1991 fj1200 abs with a frustrating running problem help!

[peteh]

Hi guys, i could really go some help with a running problem, my bike has always been very powerful and no bother. a few weeks ago i was out for a ride and doing around 60mph and the bike cut out for around a second or so, it seems to have developed a slight flat spot since that happened. the bike has progressed to now starting fine to developing a sort of misfire and begining to dump fuel from the overflows. I have had the carbs off and stripped them, mixture is approx 3 turns out on each carb and the carbs are all in synch. I have replaced the spark plugs but am having thoughts that maybe my problem is in the ignition circuit i.e intermittent coils or something? Would i be right in thinking if the bike is misfiring then any unused fuel would build up and start to run out of the carb overflow. I adore my fj1200 but i really dont know what to do next, i dont want to go down the avenue of buying this and that as to try and eliminate by clutching at straws so to speak. any ideas would be great as its like this for me

[FJmonkey]

begining to dump fuel from the overflows.

Dumping fuel out the over flows means the floats or the valve it controls did not do their job. This can also cause other problems as the carbs need the proper amount of fuel in them. Solve this problem first, You may have another problem but trouble shooting and problem solving requires fixing the known problems before moving to the next one. As an ex-boss of mine frequently said...One F%$G problem at a time.... 

[SlowOldGuy]

If you're dumping fuel, it's a carb problem.  Stuck float, bad o-ring, trash not letting float needle seat. 

One thing you can try quickly.  There should be 4 small hoses and 2 large hoses coming from the carb bank and routed around the left side behind the engine.  Make sure the 2 larger hoses are not kinked, or running uphill.  If it's a float, fuel should be running out of these hoses.

DavidR.

[yamaha fj rider]

Like FJmonkey and david said. You know there is a problem with the carbs, start there.

Kurt

[peteh]

Thanks for the suggestions,well guys i took the carbs apart, cleaned checked airways and settings, number 4 carb had a little crud sitting on the float. I put everything back together and started her up, things were fine for a while and then the engine note changed sounded like a slight misfire with the odd small pop through the exhaust, i took out number 4 plug and noticed it was black and sooty, plugs 123 are fine and show light grey, ok this is where it starts to get confusing, i put number 4 lead on number 1 plug and vice versa and then ran the bike up to warm, fine from cold but as it warmed up it started to have the slight misfire sound, turned her off and took out the plugs, number 4 light grey number 1 light grey but get this number 2 black and sooty number 3 light grey, ive not had any more fuel dumping since overhauling the carbs, strange thing is the bike will still rocket up the road but doesn't sound crisp on idle and light throttle openings. im beginning to think i have a glitch in the coils or igniter unit, there seems to be an odd ticking sound that it never had before, im sure i will get to the root of the problem but any more suggestions would be invited as id like to clock up a few more miles before winter comes to the uk

[SlowOldGuy]

Have you done the "Upside-down Blow into the Inlet Hose Test?"

Sounds like the needle seat o-rings are leaking.  You can't really do a plug test like you're describing.

If you suspect a coil, hook up a timing light to each plug and see if it glitches.

DavidR.

[yamaha fj rider]

You are talking about running poorly at and just of idle sounds like crud in pilot circuit. Some of the smallest passages in the carbs. Hope this helps.

Kurt

[peteh]

Hi guys, still running like rubbish, ive replaced all the float needle seals checked the float levels and all the airways are fine, right then i start said bike up and go for a run everythings fine for the 1st few miles, pulls from 35mph in top very smoothly, cog her down and she takes off no probs, ok so i give the bike a fast run down the bypass and then slow down for a roundabout, from then on the bike has what i can only describe as a misfire up to 2500-3000rpm as soon as the bike gets above that its fine, but shaking bikes in all gears do not appeal to me, i really do believe ive got some sort of electrical glitch thats causing this, any ideas before i start to admit defeat and stick one of these under it

[fj11.5]

kinking fuel line when it gets hot, dirty filter rust ect , fuel pump being silly

[FJmonkey]

This might be un-related but some of your symptoms were present with some of my recent issues. But not all of them so take this with the proverbial grain of salt....

I was having interment problems, one day after a short run to meet another rider and it failed to start. Charged up the battery after killing it to restart it and some cool down time, then it started and ran like stink the rest of the ride. Another ride I got 40 miles and it was like running out of fuel. Again could not restart, got a tow home and it started in my drive way. A few more rides and had other what seemed like fuel related issues. I ordered a new fuel petcock, after it arrived I checked the vacuum function of both old and new. The old one was shot. But just enough to work some of the time. Even if you have a fuel pump, the vacuum valve still controls the fuel flow out of the tank. Next time you have the Left side side panel off and you can pull the vacuum line from the carb, perform this simple test. Suck on the vacuum line. If you suck and feel a slight click and and you cannot keep sucking air then your good to go. But if you suck and can keep pulling air, you have a leak that will affect fuel flow.

Like I said, might be un-related, but the test is easy and simple. Pass and fail are quite clear.

[Dan Filetti]

Mark-

Can this test be performed with the petcock installed on the bike and fuel in the tank?  Or would you be sucking gas if the seal was not good?  Even though I have had one of these things in may hand, I can't recall enough about it to answer my own question.

Just wondering.

Dan

[FJmonkey]

Mark-

Can this test be performed with the petcock installed on the bike and fuel in the tank?  Or would you be sucking gas if the seal was not good?  Even though I have had one of these things in may hand, I can't recall enough about it to answer my own question.

Just wondering.

Dan

Very good question Dan, I was not clear on just how easy this test is. Remove the seat and Left side panel. Remove the two bolts at the back of the tank, disconnect the drain tube at the rear of the tank, prop the rear up enough to access and remove the fuel line from the petcock. Put something under the petcock to catch any fuel that will leak out during the test. The vacuum hose that operates the petcock is connected to the carb nearest you right on top. Pull the tube/hose from the carb. You can watch the petcock while you suck on the vacuum hose. Unless you have had 100% failure then some fuel will leak out when you put vacuum to the hose. The Pass/Fail is not weather fuel came out or not. However if fuel does not flow during the test and you have fuel in the tank then the result is Fail. When you put vacuum to the hose did you feel it go solid like sucking on a straw that is completely pinched off? Then the result is Pass. If you need to keep sucking because air was getting in and causing the vacuum to fail then the result is Fail. The hose can cause this problem as well so if you do get air in, check the hose and connection points before buying a new petcock. The vacuum diaphragm is not exposed to the fuel side of the petcock and will not result in sucking a mouthfull of fuel.

[peteh]

hooray its cured, a dodgy o ring and one of the brand new plugs was misfiring! my FJ now pulls like a train, thanks for your help guys