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Carbs back on, won't start.

Discussion in 'XJ Technical Chat' started by troym204, Sep 12, 2017.

  1. troym204

    troym204 Member

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    1985 XJ700 Maxim

    Put the carbs back on, tried to start and got this:





    They have been bench-synced and Fuel Levels are set within spec (1mm +/-1mm)

    Any ideas where to start?
     
    Last edited: Sep 12, 2017
  2. Timbox

    Timbox Well-Known Member

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    Did you prime them? Turn the petcock to "prime" and that way fuel will fill the bowels up. If no then you will have to do a lot of cranking and just to get fuel level to the correct level in the bowels before she will fire.

    Second think you could do is tap the bottom of each cab with a soft object to make sure the floats are not stuck in the full up position and not allowing fuel in. Try those two things and see what you get.
     
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  3. troym204

    troym204 Member

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    I'm using a home made auxiliary fuel tank so the gas should be flowing freely (there is a breather).

    I tried tapping the carb bowls and starting, no dice. So I tried really tapping the carb bowls and starting, nothing.
     
  4. Timbox

    Timbox Well-Known Member

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    I can't tell if you have pods or airbox and if the back of the carbs are open right now? I only ask because you could put your hand on the back of one of the carb opening as you try to start it. This will put extra "choke" pressure and pull fuel up in that one carb. If you have spark and everything else is correct then you should get her to fire.

    Any way to unscrew the drain screws on the fuel bow to make sure you have fuel in there....I know it is hard to get at.
     
  5. troym204

    troym204 Member

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    There's an air box and yes the back of the carbs are open, I wanted to be sure it would fire before I suited er back up. I'll give it a try with the extra choke pressure and back out a drain screw to make sure it has fuel.
     
  6. troym204

    troym204 Member

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    Bowls have gas, backed out each drain screw.

    I checked resistance on my spark plug caps, although I am seeing arc from each plug I am getting readings of:
    1- 8.5
    2-Nothing
    3-Nothing
    4-7.7

    I must be doing something wrong if I am getting no reading on caps 2&3 but am seeing arc from plug to engine, right?

    I am plugging the ground into the plug side and the positive into the wire side.

    I have my multi meter set at 20K which I believe is right, no?

    What are some other things I can look into?

    Thanks.
     
    Last edited: Sep 12, 2017
  7. k-moe

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

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    Caps 2 and 3 on the 700 were non-resistive IIRC.
     
  8. troym204

    troym204 Member

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    That would make sense.

    Any ideas what could be the problem k-moe?
     
  9. k-moe

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

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    My ponderer is tired.
    Make sure that the plug wires are on the correct cylinders.
    She want's to fire, and sometimes the first startup after a long sit is difficult; even when everything is set up correctly.
     
  10. jsngrimm

    jsngrimm Member

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    Have you tried any starter fluid? Sometimes that little kick is all they need, after sitting for a couple weeks my 650 Maxim did pretty much the same thing but a bit of starter fluid got it to fire right up
     
  11. troym204

    troym204 Member

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    Tried the starter fluid, Ill give it another go in the morning. Battery is on a trickle charge right now, wake up and give er hell.
     
  12. XJ550H

    XJ550H Well-Known Member Premium Member

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    pull the plugs see if they are fouled. when you try to start it also do a voltage drop test on the battery.
     
  13. troym204

    troym204 Member

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    Did a voltage drop test shortly before I took the bike apart 3 weeks ago, it was good. Ill give it a try in the morning as well.
     
  14. XJ550H

    XJ550H Well-Known Member Premium Member

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    XJ700 air-cooled models:

    Pick-up coils:
    120 ohms +/- 20% = 96 ohms to 144 ohms acceptable range


    Ignition Coils:

    Primary side (input from main wiring harness):
    2.7 ohms +/- 10% = 2.43 ohms - 2.97 ohms acceptable range

    Secondary side (spark plug wires, without their end caps):
    12K ohms +/- 20% = 9,600 ohms - 14,400 ohms acceptable range


    Spark plug caps:
    1985 N/NC models: 5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range
    1986 S/SC models: 10K +/- 20% = 8,000 to 12,000 ohms per cap acceptable range


    Spark plugs:
    1985 N/NC models: 0 ohms per plug
    1986 S/SC models: 5K ohms per plug
     
  15. troym204

    troym204 Member

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    Seems like I have some bad caps, going to plug into a few more things tomorrow while I'm at it.
     
