03 450 wants to start but dosent..



11 replies to this topic
  • -Biggins-

Posted December 08, 2013 - 05:15 PM

#1

Hey guys, I'm new to the racing four stroke world. (Had some XR's in the day) I picked up a 2003 yz450f the other day for the right price. I added some seafoam to the gas, and now it won't start. I took it all apart, checked the valves, (both a little tight, adjusted intake and exhaust to spec, checked for properly seated shims) timed it according to the "I" mark on the flywheel and sticking an Allen wrench in the spark plug hole. Has good spark, good compression, almost perfect timing, cleaned out the carb. Didn't try replacing the gas. Before it would start first kick every time. After I added seafoam, it smoked a little bit when I started it up, but then soon went away about after 2 seconds of running time. So my question is, what am I doing wrong?

  • grayracer513

Posted December 09, 2013 - 10:39 AM

#2

Start by replacing the gas, including draining the carb of whatever is in there.  If that doesn't clear up the matter, you may have a blocked or partly blocked main or pilot circuit.



  • -Biggins-

Posted December 11, 2013 - 06:57 PM

#3

Got new fuel, it wants to start but dosent. I took the silencer off to pull the subframe back, and I noticed there's unburnt fuel coming out of the header. It has a good vibrant spark. WTF?

  • capt justin

Posted December 11, 2013 - 07:06 PM

#4

try a new spark plug



  • -Biggins-

Posted December 11, 2013 - 08:22 PM

#5

try a new spark plug

it's LITERALLY brand new. Still won't start. New gas, new plug, valve clearances PERFECT, timed properly at TDC, has great spark, great compression, cleaned carb a week ago, unburnt gas. When I clear it out, (hold kill switch, and throttle wide open, kick it about 20 times) it does want to start. Like it will turn over a couple times, and the kickstarter will make the ratcheting noise.

  • capt justin

Posted December 12, 2013 - 05:00 AM

#6

sounds like clogged pilot jet.



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  • bryce716

Posted December 12, 2013 - 07:35 AM

#7

pilot jet

  • -Biggins-

Posted December 12, 2013 - 08:50 PM

#8

Thanks guys. I'll try that next. I need to currently get a new o ring for the slide assembly as i used carb cleaner and it ruined the gasket.

  • grayracer513

Posted December 12, 2013 - 10:22 PM

#9

It's not an O-ring, but try letting it dry out for an hour before you decide it's no good.



  • -Biggins-

Posted December 26, 2013 - 03:39 PM

#10

It's not an O-ring, but try letting it dry out for an hour before you decide it's no good.

here's where I'm at now. Re cleaned the carb, new cam chain, re-checked the valve clearances, timed at TDC,(perfectly) got it to start for a breif second with the hot start on. I noticed it had lots of Unburnt fuel in head pipe. But, it will start every time with the hot start on for a brief moment. I got it to run as I revved it, (sounded like sh*t) and it was puffing whiteish/blueish smoke. Didn't smell like coolant. Dosent burn oil I don't think. The smoke stayed around like it was burning oil. I know I need to clean the carb again because it dosent need to be leaner as it ran fine. No popping on decel or nothing. So my question is, what could be the cause of smoke?

  • timbanditos

Posted December 26, 2013 - 03:50 PM

#11

A leaking head gasket could get coolant into the chanlmber and cause smoke. Are you giving it a lot of gas to start it? Four strokes are not like two strokes, you shiuld not need to give any throttle to start a four stroke. If you do, it floods it and then it will start wfo, but that is not ideal.

  • -Biggins-

Posted December 26, 2013 - 04:32 PM

#12

A leaking head gasket could get coolant into the chanlmber and cause smoke. Are you giving it a lot of gas to start it? Four strokes are not like two strokes, you shiuld not need to give any throttle to start a four stroke. If you do, it floods it and then it will start wfo, but that is not ideal.

it dosent have that maple syrup smell. Smells like the excess fuel is burning off, or oil. No I don't give it gas to start. I've kicked it over about 500 times. That's why. But, the coolant smoke would go away quick, wouldn't it? Has good compression. It didn't smoke before. All I've done to it is shim the valves, install a cam chain, clean carb. Runs for a brief moment like I said with the hot start on. So I need to clean out the pilot circuit better, but I need to know WTF where's this smokes coming from





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