andyh
2015 Tourist
Posts: 953
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Post by andyh on Dec 28, 2021 6:47:04 GMT 10
Has anyone ever come across valve clearances getting tighter - not looser? My exhaust valves go from .1 to about .05 over a distance of 1,000k's.
This isn't new, Chris and I were trying to get our head around it when I pulled the engine 2,000 kilometres ago for the bearing replacement. The issue predates that.
Between us we thought it might be valve wear or the valve seats because everything else above the rocker, if worn, would increase the gap - which makes sense because undoing the adjustment screw tightens the gap.
Problem I am facing is I need to turn the screw into the rocker arm and am running out of adjustment.
1,000k's since the crank replacement and they have closed up again. Inlet is fine on both sides but exhausts are tight. 0.04 and 0.05 and I am running out of ideas.
I asked Graeme to look at the heads while they were off and he said they looked ok. My mistake, I should have asked him to remove the valves, measure and then check the seats.
Any ideas?
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Post by Uralee on Dec 28, 2021 7:57:47 GMT 10
Andy, something sounds wrong in your description.
Screwing the adjuster into the arm DECREASES the gap. If your clearance is decreasing, you need to screw adjuster OUT of arm……anticlockwise.
If the gap keeps decreasing the issue will be valve or seat wear or loose valve seat.
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andyh
2015 Tourist
Posts: 953
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Post by andyh on Dec 28, 2021 12:18:31 GMT 10
Must be a terminology thing but if you screw the adjuster (with the pushrod receiving cup) into the rocker arm the distance between the other end of the rocker arm and the valve stem increases  |
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bewildered
Tool for reverse shift lever removal
Posts: 276
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Post by bewildered on Dec 28, 2021 16:57:06 GMT 10
Rough as guts and treating symptoms not cause but if adjustment range runs out could you pull the pushrods, sweat the tips off and shorten the pushrods a little ?
Logical cause would be valve seat recession or valve stem stretch, would hate to think it was spring cap retaining collet wear, that could get really ugly.
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Post by Uralee on Dec 28, 2021 17:53:01 GMT 10
Andy, “terminology”….screwing in is done from the lock nut side…..clockwise decreases gap, anti clockwise increases. Either way you look at it, you have an issue and most likely one of the three I have mentioned.
Are you checking when absolutely dead cold?? The gap increases with temperature.
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Post by Uralee on Dec 28, 2021 17:59:50 GMT 10
Rough as guts and treating symptoms not cause but if adjustment range runs out could you pull the pushrods, sweat the tips off and shorten the pushrods a little ? Logical cause would be valve seat recession or valve stem stretch, would hate to think it was spring cap retaining collet wear, that could get really ugly. Cannot be valve stem stretch….opposite symptom. A collet problem has no effect on clearance between stem and rocker so extremely unlikely…….but is Andy’s motor so anything is possible. 🤣🤣 |
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bewildered
Tool for reverse shift lever removal
Posts: 276
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Post by bewildered on Dec 28, 2021 19:10:21 GMT 10
Reckon valve stem stretch would have the same effect as seat recession ?
Correct re collets, nightmare put to bed.
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Post by Uralee on Dec 28, 2021 19:31:52 GMT 10
Woops, correct, stretch decreases gap……..my bad. 👍
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Post by haitch on Dec 28, 2021 22:41:19 GMT 10
Following with interest.
I think poor Andy might need to have the heads off, again.
Unless the valve clearance when measured had some heat in them.
How about loose or incorrectly torqued rocker pivot posts?
As creaky rider says " I dunno what I'm talking about" 🤣🤣
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andyh
2015 Tourist
Posts: 953
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Post by andyh on Dec 29, 2021 6:13:49 GMT 10
Ok, now I see what you mean. I figured that since there is no slot in the adjuster (like some I have seen) and I use a 10mm spanner to turn the adjuster clockwise into the rocker arm then that would be the best way to describe it.
So its a terminology thing, thanks for clearing that up Lee.
Either way, we are talking about the same thing. I asked because I wanted to make sure I wasn't missing something. If anything on the adjustment screw side of the rocker wears - then the gap increases.
If anything on the Valve side of the rocker wears - then the gap decreases (with the exception of valve stem stretch which is worth looking at )
To answer a few questions.
I am one of the lucky ones that has a TDC mark, so the clearances are always checked on the same mark, not that it matters much as the push rods are free anyway.
Yes Cold, the bike is left for a minimum of 24 hours before checking, more often than not a few days. I also made sure that the heads were correctly torqued, just to eliminate that.
I set them as close to .1mm as I can and use .1mm go .15mm no go. (They are never tighter than .1mm or looser than .15mm)
Having said that the rocker arms are slightly notched so I have to make sure I slide the feeler in from the same direction on each rocker face. (not bad enough to get a correct reading, Chris looked at them and thought it was normal wear)
The ''gap decreasing'' issue started around 25,000k's (before the main bearing failure)
Last time the heads were off I pulled the valves, checked the seats, did a rough measure. Lapped them back in very gently and did a leak test on fitment. All seemed ok. Getting the valves out is a pain, normal valve compressors don't fit. I borrowed one that Chris had and it is with great sadness that I can't do that again.
Engine has done 3,000k's since that and been pulled down again so any previous measurement is thrown out the window as something as small as a cylinder base gasket will change the gap.
So here is the game plan.
I know that I have a decrease in both exhaust valves over 800k's. I have reset them and will do another 500k's and check again.
If they haven't settled down then the heads come off.
I am kind of hoping that the recent engine rebuild needs time to settle down although it has done 1000k's already, but I know that is wishful thinking.
Thanks for the ideas.
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