426 not firering

9 replies to this topic
  • Twindfl

Posted September 23, 2013 - 07:43 PM


I just bought a Yamaha 426 she has spark she's got compression but won't fire up evin with some starter fluid anyone ever run into this problem evin if thers low compression I she at least get something right

  • Thommo_400f

Posted September 24, 2013 - 12:49 AM


Blocked pilot jet
Bad fuel screw o-ring
Bad timing - skipped

  • Twindfl

Posted September 24, 2013 - 02:07 PM


But spraying starter fluid in her it should at least do something right
Plus carbs cleaned

  • Twindfl

Posted September 24, 2013 - 02:10 PM


And she got good spark

  • Thommo_400f

Posted September 24, 2013 - 02:40 PM


If fuel screw o-ring is perished, it will be too rich, and starter fluid will not help, just adds more fuel.

If timing is out, no amount of fluid will help, but you can damage valves.

Rings could be seized into ring groove, giving too low compression to start.


Check/replace pilot jet

Check choke plunger isn't stuck

Check Hot start isn't stuck

Check timing (just pop valve cover off, not difficult)

Get a leak down test done to check compression.

Make sure decompression lever isn't stuck

Fresh plug - try to tow start it on tarmac if you are sure timing is ok.

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  • Twindfl

Posted September 24, 2013 - 02:48 PM


How do I check hot start bc it ran one day sat for 2-3 mounths an now nothing carb is cleand but I also don't have tank on and also it was a friends that I just bought he said he got a new plug but it was one number off they were both NGK
Hot start an de comp are they the same thing

  • Twindfl

Posted September 24, 2013 - 02:52 PM


And thanks for the help

  • Thommo_400f

Posted September 24, 2013 - 02:52 PM


Hot start is red button on carby near choke.....if your model has one.

Decomp is lever on handlebars near clutch.


I am assuming you have started these before, as the routine to only kick from TDC is essential.

  • Twindfl

Posted September 24, 2013 - 03:46 PM


Ok I'll check that out and u let u know what happens and what that cause it not to start with starter fluid ?

  • Thommo_400f

Posted September 24, 2013 - 03:54 PM


Starter fluid is just more volatile than petrol, so it forms vapor easier. If the mixture is wrong, starter fluid will only help if it is pretty close to right and just mask the problem.

If you need starter fluid, you need to fix something, so don't use it.

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