FJ1200 '88(?) - possible fuel starvation

[Maniaxro]

Hello. First post, non native speaker, weird problem, so please bear with me and excuse the wall of text.

      So, this spring I decided to do some maintenance on my FJ. Changed oil + filter and checked the petcock (electrical) that seemed to have developed a leak. I dismantled it, cleaned all the parts, added a zip tie to ensure the elbow will not get out of place. Upon reassembly I checked it by creating vacuum with my mouth; it worked, but it had a small leak in the rubber gasket that envelopes the wires leading to the solenoid. Either way it seemed to work well, lots of gas pouring in at the slightest vacuum. I also replaced the hose coming out of the elbow until the Y part. I didn't found identical hose, so I used generic one for fuel, same interior diameter but a bit bigger on the outside one. I cut it to length and fitted it according to the picture. I did a short test drive and things seemed to go smoothly. 

      This is were the magic happens: my bike got stolen and then recovered after a few days. Some thugs looking for cheap rides. The ignition switch was cut with an angle grinder and when they were low on gas they tried to chisel out the tank cap. I got the bike back with empty carburetors and half a tank of gas. I had a look at it, refilled the carbs with gas and tried to get it back to running condition ever since.

      The problem I get is that apparently the carbs don't get enough fuel, it vibrates a lot when pulling on the acceleration and it seems that something is pulling back, no power, no RPMs, etc. I dismantled the petcock once again, all seems fine, the vacuum line is OK, ran the bike to see if it creates enough vacuum and it does, the fuel flows fine. I checked the vacuum valves in the tank cap and cleaned the metal surfaces from oxides to maybe get a better flow, all seems OK. When I get problems I try to open the gas cap and I don't get the woosh sound, as it would be expected when having a vacuum in the tank. The only weird thing about the tank cap is this whistling I sometimes hear when the bike is standing usually on the side with the engine cut off. It disappears when I put the key in the lock.

      The only remedy I found so far for the problem I have is to pull hard on the acceleration and after some vibrations and other unpleasantness the bike seems to get better into higher revs and normal acceleration. Now I know this might be a sign of bad ignition on one of the cylinders\bad coil but I checked all the spark plugs, cleaned them and tested them. They all look and perform the same. Also the exhaust pipes from all cylinders seem to be the same temperature. I am still trying to find the solution, at this point I can't really afford a specialized service to have a look at it and I fear they would just start to replace parts they think are troublesome until the problem is gone, which I can't really afford either before knowing what\who I should blame for the problem.

      So, if anyone had this problem before or thinks of something I should check\try please let me know, I am kind of in a mind block now and more brains are better than just one.

Thank you, Lucian   

[aviationfred]

Sorry that your FJ was stolen and damaged.   

My take on this is..... It seems that you bike was running well after your maintenance. Once the bike was returned to you, it now has a fuel starvation issue.

The whistling you here is the fuel tank venting (a good thing). My thoughts lead to you needing to replace the fuel cap. You mentioned the thieves damaged it. The damage could lead to the tank not venting properly.

Fred

[Pat Conlon]

Check your fuel line routing. Easy to pinch a line with improper routing.
Check the vacuum line to the petcock.
Too bad you don't have a 84/85 petcock, you can put those on (P) prime and open the flow.
You can't do that on the '86/88 petcocks.
So it struggles at midrange? Pull the carbs, check the holes in the needle jets, see if they are clean and open. Might as well do
through cleaning of the carbs while you're in there.
Ignition switch damaged? Could you have an intermittent electrical issue with your igniter box?


Let us know what you find.

[FJmonkey]

Look in the tank, maybe the bastards toss in some bad stuff.

[Maniaxro]

  Fjmonkey wins the quiz! Took out about half a liter of water from the fuel tank, effin' bastards. My guess is vibration mixed gas and water, taking it to the carbs thus resulting in low gas levels in the carbs. On a happier note, I got it running the same week I posted here and have been riding ever since. Thank you for your ideas and sorry for the late update.

[jagcofj]

sorry to here some 1 took a free ride on your bike, my petcock don't work - i install this inline gas valve near my fuel pump. when i pull off the cover it's right there if need to turn the gas off for anything.

Sports Parts Inc Inline Fuel Valve - 5/16in. UP-07001-1  "O" off of amazon.com you my can find it cheaper on ebay.

[FJmonkey]

Happy to hear you got it fixed and no real damage was done. Ride on and enjoy.

[JPaganel]

  Fjmonkey wins the quiz! Took out about half a liter of water from the fuel tank, effin' bastards. My guess is vibration mixed gas and water, taking it to the carbs thus resulting in low gas levels in the carbs. On a happier note, I got it running the same week I posted here and have been riding ever since. Thank you for your ideas and sorry for the late update.

There is a drain hole next to the filler, it comes out as that little tube in the back of the tank under the seat. Make sure that's clear - if it has dirt in it, you will get more water in when it rains.

sorry to here some 1 took a free ride on your bike, my petcock don't work - i install this inline gas valve near my fuel pump. when i pull off the cover it's right there if need to turn the gas off for anything.

Sports Parts Inc Inline Fuel Valve - 5/16in. UP-07001-1  "O" off of amazon.com you my can find it cheaper on ebay.

If he has an electric petcock, he does not have a fuel pump, and there would be no room to put that shutoff in.