01 426


8 replies to this topic
  • 624DOZZER

Posted January 24, 2010 - 10:42 PM

#1

when starting i have to pull the hotstart and the choke. it starts up pretty good but idles a little rough. when riding the bike it runs pretty good. i dont have to use hotstart when its warmed up. ive cleaned the carb. scratching my head. need some help. thanks

  • g-powerr

Posted January 25, 2010 - 02:53 AM

#2

I think you need to rejet, sounds like you're running too rich.

  • Dave102429

Posted January 25, 2010 - 03:53 PM

#3

My guess is g-powerr's right. Tell us your current jetting specs (i.e. main jet size, pilot jet size, needle clip position, and number of fuel screw turns).

  • 624DOZZER

Posted January 25, 2010 - 09:34 PM

#4

My main is 62, pilot is 42 and i dont know what my needle clip position is. I didnt mention that when the bike is running and i tip it over and pick it up to put it on my stand it will die. Which leads me to beleive i may need to adjust my float. Mabey? The bike really runs good when riding it. This is the second 426 i have owned. The first one never had any issues so i know something is messed up with this one. Mabey its my float?

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  • Dave102429

Posted January 25, 2010 - 10:04 PM

#5

I'll assume you meant "162" on the main. So far, sounds like you have the stock jetting, which works fine for me. The stock needle clip pos. is 4th (middle). The float should be set to 8 mm, but unless it's WAY off, I doubt that's the cause of rough idle. But check it anyway. How about your fuel mixture screw? Do you have it set between 1 and 2 turns? Stock is 1-1/4 turns. What color is the spark plug? Cleaned and freshly oiled (but not over-oiled) air filter? Any pinched vent lines? Any vacuum leaks?


While you have the carb off, and still assembled, fill the float bowl with gas and twist the throttle linkage by hand and watch the accelerator pump spray. Does it have an insanely long pump (spray) duration? On mine, the duration was just under 4 seconds. After I did the BK mod, it's right about 0.3-0.4 seconds. Throttle response is great and I haven't fouled a plug yet. When I bought my bike (used), the seller flooded the engine while showing me how to start it. I took out the plug and it was solid black. He fouled the plug at some point.

  • 624DOZZER

Posted January 25, 2010 - 11:08 PM

#6

I'll assume you meant "162" on the main. So far, sounds like you have the stock jetting, which works fine for me. The stock needle clip pos. is 4th (middle). The float should be set to 8 mm, but unless it's WAY off, I doubt that's the cause of rough idle. But check it anyway. How about your fuel mixture screw? Do you have it set between 1 and 2 turns? Stock is 1-1/4 turns. What color is the spark plug? Cleaned and freshly oiled (but not over-oiled) air filter? Any pinched vent lines? Any vacuum leaks?


While you have the carb off, and still assembled, fill the float bowl with gas and twist the throttle linkage by hand and watch the accelerator pump spray. Does it have an insanely long pump (spray) duration? On mine, the duration was just under 4 seconds. After I did the BK mod, it's right about 0.3-0.4 seconds. Throttle response is great and I haven't fouled a plug yet. When I bought my bike (used), the seller flooded the engine while showing me how to start it. I took out the plug and it was solid black. He fouled the plug at some point.

when i cleaned the carb i replaced all off the vent lines. i will check my accelerater pump like you explained. can you tell me what the bk mod is? and yes i meant 162

  • Dave102429

Posted January 26, 2010 - 08:24 AM

#7

Brian Kinney (BK) is Tim Ferry's Factory mechanic (and the originator of the BK mod) and these were his instructions.

http://m.bobbitt.hom...26fm/bkmod.html

http://motoman393.thumpertalk.com/

  • lumpy790

Posted January 26, 2010 - 08:49 AM

#8

Both hot start & choke makes no sense.

How old is the sparkplug? All of my YZF's have fouled plugs on start up when the plug gets about 1.5 months old.

Could be a valve clearance problem too.

  • grayracer513

Posted January 26, 2010 - 10:10 AM

#9

Both hot start & choke makes no sense.

How old is the sparkplug? All of my YZF's have fouled plugs on start up when the plug gets about 1.5 months old.

It's essentially the same thing as cracking the throttle slightly off idle. Lots of bikes seem to like that.

As to the spark plugs, I've never fouled one on any of my YZ450's, and I change them about once a year whether they need it or not.





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