  16. XJ550H

    XJ550H Well-Known Member Premium Member

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    no reading on 2 and 3 is open caps bad
     
  17. troym204

    troym204 Member

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    I'm not following, sorry.
     
  18. XJ550H

    XJ550H Well-Known Member Premium Member

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    if you do not get a reading when you ohm out the sparkplug caps the connection inside the cap has been broken it is refered to as open a switch is open or closed. closed conducts open does not. think of it this way hook your meter to a piece of wire you get a reading may be o ohms but some kind of reading.
    cut the wire you have no reading because you opened the circuit.

    you are getting 8.5K ohms in 1 cap 2&3 nothing and 4 is 7,7k ohms

    from xj4ever you should have the following readings

    Spark plug caps:
    1985 N/NC models: 5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range
    1986 S/SC models: 10K +/- 20% = 8,000 to 12,000 ohms per cap acceptable range

    if your bike is the 85N your caps are out of spec. 4k to 6k ohms is spec.

    if kmoe is correct you should have ) 0 ohms on the 2&3 cap

    touch your probes together and see what you get for a reading .Idealy you get 0 ohms if you get a reading you adjust your numbers but you are looking at thousands of ohms so probe error should not enter into it when measuring caps.
    there is a thread in DIY forum on using a meter.

    I can not find spec in my manual for your bike so i will default to the posting of @chacal
     
  19. troym204

    troym204 Member

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    Gotcha 550 that makes sense, I should be seeing a reading of 0 as opposed to no reading at all for caps 2 & 3.

    It must have just been a rough start, she is going now btw.

    I did replace the plugs last night and cut back some bad wire on the cap end (of the wire) as well, but there is no telling that was the cause as it wouldn't fire until today. Chances are the battery was weak by the time I did that though from previous attempts and I had it plugged up all night.

    When tuning the carbs I know they are supposed to be within a certain allowance of each other but is there a specific "acceptable range"
    in cm hg?
     
  20. troym204

    troym204 Member

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    Found recommended spec for the 85 XJ700 is 180mm hg which is equal to 18cm hg.
     
  21. Stumplifter

    Stumplifter Well-Known Member

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    Not sure what you are using for synching but; aim for "exactly equal" settle for "pert near perfect".
    You bike will reward you.
     
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  22. Timbox

    Timbox Well-Known Member

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    Good job on the trouble shooting and sticking with it, you have her running now get her purring.
     
  23. troym204

    troym204 Member

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    So I was running off of my AUX Fuel Tank and using the carbtune pro I meticulously synched my carbs I would almost even say they were perfect. She was running strong, idling at 1,050, just purring.

    Had er running for a good 15 minutes, cleaning up to that sweet sound of victory. So I thought.

    Fast forward to today, put the calipers on, bleed em and finish buttoning everything up and lastly put the gas tank back on.

    I connect the vacuum line from Carb Intake Manifold #2 to the brass nipple on the back of the freshly rebuilt petcock (thanks Chacal), attach my inline fuel filter to the side fuel supply, set to prime to fill the line and nothing flows past my filter.
    Suspecting some residue from the gas tank clogging the filter I pull it off and see if its clogged, its not.
    Fuel will flow through the filter, only when it is disconnected from the carbs.

    I was able to get gas to flow by choke starting the bike and plugging the little hose for the air intake on Carb #1, upon switching back to "ON" the fuel would immediately stop flowing. I rebuilt the Petcock using a guide that was given to me from someone on the forums, very detailed with pictures and followed to the T, polished the seat sanded the mating surfaces etc, it was a labor of love.

