08 yz450 only 4 gears?

Yamaha YZ450F

47 replies to this topic
  • dirtjunkie23

Posted March 21, 2014 - 12:26 PM

#21

Is there any way to tell what year the engine is by looking at the # on it. Grayracer says its a 2nd gen engine and its suppossed to be a 5 speed. He seems to know what hes talkin about. Ive heard that mx riders often take out gears. Could that be it. The guy that sold it to me told me it was a four speed. Now im startin to get pissed. I feel like takin it back to him and burnin rubber on his face in all FOUR gears. And if its supposed to be a 5 gear ill just have to owe him one.

  • grayracer513

Posted March 21, 2014 - 12:43 PM

#22

It's not an earlier 4 speed engine, but the Gen2's were all originally built as 5 speeds.  As far as I know, only big money teams ever bothered with changing down to a 4 speed.  I wouldn't know what else to say about it other than to really know what's going on, you'll either have to get more info from the PO, or tear it down and see.



  • dirtjunkie23

Posted March 21, 2014 - 03:26 PM

#23

It's not an earlier 4 speed engine, but the Gen2's were all originally built as 5 speeds. As far as I know, only big money teams ever bothered with changing down to a 4 speed. I wouldn't know what else to say about it other than to really know what's going on, you'll either have to get more info from the PO, or tear it down and see.

ok i guess what im asking is have u ever had a 5th gear go out on u. If so what are the simptoms? When u shift does it just stop shifting after 4 gears like its a four speed. Or does it still try to go into 5th but just not work or what. Thanks for the feedback i appreciate it.

  • lkeffersyz

Posted March 21, 2014 - 05:33 PM

#24

ok i guess what im asking is have u ever had a 5th gear go out on u. If so what are the simptoms? When u shift does it just stop shifting after 4 gears like its a four speed. Or does it still try to go into 5th but just not work or what. Thanks for the feedback i appreciate it.

if a gear goes it the symptoms of a manual trans would be it goes into gear with hesitation or it'll skip teeth possibly a stripped gear. But its not likely one gear would be stripped while all others are fine. Plus you'd have severe metal shavings causing very critical damage. I've been there with a yz 125 its not pretty.

  • dirtjunkie23

Posted March 21, 2014 - 06:04 PM

#25

if a gear goes it the symptoms of a manual trans would be it goes into gear with hesitation or it'll skip teeth possibly a stripped gear. But its not likely one gear would be stripped while all others are fine. Plus you'd have severe metal shavings causing very critical damage. I've been there with a yz 125 its not pretty.

ya thats what im sayin. It doesnt even try to go into 5th. It acts like thats frickin it. Also i looked up the dude on the pink slip and found youtube videos of him riding track. He builds airplanes and race cars for a living. So im thinking he made it a 4 gear mx bike. I hit him up on face book and asked him. So hopefully he will reply. Anyway thanx to everybody that replied. Im just tryin to avoid splittin these cases for no reason. And also i suck at bottom ends

  • lkeffersyz

Posted March 21, 2014 - 06:22 PM

#26

Haha if I knew you personally I'd let you use my case splitting machine its much easier XD

  • grayracer513

Posted March 22, 2014 - 09:18 AM

#27

Symptoms.  If any gear had all of the locking lugs broken off, but was otherwise whole, the result would be that the lever would act normal, you would feel it shift, but there there would be a neutral where that gear belonged.  Same as if one gear had all its teeth stripped (much less likely, BTW).

 

If a gear would say, break in half and fall off the shaft and stay out of the way, you could have as many as 3 such neutrals in the shift pattern.  In your case, though, you're saying that the lever stops shifting at both ends of the 4 gears that you know you have, so something is preventing the shift cam from rotating that one more position.  Either something in the shifting linkage is amiss, or it really is a 4 speed conversion.



  • schrode

Posted March 22, 2014 - 06:39 PM

#28

would there be any reason someone would have swapped out the shift drum and it is actually a 5 speed with all the gears but it can't ever get there due to the drum?  just spit balling here.



  • Greg K

Posted March 22, 2014 - 06:52 PM

#29

I am guessing that dude made it a 4 speed. No big deal just don't road race your buddies.

