04 yz450f kick starter does not engage


14 replies to this topic
  • Yasumazuhaki

Posted July 22, 2013 - 07:43 PM

#1

Went to start bike up after a stop to check the map, and the bike fired but didn't start, but the kick start lever slammed forward and stuck in the upright position. I put my foot back up to kick again, and now it's like there is no contact inside. Lever moves freely up and down, return spring still works. Bike turns over if I roll it in gear. Didn't try to roll start it, afraid of what might happen, just checking that motor does turn over.
Luckily our map stop was in a truck-accessible spot. Sent a buddy for the truck and we loaded up and headed home.
Ideas??

Edited by Yasumazuhaki, July 22, 2013 - 08:17 PM.


  • grayracer513

Posted July 23, 2013 - 06:35 AM

#2

You're going to need to open up the right side and see what's going on. There are a number of possibilities involving parts of the starter assembly.

  • Yasumazuhaki

Posted July 30, 2013 - 07:15 PM

#3

Finally started into tearing apart last night. Could NOT get the starter lever off! Perhaps someone put a little loctite in there at some point. Everything else was loose, but got hung up on that. Shot it good with liquid wrench and called it a night.
Went back at it a few minutes ago, and it popped off! Ratchet wheel is in 3 pieces. That answers part of the question. Now, to find out why!!??!!image.jpg image.jpg

Edited by Yasumazuhaki, July 30, 2013 - 07:20 PM.


  • Yasumazuhaki

Posted July 30, 2013 - 07:36 PM

#4

What is this piece with the 2 bolts in it? I can't find it listed in any of the diagrams in the manual. It appears to be in tact, but I'm not sure.image.jpg image.jpg

  • runnybunny

Posted July 30, 2013 - 07:57 PM

#5

That's the stopper for the broken piece. It stops the starter at the "top" so that the spring doesn't turn it farther then it should and so the spring doesn't lose tension.

When you put it together the broken piece sits in behind that tab. There should be a mark on the shaft and the broken piece that have to be lined up for proper spring tension.

  • Yasumazuhaki

Posted July 30, 2013 - 08:12 PM

#6

Ok, so that piece looks ok. Do these ratchets just tend to wear and break over time, or should there be some other root cause I'm looking for? I don't want to replace the ratchet and have the same thing happen again, but I don't see anything else that appears out of place.

  • runnybunny

Posted July 30, 2013 - 09:15 PM

#7

You said it fired and slammed the starter forward.

I think this means that the started didnt disengage when the motor started and it slammed the broken piece into the stop so hard that it broke it.

Therefore the broken piece is the result and not the cause of the malfunction.

The starter should ratchet ones the engine is turning faster then the shaft. For some reason it didn't. You need to find out why the ratchet mechanism didnt work.

The broken part has nothing to do with the ratcheting. It is purely a stop so that your starter can't keep spinning past "up"

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  • grayracer513

Posted July 31, 2013 - 06:53 AM

#8

You said it fired and slammed the starter forward.

I think this means that the started didnt disengage when the motor started and it slammed the broken piece into the stop so hard that it broke it.

Therefore the broken piece is the result and not the cause of the malfunction.

The starter should ratchet ones the engine is turning faster then the shaft. For some reason it didn't. You need to find out why the ratchet mechanism didnt work.

The broken part has nothing to do with the ratcheting. It is purely a stop so that your starter can't keep spinning past "up"


Eh? In the first place, the broken part is the ratchet plate, so it has everything to do with ratcheting. The pawls are on the bottom surface in the picture). It serves the dual function of driving the kick gear and the extended "ear" on the one side both stops the kick shaft on the return and disengages the ratchets by camming in behind the stop plate as it strikes it, forcing the ratchet plate to slide back away from the gear.

Secondly, the engine turns the starter gear in the same direction as the lever does, so even if the ratchet fused together it would not slam it against the stop plate by starting. Kicking back is another matter.

The truth is that the '03 and earliest '04's had problems with weak starter components, and the entire assembly was upgraded in mid year 2004. The only ones you can now get new are the revised assemblies. This one simply broke.

  • runnybunny

Posted July 31, 2013 - 08:21 AM

#9

Eh? In the first place, the broken part is the ratchet plate, so it has everything to do with ratcheting. The pawls are on the bottom surface in the picture). It serves the dual function of driving the kick gear and the extended "ear" on the one side both stops the kick shaft on the return and disengages the ratchets by camming in behind the stop plate as it strikes it, forcing the ratchet plate to slide back away from the gear.

Secondly, the engine turns the starter gear in the same direction as the lever does, so even if the ratchet fused together it would not slam it against the stop plate by starting. Kicking back is another matter.

The truth is that the '03 and earliest '04's had problems with weak starter components, and the entire assembly was upgraded in mid year 2004. The only ones you can now get new are the revised assemblies. This one simply broke.


You're right. I'm wrong. :|

My bike has a separate ratchet gear from the stop though.

Edited by runnybunny, July 31, 2013 - 08:24 AM.


  • grayracer513

Posted July 31, 2013 - 08:48 AM

#10

Not if it's a Yamaha it doesn't. There are, of course, two parts with ratchet teeth cut on them, and one is the gear that the ratchet plate drives.

In operation, with the lever at rest, the ratchet plate is held inward by the stopper plate, out of contact with the gear. As the lever is moved rearward, the extension rotates out from behind the stop plate, and a compression spring on the shaft moves the ratchet plate outward along its splines to engage the gear and drive it. The splines on the shaft connect the ratchet plate to the shaft, and the spring keeps the ratchet engaged. The ratchet overruns as the engine starts, and as the lever is returned to the at rest position, the extension catches the edge of the stop plate, which draws it back in away from the gear again.

  • Yasumazuhaki

Posted July 31, 2013 - 11:07 AM

#11

In operation, with the lever at rest, the ratchet plate is held inward by the stopper plate, out of contact with the gear. As the lever is moved rearward, the extension rotates out from behind the stop plate, and a compression spring on the shaft moves the ratchet plate outward along its splines to engage the gear and drive it. The splines on the shaft connect the ratchet plate to the shaft, and the spring keeps the ratchet engaged. The ratchet overruns as the engine starts, and as the lever is returned to the at rest position, the extension catches the edge of the stop plate, which draws it back in away from the gear again.

Very nice synopsis. I've been staring at the pieces of this thing trying to rationalize how it works. All makes sense now. I figured it would make sense once I had it together, but I was having trouble picturing it as it sits now.
Have new ratchet wheel, circlips, and small spring on order. Anything else u recommend replacing while it's apart?

Edited by Yasumazuhaki, July 31, 2013 - 11:08 AM.


  • grayracer513

Posted July 31, 2013 - 02:30 PM

#12

Look the shaft and gear over carefully for cracks.

  • runnybunny

Posted July 31, 2013 - 03:18 PM

#13

Make sure there aren't any other parts floating around, especially behind the clutch. And check the gear around the clutch for damage too.

  • grayracer513

Posted July 31, 2013 - 06:59 PM

#14

Make sure there aren't any other parts floating around, especially behind the clutch. And check the gear around the clutch for damage too.


Absolutely. It's really worth your time to pull the clutch apart so you can be sure that none of the smaller drive gears were damaged. It's a good sign that your starter gear is intact, but you might save a lot of grief by taking a look.

  • Yasumazuhaki

Posted October 01, 2013 - 04:04 PM

#15

Ok, so it took a while to get around to working on it, but we're back up and running for $50 parts and fresh engine ice and oil. Felt pretty good about getting it back together in one attempt with no pieces leftover after it sat in the garage apart for 2 months! Thanks, guys, for all your help.





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