another cam question

10 replies to this topic
  • efan450f

Posted June 15, 2007 - 10:38 AM


i own a 05 yz 450f, i am the second owner, and have done some extensive motor repair on it. i brought it to my dealer to have the valves adjusted before i raced it just to be safe. i did ride it a couple times before bringing it to the dealer, and it felt like it was fine. the dealer called me and said it needed five new valves,five new valve cups,and it had a crack in the head (i seen the crack and it did not go through to the combustion chamber). i am mechanically inclined and from then on i do all the maintenance i can (except for the bottom half mainly because i don't have the tools required) the dealer told me the only thing they could reuse were the cams. (they said they miked them and were not out of tolerance) now i was checking my valve clearance the other day and i noticed when putting it together before i put the timing chain on that my exhaust cam seems tight compared to the intake cam(I don't mean tight to the valves i mean tight like it was hard to turn). i didn't think to move the cams before i took it apart to see if they moved freely with out the timing chain on. it does not take a ton of force to move it, it's just not as easy to move as the intake. as a side note i took the cam back out thinking the bearing was semi seized and it's not it moves nice and smooth. so any input here would be great i just want to know if anyone else has experienced this. is it normal for the exhaust cam to be a little tighter or did my cam go out of whack when my head cracked. it cracked right between the two cams from left to right. just don't want to buy a new cam if i don't have to. also there is not scoring or blueing on anything i can see(cam towers,head,cam,cam bearings, anything. even what you would think might be a stupid suggestion let me know. hopefully it's normal but i doubt it. they replaced everything in the head accept the cams,and the cam tower caps.replaced:head,valves,cups,spings,guides

  • King_Air

Posted June 15, 2007 - 11:48 AM


Are you following the torqueing sequeance call out in the manual for the cam caps? They are sensitive to the sequenance and torque value. Some use a lower torque setting than the manual calls for, as they feel it is too much. I still use the book value, but their arguement is strong for the lower setting. I don't recall what value they use, but a search in the decomp thread might find it.

  • grayracer513

Posted June 15, 2007 - 12:23 PM


What you describe is not uncommon. The best thing to do is to check the clearance at the cam journals with Plastigage as shown in the manual, and always be sure to torque the cam caps to the correct value (or less, I use 75 in/lb rather than 86) and in the right sequence.

  • CaptainKnobby

Posted June 15, 2007 - 04:01 PM


Where can you get those plastigauges?

  • grayracer513

Posted June 15, 2007 - 06:18 PM


Auto parts stores.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • efan450f

Posted June 16, 2007 - 06:02 AM


yes i have tightened the bolts in the correct order, but i did tighten them to the recommended torque value in my yamaha manual you think that is too tight.i will try to plasti-gauge them,and re-torque to the lighter setting.i assume that means that both cams bolted down with no timing chain on them should move with about the same resistance,no? one other thing how would i go about adjusting the gap between the cam and camcap... emery cloth or what? thanks everyone for the input

  • ncmountainman

Posted June 16, 2007 - 06:32 AM


i'm thinkin a cracked head is just that; a cracked head!!! it could be slightly tweaking the cam stays enough to bind it. its also gonna be like a windshield crack....its not gonna just stop; especially with the heat cycles that these motors endure. it might be fine though:excuseme:

  • grayracer513

Posted June 16, 2007 - 07:30 AM


one other thing how would i go about adjusting the gap between the cam and camcap... emery cloth or what? thanks everyone for the input

IF the clearance is actually too low, which would surprise me, you should have a competent specialist machine shop deal with it.

  • efan450f

Posted June 16, 2007 - 08:32 AM


ncmountainman i appreciate the words of advice i was thinking the same thing but the head was already replaced so i just dont know how long it was run with the cracked head and if it tweeked anything. im going to plasti-gauge the cam journals tonight like grayracer said and see what happens. the only thing that worries me is that the so called (qualified repair shop) around here is not that great to deal with. the cam has been tight since the replacement of the head i just wonder if they knew it and didn't tell me. you would think the mechanic would notice it being tight when re-assembling the top end, but i guess you wouldn't normally check it. i'll check my clearance's and post what i find.thanks guy's.

  • grayracer513

Posted June 16, 2007 - 10:43 AM


There's always EDCo

  • ncmountainman

Posted June 17, 2007 - 05:38 AM


sorry,i was under the impression you reused the cracked head. there isn't much it could have done to the cyl jug, unless the whole cyl got warped:excuseme:

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