Question about Yamaha YZ 450 F Motorcycles

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2008 yz450f wont idle, bogging like crazy, gas in air box

Ok so today as i was getting ready to go riding i decied to ride my 2008 yz450f around the block real quick as soon as i started it, it was not reponsive at all. i made sure the choke was off it was only idleing at 1300rpm i have the idle set at 2000 or so i put it in gear started to take off and it was boging like crazy and the intake box was wisling like crazy too. so i pulled back in my driveway took off my seat to see if my i left a rag in the intake box when i cleaned the filter no took off the filter nothing but gas. what is wrong and how do i fix it the bike would only respond good passed 7500 rpm

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  • Expert
  • 185 Answers

The is few possibilities with this issue but my first thoughts would be leaking intake valves or maybe one has stuck open or they might just be worn out allowing compression to blow back through carbie, My next thoughts would be are all the breather hoses on the carbie clear and free of blockage maybe one has melted from heat or got blocked from mud debree etc?

Check valve clearance or get leak down test done would be my first recommendations.

Cheers... Motoxpartsonline.com

Posted on Mar 13, 2013

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6ya6ya
  • 2 Answers

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Posted on Jan 02, 2017

DoubleClutch
  • 376 Answers

SOURCE: 2000 Vulcan Nomad 1500 FI - Bike was sitting for 6

You need to remove the carbs and dismantle them completly and adjust them to spec. Also change the fuel filter.

Posted on Oct 28, 2009

tellme2
  • 137 Answers

SOURCE: GSX 600F idle and throttle probs

hi m8,, just a couple things,, wen u stripped the carbs down and cleaned them,, did u take the main jets and cold start jets,ie the jet that the needle in the carb sits in,, and poke the dirt out with a pin,, so u can see threw all the holes wen held to the light, u have a blockage still in the carbs,, undo bottoms of carbs take the main jet and the needle jet out ,,and clean ,, make sure your airbox is sealed down on the carbs and jubilee clips are tight,,,1 at a time pull off the spark plug cap and pull off the cap from its ht wire and snip a little bit off the end so u can see copper or brass stranded wire then screw cap back on ,do that to all 4 caps, do these checks ,the bike will run good, ,, look more in2 the carbs tho ,, its almost certain u have a bloked jet still

Posted on Jan 27, 2009

  • 126 Answers

SOURCE: wont run /idle

i'd start with removing the carbs and giving them a thorough cleaning as when bikes sit for so long, the carbs begin to get gummy/varnished from the old gas.

check for blocked holes in the pilot jet & main jet and look for "hard & dried up" gas in passages. be careful of the float bowl gasket as to not tear it or you will need a replacement.

Posted on Mar 06, 2009

  • 5 Answers

SOURCE: bike will not idle witout having choke on a bit

I have a supermagna and used fuel stablizer once and it wasnt fit it gummed my carbs up,ive cleaned mine often and it isnt rocket science,remove the tank airbox assembly,loosen up the boot flanges that hook the carbs to the motor(ones on carb)then remove the carbs,then the cables,choke and throttle,do not remove carbs from assembly(leave all 4 together)remove the bottoms and tops of a carb,removefloat and jet,then remove all the brass jets and clean them so you can see through holes,,blow out all the holes in carbs,and reasemble,works for me every time,about two hours to do,good luck

Posted on Apr 05, 2009

wd4ity
  • 4565 Answers

SOURCE: High Idle On Start-up.

Most fuel injected motorcycles do start up in a "fast idle" mode. Although I don't know much about fuel injection on Harleys (H-D will not tell you much about it unles you are one of their technicians), I don't think the system is equipped with an engine temp sensor. Since the crank case sensor get it's pulses from pockets cut into the outer edge of the left side flywheel half, the sensor will have oil on it.

Posted on Sep 24, 2009

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