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My XJ 600 refuses to start. I checked the battery and the spark plugs. I believe there's water in the carburetors. It has been staying unused for too long in winter. Besides, it stands outside under a cover that tends to retain moisture, if that matters.

I found the carburetors purge screws:

Carburetor purges

When purging I obtained a layer of close to transparent liquid (water ?) with a yellow layer on top of it (gas ?). I suppose my assumption (water in the carburetors) is correct. The picture is not that good.

Water/fuel mix from carb purge

I tried to start the engine again. No success. Purged again. Same output.

I then checked the gas tank output by unplugging the pipe after the gas valve. When on PRI position, the gas flows and it looks fine, homogeneously yellowish.

Fuel valve

On the left, the sum of all carburetor purges (not as transparent as said above because the can was dirty already), on the right, gas from the tank:

Carb and tank purges

My conclusions:

  • Tank looks OK (there might be water in the reserve, though, I can't tell from that test)

  • Water in the carburetors but I won't get it out in one go. Looks like I need several start/purge cycles. There must be water not only in the carbs themselves but also in the pipes above, in the gas pump, etc.

Are those conclusions correct?

How should I proceed? Should I keep on starting/purging and it will be fine after a few cycles? Or is there another method to flush the water with gas without actually trying to start the engine? I left the valve on position PRI but even after two hours or so, nothing would come out of the carb purges.

(I lack both skills, tools and time to take the carbs off and clean them, so either I can get away with this by purging in place, either I push the bike to the repair shop.)

  • Welcome to Motor Vehicle Maintenance & Repair! I would suggest you have water in your tank and you need to drain everything you have and start with fresh fuel. What you have in the right jar looks just like what you have on the bottom of the left jar to me (bottom pic). – Pᴀᴜʟsᴛᴇʀ2 Feb 17 '18 at 22:22
  • Thanks. When purging the carbs in the clean jar, there was clearly two layers, a transparent one and a yellowish one, while what went out of the tank was homogeneous and the color looked closer to the upper layer of the carb purge. I realize it is a bit hard to tell from the picture. Anyway, I don't mind throwing the gas from the tank away to try with clean gas. Thank you for your feedback. – Jérôme Feb 17 '18 at 22:30
  • How should I proceed after I replace all the fuel in the tank? Start/purge cycles as described in the question? How many cycles would be necessary to assume the dirty fuel is flushed from the pipes and carburetors and replaced by the new one? – Jérôme Feb 17 '18 at 22:33
  • Get rid of all the gas in the tank. Then refill with good gas. Put some "Heat" or some other water treatment in the fuel to get rid of any residual. Purge everything out of the carbs before you put any clean gas in it. Then open the tank to the carbs to refill them. After this, you shouldn't have to purge anymore. Just try and fire it up and see how it does. Double check to make sure you haven't fouled the plugs out. – Pᴀᴜʟsᴛᴇʀ2 Feb 17 '18 at 23:47
  • Thanks @Pᴀᴜʟsᴛᴇʀ2. I replaced the gas in the tank and purged everything and it started. The purge was not a trivial step. I describe how I proceeded in my answer, in case it can help anyone. Pretty unprofessionnal, but it worked. – Jérôme Feb 18 '18 at 22:51
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I finally got the motorbike to start!

As suggested by @Pᴀᴜʟsᴛᴇʀ2 in question comments, I purged both the carbs and the tank.

The picture is not that great, but the fuel in the right jar on the last picture was clean. However, there was indeed a bit of water in the tank, as I was soon to discover.

For the carbs, use the screws shown in the first photo. For the tank, unplug the hose after the valve (see third photo) and set the valve on PRI position.

Good, but there is still some fuel left in both the carbs and the tank after that, and when pushing the start button with the fuel hose off, I can clearly see that the fuel coming from the valve is dirty (water layer at the bottom).

I managed to remove the rest of the fuel by pushing the start button with the carb purges open and the fuel hose unplugged. For the carburetors, push the start button 2 or 3 times. For the tank, it takes so much more I had to recharge the battery. I suppose the proper way would be to remove the tank.

I ended up proceeding like this:

  • Set valve on RES position (reserve)
  • Shake the bike strongly (standing on its left, push it away, then stand on the centre stand pedal to bring it back) two or three times
  • Set valve on PRI position -> the valve spits a small drop

After a lot of iterations, the tank was empty.

Overall, the operation was pretty dirty...

Once this was done, I refilled with new fuel, pushed the start button twice to check what was coming out of the fuel valve, then plugged back the fuel hose, and the motorbike started pretty easily.

  • Glad you were able to get it fixed and then posted the fix action here. Don't forget to select your answer as the answer when it allows you to. – Pᴀᴜʟsᴛᴇʀ2 Feb 18 '18 at 23:22
  • Yeah, this might not be the most professional and efficient method, but it worked as a cheap trick. At least I hope the pictures can help other beginners to find the purges and all. (I imported them on stack.imgur to be sure they don't disappear.) Thank you for your support. – Jérôme Feb 19 '18 at 8:26

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