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85 Maxim X Finally Back Together!

Discussion in 'XJ Technical Chat' started by Medici, Feb 24, 2017.

  1. dkavanagh

    dkavanagh Well-Known Member Premium Member

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    Stumplifter recommended "switch to prime" because you can remove the vacuum line going to the petcock and attach your manometer.
     
  2. Stumplifter

    Stumplifter Well-Known Member

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    You have a Maxim X - what I know about pertains to an 81 Maxim - I do not know for sure if they are apples to apples but . . . .
    Traditionally the vacuum line for the petcock runs to the vacuum port on carb #3. As you already know it needs to be removed so that a manometer can be attached. As XJOE550 said the Petcock set to PRI will allow it to function without a vacuum source, so just pull the vacuum line off of which ever carb it is attached to and let it dangle.

    I use a ho-made two bottle manometer so when synching 1 to 2 one of my vacuum port caps has to go on to #3 since it was exposed after removing my petcock vacuum line. Point being - all vacuum ports should be covered during the synchronizing process, whether they are all attached to 4 hoses like on a Morgan Carbtune or 2 connected to a two-bottle with the other two ports then getting capped.

    Good luck and keep asking questions until it makes sense to you.
     
  3. Medici

    Medici Member

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    Stumplifter the vacuum line is on the engine-to-carburetor boot (the one that connects to the petcock normally). When you are referring to the vacuum port caps are you meaning those on the boots I just mentioned? or is there something on the carb body itself that gets connected to a vacuum line? If not what's the best way to get those little vacuum caps off the boots? I tried to do it when the boots were off but out of fear of tearing them I decided not to.
     
  4. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    The caps just need to be pulled off. If you need to use pliers, then use pliers. If they tear, no big deal; new ones are available at any auto parts store for a few dollars.
    The only vacuum ports are the ones that you see on the intake boots. None should be left uncapped, or unhooked, while the engine is running.
    The only vacuum line is the one that goes to the petcock.

    This video should clear up how to hook up a manometer for a running synch.
     
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  5. Stumplifter

    Stumplifter Well-Known Member

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    Yes those boots have the vacuum caps/ports.
    As Kmoe said use whatever it takes to get them off.
     
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  6. Medici

    Medici Member

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    Stumplifter so my final question is what is going to be connected to the vacuum side of the petcock while I'm running the sync?
     
  7. quebecois59

    quebecois59 Well-Known Member

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    You won't need anything to be connected there while sinc'ing because if you put the petcock selector on PRIME, the fuel will be gravity fed, then no vacuum is needed to open the petcock and let the fuel flow.

    Actually you may use any auxiliary source of fuel with a manual valve during the process, as long as it is connected to the carb fuel intake
     
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  8. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    I use a snowblower gas tank when I sync.

    Sync screws are different than mixture screws.

    Bench sync is only so you can get the bike to warm up SO That you can do a running sync. It is the base starting line. It may be darn close, but it's still not dialed in. You might think it is, but it ain't.
     
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  9. quebecois59

    quebecois59 Well-Known Member

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    Lawnmower fuel tank for me !
     
  10. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    I just carefully balance the regular tank sideways on the frame.
    I am also an idiot.
    A lucky idiot.
     
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  11. BigT

    BigT Active Member

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    I made my auxiliary tank from a universal radiator coolant overflow tank I found at the parts store for about $9. Just added a metal coat hook to hang it on the handlebar and a shut off valve. It's clear so easy to see the fuel level.
     
  12. Medici

    Medici Member

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    Right, I understand that I will have to run the vacuum sync. The sync screws are the 4 brass slotted screws on the fronts of the carbs sticking straight up sitting in the posts? To be honest I don't really see any other screws, I did hear a lot about the regular maxim (non-x) having only 3 sync screws so you have a baseline to sync to. I do not see this on my mikunis as I have the maxim x. I have a question regarding syncing in general though. I understand the concept of keeping the fluid level in the manometer equal across the carburetors, but with the usage of a common 4-pillar manometer you can have an equal sync but the pressure (or rather vacuum) level can be at 22 cm/hg but can also be at 24 cm/hg. If one carb is adjusted will it naturally pull the other vacuum down to equilibrium? And if I'm using a diy/bottle manometer (let's assume two bottles) and get the fluid levels to stop moving with respect to each other is that a complete sync? or should they equalize out level? I understand these questions may be somewhat complicated but for my sake I feel that I should know.
     
  13. Stumplifter

    Stumplifter Well-Known Member

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    Good questions, cause you want to know for sure before you start.

    The synch screws (on Hitachi) are 'connected' to the butterfly valve shafts, they slowly open/ close the valves to fine tune the bench synch. Not being familiar with Mikunis it sounds like you may be talking about the air/fuel mix screws. ?

    With the 4 pillar models, equal is equal, no matter what value. Two bottle, I was told no movement is equal, being the anal, over-thinking-it-again kinda guy, I got my two bottle very close to even and equal.

    Note on two bottle construction; if your connecting tube between the two bottles is too narrow, the device will work like shite and you will say nasty words! < fact :p
     
  14. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    The four screws on the top of the carbs are the MIXTURE screws.

    The sync screws are down between the carbs at the ends of the butterfly shafts. Thee are 3 of them. 1 is between carbs 1 and 2. The second one is between carbs 2 and 3. The 3rd one is between carbs 3 and 4.

    The screw between 1 and 2 balances those two to each other. The screw between 3 and 4 balances #4 to #3.. The screw between 2 and 3 balances the 1&2 pair to the 3&4 pair.

    There is no adjustment for 3. They all get adjusted to #3. Idle speed is maintained with the idle screw in the rear middle.

    For all the hassle of trying to build a manometer that actually works correctly, and consistently. I chose to do the simple thing--I bought the Morgan Carbtune Pro. I"d recommend that over anything........buy it, wait for it to arrive, never have any trouble again.

    Dave
     
  15. quebecois59

    quebecois59 Well-Known Member

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    Here are the three sync screws.
     

    Attached Files:

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  16. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    That's where there are-------just realize the screws are on the top, of course........springs and supports are on the bottom
     
  17. Medici

    Medici Member

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    So I'm assuming all of these screws (in order from cyl 1-4) control carbs respective to cylinder 1, 2, and 4? 3 is essentially the "vacuum baseline" per se?
     
  18. Stumplifter

    Stumplifter Well-Known Member

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    3's butterfly is controlled by the idle screw, not really a vacuum baseline per say . . . You don't measure 3's vacuum and match the other carbs to it. I believe the manual says you synch 1-2 then 3-4 (3 is not adjustable per say, so you synch 4 to 3) and finish synching the 'left bank' with the 'right bank' .
    Some members start with 3-4, this can help prevent a condition where your idle needs to be adjusted to keep the bike idling properly while you synch all 4. . . . .

    I don't think I am being very succinct with my explanation. . . long week.
    A 4 line manometer (as Dave mentioned) really does make the process easier.
    This may help, he offers good tips, like not pressing on the screw driver.
     
  19. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    As I said
     
  20. quebecois59

    quebecois59 Well-Known Member

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    With the air cooled XJs it is important to run a big fan in front of the bike during the process. The engine has to be fully warmed up before you start to sync the carbs, but then you need a fan to keep the engine from getting too hot, because the process may last several minutes.

    Your Maxim-X is liquid-cooled, so theoritically you don't need an extra fan, unless you know for sure your cooling fan doesn't work properly or the thermo switch won't kick the fan on at the right time.
     

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