    It would run on "PRIME" for a few minutes, even around the block but it was definitely pulling less and less fuel each time I stopped to look.

    Does anyone have any ideas what could be happening?

    Edit: I just went down and checked, I had it set to "PRIME" when I last checked there was no fuel in the line. Just checked and the Fuel Line was full, started the bike and it quickly pulled all of the fuel out of the line (possibly 15 seconds or so). Is it possible its just slightly clogged? Not sure if that explains the bike running choppy suddenly when I took it around the block.
     
    Last edited: Sep 16, 2017
  24. Stumplifter

    Stumplifter Well-Known Member

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    Sounds strange. Maybe the gas cap vent is schmecked up. Trying popping the tank cap open and see if the fuel flows better.
     
  25. troym204

    troym204 Member

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    Already attempted that, one of my first thoughts as well.

    I am thinking the fuel filter is partially clogged (although air passes through it no problem?) and that fine rust particulate (the tank sat dry the 4 weeks it was off and there was some rust in it) made it past the in tank filter and the in line filter as well and got into the carbs. What do you think?

    Its showing symptoms of a clogged fuel filter, I think I will just:

    1) Clean the fuel tank with Muriatic Acid (any suggestions, tips or better methods?)
    2) Replace in line fuel filter
    3) Take carbs out and open them up (without breaking rack) to shoot some cleaner and compressed air through just in case the fine particulate made it through (from some reading it seems very possible something passed through both filters clogging the carbs back up)
     
  26. k-moe

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

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    What type of filter did you get? Not all filters will flow enough gas with a gravity-fed system.
    I prefer filters with a sintered bronze element.
     
  27. troym204

    troym204 Member

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    It's the same filter that the PO had, seemed to be working fine to me. It looks as though it's got the sintered bronze element.

    It looks just like this, may even be it.
    https://m.summitracing.com/parts/knn-81-0221

    Correct me if I'm wrong but I thought that the petcock was vacuum operated, so that wouldn't add up as it also would not flow when set to the "ON" position.
     
  28. k-moe

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

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    That's the filter I used to use, and it works well. Just check it once-a-year as the filter body becomes brittle and will fail.

    The petcock will only flow fuel in ON and RES positions when the engine is running. Use the PRI position to check for fuel filter blockage, and general fuel system issues.

    You may be looking at a plugged gas cap vent as the culprit.
     
  29. XJ550H

    XJ550H Well-Known Member Premium Member

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    do you have the cone facing gas tank?
    how much gas do you have in the tank?
    is hose after filter below the level of the petcock?

    how to clean gas cap

    Your Gas Cap and You
     
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  30. troym204

    troym204 Member

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    K-moe
    Would leaving the Gas Cap open tell me if this is the case or not? The fuel would very slowly flow, just enough to barely maintain idle and once throttle is pulled it bogs and almost dies before getting some gas and revving.

    XJ550
    The fuel filter is oriented correctly
    Full tank
    Hose after filter is below the petcock
     
  31. XJ550H

    XJ550H Well-Known Member Premium Member

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    gas cap open would tell you if cap was clogged.

    spray carb cleaner from the output side of your filter through to inputside will clean out the crap
     
  32. Stumplifter

    Stumplifter Well-Known Member

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    Is the fuel line kinked somewhere?
     
  33. XJ550H

    XJ550H Well-Known Member Premium Member

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    did you buy a rebuilt petcock or the kit to rebuild it?
     
  34. Timbox

    Timbox Well-Known Member

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    Reading down through the new problems. Is there a way you can leave the stock tank on the bike and then hook the AUX tank back to the fuel line? See if the bike will run correctly that way. If it does work correctly you have isolated it to the tank.

    Either the petcock is messed up or something inside the tank around the two tubes that go up into the tank. There are little screens on these tubes that can get all full of stuff and block the flow of fuel as well. Don't take air pressure and fire it up from the bottom, sometimes will will blow off the tubes that are on top of the petcock.
     
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  35. troym204

    troym204 Member

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    Popped lid on the tank, still just a dribble.

    Stumplifter:
    Fuel line was not linked anywhere .

