Cannot line up timing marks after front CCT failure

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mattycoops43
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Re: Cannot line up timing marks after front CCT failure

Post by mattycoops43 »

7moore7 wrote:
mattycoops43 wrote: Anyway, is it possible for the chain to slip on the crank or is that not possible with the bottom half built up?
The rest made perfect sense, but the chain could slip 10 teeth and not matter in this case (which it is indeed possible with the bottom build up) The chain isn't lined up to anything on the cranks themselves, and unless it has uneven links you are really lining the bottom crank sprocket with the two cam sprockets. The chain is merely connecting them via a certain length. It isn't part of the actual timing, it's just transferring the rotation from the bottom to the top.
Kind of, but what you have to remember is that if the chain was a tooth out on the crank, it would be half a tooth out at the top, however, if it then slipped a second tooth at the crank, it would be back in line at the top again.

Following me now? I know the chain is not timed to the engine as such, each link is identical, but it does have to be in line out of the two possible positions.

It took me several hours of arguing with him, despite us not being able to time in my fazer closer than half a tooth, before I cottoned on to what he was on about.
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mattycoops43
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Re: Cannot line up timing marks after front CCT failure

Post by mattycoops43 »

Another way of explaining it.

I was convinced that in theory you could rotate the chain around the crank and cam gears without anything being affected, but you cannot. Due to the difference in the size of the gears, it will not line up again until you have gone two teeth on the crank.

I don't necessarily think this is what's up with this engine, I just think it's an interesting point.
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7moore7
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Re: Cannot line up timing marks after front CCT failure

Post by 7moore7 »

Ah I see what you mean... but I still think that as long as you're on the FT mark at the flywheel, then it won't matter.

You're saying that if it were to slip one tooth at the bottom, then the top would be 1/2 tooth off (makes sense). But when lining it up, you can only mess this up if the crank is 1 full tooth off (very noticeable at the FT mark because of the flywheel's larger diameter).

The other reason I think this is that there is no caution against it in the manual, and being that the cam chain can indeed slip down into the case, I would think it would advise to be very cautious when putting it on the bottom sprocket if you needed to line it up on every even tooth, and not the odd ones...

Edit:
It is a good point to spin the crank around a couple of times when you're done to double check the timing though, because if you mess up it will be apparent once they go around once and the crank goes around twice.
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Watty
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Re: Cannot line up timing marks after front CCT failure

Post by Watty »

I've seen this lots of times over the years mate on various engines not just bikes! Had the same on my storm when I did my manuals, but she starts first time and pulls hard to the red line :eek2 so all good :thumbup: . But! It's good to be cautious and I'm certainly not too shy to ask anyone on here for help and advice if I'm unsure :D
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tony.mon
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Re: Cannot line up timing marks after front CCT failure

Post by tony.mon »

This doesn't make sense to me.
The chain has to be engaged at the crank, and properly engaged in the sprocket. AT the top, on the cam sprockets, same thing.
You can't be half a tooth out, as that would mean that the sticky-out bit on the chain would be lined up with a tooth on the sprocket instead of sitting in the valley between them.

I think you may be confused because the crank turns twice to each time that the cam sprocket turns, and this, you think, means that therefore the sprocket teeth line up every other time round. But the cam sprockets are twice the size, in terms of number of teeth.

So if you have one tooth moved forward on the crank sprocket, there would have to be a tooth moved forward on both of the cam sprockets in order to keep the timing between all of the sprockets in proper coordination.

You can't have half a tooth.....sorry.

The timing marks don't always line up exactly, that's normal. all you can do is to get it to the nearest whole tooth, as once again, you can't have half a tooth.

As the chain and tensioner blades wear, (both the active one that the cct pushes against, and the passive one , that stops the chain flapping onto the cam chain tunnel) then the timing effectively slips a little way. Not really enough to cause a problem, though. The problem would occur if the timing slipped far enough out (two teeth or more) to allow the piston to hit the valves.
But the chain will never wear that much. As, after many years and miles, the chain wears to be a whole tooth out, you merely need to moved the cam one tooth round under the chain, and it will be exactly back into alignment. So the second tooth never arrives.

Not sure if I've argued this very clearly, but I hope that it helps.
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parkergb6
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Re: Cannot line up timing marks after front CCT failure

Post by parkergb6 »

Guys really appreciate all the input and it has reassured me quite a lot. I will get back on this tomorrow afternoon or Saturday and get it all up and running hopefully and see where I go from there. Really interesting to see every ones view and it helps me sanity check my thought process.
Not sure why I need to replace an exhaust shim I'm guessing its where I reseated all four valves when I had the head off.

