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Discussion Starter #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?
 

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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.
 

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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?
 

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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:


 

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Discussion Starter #5
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:


Woow this one's interesting may be even I have adjusted clearance wrong! I used normal feeler gauge
 

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Discussion Starter #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
 

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Discussion Starter #7
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.
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
 

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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.
 

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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
If your valves are within spec, you shouldn't change the shim size to attempt to cure a noise. If you're talking about moving a slight amount to try to decrease the clearance just a hair (say 0.05mm), as long as you're within valve spec that's fine. But jumping .2mm is wayyyyy too much and you'll be out of spec.

May I ask: Are you entirely sure what you're hearing is tappet noise? You may want to check your cam chain tensioner.
 

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Discussion Starter #10 (Edited)
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
If your valves are within spec, you shouldn't change the shim size to attempt to cure a noise. If you're talking about moving a slight amount to try to decrease the clearance just a hair (say 0.05mm), as long as you're within valve spec that's fine. But jumping .2mm is wayyyyy too much and you'll be out of spec.

May I ask: Are you entirely sure what you're hearing is tappet noise? You may want to check your cam chain tensioner.
Yes cam tensioner is well set and also I here this noise only after reaching the optimum temperature so I thought this should be problem of clearance itself.

Between I didn't mean I'm trying that 0.2mm shim change now after its In spec.
My previous shim while it was out of spec was 1.98mm and I bought 2.2mm shim to bring it back to spec
And now I still hear noise after 6000rpm so I thought changing 2.2mm to 2.25mm which is next size.

Is this leap of 0.2mm common? Or should I get engine head check?
No issues with mileage and performance just that noise at high rpm
 

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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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