Adjusting valves

5 replies to this topic
  • eng208

Posted March 29, 2015 - 07:43 AM


I bought my bike on Monday, as I posted before. The bike is very clean and appears to be low hours. I rode for a few hours yesterday and decided to check my valves today. I could tell that someone has been into the valve cover before, due to very slight marks on the bolts. I checked the valves and they are all on the low side of spec. I realize this is the way they will wear, but at what point do I need to inspect the valves? I have not pulled the cams yet to look at the shims in place. I will do that this evening. For now, I promised my daughter I would take her to see "Home".

  • mikedabike

Posted March 29, 2015 - 08:06 AM


Check them again in a few hours and see if they have moved from your previous inspection. Low side of spec is fine. The 3 yz450s I bought new all were on the tight side from the factory and that is where they remained until I sold them with approx 300 hoirs on them.

  • grayracer513

Posted March 29, 2015 - 10:29 AM


True.  The factory sets them all up as near the minimum clearance as possible, and uses shims in .01mm increments to accomplish that.  in good condition, the valves will hold that adjustment for a very long time, and the lower clearance reduces certain stresses on the valve train as a whole.


They should be be adjusted any time they move outside the specified clearance range either way.

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  • eng208

Posted March 29, 2015 - 02:53 PM


Thanks. Gray, you contribute so much to owners of these bikes. Thank you for your willingness to share what you know. I measured them several times and triple checked the dots on the cams. The intakes are exactly 0.10 mm and the exhaust are 0.20. I was going to loosen them up to the middle or top end of spec, but it sounds like I shouldn't worry about it. I did check with the previous owner. He stated the bike was serviced including checking the valves after break in at the shop but he is unsure whether they had to adjust them or not. I found several receipts for oil changes, service, air filter cleaning, and spark plug. for $122. That is why I started working on my own bikes when I was 8 years old!!!

  • GHILL28

Posted March 29, 2015 - 04:31 PM


This is what I found with my 2014 at around 18 hours on it.  Valves were at the very lowest end of the range, which I've been hearing is exactly where Yamaha puts them.  Nice...

  • eng208

Posted March 29, 2015 - 04:51 PM


Good to hear from others. I checked my cam tower bolts very closely. Doesn't appear to have been removed. Best I can tell, the valve cover has been off, but the towers have not. The chain tensioner had not been removed either. I left them where they are. I will check them again in about 10 hours. I don't race. so the bike isn't run very hard or under adverse conditions. Worst I do is shift up through the gears on a straightaway every now and then. Most of the bike's time will be spent in the woods. 


Incidentally, I rode some ATV trails with the guys this weekend and had a blast. I grew up riding the woods on two strokes. It has been about 12 years since I ran any trails and man did I miss it. Also, I don't know why people talk about the 03 450 being hard to handle in the woods. I found it to be a dream. That explosive power just launched me right where I wanted to be any time I desired. It was awesome to be able to jump stumps with the twist of the throttle instead of having to snag the clutch and hope the bike would hook enough. I was riding with guys on 05-06 CRF450X models and even they admitted there was no comparison. The suspension on the X model is softer, especially the fork, but on the few hills I was able to jump, I bottomed them out where mine just soaked it up. It was very easy to go fast. 


I love this bike. 

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