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Knowing more about shims

12K views 13 replies 6 participants last post by  jsonder 
#1 ·
Hey everyone,
I just wanted to know more about shims and how to read them
I watched YouTube videos about this and I came to know that the shim clearance directly answers to many questions like valve wear, valve bend and carbon deposits on valve.
I just need to know more except this

My bikes running at 17000 kilometers and the previous owner of my cbr250 might have not maintained it properly.

Also my valve clearance have increased 0.2mm and I have replaced the shims of correct size and it's working well
Is this normal at this stage of the bike?

Getting a bit of vibration after reaching 7000rpm but it's tolerable,
any possible causes for this?
 
#2 ·
There's too much vague information in your post, many of which we can't really address together.

I can however direct you to a great tutorial for measuring your valves and information on calculating the proper shim size you need for your clearance adjustment. "Normal" gap at a certain mileage isn't really definable; it's just supposed to be within a range an if not, it needs adjustment. It alone is not an indicator of a problem with valves; unless of course you've dropped a valve into the head and the clearance is way too high.

2012 Honda CBR250R Valve Adjustment Procedure - Page 1

Vibration is likely tire or chain related.
 
#7 ·
I have previously adjusted clearance by visiting this website.
And bikes having good above average mileage no issues with that
The valve tappet sound have shifted from initial rpm to 6000rpm after adjusting them to spec
I'm replacing next size shims and try solving it

I just needed to know if things like this is possible like direct jump from 1.98mm shim size to 2.2mm size
 
#3 · (Edited)
Getting a bit of vibration after reaching 7000rpm but it's tolerable,
any possible causes for this?
Depends on what type of vibration and how strong. The CBR has a single cylinder engine that will always vibrate a bit and the higher it revs the stronger the vibrations. Did it always vibrate like that or is this a recent thing?
 
#4 · (Edited)
Also, shim under bucket and shim under rocker arm adjustments usually require a smaller (thinner) shim because the valves beat into the seats and clearance decreases.

What you described is not normal, but the previous owner could have misread the clearance (a narrow feeler gauge is needed because the shim may be down in the valve spring retainer).

see below:


 
#6 ·
Getting a bit of vibration after reaching 7000rpm but it's tolerable,
any possible causes for this?
Depends on what type of vibration and how strong. The CBR has a single cylinder engine that will always vibrate a bit and the higher it revs the stronger the vibrations. Did it always vibrate like that or is this a recent thing?
It vibrates while standing still and disappears while riding
I think it's due to tyres as it has been hardened
And I'm experience this recently
 
#8 · (Edited)
When I did the valves on my CB500X at nearly 15K miles, I needed to decrease the shim thickness by two sizes, i.e., by 0.05 mm. But my valve clearances were at or slightly less than the minimum allowed value.

I replaced all eight shims with ones 0.05 mm thinner.

To increase your stated thickness by two sizes you would go from 1.98 to 2.02 mm. These are actually 1.975 and 2.025 mm shims.

2.2 mm would be way too thick.
 
#11 ·
That's a pretty big jump in shim thickness, but depending on how long it had been since an adjustment, I wouldn't say it was out of the question for a still properly functioning bike. Luckily it was on the loose side and not tight. That's when the really bad things happen. :)

If you only hear the noise after it's warmed up, it's not likely to be shim clearance issues. These you normally hear when the engine is cold, then they lessen in intensity as the metal expands when the engine warms, and the clearances tighten up a bit. My guess is you're not hearing valve noise.

Also, if it's after 6000 RPM, many of these engines have a characteristic "rattle" in the 6-8k RPM range. Just do a search for "engine rattle" and you'll get bombarded with results. There's nothing to worry about if that's what you're hearing; sounds kind of like BB's in a can rattling around.
 
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#13 ·
Hey everyone,
I just wanted to know more about shims and how to read them
I watched YouTube videos about this and I came to know that the shim clearance directly answers to many questions like valve wear, valve bend and carbon deposits on valve.
I just need to know more except this

My bikes running at 17000 kilometers and the previous owner of my cbr250 might have not maintained it properly.

Also my valve clearance have increased 0.2mm and I have replaced the shims of correct size and it's working well
Is this normal at this stage of the bike?

Getting a bit of vibration after reaching 7000rpm but it's tolerable,
any possible causes for this?
I need 2012 cbr250r shim part number can anyone please send it.
 
#14 ·
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