Bike wont start. Dont know what to do


15 replies to this topic
  • zippor25

Posted April 25, 2009 - 08:34 PM

#1

So I bought a 07 yz450 2 weeks ago and on my first ride I noticed a lot of miss firing and poor throttle response so after the ride, I changed the spark plug. Went out today, started fine but after a few minutes it started missing again. As time went on problem got worse and worse. Stalled probably 10 times. One time it took me about 20 kicks to get it started. My buddy said it sounded like I was running it with the choke on but I checked it and that wasnt the case. I ran out of gas at one point and after i filled it up, It seemed to get worse(maybe just coincidence). So I loaded up and went home. When I got there, I noticed about 8 or 9 big drops of oil from the cylinder head breather hose. I didnt have any oil on the garage floor before today. I went ahead and cleaned the bike and when I was finished I tried to start it and nothing. 30 cranks later and nothing!!! Any ideas? I have all day tomorrow to try and figure it out so any ideas would be great. thanks

  • grayracer513

Posted April 25, 2009 - 10:22 PM

#2

  • Check for spark
  • Check the cam timing
  • Check for water or dirt in the carb


  • zippor25

Posted April 26, 2009 - 07:16 AM

#3

should i be worried about the oil coming from the breather hose?

  • grayracer513

Posted April 26, 2009 - 08:06 AM

#4

Not yet.

  • ezsemanate

Posted April 26, 2009 - 10:25 AM

#5

Sounds like a fouled plug. My 426 had identicle symtoms. Pilot one size smaller.

  • cliff1818

Posted April 26, 2009 - 02:16 PM

#6

the reason the oil driped is because you over filled it and it build pressure because oil expands when heated so it leaked. also if your bike is not jetted for your altitude than it will run crappy and foul you plugs or cause it to run real hot if it is to lean. also cheak your timing could be off a little.

  • 400f mech

Posted April 26, 2009 - 09:14 PM

#7

blowing oil out of the breather is an early sign on loosing compression, (bad rings). could be the gas, did you fill it back up with the same gas? if so maybe try getting some fresh gas after checking the other things everyone mentioned

  • swatdoc

Posted April 26, 2009 - 11:10 PM

#8

Gray - when you check for spark - obviously you've got the plug out of the head, in the spark plug cap, and have the threads against a suitable graound like one of the head bolts. When i then move my kickstart lever by hand, i don't actually see a spark, but can feel my hand holding the plug getting zapped a little.
Do you do see the spark when you do this, or is there some other method you use?

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  • davidl9999

Posted April 26, 2009 - 11:14 PM

#9

If it sparks, you can hear it. If you can't see the spark, try turning the lights out in the garage. Is this a N.O.S. bike or one from a private party that's been ridden?

  • grayracer513

Posted April 27, 2009 - 06:39 AM

#10

Gray - when you check for spark - obviously you've got the plug out of the head, in the spark plug cap, and have the threads against a suitable graound like one of the head bolts. When i then move my kickstart lever by hand, i don't actually see a spark, but can feel my hand holding the plug getting zapped a little.
Do you do see the spark when you do this, or is there some other method you use?


If it sparks, you can hear it. If you can't see the spark, try turning the lights out in the garage.

That's your answer. Remember that is a magneto, and generates more energy the faster it turns. The 450's should produce a decent spark at fairly low speed, though.

  • kxrider93

Posted April 27, 2009 - 06:43 AM

#11

from my past experiences i would think it could be a number of things. One could be your carb could be pluged. The other is it could be your vetting is off. But the oil part i'm not to sure about

  • zippor25

Posted April 27, 2009 - 05:07 PM

#12

Well since I have been wanting to break it open and play around a bit, I decided to go ahead and pull the carb, clean it thoroughly and then rejet. I ordered the JD jet kit. should be here on Wednesday. After that Im gonna dump the gas(in a suitable receptacle of course) and see what happens. I noticed today that its leaking a little oil from the clutch cover(bad gasket Im guessing). Man I hope I didnt buy a lemon!!!!!

  • swatdoc

Posted April 27, 2009 - 06:06 PM

#13

how would you be able to determine if any of the internal passages of the carb are blocked? Obviously, it's easy to pull the main, pilot, and starter jets out and shoot them with carb cleaner, and even look thru them with a magnifying glass to see that they are clear, but again, how would you know if the internal passages in the carb body are clear - especially the areas where the pilot and starter jets go ? And if they are clogged, how could you unclog them?

  • davidl9999

Posted April 27, 2009 - 06:13 PM

#14

compressed air.
Use the rubber nozzle thingy.

  • grayracer513

Posted April 27, 2009 - 07:06 PM

#15

how would you be able to determine if any of the internal passages of the carb are blocked? Obviously, it's easy to pull the main, pilot, and starter jets out and shoot them with carb cleaner, and even look thru them with a magnifying glass to see that they are clear, but again, how would you know if the internal passages in the carb body are clear - especially the areas where the pilot and starter jets go ? And if they are clogged, how could you unclog them?

Carburetors are usually simple enough that you can see how the passages connect to one another and where they end up going. They do have to be drillable, after all. Also, most of the passageways are fairly large compared with the jets that meter them, so they aren't too hard to clear out. Compressed air is extremely valuable here.

Carb spray is often more useful for diagnosis than cleaning hardened varnish. Spraying into the passageways and watching to see if it comes out of the right place as it should can be quite instructive.

Clearing obstructions should be approached progressively, using air and solvents before any more aggressive methods. If that fails, wooden toothpicks or stiff plastic bristles like those of rifle brushes can be used. In the case of pilot jet orifices, most of these items are too large to pass through them. In cases where something is stuck in a pilot, the first choice should be brass wire. Again, one might pick these from a brush, or use a single strand of copper electric wire. Anything more aggressive must be employed VERY carefully so as not to alter the shape of the jet orifice in any way.

Drill bits can be used (in a pin vise or in your fingers only), and I often use them myself, but they should always be left as an absolute last resort unless you are accustomed to their use for this purpose, and the size chosen very carefully. I usually use the shank end, rather than the cutting end, as a probe before becoming more aggressive. You need to know, too, that the sizes need to clear pilots are very small. The drill I used to clear a #45 pilot was a number 78, which is .016", and about a #68 to clear the cross holes. You'll need to buy a small set if you want to take this approach.  Keihin jets are marked with their actual orifice size in hundredths of millimeters.  A number 45, then is .45mm in diameter.  A #170 main is 1.70mm, so on.

Here's a chart of the number drill size equivalents for a range of Keihin pilot jets, courtesy of TT Member todds924:

Drill _ Jet
Size _ Size
80-----33
79-----35
78-----40
77-----45
76-----50
75-----53
74-----56
73-----60
72-----63
71-----66
70-----70

If you have a jet size not listed, use the next smaller drill. For example, use a #78 to clear a #42 pilot, not the larger #77.

Attached Thumbnails

  • FCRcutaway.png


  • swatdoc

Posted April 28, 2009 - 01:21 AM

#16

Good info - thanks guys!





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