Y'all explain how but, why? I need motorheads

2 replies to this topic
  • jeffpaff

Posted October 31, 2012 - 08:22 AM


I bought a 2004 WR 450 recently and am going through it. Sorry for the lack of knowledge however, I need some info. I went in and checked the gap on my valves and they were tight so I loosened them up using this site and the manual. What I need is some knowledge.

Why, how does the bike run if the valves are tight and or if they are loose? Also, the whole timing issue. while I was assemblying, the chain slipped so I had to to the timing thing from scatch. I lined everything up, again using this website and the manual, got it back together and it fired up and ran but I was very concerned that my cams may have been one pin out when I reassembled based on looking at the lobes. How would it run if it was one pin out?

I just need some basic engine knowledge!

I have replaced the exhaust with a FMF Q4, sent the carb to Zip-Ty for a rebuild, installed a scotts stabilizer, put in a rekluse z-start pro and left hand brake all over the course of a week. Should run and feel like a new bike when I am done. Problem is I don't know what a new bike is suppose to run like!

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  • L. Euler

Posted October 31, 2012 - 09:26 AM


I can tell you that if the valves are too tight there is a chance that one or more may hold slightly open at TDC. If that happens you will have a devil of a time getting it started. Been there! If too loose possibly loss of power and valve noise. On the timing it depends on which cam is out. I don't have knowledge on how it would run, if at all, with the timing out.

Edited by GammaFunction, October 31, 2012 - 09:27 AM.

  • MANIAC998

Posted October 31, 2012 - 04:45 PM


On my '06, I count the cam chain "pins" between the cam marks at the top of each cam, and in my case, there is 14 cam chain pins between the marks.

If the valve clearance is too tight, the valve will overheat as the only way it can shed it's heat is to make contact with the head and transfer the heat into the valve seat and on into the head. Or if the valve is way too tight, it can make contact with the piston, and then you have major engine damage.

If the valves are loose, you will lose a small amount of power, and the top-end will be noisy, as the valves will "Clatter" as the cam lobe slaps them open instead of opening them gradually.

The bottom line is, that Yamaha specifies a certain spec, and if you follow there advice, you will have a strong running engine for a long time.

Edited by MANIAC998, October 31, 2012 - 04:52 PM.


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