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85 xj700 (air) starts, but won’t stay running…

Discussion in 'XJ Technical Chat' started by Ray Rath, Jun 11, 2025.

  1. Ray Rath

    Ray Rath New Member

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    So full disclosure, I’m new to motorcycles and this is my first purchase, so I’m using this to learn about riding and maintaining.
    I bought an 85 XJ700 (air cooled) and I have been going through all the things! It was a barn find, guy sold me 2 (xj700 and xj700x) and I’ve been restoring the xj700. I’ve replaced all the cables, got new filter and oil (20w-40) on it’s way, replaced the master cylinder, rebuilt the carbs (yes I did try an eBay kit, but pulled the jets out and put the originals back in [and yes! I soaked them, I soaked them, I soaked them!!!]) and I also have some minor cosmetic things on the way (mirrors, side panel and tires)
    But I’m running into an issue. After all the work, I can get the bike to start, but it won’t stay running. I was told the other day to feel the pipes once I get it going for a bit, and one pipe isn’t getting hot (it’s the third pipe) (also not sure which POV everyone uses when saying these things, so, sitting in the bike third from my left, looking at the bike from the front third from my right). Who ever told me to check the temperature, did say why, but I kinda spaced on that part (I blame my ADD) . So could someone let me know the significance of the one pipe not getting hot? Also could this be the issue keeping the bike from running?

    Thank you in advance,
    Ray
     
  2. Timbox

    Timbox Well-Known Member

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    Welcome to the forum. I know this is going to sound bad, but I pulled my carbs off my firt XJ project bike six times before I got it right. Everything from missing this jet.
    [​IMG]carbs_floatbowl_choke by Tim Brown, on Flickr
    This jet is the chock ckt jet and needs to be cleaned with a very thin wire, carb cleaner and compressed air. If you have liquid passing through the jet you should be good to go.

    To not doing a wet set on the float bowls and messing it all up. It takes a while, so no worried, just keep lugging at it and you will get there.

    You will need a manual, either paper or electric type. That will help so much and does not cost that much.

    Getting an inferred temp gun is really nice to have for the pipes, that way you will not burn your hands.

    Yes, all orientation on the bike is from the rider sitting on the bike. So yes, the cylinders start on the left side being one and end with the far right one being four.
     
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  3. Ray Rath

    Ray Rath New Member

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    First off, the float bowls on my carbs look nothing like that. Going to assume it’s due to different model.
    Also funny you should mention the IR temp gun cause I just learned how hot those pipes get .
    But I did make sure all the passages were clear. Hit everything with carb cleaner, then used canned compressed air and realized it wasn’t enough, so I bought a small compressor and hit all the tubes with that.
    But I did just find that two of my spark plugs are wet, and now only 1 pipe (pipe 4) is getting hot, and found that out the hard way :-/
     
  4. Timbox

    Timbox Well-Known Member

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    The end of the spark plug wires might need to be trimmed just a short bit. I mean 1/8th to get a good copper connection to the plug boot. I would start to remove each wire connector one at a time, inspect, clean, dielectric grease and then put back together. That will help with any other electric gremlins that might pop up in the future.

    Pulling all the plugs out of the cylinders. Put the plugs in the plug boots and have the metal end of the plug resting on metal on top of the engine. With dim light, turn the ignition on and try to start the bike. Looks for spark at each plug.
    I should have put in the above post that those carb bowls are just for reference. Your bowls don't have that jet in them?
     
  5. Ray Rath

    Ray Rath New Member

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    Mine look like this (it’s a google photo, not mine)
     

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  6. Ray Rath

    Ray Rath New Member

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    Also I have tested each plug and cable, I’m getting good spark from each. But I did find I’m getting some flooding and I believe it may be from too much oil. I’m now waiting on a new oil filter and oil to come is so I can correct it and see if that is the issue

    I live in a rural area and have to order everything :-(
     
  7. Timbox

    Timbox Well-Known Member

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    A good rule of thumb is to fill the oil until it is halfway on the oil window. I would guess you are getting gas seep through your carbs and it is going into the oil. If the window starts out at half but by the next morning is over half, you have fuel getting into your oil. Happens all the time with CV carbs.

    If you remove the oil cap and take a sniff of the oil, it might smell like gas. Don't run the bike very long once the oil is contaminated with fuel, it will hurt some of the moving parts in there.

    Why do you think to much oil? Flooding normally only happens with fuel getting into the cylinders. This is because the float bowls are not the correct height, or the bowl jets are bad and not stopping the fuel flow once the floats do their job.
     
  8. hogfiddles

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

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    Yes, because yours is an air-cooled engine……you have Hitachi carbs. The one shown looks like it is a mikuni, but I’m not sure what it’s really from…….none .of our mikuni’s have a big hole in the bottom like that. It looks more like a snowmobile carb. Ours have a small port to the side for the drain screw and the fuel level tube.
     
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  9. Ray Rath

    Ray Rath New Member

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    when I first got the bike I didn’t take a look at the window and added a quart and a half of oil just to make sure that as I was testing to see if it would start, I wasn’t damaging anything internally
     
  10. Ray Rath

    Ray Rath New Member

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    I’m gonna go out on a limb here and say I might have had a TINY bit too much oil in the bike…. :(

    took 1 and a half oil pans to catch all the oil
     
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