Just to clarify on the valve clearances

Tolerances are Inlet 0.13-0.19 and exhaust 0.28 to 0.34. I have measured all four valve clearances and two are out of tolerance one exhaust at 0.26 and one inlet at 0.11. This means I have to increase the gap on the exhaust by a minimum of 0.02mm and the inlet by a minimum of again 0.02 and as shims only come in increments of 0.05 I would have to decrease the width of each shim by 0.05 to widen the gap. The exhaust shim is currently 2.00 so need to reduce this to 1.95 and the inlet is currently 2.05 so need to reduce this to 2.00. This in theory should make the exhaust gap 0.31 and the inlet 0.16.

Unless you guys think I shouldn't worry about a difference of 0.02 and let it bed in for a while and check it again in say about 1000 miles?

Again once again this forum and it users have given the confidence and answers to crack on.
Thanks
Geoff

:thumbup:
7moore7
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Re: Cannot line up timing marks after front CCT failure

Post by 7moore7 »

None of this should be an issue as you said, tony, because when actually setting the timing you are not concerned with rotation, just lining the marks up.

Matty's description is making this slightly confusing...

But in theory, if you were to skip one tooth on the bottom, you would have to rotate the cam sprockets two teeth to make up for it, not just one... (I think this is what was throwing things off). It wouldn't happen in the real world very easily. I think I said it backwards a couple of posts up where you'd be one tooth off on the crank and 1/2 on the cams... it should be 1/2 a tooth's rotation off the crank to be 1 tooth off on the cams.

And I'd adjust the tolerances to get it in spec like you said. May as well while you're in there, and it does make a difference ;)
tony.mon
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Re: Cannot line up timing marks after front CCT failure

Post by tony.mon »

You are exactly right, Geoff, you need to change the shims as you suggest.
Ideally you aim to have the clearances in the middle of the range, but be aware that any wear on the seat or the valve seat face leads to the gap closing. Therefore it is wise to move to between the middle of the range and the larger end of the range, because that will lead to a longer period- more miles- before you have to re shim the clearances.

But the drift towards too small a gap is slow, and often when you check the clearances there is no need to take any action.

I think we've all said it, no need to think about how many teeth or degrees, just make sure that the chain is pulled tight towards the tensioner over the cam sprockets and get the marks on those sprockets lined up as near as you can to the top of the cylinder head,
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parkergb6
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Re: Cannot line up timing marks after front CCT failure

Post by parkergb6 »

Well what a pain in the butt. Put the new shims and re measure clearances and I they are still out. Does anyone know a cost effective place to buy a shim kit instead of one at a time so I can just get this bloody job done in one hit? Seen some on ebay from states for £88 seems a bit steep but perhaps not.
tony.mon
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Re: Cannot line up timing marks after front CCT failure

Post by tony.mon »

Found these:
http://www.ebay.co.uk/itm/Hot-Cams-Valv ... 5af7dbe6ab

£54 or so for a full kit but Lytle racing in the states do 30 shim sets, which should be plenty.
You'll need 1.75 to 1.95 mm sizes but make sure you get the 9.48 diameter ones.
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lloydie
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Re: Cannot line up timing marks after front CCT failure

Post by lloydie »

tony.mon wrote:Found these:
http://www.ebay.co.uk/itm/Hot-Cams-Valv ... 5af7dbe6ab

£54 or so for a full kit but Lytle racing in the states do 30 shim sets, which should be plenty.
You'll need 1.75 to 1.95 mm sizes but make sure you get the 9.48 diameter ones.
I am thinking of getting that hot cams shim set , are they any good ?
tony.mon
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Re: Cannot line up timing marks after front CCT failure

Post by tony.mon »

Yes, definitely, but if you use them lots, you'll end up with lots of one size and none of another, so you end up buying a few here and there to keep the set stocked- I prefer to keep at least two of each size.

Just be aware that they make two main diameters, don't buy the 7.5 mm set by mistake.

It's worth adding, though that these sets are in .05mm increments, which is ok to get within tolerance; if you want it spot on in the middle of the range you'll have to order the exact size from Honda. They supply in .02 increments, but may not be in stock at the dealer.
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parkergb6
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Re: Cannot line up timing marks after front CCT failure

Post by parkergb6 »

Thanks Guys just found these and they seem a good buy as well,
http://www.ebay.co.uk/itm/NOS-HOT-CAMS- ... 5440427%26

Micrometer arrived yesterday and hopefully my new feeler gauges will arrive tomorrow then I start again.....
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lloydie
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Re: Cannot line up timing marks after front CCT failure

Post by lloydie »

Thanks tony I will get a kit after Xmas :-)
tony.mon
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Re: Cannot line up timing marks after front CCT failure

Post by tony.mon »

lloydie wrote:Thanks tony I will get a kit after Xmas :-)
Put it on your Christmas list- I have a carbon mudguard on mine.
That's the only thing, so they haven't got any other choices!

That should work....... :think:
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