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Valve Clearance Philosophy

5K views 22 replies 16 participants last post by  badassjake 
#1 ·
Bit of a philisophical question for everyone: When adjusting valve clearance, there is a range specified by the service manual, i.e. .17 - .22mm for exhaust.

Do you adjust for middle of the range (19.5mm for exhaust)? Or do you aim for the tight side (17mm) or loose side (22mm)?

Advantages/disadvantages for a particular method that you're aware of?

Just curious, and about to tear down for a major winter service.

Thanks,
CC
 
#2 ·
Yo CC; I have alot of experience adjusting valves, most if it on a Chevy
small block. However, in my humble opinion I would aim for the middle of the spec and if you have to err, I would say looser instead of tighter.When I
do valves of any sort I always go thru the process twice. Some people have recommended the go, no -go method of valve adjusting. For me, when I adjust I do the entire process twice.
 
#3 ·
Yeap, shoot for the middle of the range. I purchased a entire kit of shims made by hot cams for my dirtbike. About $70 but if you got a buddy with the same bike split the cost, because as you know otherwise the shims are about $4 each.
 
#5 ·
Often there will only be one possible readily-available shim size that results in the valve clearance being within specifications. The normal shim thicknesses are in 0.05mm increments, so there might not be a whole lot of choice in the matter. If there is a choice, loose is better than tight.
 
#6 ·
I did my 10's valve clearance myself last fall. Its safer to go loose than tight. A lot of riders neglect checking their valves, because of the price or work involved. Most of them go by ear, and listen for any valve chatter. This is not good coz tight valves don't make noise like loose ones. You can bring it to the shop for 400 bucks or you can do it yourself to save money.

You've been WARNED! its one of the hardest bikes out there to do.


The shims will run you from 8 - 10 bucks a piece.
 
#8 ·
I like em tight cause they just get looser the more you ride 'em. Valves on the other had are just the opposite!:lol:
 
#9 ·
*** You can not hear shim under bucket valves when they get loose****

Unno what clatter people hear, maybe cam chain; but it aint shims under them buckets. And if it is that loose that you can hear it....that motor won't be making that noise for but a few moments until it pukes and floats a valve.
 
#10 ·
If you set them to the loosest spec you will loose some top end and pick up some mid range.

If you set them to the tightest spec you will trade some mid range for top end.

If you want to go with either of the two extremes exactly you will need to make some shims in custom sizes.
 
#11 ·
Middle to loose

Middle to loose is best IMHO. Tight is not best because it's critically important that the exhaust valve seats fully to allow for heat dissipation into the cylinder head. Hard to believe but if the exhaust valve is too tight when the motor is running hot(full operation temp.)it will not fully seat properly and the result could be a burnt exhaust valve. That's why it,s sometimes normal for racing engines to have valve train clicking noise at low speed to be sure the valve face has that precious time to contact the valve seat and dissipate some of the 3400 degree combustion temp. A motor runs and sounds like crap with a burnt valve so I don't think it's worth the risk to go tight. A burnt valve sounds like an exhaust leak,without the exhaust leak:headshake
 
#13 ·
valves

while installing a high flow air filter i thought i would take a look down the throttle bodies with a flash light. i saw that what i believe is the valve had a black ring around the outside of the valve base seated end ???? is it o.k. 2400 miles 06
 
#21 ·
Thanks for that, I was aiming for 0.20 throughout but what would you suggest for IN and EX numbers to aim for on the looser end? I am working on my 05?

Exhaust 0.17 ∼ 0.22 mm
Inlet 0.15 ∼ 0.24 mm

Thanks for the replies, I realize that they get tighter as they wear. But I am also curious to know of any benefit of being uniform. Let me explain, you got 8 IN valves and 8 EX valves. The question is when setting all IN valves on the looser end for example is there a benefit to making an effort that they are all at the same number. Say you aim for 0.22 on all the IN valves, but you can't get all of them to 0.22, some are at 0.21 and some at 0.23? Your still in specs so your fine, but is there a extra benefit to getting all of them at 0.22 uniform all through the 8 valves and same question for the EX side.
 
#23 ·
In all reality......the actual thickness in question is so marginal that it can be debated to exhaustion......considering we are talking about the thickness of a piece of paper sliced into 3 or 4 thin pieces. get them close and worry about cam tensioner failure or generator failure instead, LOL
 
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