how to adjust valves with timing key installed

[cals400ex]

i was just wondering what tips you had for adjusting the valves after you installed the sparks timing key. do you use a tool to find top dead center or do you just guess what 6 degrees really is? and help would be great.

[UglyMotha™]

you can put it on your normal tdc mark and they'll be loose just just turn it to tdc if want want to go 6 degrees that's fine but it's really not much just pull you valve caps and if you can jiggle the rocker are then you can adjust it

[cals400ex]

i am a little confused with that. i thought if i line it up with the T mark(tdc) with the key installed it won't really be at top dead center.

[UglyMotha™]

it won't be true tdc but there is enough rotation in the cam before the lobes come around again that you have free play a little before and after tdc

[Bad Habit]

What I do is line up the "T" mark with the edge of the sight hole, not the mark in the center line of the hole. This gets it pretty close to TDC.

[cals400ex]

ok i think i got you now. so, when the timing is advanced 6 degrees, would the correct TDC be a little before or a little after the T mark? i would think it would be a little after. also, i guess your saying that when you are normally adjusting the valves, you don't have to get the T mark exactly lined up but just somewhere relatively close? thanks also, did you see any gains with this? or did you put it in when you did other mods? some people seem to get a little more power and others say its a waste of time. thanks

[chad502ex]

Originally posted by Yellow416ex
What I do is line up the "T" mark with the edge of the sight hole, not the mark in the center line of the hole. This gets it pretty close to TDC.

yellow, you are correct!! The new TDC mark is with the "T" to the left edge of the sight hole. Place the top of the "T" to the left edge. Way back, when I rebuilt my 490 motor, I figured out the new "T" mark position by aligning the marks on the timing gear parallel to the head surface (like in the manual) then looked at the "T" mark,.... it was exactly to the left edge of the sight hole.

Hope this helps.

Chad502EX.com

[cals400ex]

but do you align the T itself or the TDC mark on the left side of the hole? sorry, this is just confusing me and i want to get it about perfect because i know an atv with the valves not adjusted properly will run like crap. thanks would it be easier to just take the fly wheel off and measure 6 degrees and make your own mark on the flywheel? also, that means the T itself is laying on is side where it is making a 90 degree angle?

[UglyMotha™]

i can't tell you what kinda gains to expect cause i pretty much did everything at once if you wanting to find the exact place leave the flywheel on and take your head cover off and then turn the motor until it is tdc and then look and the marks on the cam sprocket and turn it until those are level with your head and then thru the peep hole take either a engraver or a permanent marker a put a mark on your flywheel i put a mark with a marker and it's still there after 6 months of riding

[Drtridr18]

It's pretty easy...just line up your marks like usual...that's the TDC you'd usually use if you didn't have a key....now turn it a little bit more, until all 4 rocker arms have play and make your adjustments. That's what I did, for 15 bucks and a slight hassle, it was a decent gain for that.

[Bad Habit]

Originally posted by chad502ex
Way back, when I rebuilt my 490 motor, I figured out the new "T" mark position by aligning the marks on the timing gear parallel to the head surface (like in the manual) then looked at the "T" mark,.... it was exactly to the left edge of the sight hole.


Chad, that's exactly the same way that I discovered this. Kinda amazing what you figure out when you pay attention to what you're doing.:D