Valve issue.


27 replies to this topic
  • NewGuyonaBike

Posted March 10, 2016 - 07:20 AM

#1

I have an 05 yz450f that I bought 2 months ago and can't ride. It was running when I bought it but wouldn't idle so I thought no big deal I can fix that. Well after replacing almost every seal in the thing, air filter, spark plug, pilot jet, oil filter and giving the carb a good thorough cleaning, drained old gas and put fresh 93 octane in it the bike still won't start with out throttle. I checked valve clerances and timing and this is what I found. The left and right intake are at .009mm the center intake is so tight I can't fit .004mm (smallest feeler I have) right exhaust is at .023mm left exhaust is .025mm. Why is the middle intake so much tighter? Also the I on the flywheel is off to the left if both dots on the cams are lined up. Could that be why it's off? I'm really getting tired of messing with this thing.

  • 0bigsilver6

Posted March 10, 2016 - 07:26 AM

#2

I have an 05 yz450f that I bought 2 months ago and can't ride. It was running when I bought it but wouldn't idle so I thought no big deal I can fix that. Well after replacing almost every seal in the thing, air filter, spark plug, pilot jet, oil filter and giving the carb a good thorough cleaning, drained old gas and put fresh 93 octane in it the bike still won't start with out throttle. I checked valve clerances and timing and this is what I found. The left and right intake are at .009mm the center intake is so tight I can't fit .004mm (smallest feeler I have) right exhaust is at .023mm left exhaust is .025mm. Why is the middle intake so much tighter? Also the I on the flywheel is off to the left if both dots on the cams are lined up. Could that be why it's off? I'm really getting tired of messing with this thing.



Yes valves are most likely your issue. Along with timing.

Time the cams to the flywheel, not the other way around, and get the valves in spec. Will probably be like a whole new bike. Then if you have issues, come back.

  • NewGuyonaBike

Posted March 10, 2016 - 07:28 AM

#3

Ok what is the best way to get shims... buy the kit or figure out what size I need and order individually. Never adjusted clearance so I don't know how hard it is to figure sizing out.

  • grayracer513

Posted March 10, 2016 - 08:19 AM

#4

You can download a manual here:

 

http://www.yamaha-mo...uals/index.aspx

 

http://www.yamahaown...ook.com.au/?r=0

 

First off, the shims are marked with a three digit number indicating their thickness, but that mark is subject to wearing off, so you will need a vernier micrometer to measure what you have in case the number is gone.  The mark also leaves out the decimal point, so you have to add that back in yourself.  For instance, a 185 shim is actually 1.85 mm thick.  Service shims are made in increments of .05mm, 175, 180, 185, etc.  In a typical stock bike that has never had a whole set of shims shuffled out, you will almost certainly find "odd sizes" like 176, or 178.  These are shims used by the factory to precisely set the clearance as near the low limit as possible.  These are why you need the ability to measure very small differences in size, as .02mm is less than .001". 

 

Selecting a shim size is simple math.  If the valve needs more clearance, the shim has to be thinner to provide that.  So, let's say you take out the shims from the two intakes at .09mm and find a 180 on the right and a 185 on the left. You need clearance of at least .10mm but not more than .15mm.  So subtract the clearance you have from the clearance you want:  minimum = .10 - .9 = .01, max= .15-.9= .06.  That tells you you need a shim that is between .01 and .06mm thinner than the one you have.  If those were the only two valves in the engine needing correction, you could use the 180 from the right valve to correct the left valve, and buy one 175 shim. 

 

The center intake always wears the fastest in a Genesis (Yamaha 5 valve) head because due to the dynamics of the thee valve intake, most of the fuel runs down the center port, washing that valve free of any gummy residue that might serve to "lubricate" the valve face.  Sizing shims for such a valve has to start with placing a much smaller shim under it so as to be able to measure some clearance, which is then used to calculate the correct shim size. You may even have less than zero clearance, so it's a good idea to start with shim .15mm smaller than what you find, measure the clearance with that, and go from there.

 

Unfortunately, it is also true that whenever you find a valve that needs a shim two sizes (.10mm) or more smaller than it started out with, that valve needs to be replaced, as the hard coating on the valve face will have been worn through, and the valve will wear rapidly from that point and may fail catastrophically.

 

A full Hot Cams shim kit is around $100, has only three of each size, and includes several sizes no Yamaha will ever need.  They make "refill" kits that have 5 each of six sizes, and if you buy two of these, you will have 5 each of a range of sizes you'll be more apt to find in your engine and be able to use.  The two usually run about $70 for both.

 

OTOH, single shims are $7 each or so, and if the Yamaha dealer doesn't have them, a Honda dealer certainly will (same for CRF450)

 

Here's a tip:  You can "trial measure" the shim size without completely retorquing the cams in place just by seating the cam in the head and holding it down by hand as you measure.  Obviously, you'll want to double check once everything really is bolted down, but you can save some time that way.

 

  • Never pull the cam caps down with the bolts; seat the cap by hand, perhaps with the help of gentle taps from a driver handle.
  • Always torque the caps in stages and in the proper sequence
  • Never over torque.  I don't even use the full specified 87 inch pounds.  I stop at 75 in/lb. 


  • 0bigsilver6

Posted March 10, 2016 - 08:36 AM

#5

[*]Never over torque. I don't even use the full specified 87 inch pounds. I stop at 75 in/lb.
[/list]

Woah. Those numbers seem awfully high... If I recall correct, my manual says 10in/lb. is the newer 450 that much difference from an 02 426?


