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How far out off nominal can a GL1800 valve be before damage

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32K service. All valves in tolerance, roughly -.01 or -.02mm tighter than the nominal, save for one Exhaust Valve. The cylinder 1 exhaust valve was .05mm too big of a gap (+.02mm out of tolerance).

My years of engine work tells me that too large of a clearance robs some power, making the engine not run smoothly and results in ticking, but causes no damage. I hear no ticking, the injectors are certainly louder, and I feel no uneven running, so my hunch is I also have no loss of power or mileage to concern myself over.

I have decided not to pull the camshaft to inspect the current shim and possibly set the clearance down and instead wait for the 64K service where I expect that all the valves may tighten up an additional .02mm putting that exhaust valve into tolerance and all the others on the verge of being too tight. Main reason for deciding not to adjust is the disturbing a functional valve train and the bother of waiting for the shim to be ordered with no practical gain. I suspect the factory made the similar decision when they discovered they put an out-of-specification shim in.

Now to the reason for this posting, each engine is different nonetheless, and as a result I do have some small doubt as to my decision; 2mpg or 5hp would be worth it. For those more practically or pragmatic minded (perfectionists need not apply); any Confirmation or Dissenters?

ObligatoryDisclaimer: I deny the above posting when it comes to warranty adjustments, the above is for entertainment only. For example, I decided to add a thin coating of Velveeta to resolve the clearance problem to mitigate the engine damage. Prove me wrong.
 

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salyzyn said:
My years of engine work tells me that too large of a clearance robs some power, making the engine not run smoothly and results in ticking, but causes no damage.
This is only partially true. If the clearance get too big, the cam lobe will began "banging" against its contact point instead of a gradual contact and that is what causes the ticking sound -- and if severe enough it can lead to cam lobe damage. I don't know where a loose clearance will cause noticable ticking on a GW but if you can hear ticking then it is time to adjust those valves.

While in theory tight valve clearances result in increased power and loose valve clearances increase low rpm performance, it would be hard to detect a difference on a dyno if the clearances are within the manufacture's specifications and those are probably very conservative clearances, the valves could probably be .002 out of tolerance without any danger to the engine and without any loss of power or gas mileage.

However, the question is where the clearances are going to be tomorrow. I think you need to assume that they were in tolerance when the bike was new and since they have changed there is a chance that they will continue to change, especially if they are tight. I wouldn't worry about a slightly loose clearance but I would be concerned about a tight clearance since the clearance normally tightens over time.
 

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mcrider007 said:
salyzyn said:
My years of engine work tells me that too large of a clearance robs some power, making the engine not run smoothly and results in ticking, but causes no damage.
This is only partially true. If the clearance get too big, the cam lobe will began "banging" against its contact point instead of a gradual contact and that is what causes the ticking sound -- and if severe enough it can lead to cam lobe damage. I don't know where a loose clearance will cause noticable ticking on a GW but if you can hear ticking then it is time to adjust those valves.

While in theory tight valve clearances result in increased power and loose valve clearances increase low rpm performance, it would be hard to detect a difference on a dyno if the clearances are within the manufacture's specifications and those are probably very conservative clearances, the valves could probably be .002 out of tolerance without any danger to the engine and without any loss of power or gas mileage.

However, the question is where the clearances are going to be tomorrow. I think you need to assume that they were in tolerance when the bike was new and since they have changed there is a chance that they will continue to change, especially if they are tight. I wouldn't worry about a slightly loose clearance but I would be concerned about a tight clearance since the clearance normally tightens over time.
I have a different opinion than either of you. In the extereme, you're both correct. However, with a shim under bucket design, it would be rare to reach an extreme condition... there is no adjustment except to put in a different shim, and shims don't wear much. Concerning the valves being in spec from the factory, that's an assumption I wouldn't make. lol

With solid lifters, the cam is never in contact with the bucket except when it starts to lift the valve open. Engines with solids will always "tick" - it's the nature of the beast, although with such a tight spec tolerance, they won't tick much.

Concerning clearances, with a tighter tolerance, the valve will open sooner and close later. With a loose tolerance, the opposite is true, open later and close sooner. In order for these conditions to affect performance the tolerance would have to be substantially larger than the spec, which is +/- .03mm which is only +/- .001", which IMO is an unbelievably tight tolerance. One may see some performance difference at maybe +/- .10mm but I doubt it would be noticable unless the bike was put on a dyno, like mcrider suggests.

To answer the original question, a tolerance of +/- .06mm wouldn't hurt the engine at all. If I remember correctly, clearances with pushrod/rocker arm systems were around +/- .030" - you heard a lot of ticking then. lol

Oops - I mis-spoke. Pushrod engines with solids had clearances of .030" and tolerances of +/- .003". Sorry. :oops:
 

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Be careful you don't confuse inches and millimeters. Valve clearances are listed in both on page 3-8 of the manual.

According to the manual, you really don't HAVE to change shims until a valve is out by .002 inches (2 thousandths or .0508 mm) out of tolerance. But I typically like to bring them back to center spec when they are .001 inches out. Also be aware that loosening the cam chain tensioner can make about half a thousandths difference on the measurements on the forward most valves.

Valves on this bike should never get loose, they will normally only get tighter. If the clearance decreases too much, you will eventually burn a valve, but I can't say I know exactly how tight it would have to be for that to happen.

The valves on this bike don't seem to change much so there really is no good reason not to bring them back to center spec once every 100K miles or so. As infrequently as they need to be adjusted, it just makes sense to do this. It's not like you have to get in there and change shims every 6 months.

Also, keep this in mind, if you have to pull a cam because one valve is out of spec, make sure to record the shims under each bucket so you know what to order in advance for the next time, and don't mix up the buckets. Check each of them one at a time so you put the bucket back on the valve it came off of. And as long as you are pulling the cam to change a shim, you might as well set ALL of them on that head to center spec while you have it apart. But remember you can only change by .025mm (about .001 in) since the shims only come in .025mm increments. If a valve is only out .012mm (or .0005 in) then you have to either leave it alone, or set it on the loose side (knowing it will only tighten up as the valve wears).
 
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