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1980 XJ650 Carb Tuning

Discussion in 'XJ Technical Chat' started by Dave30, Oct 7, 2020.

  1. Huntchuks

    Huntchuks Active Member

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    Calipers are harder to get a good measurement and are only accurate to .0005" or the metric equivalent. Mics are easier to get a good reading and can read to .0001". Convert the measurement to metric and will be more accurate than calipers. Same reason to use metric shims as opposed to standard.
     
  2. k-moe

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

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    All true, but the required resolution for shim changes is only to 0.05mm (0.002"). More resolution than required to read that isn't needed, and calipers are a more versatile tool. I do have both, but then I have need for a micrometer more often than most hobby mechanics.
     
    Last edited: Oct 16, 2020
  3. Dave30

    Dave30 Member

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    Alright, so I've taken measurements and after seeing some other people's measurements I'm wondering if my gauges don't measure in fine enough increments. From 1-4 my measurements are:
    1. I .08mm E .10mm
    2. I .10mm E .13mm
    3. I .10mm E .10mm
    4. I .04mm E .10mm

    Also if these measurements are too broad, could someone suggest a range I should be looking for in order to get better gauges?
     
  4. k-moe

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

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    If you're using metric feeler gauges then you're doing it right. A fair number of people use SAE feeler gauges, which works, but isn't ideal.

    #1: Intake is tight, Exahust is very tight.
    #2 Intake is tight, Exhaust is tight.
    #3 Intake is tight, Exhaust is very tight.
    #4 Intake is very tight, Exhaust is very tight.

    Odds are that you will be able to swap at least some of the exhaust shims to the intake side.

    Next step is to pull shims one at a time and make a chart of what's installed where.
    Then figure our what can be swapped, and what shims you need.
    Use the chart in the following thread. In-spec is In-spec. Use the size of shims that the chart calls for.
    bigfitzs-airhead-valve-adjustment-with-pics-parts-i-ii.116006
     
    Last edited: Oct 17, 2020
  5. Dave30

    Dave30 Member

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    Thanks K-moe, I'll pull them out after lunch and see about getting some numbers.
     
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  6. Dave30

    Dave30 Member

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    Ok got the shim numbers, luckily all were legible!

    1. I Y280 E Y265
    2. I Y275 E Y250
    3. I Y275 E Y270
    4. I Y285 E Y 280

    So how i read the chart these would be the replacement numbers:

    1. I 275 E 255
    2. I 270 E 245
    3. I 270 E 260
    4. I 275 E 270

    Meaning that after I swap the 3 I have on hand I will still require:
    245
    255
    260
    270 x2
     
    Last edited: Oct 17, 2020
  7. k-moe

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

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    Your spot-on. Start a conversation with @hogfiddles with a list of which shims you need.
     
  8. Dave30

    Dave30 Member

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    Conversation started! Ill also see about getting replacement gaskets for the side and valve covers.
     
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  9. Dave30

    Dave30 Member

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    So the new gasket and shims should be arriving this Saturday and I'm looking forward to vacuum syncing the carbs afterwards. Once that's done i want to go through some safety items with you guys to make sure its not a better running death trap ie. brake lines/drum brake shoes.
     
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  10. k-moe

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

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    Check the date codes on the brake lines. Replace if over 4 years old (unless they are teflon lined/steel braided).
    Rebuid the master cylinder and calipers.
    Replace the rear brake shoes (older shoes will delaminate from the backing plate, and make you go BOOM).
     
  11. Minimutly

    Minimutly Active Member

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    Where does this 4 yr old replacement of brake lines come from? Sounds like overkill to me, 8 or 10 yrs would sound more realistic?
     
  12. Dave30

    Dave30 Member

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    I got a replacement brake lever and master cylinder already but will check it again. I have new OEM brake lines and rear brake shoes coming from Len. I also forgot to order the cam-end plugs so I cant put it all back together today. This may be a sign from divine powers as by the time I get the plugs ill also have the new brake lines/rear drum shoes. No big deal I almost have my other bike up and running. Todays objective is to replace the shims!
     
    Last edited: Oct 24, 2020
  13. k-moe

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

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    From Yamaha.
    [​IMG]



    It's truly scary how many motorcycles still have their original rubber brake lines after 20, or 30+ years.
    Why You NEED TO REPLACE Original brake lines w/pics
     
    Last edited: Oct 24, 2020
  14. Minimutly

    Minimutly Active Member

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    I kind of guessed that, but it was written 40 years ago, surely the material spec has improved many times since then? What do yamaha specify for more modern times? Allways assuming (that word again) that the lines you can buy now are more modern?
     
  15. XJ550H

    XJ550H Well-Known Member Premium Member

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    i would think if you looked in a newer factory repair manual for a newer bike you would find that answer.
     
  16. k-moe

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

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    Again...it's scary how many motorcycles still have the original brake lines on them after 20 or 30 years.
    They may be more often overlooked than valve clearances.
    My son's 2003 Honda Shadow also called for brake lines to be replaced after less than 10 years (The service manual is still in a box somewhere or I'd quote the actual interval).
     
  17. Franz

    Franz Well-Known Member

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    Steel brake lines that are corroded should be picked up at the MOT test here on older cars in the UK. Motorcycles because they don't have steel lines that can corrode pass if they are not leaking. Sometimes it is easy to overlook the fact that lines are old on our bikes.
     
  18. Dave30

    Dave30 Member

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    New shims are in the bike! Looks like brake lines and rear drum shoes will get here just before I put the valve cover back on.
     
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  19. Dave30

    Dave30 Member

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    Update: I got the valve cover back on the bike, replaced the front brake lines, and also replaced the rear shoes. They were bad however I simply didn't want to chance something bad happening. I tried to start the bike in order to get it synced and the battery was so low it wouldn't crank. No big deal, so I bought a new one because I didn't trust the previous owners work after seeing some of the stuff he did while fixing it. Put the new battery in, and now the main fuse pops every single time I try to reconnect the negative side. Perhaps the fuses I'm buying aren't the correct type.. they are 20A AGC Fuses but they look different than the one I pulled out of the bike. That one has fat ends with a thinner middle. The new ones are thin all the way across. I would be lying if I said this didn't completely ruin my day. I finally get it all together and now some unknown electrical issue has stopped be right before getting it back on the road.
     
  20. Minimutly

    Minimutly Active Member

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    Retrace all your steps to find what you did to cause this. Start with battery polarity -ve to earth....
     

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