  • dirtjunkie23

Posted March 22, 2014 - 07:58 PM

#30

Thanks to everyone. For the feedback. I got the valves dialed in and put it back together. I romped on it for about 2 hours then the sun went down so i had to go home. If its a broken 5 speed then it really works good for a broken bike. And there is a pretty big difference between 3rd and 4th. So i think its just a 4 speed conversion. Also i got a question about the front forks. I will start a new post and maybe u guys can tell me if these are stock or not

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  • lkeffersyz

Posted March 22, 2014 - 11:09 PM

#31

I'm here to help anytime u have a question

  • grayracer513

Posted March 22, 2014 - 11:32 PM

#32

A 4 speed conversion is really pretty simple on the Gen2, but does require some custom work.  All that needs to be done is to remove 5th, replace 4th gear with the gears from a Gen2 WR450, and then fab a stop for the shift cam, which can be as simple as welding a bridge on the cam slot to stop it from rotating any farther than 4th.  Ratio-wise that gear set is identical to the '03-'05 4 speed.



  • NitrousR1

Posted March 23, 2014 - 05:34 AM

#33

We did a 4 speed comversion on one of our race bikes, it's not bad at all. Just a little fab. The rider liked his old 4 speed yz450 ratios better then the 5 speed.
Usually any bike that has went through all the work of swapping in a 4 speed will have telltale signs of being a race bike.
Usually it would have a very low number vin but yours doesn't. What's the serial number stamped on the engine. Is that a low serial number? Maybe someone swapped in a modified engine with the 4 speed swap. I can look it up and see if its the original engine.

  • grayracer513

Posted March 23, 2014 - 05:44 AM

#34

What's the serial number stamped on the engine. Is that a low serial number? Maybe someone swapped in a modified engine with the 4 speed swap. I can look it up and see if its the original engine.

 

What source do you use for that info?  Most Yamaha dealers will tell people they can't look up the engine numbers anywhere.

 

One thing to keep in mind if doing the 4 speed conversion is that only the 5th pinion (main shaft) can be removed.  The 5th "wheel" (output shaft) is necessary for 1st and 3rd to function.  The gear teeth could be removed for weight, but the rest of it has to stay.



  • Calebxmaxx

Posted March 23, 2014 - 06:27 AM

#35

http://www.thumperta...elect-5th-gear/

Sounds like the same problems your having.

  • NitrousR1

Posted March 23, 2014 - 06:50 AM

#36

What source do you use for that info? Most Yamaha dealers will tell people they can't look up the engine numbers anywhere.

One thing to keep in mind if doing the 4 speed conversion is that only the 5th pinion (main shaft) can be removed. The 5th "wheel" (output shaft) is necessary for 1st and 3rd to function. The gear teeth could be removed for weight, but the rest of it has to stay.

I'm a 34 year Yamaha Master Tech. Yamaha has a online network where you can look up engine serial numbers to make sure it matches the chassis VIN.
Mainly used for warranty work to verify it hasn't been swapped out, but the same system where you can look up TSB's, tech tips, service manuals, wiring diagrams and there tech hotline. You can also look up warranty history and service history by VIN.
I've offered to look up info before but there's always someone who claims to know it all first. Usually spreading old info

  • grayracer513

Posted March 23, 2014 - 07:16 AM

#37

Then the typical response most people get from dealers saying that it can't be done is because they're too lazy, or more likely just that the customer asked the guy at the parts counter instead of somebody in service?  That would be pretty typical.

 

Is there a year model code embedded in the engine number, or not?  How is it deciphered? 



  • dirtjunkie23

Posted March 23, 2014 - 02:23 PM

#38

Ok so i put it up on the stand and went through the gears manually. Now it acts like it has five gears. S.o.b well guess im gunna do my first bottom end. Thats just great

  • dirtjunkie23

Posted March 23, 2014 - 02:58 PM

#39

Ok so trip out on this!! Iike i said i put it on the stand. Went through the gears. It went into 5th gear. So i figured what the hell ill take it for a ride. Went through all the gears 1 through 5 about 15 times no problem. What the hell??? What was keepin it from going into 5th? All i did was run it through the gears on the stand and now it works like a champ. But now im trippen that there might be something floatin around in there that might mess things up.

  • dirtbeater

Posted March 23, 2014 - 03:13 PM

#40

The opposite happened to me on my ken smoker. On the end of the interchangeable powervalve spring is a small piece to hold the spring to the rod. This fell off the spring and wound up under my shifter fork. I guy or stuck in 5th gear, in the dunes, a few miles from the truck. Talk about clutch abuse. May be able to take clutch cover off and clutch out and see what's going on
Edit. Not ken smoker but ktm. Auto correct sucks.





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