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TDC mark (timing inspection hole) NOT aligned!

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Sway
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TDC mark (timing inspection hole) NOT aligned!!

Post by Sway on Thu 23 Jun 2016, 9:40 am

Hi guys, hope to get some clarity in this problem of mine..

Recently bought my first CB500, great bike and really happy with it, no service manual/receipts what so ever so decided to give it a full service including valve clearance etc.

I've got the haynes manual, and it states that the "T" mark is supposed to be aligned with the static lines in the timing inspection hole, when the cams are at TDC. Thing is.. The "IN" and "EX mark on each cam sprockets (on the outside of them) are NOT aligned with the head when the "T" mark is aligned with the static marks. It's off by about a centimeter. I ignored the "T" mark in the inspection hole and just aligned the cam sprocket markings with the head when I checked the clearance. The nothes were both pointing outwards so I guess they were'nt putting pressure on the shim buckets. Correct?

When Im going to remove the cam shafts the manual says to align the "0" mark to the static lines in the inspection hole, but of course its the samt thing here, the sprockets "0 lines" are aligned with the head when the "0" mark is off by a centimeter in the inspection hole (BARELY visible!!) This makes me a bit worried...

Ive read a couple of other threads where people have had the same issue, and they all say it's nothing to worry about, that it's probably the cam chain that has stretched a bit. Bike has 3600 metric miles, think equivalent to 22639 english miles.

Help a lady in need out Smile)
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eternally_troubled
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Re: TDC mark (timing inspection hole) NOT aligned!

Post by eternally_troubled on Thu 23 Jun 2016, 3:42 pm

Hello!  You will have to excuse me if you have tried all these things already, but here are my thoughts:

Firstly, yes, 36000 km is about 22,500 miles and I agree it is a good thing to check your valve clearances!  I had to look up what you meant by 'metric miles' (for those who are interested look here).

First question:  are you turning the engine in the correct direction (anti-clockwise as you look at the left side of the engine) *and* have you removed the cam-chain tensioner yet?

I suspect that if you happened to be tensioning the cam-chain 'in reverse' it might throw things out a little, plus you *shouldn't* remove the cam-chain tensioner when measure the valve clearance.

Second question:  did the bike work well before you took it apart?  I would suggest that if the bike worked fine then you should keep the timing the same as it is.


As for a slight solution to your problem:  you can measure 'where' TDC is and see how that relates to the various marks on the cams, on the flywheel and the position of the cam lobes.  

All you need is a wooden or plastic stick and a bit of string - a wooden spoon might well be ideal!  You secure the string to one end of the stick and tie the other end of the string such that the stick can't disappear into the cylinder bore.  You then insert the stick through the spark-plug hole until it contacts the top of the piston - it is then possible to see the stick going up and down and determine when the piston has reached the top of its stroke (i.e. TDC).

I suspect that TDC will be when the 'T' mark on the flywheel is aligned with the mark on the case and that the chain/valve gear will be slightly 'out' - this is only a guess, you will have to find out for yourself!

You also may have noticed, by looking at the shape of the cam lobes and their positions at (or near) the TDC point, that there is a the possibility of being a little 'way out' on the alignment but still have the valves closed at TDC - this is good, as it allows the timing to vary slightly without a (too) detrimental effect.

Anyway, good luck with doing your valve clearances and getting it all back together!  You will have to post a picture of the finished article once you are up and going again.

sullivj
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Re: TDC mark (timing inspection hole) NOT aligned!

Post by sullivj on Thu 23 Jun 2016, 7:03 pm

I seem to remember that there is an error in the Haynes manual, about the way to turn the engine. A search on here will explain that.
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Sway
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Re: TDC mark (timing inspection hole) NOT aligned!

Post by Sway on Thu 23 Jun 2016, 8:04 pm

Eternally troubled: Thank you for your quick reply! Yes, Im turning the engine the right way (anti-clockwise), but Ill look into what "Sullivj" wrote! The tensioner is still on there :-)

I will try the wooden-spoon thing tomorrow, great tip, didn't think of that!

I actually didn't realize I was posting this in the "guides" section, ehrr.... It's totally ok if you delete this one, as Im going to repost it to the "workshop" section, would be nice to hear from people who has had the same issue - hope that's ok! Smile

dado_dassler
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Re: TDC mark (timing inspection hole) NOT aligned!

Post by dado_dassler on Thu 23 Jun 2016, 9:52 pm

sullivj wrote:I seem to remember that there is an error in the Haynes manual, about the way to turn the engine. A search on here will explain that.
you're right about that error, it's 180° clockwise or 540° anti-clockwise, not the 180° anti-clockwise.

post no. 8 in this topic might have the answer you're looking for.
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alanp
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Re: TDC mark (timing inspection hole) NOT aligned!

Post by alanp on Fri 24 Jun 2016, 3:33 pm

I'm just part way through doing my valve clearances and have a similar thing, although not quite to the extent that you describe. On mine, the IN and EX marks were not quite right when the static T was lined up. On mine, it looked like the inlet camshaft had been reassembled one tooth out on the cam chain by whoever last did the valve clearances. I'm hoping to get it into proper alignment when I reassemble it (just waiting for the shims in the post).

Like you, I checked the clearances with the cams in the proper position, ignoring the marks which were misleading.
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eternally_troubled
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Re: TDC mark (timing inspection hole) NOT aligned!

Post by eternally_troubled on Fri 24 Jun 2016, 8:33 pm

I merged your two topics into this one.... good luck!
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Sway
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Re: TDC mark (timing inspection hole) NOT aligned!

Post by Sway on Sat 25 Jun 2016, 10:02 am

alanp wrote:I'm just part way through doing my valve clearances and have a similar thing, although not quite to the extent that you describe. On mine, the IN and EX marks were not quite right when the static T was lined up. On mine, it looked like the inlet camshaft had been reassembled one tooth out on the cam chain by whoever last did the valve clearances. I'm hoping to get it into proper alignment when I reassemble it (just waiting for the shims in the post).

Like you, I checked the clearances with the cams in the proper position, ignoring the marks which were misleading.



The manual says to remove the camshafts when the 0 mark lines up, but I reckon you're going to remove yours when the 0 on the cam sprockets lines up with the head? Just trying to figure out how to put everything back together not to screw up the timing Very Happy

I going to give Eternally troubled's tip a go, by "measuring" where TDC are, and just ignore the position of the cam shafts and the static T.

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