kit off Ebay, but then thought about the jetting. The bike ran great before I started tearing everything down for a rebuild (bought it off my friend-he used it as a commuter before the wife grounded his two wheel antics), I'm sure it had to of been jetted correctly for the mods. But, like a dummy, I threw away the old jets (except for the main jet and needle jet since it didn't come in the kit). Does anyone else have this basic set up so I can use those jet sizes for a starting point? My main jet is a 140 size FYI. I've got a good understanding of the VM rebuilding process. I just need approximate settings/jet sizes-for my specs. Thank you! PS(I"ve used the search function-can't locate a bike readily with this info)

    #2
    Uhm... Im having a REALLY REALLY hard time believing your main jet is a 140. You sure thats not the air correction jet out of the carb throat? The STOCK 79 750 jet was like a 102?? Somewhere around there, and with a FULL set of Pod filters and a VH 4into1 or the like most guys are ending up around the 117-127 range, depending... 140 is larger than a GS1100E would take for a main, even larger than a DJ 1100E main with pods and pipe and they're measured larger than the stock mikuni sizes.. Basicly what im saying is that you need to double check that size. There is no way that bike is running on that jet without fouling the plugs black as coal, if it would even start to begin with....

    As I said, with a K&N airbox drop in filter, which Im assuming is what you're talking about having, and a decent 4-1, you would probably end up around the 110 or so range on the main jet. The stock pilot jet size should work just fine, especially in your application, which is a #15 size. I think the jet you have is likely the air jet, maybe a 140? Needle should be fine in the stock middle clip setting. You shouldnt have thrown your old jets away, there was nothing wrong with them. The "Rebuild Kits" are garbage, and use inferior brass and horribly measured jets. You have no idea what the REAL sizes are, despite what they say. I would suggest you go to www.z1enterprises.com and buy a BRAND NEW set of Mikuni main jets, and pilot jets. They're only a couple bucks each and are the real deal. Then, get a set of carb orings from www.cycleorings.com and maybe you can sell those rebuild kits to someone else or on ebay or something. If you install those kits, and the jets you have, you're going to be back here shortly wondering why your bike is running like crap..or not running at all..

    Once you have the parts above, follow the carb rebuild and cleaning tutorial on the Garage section here TO THE LETTER, DO NOT skip any portion. If you do, you will likely miss some little crud somewhere in a passage and you will be angry because the bike wont run right. If you follow the instructions, that 750 of yours should run like a scalded dog with the right jet set up, and they are one of, if not THE stronges GS motor ever..And, even though they arent the most powerfull of the lot, they are pleanty punchy, and a personal favorite of mine. I have a few of those puppies.

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      #3
      Thank you SO MUCH for the responce Cafekid!

      Here is a pic of the main jet (my camera won't focus on the small details, the number on the main jet is 140). I am running K&N pods (I forgot they do make the airbox version)

      Here's the pic

      <a href="http://s178.photobucket.com/albums/w...S2010059-2.jpg" target="_blank"><img src="http://i178.photobucket.com/albums/w...S2010059-2.jpg" border="0" alt="gs 750 jet"></a>

      <a href="http://s178.photobucket.com/albums/w...S2010059-2.jpg" target="_blank"><img src="http://i178.photobucket.com/albums/w...S2010059-2.jpg" border="0" alt="gs 750 jet"></a>

      I don't doubt you one bit as to it sounds way too big. I'm not a carb expert by any means. Do you think my buddy could have run this jet because something else was a miss (such as another jet clogged or of the wrong size?) The pilot fuel screw and needle jet don't have any visible sizes on them.

      Is the "Air Correction Jet" screw the same as the Pilot air screw?

      I'll definately get my jets from Z1, I love that they support us "old soul's"

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        #4
        the jets in my 750 when i got it was 100's currently there is 120's woohoo

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