Edit: eh scratch that. I was doing it with Neuton meters, which is 10. My mistake.

Edited by 0BigBlue7, March 10, 2016 - 08:39 AM.


  • Islay426

Posted March 10, 2016 - 09:57 AM

#6

Don't think you need any more help with the shims but but in regards to the timing looking like it's off, my 426 was similar to what you described when you said it was just off if you line the cams up. I found that it was as if it was half a tooth off each way, mine runs great now anyway so not worried about it.

  • grayracer513

Posted March 10, 2016 - 10:05 AM

#7

The dots will only line up just so well, usually because of chain wear.  Imagine the timing mark on the cam sprocket being one tooth either way from where it is.  Better? if so move it, if not, leave it.



  • NewGuyonaBike

Posted March 10, 2016 - 12:15 PM

#8

Gray thanks for the in depth advice. Sounds rock solid, I like the thought of a refill pack and not having a bunch of extra lying around that I will never use. What is a sign that the coating is wore out. I don't have the money to replace a valve at the moment, probably won't for a little while, but I don't want to run the risk of a catastrophic failure (way too expinsive). Who makes a reliable valve that is not too cheap but not pro race quality either? I don't want to put cheap parts in it, but I'm also not gonna be a pro anytime soon, and I certainly don't ride like one.

  • grayracer513

Posted March 10, 2016 - 12:45 PM

#9

 What is a sign that the coating is wore out. 

 

As I said:

 

 

Unfortunately, it is also true that whenever you find a valve that needs a shim two sizes (.10mm) or more smaller than it started out with, that valve needs to be replaced, as the hard coating on the valve face will have been worn through

 

The valve you have at zero clearance obviously needs a shim at least two sizes smaller right now.

 

There aren't any shortcuts.  The best valve for the money is Yamaha genuine original.  Nothing wrong with replacing just one.  



  • NewGuyonaBike

Posted March 10, 2016 - 12:48 PM

#10

I was afraid of the no short cuts, but I feel the same way. Good to hear I can just replace one, but hurts to hear I have to replace it. Now I can't ride for another month or two. When I get the oem valve could I use the stock shim from the old one, or does it not work that way?

Edited by NewGuyonaBike, March 10, 2016 - 12:50 PM.


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  • grayracer513

Posted March 10, 2016 - 02:56 PM

#11

Probably not, because you will need to have the seat refinished, which removes a small amount of material to restore the seats correct shape.  That lets the valve rise a little farther up into the head, so the shim that comes out of it now would almost certainly be too thick.  have to try it out and see.

 

DON'T mix the lifters up; return each to its original location for the best results.



  • NewGuyonaBike

Posted March 10, 2016 - 03:23 PM

#12

To get the seat redone is that something you can do yourself?

  • grayracer513

Posted March 10, 2016 - 03:28 PM

#13

No, not normally. Special tools required.  The local dealer should have a machinist they send work out to, and they will usually charge about $25 for each seat. 



  • NewGuyonaBike

Posted March 10, 2016 - 04:01 PM

#14

Ok. Thanks for all the advice. I would have just shimmed it and went for a 6 hour ride next weekend. Do I need the new valve to get the seat fixed or would they know what to do?

  • 0bigsilver6

Posted March 10, 2016 - 04:08 PM

#15

Ok. Thanks for all the advice. I would have just shimmed it and went for a 6 hour ride next weekend. Do I need the new valve to get the seat fixed or would they know what to do?

The shop I was going to have do mine said they would like to have the new valve so they can make the angle on the seat. So probably best if you have it for them to see. And being that the center intake valve is different than the other two they can't go off those.

Edited by 0BigBlue7, March 10, 2016 - 04:09 PM.


  • NewGuyonaBike

Posted March 10, 2016 - 04:09 PM

#16

The shop I was going to have do mine said they would like to have the new valve so they can make the angle on the seat. So probably best if you have it for them to see.


That's what I was thinking but didn't know... well looks like I'm just gonna be reading and living vicariously through TT till I can ride again. Haven't been doing it long but man I'm hooked lol

  • 0bigsilver6

Posted March 10, 2016 - 04:14 PM

#17

That's what I was thinking but didn't know... well looks like I'm just gonna be reading and living vicariously through TT till I can ride again. Haven't been doing it long but man I'm hooked lol


I feel your pain. I just rebuilt my bike and since I finished it, it's been raining every day, so I haven't been able to ride. Driving me crazy. Gotta love Seattle. Hopefully I get to move to AZ soon!

  • grayracer513

Posted March 10, 2016 - 04:15 PM

#18

Ok. Thanks for all the advice. I would have just shimmed it and went for a 6 hour ride next weekend. Do I need the new valve to get the seat fixed or would they know what to do?

 

They need it to match the seat to it correctly.



  • NewGuyonaBike

Posted March 10, 2016 - 04:29 PM

#19

I feel your pain. I just rebuilt my bike and since I finished it, it's been raining every day, so I haven't been able to ride. Driving me crazy. Gotta love Seattle. Hopefully I get to move to AZ soon!


Man that sucks. The weather here in Arkansas just got good. In the 70's everyday and plenty of sun, then out of no where it has been raining every day since monday. Supposed to stop this sunday, would be fun to hit the national forest for a sunny Saturday in the mud.

  • NewGuyonaBike

Posted March 11, 2016 - 04:33 AM

#20

They need it to match the seat to it correctly.


How do you get a seat out? Can't find anything about it and I'm hoping I don't have to buy one.





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