Replacing cylinder head cover

If it's broken or just needs tweaked

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nickjtc
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Replacing cylinder head cover

Postby nickjtc » Tue Oct 31, 2006 12:06 am

Possibly a no-brainer question, but here goes. If I replace the cylinder head cover do I have to replace the cylinder head and camshaft too because of a potential mismatch in the camshaft bearing surfaces?
.....to be myself, a pattern for others.

1979 CB650
1971 Norton Commando
1968 CB175

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Volker_P
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Re: Replacing cylinder head cover

Postby Volker_P » Tue Oct 31, 2006 2:33 am

Good question.
But nothing to worry about here, only surfaces have to be smooth. If they look smooth but very used, one shoud also check the wear limits.
Crankshaft is different, there is in fact a number/letters code for the main bearings which should be obeyed.
BTW, what happened to the cover?

Robert
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Postby Robert » Tue Oct 31, 2006 5:31 am

Hi, it was some months ago (this might interest you as well, Volker :°) when I replaced the camshaft (exchanged 50 hp camshaft with 63 hp camshaft). Cylinder head cover staid the same. My "bucket" runs a tiny bit rougher now, I figure this is more due to the increased moved mass (higher cams) and not at all because of a bearing mismatch.

I'd say go for it, no mismatch. And for the cylinder head, I don't see any reason to match the cylinder head with the cylinder head cover.

As a sidenote, I'm pleased with the results (50hp->63hp), there is a noticable power gain at low rpms (not much) and some more power gain in the mid- and toprange.
top speed w/ 50 hp cam was about 170 km/h, now it's about 190 km/h (nothing else changed).
Interestingly mileage is virtually the same. Naturally engine temperatures are a bit higher now.

Robert

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Volker_P
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Re: Replacing cylinder head cover

Postby Volker_P » Tue Oct 31, 2006 7:15 am

Hi Robert,
good to hear you are still alive :D .
Your 63hp change results are interesting for me. I even could check it out myself for one day this spring with a slightly damaged 63hp cam I found in a parts box (see "An Easter story on seals and camshafts."). It ran slightly but noticeable better at low and medium revs, I did not want to try out higher revs with that camshaft however. A mileage change was also not noticeable during my test, but I had it installed only for about 200km.
Presently I have a weak chance to get also a good 63hp camshaft. The guy that promised to check out for one in the depths of his workshop confirmed that it should run fine without changes to the carbs, but one may get rid of a power hole by using a different jetting. I have no details to that point so far, however.
Would be interesting whether TÜV/paper stuff caused any problems. :)

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nickjtc
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Re: Replacing cylinder head cover

Postby nickjtc » Tue Oct 31, 2006 9:18 am

Volker_P wrote:Good question.
BTW, what happened to the cover?


PO buggered up the threads for the left hand valve adjustment cover and I have been wrestling with the idea of putting in a helicoil/timesert. This way I can replace the threads with 'originals' and get to do some top-end exploration.....maybe even see how the cam chain tensioner is looking and deal with that.

I know, I know, why not just stick to the KISS priciple.....???
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1979 CB650

1971 Norton Commando

1968 CB175

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Volker_P
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Re: Replacing cylinder head cover

Postby Volker_P » Tue Oct 31, 2006 9:45 am

nickjtc wrote:....maybe even see how the cam chain tensioner is looking and deal with that.


Having a look is allright, you may release the adjuster nut to check for free movement and available range, but don't try to get the tensioner out for that. It's tricky enough to get it back correctly into its groove. :?
And be very careful with the 22 head cover bolts (a small enough torque wrench is a must here!) or you may run into more than this one helicoil.
I would prefer helicoil against an unknown cover with intact threads because in case it is slightly bent you will run into problems to get it tight. For the same reason, place it on something really flat for inserting the helicoil or do it in place if you can make sure you don't loose filings into the engine.

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Re: Replacing cylinder head cover

Postby Guest » Tue Oct 31, 2006 2:12 pm

Volker_P wrote:
nickjtc wrote:Having a look is allright, you may release the adjuster nut to check for free movement and available range, but don't try to get the tensioner out for that. It's tricky enough to get it back correctly into its groove. :?
And be very careful with the 22 head cover bolts (a small enough torque wrench is a must here!) or you may run into more than this one helicoil.
I would prefer helicoil against an unknown cover with intact threads because in case it is slightly bent you will run into problems to get it tight. For the same reason, place it on something really flat for inserting the helicoil or do it in place if you can make sure you don't loose filings into the engine.


Thanks for that, Volker. A bid is in on eBay, so we'll see how it goes.

