yzf 400 no go

8 replies to this topic
  • ddb2014

Posted February 08, 2015 - 11:48 AM


Hey all well I've got a yzf 400 and having a problem staring it and running. I've got a spark and the compression is there. I have started her but as soon as she's tide a couple of metres she cuts out and won't start again for a few 100 kicks.

The previous owner had bought it from Spain and rode around there in her. He moved back to the UK with her and I bought her. I've tried the mixer screw but it doesn't seem to make a difference there's no visable air leaks I've also cleaned the carb but no joy she's doing NY head in now

Any help would be appreciated thanks in advance

  • Swes

Posted February 08, 2015 - 01:55 PM


Sounds like the bikes overly rich , I would reset everything stock on the jetting or if the bike has an after market exhaust go at most one size up then go from there. If all the jets are stock then it's goes to be a bit of a chase To find the exact problem...

You can't see air leaks other than really obvious ones like no airfilter ( not really an air leak but will cause a lean condition ). The way to check is to lightly spray a flammable aerosol around the intake and see if you can find an area where the idle changes when you spray .

  • Swes

Posted February 08, 2015 - 02:05 PM


It could also be way to lean and you're float height something isn't working . So the bike gets fuel built up , starts then burns it off and dies

  • ddb2014

Posted February 08, 2015 - 05:59 PM


Thanks for your time on this mate. I will try tomorrow. Its stock exhaust how far should I screw the mixer in and out to put it back to stock ???

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  • Thommo_400f

Posted February 10, 2015 - 03:17 AM


Set carb back to stock and list the jets here.

Fuel screw Should be 1 3/4 turns out.
Needle usually 4th clip from top.
Check that fuel flows freely from tank.
Make sure tank breather is clear.
Fresh plug cr8ek won't foul.
Make sure slide plate isn't upside down.

  • ddb2014

Posted February 28, 2015 - 12:53 PM


Hey all again thanks for your input. I've been away do sorry for the long wait. I have had the carb off today ultrasonic cleaned and back on she took a few good kicks and started with the choke on soon as I took it off she died. I've tried my best to start her again she fire a bit then dies and other times just back fires. Any help would be appreciated guys I'm always gratful I did notice the main jet was 175 I couldn't see the numbers on the other s

  • Krannie McKranface

Posted February 28, 2015 - 01:13 PM


Put in a BRAND NEW pilot jet

Clear the passage above the pilot with fishing line and spay cleaner


Ultrasonic does not remove strong corrosion....

  • ddb2014

Posted March 02, 2015 - 07:47 AM


I've just read some where that once she starts from cold QOUTE since this model is equiped with a accelerator pump if the engine is raced (the throttle fully opened and closed ) the air fuel mix will be to rich and engine may stall. Also unlike a 2 stroke engine this model can idle UNQOUTE. Wen I've started her I have let it run for a min and began riding not hard just steady I'm thinking after reading this that this is reason behind the stall because um not allowing 2 3 mins to warm up. What does any 1 think ???????

  • Krannie McKranface

Posted March 02, 2015 - 07:26 PM


1-3 min warm up every time, with NO THROTTLE hogging. 

Once hot, adjust the fuel screw for highest idle.

If too high, lower idle with idle screw, and repeat.

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