450F Does it make big difference if specs is barely off???

TheChasers

TheChasers

Question question,I checking my valve clearance on yz450f.
Specs for Exhaust Camshaft 0.20-0.25
Specs for Intake Camshaft 0.10-0.15.

Intake camshaft seems to be ok, 0.15 wont fit in,but 0.10 fits in and 0.13 little too tight,so thats at least in between specs.But exhaust isnt passing,at least for the 1st vavle,its 2 on the exhaust and the last ones is in specs but first one only 0.18 can fit in,not even the 0.20..So is that 0.02 making any difference,could it cause any issues?if so please explain.Also even though its not a big difference should I go ahead and adjust by replacing shim??Please respond asap.Thanks in advance
 
Mihylo33

Mihylo33

TheChasers:
Question question,I checking my valve clearance on yz450f.
Specs for Exhaust Camshaft 0.20-0.25
Specs for Intake Camshaft 0.10-0.15.

Intake camshaft seems to be ok, 0.15 wont fit in,but 0.10 fits in and 0.13 little too tight,so thats at least in between specs.But exhaust isnt passing,at least for the 1st vavle,its 2 on the exhaust and the last ones is in specs but first one only 0.18 can fit in,not even the 0.20..So is that 0.02 making any difference,could it cause any issues?if so please explain.Also even though its not a big difference should I go ahead and adjust by replacing shim??Please respond asap.Thanks in advance
Click to expand...


Yea it makes a difference. Re shim accordingly and if you are maxed out time for valves and some head work.
 
SRAD97750

SRAD97750

Moderator
Staff member
Alo,
You're going to want to shim it to the highest spec and check regularily to build up a good amount of data.

Metals expand as they heat up.
At operating temperature the clearances are tighter than when cold. This clearance you measure when cold may be all but completely taken up by normal thermal expansion at operating temps.

Why the clearance changes over time:
A valve stretches either at the stem or the face as it gets pounded vigorously in and out of it's seat. The more vigorous you are on the throttle, the more pounding the valve receives. This stretch is different than the thermal expansion, but rather a physical deformation due to use.

Like it or not valves are wear items that should be expected to move over time and once the 'acceleration of wear' increases, the valves/seats are on their way out.
Just my nickle fifty... -BIG DAN :thumb:
 
TheChasers

TheChasers

These are my readings from the shim from tight valve,,measurements in "mm,in,and fraction.On the shim i see numbers "179",but dnt know how to compare to the readings im getting off meter..Please help me understand this a lil more
 
SRAD97750

SRAD97750

Moderator
Staff member
You want to measure the thickness instead of the diameter.
Then subtract the difference in the spec and measurement, in your case 0.07mm? That would bring you back to 0.25mm
Order the shim of that size, reassemble, and try this all again when you have the new shim. I've heard of sanding them down, but I don't recommend it.
-BIG DAN:thumb:
 
TheChasers

TheChasers

SRAD97750:
You want to measure the thickness instead of the diameter.
Then subtract the difference in the spec and measurement, in your case 0.07mm? That would bring you back to 0.25mm
Order the shim of that size, rps20160621_203916.jpg reassemble, and try this all again when you have the new shim. I've heard of sanding them down, but I don't recommend it.
-BIG DAN:thumb:
Click to expand...
This is the reading I got off thinkness,,excuse me for neing completely lost but can you break down the exact numbers that I need to be having involved in this "equation"...also read from a forum online where someone said its better to b a lil loose instead of of tight,so was thinkin,since on the intake size,specs was 0.10- 0.15 but i couldnt even get a 13 in,should I be checking and chaning those to at least get a 0.15 feeler inside? ??
 
snowflake

snowflake

I shim towards the biggest end of the spec, although you are correct in that the tight end of the spec is still in spec, you do have a valve that is out of spec so you may as well shim them all.

My rule of thumb is that the valves get replaced after 3 shim jobs OR they tightened up really quick (within 5 hours of the last shim job)
 
snowflake

snowflake

TheChasers:
This is the reading I got off thinkness,,excuse me for neing completely lost but can you break down the exact numbers that I need to be having involved in this "equation"...also read from a forum online where someone said its better to b a lil loose instead of of tight,so was thinkin,since on the intake size,specs was 0.10- 0.15 but i couldnt even get a 13 in,should I be checking and chaning those to at least get a 0.15 feeler inside? ??
Click to expand...
the equation for calculating your new shim size is
Replacement shim thickness=(measured valve clearance-specified valve clearance)+ current shim thickness
 
TheChasers

TheChasers

snowflake:
the equation for calculating your new shim size is
Replacement shim thickness=(measured valve clearance-specified valve clearance)+ current shim thickness
Click to expand...
Ok,thanks for the response,getting ready to take off intake cam shaft now so can measure shims on that side.One thing tho,my feeler gauge kinda skips numbers,so it jumps for .10 to .13,and as i stated,the 13 dont fit in so i dnt know how to determine if its .11 or .12.any suggestions?
 
snowflake

snowflake

TheChasers:
Ok,thanks for the response,getting ready to take off intake cam shaft now so can measure shims on that side.One thing tho,my feeler gauge kinda skips numbers,so it jumps for .10 to .13,and as i stated,the 13 dont fit in so i dnt know how to determine if its .11 or .12.any suggestions?
Click to expand...
you can buy a feeler gauge that has the .01 differences at oreillys for about $10
 
TheChasers

TheChasers

Damn,yesterday I thought of them for a sec,already got one from autozone,which im stuck with because lost receipt and just picked up one today from chapperal...ok,will just continue this job tomorrow after get off work and stop at O Reillys
 
TheChasers

TheChasers

snowflake:
the equation for calculating your new shim size is
Replacement shim thickness=(measured valve clearance-specified valve clearance)+ current shim thickness
Click to expand...
On last thing I would be grateful for,please help me understand how to calculate measurement correctly...measured valve clearance was 0.18mm,my specification valve clearance is 0.20- 0.25,which one and I supposed to pick?The shim thickness is 1.78mm..please help me solve that 1st one so I can better do the others with full understanding.Been awhile,but all decimals should be lined up correctly?and dnt know which number is supposed to be picked out of the "spec" clearance???
 
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