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Discussion Starter #1
How important on the fuel tank breather hoses?

When I was fixing up my 2004 model bike, I removed them temporarily, then never bothered to refit them. The bike ran fine for about 300 miles, but has recently started running badly, and the gas mileage is really bad now.

Problem started off as only being when the bike was warmed up, but now its all the time even from cold.

The bike runs badly under 6-7,000 rpm, but clears up when you really give the bike full throttle. From 7k to the redline it's fine. But as soon as you stop at a traffic signal it idles badly (maybe on three cylinders) and slow riding it will stall unless you really slip the clutch).

Things I will check/replace over the Xmas holidays are:
New spark plugs
New battery

After that, is it worth connecting the fuel tank breather hoses?

MAP sensor hose?
Unplug all connectors and clean them up
Maybe new rectifier?
New coils?

Any ideas guys?

Thanks in advance
 

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Hmm, there was a thread a while ago.....poster had a strange run problem that was only figured out by a sharp dyno operator...he found a partially connected lead to a spark plug IIRC.......check that the ignition coils and the clips to the plugs are on correctly and in good condition...if it was sensor related the MIL light s/b showing code.....and you're in Japan....can you find shop with a good tech, they s/b pretty thick on the ground over there....?
 

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Make sure you've connected all the hoses to sensors.

One of your sensors maybe broken. If the air temp sensor, or engine temp sensor is broken the ECU doesn't know if the motor is hot or cold and will fuel it incorrectly.

What work did you do to the bike before the problem occurred? Usually if you've worked on the bike and it runs badly afterwards, it means you've forgotten to connect something. Retrace your steps and check everything you undid.

Removing the breather hoses shouldn't cause an issue, but it the breather is blocked then that could cause you issues.
 

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Discussion Starter #4
Make sure you've connected all the hoses to sensors.

One of your sensors maybe broken. If the air temp sensor, or engine temp sensor is broken the ECU doesn't know if the motor is hot or cold and will fuel it incorrectly.

What work did you do to the bike before the problem occurred? Usually if you've worked on the bike and it runs badly afterwards, it means you've forgotten to connect something. Retrace your steps and check everything you undid.

Removing the breather hoses shouldn't cause an issue, but it the breather is blocked then that could cause you issues.
I have basically had the bike apart for cleaning it up. Had the throttles off, forks out etc.

I am starting to think it is more than likely a faulty sensor, vacuum hose to MAP, or plug/voltage related.

Over the new years break I will change the plugs, get a new battery and remove the airbox to check for any broken connectors, plugs, hoses etc. I'm going to replace the regulator rectifier too as they're cheap to replace and I wasn't too careful when cleaning the bike with a power wash. Going to unplug EVERYTHING too and make sure nothing is corroded.

I'll report back in the new year.
 

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Hmm, there was a thread a while ago.....poster had a strange run problem that was only figured out by a sharp dyno operator...he found a partially connected lead to a spark plug IIRC.......check that the ignition coils and the clips to the plugs are on correctly and in good condition...if it was sensor related the MIL light s/b showing code.....and you're in Japan....can you find shop with a good tech, they s/b pretty thick on the ground over there....?
I'm thinking its going to be something like what you suggested. I will check everything over the new years holidays and report back. Just got to get all the parts before the whole country closes down on the 29th...
 
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