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stuck on removing valve cover


potatobroxd
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im about to do a valve clearence check on a cb125f & got myself a haynes manual; although ive run into some issues:


1. How do we determine size of an o-ring?


2. It said to 'blow through the oil passage in the cover with compressed air to ensure it is clear' i dont have compressed air neither can I blow in it as the engine will still be on the frame.


3. Does the valve adjuster locknut need to be torqued accurately?


4. Image 6.5b, what does it mean by 'ensure dowel is secure'?



Ive attached an image for better explanation, notice point 5 and 7

20190319_001126.thumb.jpg.1a825c746acc0a151369a80c27791c51.jpg

Edited by potatobroxd
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You determine the size of an O ring by measuring it with a ruler . Tappets are almost certainly 8 mm and if you haven't got compressed air just put it to your lips and blow .

Edited by fastbob
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Don't bother changing the o-rings unless they're cracked/falling apart.


Look at the inside of the rocker cover - only worry if there's a build up of solid black gunk.


I think the nuts are 10mm for the cover and rockers (the tool kit on the bike should have all tools required). The threaded part of the adjuster can be twiddled by hand after the lock nut is undone. Don't forget to do them up again afterwards!

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Don't bother changing the o-rings unless they're cracked/falling apart.


Look at the inside of the rocker cover - only worry if there's a build up of solid black gunk.


I think the nuts are 10mm for the cover and rockers (the tool kit on the bike should have all tools required). The threaded part of the adjuster can be twiddled by hand after the lock nut is undone. Don't forget to do them up again afterwards!

 

The threaded part can indeed be twiddled by hand but you still have to hold it absolutely still when you tighten the lock nut . This is where a Clock Key comes in ( never thought of that Megawatt! ) I use an old spoon handle with a slot cut in it . You can buy tappet adjusting tools but where's the fun in that .

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What others have said about the o-ring. The tappet locknut will be 10mm - make sure you use a ring spanner to loosen/tighten it and hold the adjuster still when you retighten it otherwise it WILL move. A small adjustable spanner will be fine to turn the adjuster. Then remove feeler gauge, turn the engine over by hand and recheck clearance. The feeler gauge should be a "tight slip fit" when all is correct - it will feel tight-ish but will still slide in the gap. If the feeler blade won't move its too tight and if it slips around easily, it's too loose. If you're going to err, err on the side of looseness.

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The o ring looks like it seals the oil feed into the rocker cover which sprays the cam and rockers.

Any loss of pressure could end up in a big failure ,don't muck about just change it.

I looked on David Silver and they are about £1.30


The advice to blow air through the cover will be to check those passage ways are clear, use an oil can to pump oil through or a wd40 aerosol.


A very loose valve clearance can be damaging as the valve is not gradually opened or closed by the ramp of the cam.The sudden acceleration and deceleration can smash the valve train.

And likewise a tight clearance can burn valves out as the valve cannot lose its heat into the seat properly.

If you've not measured anything with feelers before, start smaller than the clearance and work your way up in one thou steps, you will find the correct clearance just has a slight resistance to going through.Be mindful that it could be possible to shove a thicker feeler in and it compress the spring giving you a false reading ,As S23 says erring to the higher end of the tolerance is safest.

Obviously there is more to the clearance check, engine temp (probably cold) and the position of the crank so the valves are fully shut and off the ramp of the cam.

Mr Haynes should explain all.

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The o ring looks like it seals the oil feed into the rocker cover which sprays the cam and rockers.

Any loss of pressure could end up in a big failure ,don't muck about just change it.

I looked on David Silver and they are about £1.30


The advice to blow air through the cover will be to check those passage ways are clear, use an oil can to pump oil through or a wd40 aerosol.


A very loose valve clearance can be damaging as the valve is not gradually opened or closed by the ramp of the cam.The sudden acceleration and deceleration can smash the valve train.

And likewise a tight clearance can burn valves out as the valve cannot lose its heat into the seat properly.

If you've not measured anything with feelers before, start smaller than the clearance and work your way up in one thou steps, you will find the correct clearance just has a slight resistance to going through.Be mindful that it could be possible to shove a thicker feeler in and it compress the spring giving you a false reading ,As S23 says erring to the higher end of the tolerance is safest.

Obviously there is more to the clearance check, engine temp (probably cold) and the position of the crank so the valves are fully shut and off the ramp of the cam.

Mr Haynes should explain all.

mainly check all clearances before you adjust any .Who knows they may be within tolerance .


