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took the carbs to church and now I cant get the bike to start

Discussion in 'XJ Technical Chat' started by NikoRx, Mar 1, 2020.

  1. NikoRx

    NikoRx Member

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    Exhaust .16-.20mm
    1-2-3-4
    .20-.23-.26-(.23/.24)
    Intake .11-.15mm
    1-2-3-4
    .15-.15-(.20/.21)-(.20/.21)

    soooo either I was measuring wrong last time or I wasn’t being forceful enough. This time I really forced and slid the gap measurement tool between the shim and lobe. I am going to double check my shims as well since I do not trust my past self anymore. Hopefully this fixes my f****ing idle issue and it was as simple as that!

    I also put the carbs back together today after a thorough cleaning using carb cleaner, wires, compressed air, and seafoam. I also replaced the dust covers as well! Going to recheck the fuel levels to be oh so sure they were done right
     
  2. XJ550H

    XJ550H Well-Known Member Premium Member

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    do not force, it is a go/nogo test. if 14 slides in and 15 has to be forced its 14.
     
    hogfiddles and chacal like this.
  3. NikoRx

    NikoRx Member

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    Well shoot... disregard those numbers then haha
     
  4. hogfiddles

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

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    Light drag on the feelers is all you want. Now, make sure you’re doing this with the bike overnight-cold. Don’t fire it up first.
     
  5. NikoRx

    NikoRx Member

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    It is cold and light drag if I couldn’t get it in with a gentle press I didn’t count it, so here are the updated clearances
    Exhaust
    0.17-0.21-0.22-0.21
    Intake
    0.11-0.13-0.16-0.16
     
  6. hogfiddles

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

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    Exhaust 2,3,4 are out of spec too fat
    Intake 3, 4 are out of spec too fat

    that is uncommon. It makes me wonder a few things:

    1. Did someone do a shim swap and do it wrong
    2. ARE VALVES HANGING OPEN AND NOT CLOSING ALL THE WAY......do a compression test and find out
    3. Did someone swap cams
     
  7. NikoRx

    NikoRx Member

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    I did do a shin swap last summer! Very possible I messed it up. I did a compression test and they were 165-175psi much too high and makes me think I have too much carbon built up. My family did take it to a mechanic when I was away but I am not sure if they switched the cams, I doubt it.
    When I put the correct shims back in and wrap that up I’m going to do a leak down test
     
    Last edited: Jun 9, 2020
  8. NikoRx

    NikoRx Member

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    Performed the leak down test, heard major Air loss from 1&2 via the intake manifolds(25%) 3&4 had hardly any! (So much so I thought something had broken or I wasn’t tdc and double checked 1&2), if I covered them with my hands the noise was more muffled and I could feel pressure, not sure what to do from here and might go take it into a mechanics.
     
  9. Polock

    Polock Well-Known Member

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    somethings not right somewhere
     
  10. NikoRx

    NikoRx Member

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    Did a leak down test and 1&2 were 25% with air coming out of the intake and hardly any coming out of 3&4. I did it TDC as well. I think I’m going to take it in to a mechanic to check the piston rings and clean the combustion chamber and to double check my work. Valve clearances are in spec as well now.
     
  11. Polock

    Polock Well-Known Member

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    you should take the head off yourself. you might not need a mechanic, if you can find one.
    if you do it will save you a bunch of money
     
  12. Polock

    Polock Well-Known Member

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    how can you have so much leakage on 1 2 but still have those compression numbers. even if your gauge is off, their all really close.
    me thinks re-tests are in order
     
  13. NikoRx

    NikoRx Member

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    So retested today, engine cold, carbs off spark plugs out and coils disconnected along with the TCI 1,2&4 around 180, 3 is now at 150. Held the starter button until the reading on the gauge didn’t go any higher
     

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  14. jaxcob93

    jaxcob93 New Member

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    Someone correct me if wrong, but I think some engine oil down the plug holes and then compression test will show you if its the rings or valves. If the numbers go up after the oil, its the rings and if not its the valves or valve seats
     
  15. XJ550H

    XJ550H Well-Known Member Premium Member

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    you are correct in that test.
    his compression numbers are high

    The Information Overload Hour
    XJ650 and XJ750 air-cooled engines:
    Minimum: 128 psi
    Standard: 156 psi
    Maximum: 171 psi
    Max. variance between lowest and highest: 14 psi

    could be carbon build up


    but he says he has a leek down issue too.
    f) if a cylinder or cylinders have good compression that rapidly "leaks away" (best determined by the use of a Leakdown Tester gauge as listed further below), this points to burned or otherwise problematic valves.

    more
    2) If one or all of your cylinders are too HIGH in pressure, it means that:

    a) you piston domes (tops) and/or the cylinder head combustion chamber have a significant accumulation of carbon upon them, which should be cleaned via some type of chemical treatment or engine dis-assembly and manual removal methods. Note that higher cylinder pressures caused by such build-up may be "masking" or hiding other problems that might cause LOW cylinder pressures, such as worn rings, etc.

    b) your engine has been fitted with aftermarket, high-compression pistons, or has had the cylinder head "shaved".

    NOTE: high cylinder pressures are NOT a good thing, as they tend to blow out head gaskets and can cause accelerated piston, piston ring, or bearing wear.


    You can also test for piston ring and cylinder wall condition by performing a "leak-down" test, which consists of forcing a measured amount of compressed air into a cylinder, and then seeing how long before this air "leaks" out of the combustion chamber and down into the crankcase (past the ring seal):

    http://www.dietersmotorsports.com/Compression-leakdowntest.htm


    NOTE: be aware that some of the ultra low-priced gauges that are typically advertised on eBay, etc. can be quite un-reliable in their readings, and may regularly indicate a false (low) compression reading.
     
  16. NikoRx

    NikoRx Member

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    at this point I am going to attempt to remove the head and follow the steps in my Clymer manual to clean and replace what I can. then probably take it into a mechanic who has the right tools to measure and make sure everything is in spec and then put it back together. I have been so confident that this issue wasn't my carbs, I really took those suckers to church and made sure they were bench synched and fuel levels were good! I am hoping this cleaning and replacing of parts will let me get that bike to idle like its new.

    Any advice on how to go about this process will be much appreciated. When I do it I will be uploading pics!
     
  17. hogfiddles

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

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    I’m curious—- are you counting cyl 1 being by your left knee as you sit on the bike: 1 to your left, 4 to your right (which is the correct way)........ or are you Counting cyl 1 by your right knee as you sit on the bike ? Not the correct way)?
    Dfox
     
  18. NikoRx

    NikoRx Member

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    the correct way, as if I was riding the bike left to right
     
  19. Timbox

    Timbox Well-Known Member

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    NikoRx, before you pull the head (unless you really want to) shine a flashlight into each cylinder and see if there is a large build up of carbon. There are ways to clean the carbon off most of the piston and valves without pulling the head. That is up to you, just trying to save some work.
     
  20. NikoRx

    NikoRx Member

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    there is definitely some carbon build up in there (especially in 1), I ended up buying the top end gasket and seal kits, figured I might as well check and do some valve lapping to just be sure. I am having some weird stuff that just isn't making any sense to me, high compression test all pretty close to each other and yet 1&2 are leaking air out of the exhaust and intake?

    how would you recommend I clean them? the carbs are off since I can't get the bike to idle under 3k, but perhaps I should try this method first and see if it fixes the issue and then break the head if it doesn't
     

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