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nickjtc
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Re: Replacing cylinder head cover

Postby nickjtc » Tue Oct 31, 2006 2:13 pm

Anonymous wrote:
Volker_P wrote:
nickjtc wrote:Having a look is allright, you may release the adjuster nut to check for free movement and available range, but don't try to get the tensioner out for that. It's tricky enough to get it back correctly into its groove. :?
And be very careful with the 22 head cover bolts (a small enough torque wrench is a must here!) or you may run into more than this one helicoil.
I would prefer helicoil against an unknown cover with intact threads because in case it is slightly bent you will run into problems to get it tight. For the same reason, place it on something really flat for inserting the helicoil or do it in place if you can make sure you don't loose filings into the engine.


Thanks for that, Volker. A bid is in on eBay, so we'll see how it goes.


That was me!! Forgot to log in!
.....to be myself, a pattern for others.



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Ibsen
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Postby Ibsen » Wed Nov 01, 2006 1:53 am

It is easy to strip those threads if the cover is bolted down with too much torque. With good rubber gaskets for the valve covers, and good rubber seals for the bolts you don't have to use much torque to get them oil tight.
Normally, at the factory the cylinder head and the cylinder head cover is machined to fit as a pair. They are bolted together and the bearing surfaces for the camshaft bearings are bored out in line. When that is said, replacing the cylinder head cover only, is probably going to work, but as Volker said, if the only problem is the stripped threads, I would probably repaired the old cover, just to be on the safe side. But having a spare cover is a good idea though since you then will have a complete set of rocker arms extra. :)

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Volker_P
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Re: Replacing cylinder head cover

Postby Volker_P » Thu Nov 02, 2006 1:47 am

Now that I read this, I remember something important:
The basic point is that you can screw in the bolts of the valve covers right until the end of their thread. The pressure for the covers is just provided by the rubber tension. If rubbers are worn, higher torque will do nothing for tightness but just ruin the thread. What you have to do is get new rubbers or file down 1mm from the ending of the bolts :wink:
The smooth outside valve covers of the custom models (without SOHC and fins on them) are different, they have usual bolts with copper(?) washers. But here also too long bolts may end up in thread damage.


Ibsen wrote: Normally, at the factory the cylinder head and the cylinder head cover is machined to fit as a pair. They are bolted together and the bearing surfaces for the camshaft bearings are bored out in line.


Hmm, if they really manage this (from where they drill?) , I need to have this drilling machine! :D

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Ibsen
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Postby Ibsen » Thu Nov 02, 2006 4:15 am

I'm not shure how critical this is for the camshaft bearings since they don't have to carry so much load, but they do it the same way for the crankcases, and because of the crankshaft bearing alignment you can't mix crankcase halfs from two different engines.

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Volker_P
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Re: Replacing cylinder head cover

Postby Volker_P » Thu Nov 02, 2006 5:40 am

Thanks for the picture Ibsen. Very impressing!
I completely agree for the crankshaft, the bearings available in different sizes indicate that even then still machining tolerances have to be compensated to hit the requirements. Camshaft seems to be less demanding here.
But my basic concern is how to drill the holes. At the camshaft endings of the CB 650 head there is just solid material, no plugs or so like I think I remember there are in some DOHC. That is my basic worry why I think they could not just drill along the axis with both parts together. Except they have a really perfect drill-around-the-corner tool. Something which is still missing to my workshop equipment. :D

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Ibsen
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Postby Ibsen » Thu Nov 02, 2006 6:53 am

Maybe you are right about the CB cylinder head and the cam bearings. I might have mixed it up with the cylinder head on my Kawasaki. All the Kawasaki cylinder heads from the 70's and early 80's at least, was line bored. That is the reason those cylinder heads have got cam end plugs.

Yes, that's a machine to wish for. :D

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nickjtc
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Postby nickjtc » Thu Nov 02, 2006 11:23 am

And the line boring thing was supposed to have been one of the reasons for Honda's disaster with the first VFR750 engines. The cam retainers were not line bored with the cam supports. That minute discrepancy, coupled with questionable oil flow to the top end and possible incorrect torqued values holding everything together, plus cam lobes made of chocolate, led to a spate of warranty work which did the company's reputation no good at all.

It's that situation which prompted me to ask the question about the 650. The manual does not indicate that the components have to be replaced as sets so I am hoping for the best....assuming I get the replacement parts, that is.
.....to be myself, a pattern for others.



1979 CB650

1971 Norton Commando

1968 CB175

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kbailey
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Re: Replacing cylinder head cover

Postby kbailey » Fri Nov 03, 2006 1:25 am

Have you ever had Japanese chocolate? its delicious! give them a break!


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