    XJ550:
    I used a rebuild kit, meticulously polished and honed inner workings, followed the guide to the T.

    Timbox:
    I've been waiting to find the time to test with the AUX tank all day, great suggestion. Hooked it up and had fuel flowing enough to keep her idling, it wasn't pretty though.

    It was getting enough fuel with the AUX tank to run, seemed like it wasn't getting quite as much as it should have been though there was a nice pocket of air after the filter, more so than before anyways.
    It was running poorly though, nothing like before I put the tank back on, something had to of made it through to the carbs.
    I'm getting ready to pull the petcock off the tank, I'd imagine the new in tank filter screen is clogged up badly or debris has even made it through to clog up my newly honed valve seat or something.
    I replaced the inline fuel filter as well, I don't think it had been replaced in years. Potentially allowing anything that made it through the petcock to make its way to my zesty new carbs, bummer.
     
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  36. Timbox

    Timbox Well-Known Member

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    Don't feel bad, I think the fist xj I did I pulled the carbs 4-5 times between cleaning the tank and getting all the other bits in the carbs to work right. I was wondering if you replaced the fuel line as well, it can get old and flake off the inside and really plug things up. Also if you did make sure you are using "1/4" ID fuel hose for good flow. I might have that wrong and if I do it will be corrected by others ;)

    Keep plugging away at it, you are close.
     
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  37. troym204

    troym204 Member

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    I'd like to go the Muriatic Acid route to clean the tank, coating it directly after a couple of rinses as it'll be prone to flash rusting.

    Anyone have any suggestions on how to block up the tank lid and the holes for the petcock on the bottom of the tank? (Petcock and Cap will be removed)
     
  38. troym204

    troym204 Member

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    Hopefully I can have her going after this next pull. Replacing the fuel line is a great idea, it could easily be overlooked. Who knows how long it's been there.
     
  39. Timbox

    Timbox Well-Known Member

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    U can use the same petcock screws and just make a little plate and cut a rubber gasket. Sheet metal works good and then almost any rubber thick enough to make a gasket. As for the top, I just fill it as close to the top as possible and let it set. I don't like to improvise a top and then have it leak on me.....not saying it can't be done, just not me.
     
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  40. XJ550H

    XJ550H Well-Known Member Premium Member

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    auto parts store rubber expansion plug tight fit to start but works good
    [​IMG]
     
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  41. troym204

    troym204 Member

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    Finally got around to getting the carbs back off the bike to clean them (again), and more than likely not to anyone's surprise the JB Weld I allowed to cure for 48 hours to secure the Float Pillar in my third Carb Body was deteriorating badly, I wouldn't suggest ANYONE do this although I am sure it would have done the job for a while had I not had to pull them back off.

    Would I be able to replace just the one carb body, or do I need to get a whole new rack?

    Suggestions on Fuel Tank worked great. Major learning curve on the whole process though, took some pictures will probably put a guide together here when I have the time, after my bikes running of course. (Unless there is already a definitive guide floating around I am unaware of, which would be nice to know about)

    Anyone getting ready to clean your Carbs, do yourself a favor. DON'T pick up an old bike, clean the Carbs and not deal with the Fuel Tank. (Amongst many other things)

    EDIT: Its a 1985 XJ700 if that makes any difference. Also if I can replace just one carb body does anyone have one laying around?
     
    Last edited: Sep 22, 2017
  42. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Hey Troy, we should have a good used one, send me a note and let me know if your bike is a California model or the 49-state model............
     
  43. MattiThundrrr

    MattiThundrrr Not a guru

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    Chacal is one step ahead of me again. All I was wondering was if it was an x. Thank goodness I don't have to deal with any of the awful responsibility of being him.
     
  44. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    It is a burden I suffer with great cheer and steely resolve.........
     
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  45. MattiThundrrr

    MattiThundrrr Not a guru

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    I couldn't do it. Thankfully, I'm only cumbered with the responsibility of being so damned handsome.
     
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  46. hogfiddles

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

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    Coffee sprayed
     
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