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Jets for Pods and header

Discussion in 'The Garage' started by Steven LaPlume, Nov 18, 2020.

  1. Steven LaPlume

    Steven LaPlume XS400 Member

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    I have a carb rebuild kit coming from Mikes XS. My carbs work fine now. However I am changing to Pods. The pipe I have is actually from an XS-650 but it seems to work fin on the XS-400. The muffler is I guess what's called a tapper tip style.

    I had read that the jets are different sizes for each carb because of how the air box is configured?????

    So with pods and this exhaust I have no clue what size. This is going to be a cafe racer when I get done. And yes I am building it in my living room over the winter. Because I am single and can do that :) Thanks for any help you can give me.

    I am an ex Superbike racer so I have no issue removing carbs and replacing jets and adjusting needles But a starting point will be quite helpful.

    This is the first XS I have worked on. I had an XS 650 but before I did anything with it my buddy bought it off me so I kept the bulk of the parts for the 650 until I can figure out what I can use or graft on to the 400.
    20201118_163217.jpg
     
  2. amc49

    amc49 XS400 Addict

    Are you SURE that header pipe fits tight all the way around at the head? The fitup there looks loose but the head stud and pipe coming out look out of parallel and I for one find 650 fitting 400 somewhat odd. And looks like 2 into 2 which is NOT a header.

    But I've been wrong before.
     
  3. Steven LaPlume

    Steven LaPlume XS400 Member

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    It's just sitting there loose with no gaskets in just to show what the pipe was. I have to do some welding so did not want to fit it on permanent.
    I don't know what its called technically, nor do I care. That's why I provided the pic so you can see what I have and offer a suggestion to my question.
    So do you have a solution/answer or do you just want to bust my balls for your own edification?
     
    spectra likes this.
  4. spectra

    spectra XS400 Junkie Top Contributor

    Remember you are also working with a DOHC bike...........they are a different animal.........

    I upped my mains I think one size on my SOHC when running UNIS I would not run Pods if I was you......I am doing a DOHC bike now and had the carbs rebuilt and he swapped out the jets but not sure whats in there........been a few years and the project was put of the shelf........just picking it back up now....

    Start a build thread on your bike. Interested to see what way you go with it.........

    Good luck!
     
    xschris and Steven LaPlume like this.
  5. amc49

    amc49 XS400 Addict

    The solution is the pipe may not work. Need to go there to verify it before any ideas of jetting.

    Before you start in you should know I have built hundreds of engines both car and bike 2 and 4 stroke, I have jetted just as many. Lots of racing stuff up to 700 inch+ 1500+ hp. pro stock big block Chevrolet running 7's at over 200 mph.
     
  6. Steven LaPlume

    Steven LaPlume XS400 Member

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    OK but if the pipe is the exact same diameter as the stock one I do not see the issue. It literally bolts right up once I get the gasket in there and tighten everything down. The only issue I see is the header part (Which is what Mikes XS was calling it) is needing to be cut back a few inches as the can/muffler part sticks out the back a bit more than I would like.

    I realize everything works together and has an effect on each other. I'm honestly not going to do things like jetting until the spring. once I put on pods and with the new exhaust I figure I'm looking at a few full days and a lot of logging things in and testing before I get the jetting where it needs to be. I might not even get where I need to be with these carbs. Maybe I will need to put on some other ones but I would rather try with these and invest in a lot of jets than buy 400 bucks worth of high performance carbs, which I can't afford at this time.

    Yes I have built quite a few Superbikes but this old bikes a bit new to me. I would think the same principles apply to some extent. I guess I'll see. If all else fails I will get a good after market exhaust made specifically for the XS400 and try again.
     
  7. Steven LaPlume

    Steven LaPlume XS400 Member

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    Unis really? Why them as apposed to the traditional air pod type filters? Does it have an air flow difference that makes it run better? I just like the look of the pods is why I was going with them but I can change it up. Not afraid to chose function over form.
     
  8. amc49

    amc49 XS400 Addict

    I use foam as well, the K&N type will work but they pass more dirt. Hold a run in one up to sunlight and see all the pinholes where dirt can pass through without even touching the filter media at all, Uni types foam do not do that, the route is more circuituous and the twists and turns pass less dirt.

    The front tube IS called a header but differentiate that from true header, which is a pipeSET with a number of pipes matching the cylinder count that all dump into a common collector to mass scavenge individual cylinders.

    Jetting? Go a couple sizes and leave needle alone and call it a day, nothing sophisticated about a non-tuned setup like that one will be. CVs tend to not like pods as it lowers resistance enough to lower the slide action, it depends on a somewhat rarified environment to lift slides faster and the other carbs if all are under a slight vacuum tend to aid each other to work slide faster too. The problem being one of if slide opens a bit slower it's rich while making the actual move but may be not rich once moved and how does one tell the difference when it comes to jetting?; it drives people batty.
     
    JPaganel likes this.
  9. Steven LaPlume

    Steven LaPlume XS400 Member

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    Appreciate the insight.
     

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