And don't forget that you need to retighten the adjuster lock nut and in this process keep the tappet adjuster in position ...it gets fiddly

So as above start with your measured clearance at the higher end as this gives you a bit of wiggle room .


recheck clearances after tightening the locknut and a couple of hand revolutions of the engine before reassembling the engine .

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All good advice. Just to add do not be surprised or disheartened if having set your valve clearances they they change all by themselves. Sometimes it can take a few goes to get them spot on. I always check, check again and check once more. I am rarely happy with the first attempt.

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The o ring looks like it seals the oil feed into the rocker cover which sprays the cam and rockers.

Any loss of pressure could end up in a big failure ,don't muck about just change it.

I looked on David Silver and they are about £1.30


The advice to blow air through the cover will be to check those passage ways are clear, use an oil can to pump oil through or a wd40 aerosol.


A very loose valve clearance can be damaging as the valve is not gradually opened or closed by the ramp of the cam.The sudden acceleration and deceleration can smash the valve train.

And likewise a tight clearance can burn valves out as the valve cannot lose its heat into the seat properly.

If you've not measured anything with feelers before, start smaller than the clearance and work your way up in one thou steps, you will find the correct clearance just has a slight resistance to going through.Be mindful that it could be possible to shove a thicker feeler in and it compress the spring giving you a false reading ,As S23 says erring to the higher end of the tolerance is safest.

Obviously there is more to the clearance check, engine temp (probably cold) and the position of the crank so the valves are fully shut and off the ramp of the cam.

Mr Haynes should explain all.

 


The o-ring, how do you know the size of it? Do o-rings all come in the same size? Also, will an air duster from poundland work? Lastly, can I just estimate the torque on the locknut or will a torque wrench be necessary?


Also thanks for such a long reply!

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Get yourself something like this and you will always have the size you need ready to go. I've had one for years, makes life easier :thumb:

 

272073575_Screenshot2019-03-21at21_52_27.png.b7fc9d0a8ce2b60cf339053b6e717b45.png

 

https://www.ebay.co.uk/itm/419-Pcs-Rubber-O-Ring-Oring-Seal-Plumbing-Garage-Set-Kit-32-Sizes-With-Case-4-34/221854546225?epid=1960364672&hash=item33a78fb931:g:c60AAOSwJQdXARmq

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The o ring looks like it seals the oil feed into the rocker cover which sprays the cam and rockers.

Any loss of pressure could end up in a big failure ,don't muck about just change it.

I looked on David Silver and they are about £1.30


The advice to blow air through the cover will be to check those passage ways are clear, use an oil can to pump oil through or a wd40 aerosol.


A very loose valve clearance can be damaging as the valve is not gradually opened or closed by the ramp of the cam.The sudden acceleration and deceleration can smash the valve train.

And likewise a tight clearance can burn valves out as the valve cannot lose its heat into the seat properly.

If you've not measured anything with feelers before, start smaller than the clearance and work your way up in one thou steps, you will find the correct clearance just has a slight resistance to going through.Be mindful that it could be possible to shove a thicker feeler in and it compress the spring giving you a false reading ,As S23 says erring to the higher end of the tolerance is safest.

Obviously there is more to the clearance check, engine temp (probably cold) and the position of the crank so the valves are fully shut and off the ramp of the cam.

Mr Haynes should explain all.

 


The o-ring, how do you know the size of it? Do o-rings all come in the same size? Also, will an air duster from poundland work? Lastly, can I just estimate the torque on the locknut or will a torque wrench be necessary?


Also thanks for such a long reply!

Just buy the real thing from Honda.

Not only do you need to get the right size but also the right material.If its the wrong grade of rubber it could deteriorate quicker,cause an internal leak and loss of pressure and flow to the rockers. If its too small it won't seal properly, too big and it might not have enough space to compress into ,hold the cover off or crack the housing.

Not sure what an air duster is but the objective is to flush the gallery of any dirt or gunk and ensure the spray jets are free flowing.A tin of brake cleaner in aerosol from Halfords would do the trick.

Cam covers can be notorious for building up black gunk that can solidify and cause grief,make you you clean it out well.


No doubt there will be a torque setting on the lock nut but everyone will just do it up by hand.

Generally you would use a ring spanner and something to hold the adjuster, small spanner or a clock key has been mentioned as suitable.

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Thanks for the reply guys; I've just added one more question to the thread, the image 6.5b says 'ensure dowel is secure' so I'm not entirely sure what that means?

 

Just means located correctly in the bore of the head.Just make sure It's pressed back into the hole as it came out.

It's use is to act as a passage way for the oil and to provide some centralisation to the cover.

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