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FJ1200BristolRuss

FJ1200 running problem

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Hoping someone can help!

When I bought it I took it for a few short rides - no issues. One day it really didnt want to run and was only runing on a few cylinders. I thought it was dirt in the carbs so cleaned them out - pilot jets werent great so took the opportunity to replace. No change. It seemed like it could be ignition issues so i replaced the coils - no change - I then found that one of the plugs was faulty, so replaced all and it then idled well but would bog down/had no power.

To me it seems like its got to be the carbs, I just cant tell what difference it is making when i pull it apart and rebuild it. Everytime it purrs after the build and im grinning like an idiot for about 3 miles before the issues start.. The issues are that it will idle pretty happily but opening the throttle past 3k will result in the engine 'hunting' and dying out. Adding choke just makes things worse.


The bike is factory engine wise other than a free flow exhaust.

So far I have:
Changed coils, spark plugs
changed the fuel
new fuel filter
replaced carb gaskets, float needles, idle jets, main jets,
new battery

Diagnositics
Tried running with petrol cap open and shut (no difference)
Checked pump operation
Checked float levels
checked diaphram for damage
reset mixture setting to factory (+plus 1 turn to take into account the exhaust)
Inspected fuel bowls (clean)

the most recent item was the float needles - i though perhaps it was getting over fuelled. After I rebuilt it all - again, runs perfectly for 3 miles and then i have the issues.

any ideas?

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Billy Basic here, but have you checked the fuel breather in the tank, including the tank cap. A blocked breather will give the "hunting" symptoms you describe 

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Yeah as Jimmy said that would have been my first port of call but your list said you had run it with the cap open so obviously not the problem, just to be sure you do have the fuel filter the right way round? some are direction specific, not saying you didn't know just it's the little things that catch you out. I had an old bike which had really soft rubber fuel lines, took me ages to work out they were too small and collapsing under the pressure of riding but fine when you were on tick over. Hunting usually implies a fuel starvation problem so it really has to be in the fuel delivery system, you seem to have covered most of the other stuff I would have thought of anyway. Is there anything in the fuel tank that's floating about? old filer or rust treatment I had a spare tank for my FJ and that had loads of stuff that had broken away after the tank had been leak proofed, just guessing now. Good luck hope some of this ramblings helps you sort it.

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Ooops I never read that far down

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Only clutching at straws, but could it be to do with this?

The bike is factory engine wise other than a free flow exhaust.
Mike.

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Russ - you live "just around the corner" from Phil Hacker (of the UK FJOC) - if all else fails and no one here can't give the answers, spend £20, join the club and talk it over with Phil - he's the UK guru on FJ's.s

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