Wildguzzi.com
General Category => General Discussion => Topic started by: GuzziNZ on January 10, 2026, 01:32:09 PM
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The valve clearance on both sides for the intake valves is spot on at TDC but as the engine is advance past TDC the clearance doubles.
Any ideas?
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How sure are you about TDC compression for each cylinder?
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The valve clearance on both sides for the intake valves is spot on at TDC but as the engine is advance past TDC the clearance doubles.
Any ideas?
What bike is it and have you had the camchain sprockets off ?
Has the woodruff key in the crank or camwheel sprocket sheared off ?
Are you winding the crank in the correct direction ?
Unless you have a liquid cooled V100 variant, it should be rotated clockwise when viewed from the front.
It sounds like the camshaft is not in exactly the right position when you are at TDC, how are you determining TDC ?
Also for clarity, it can be counterintuitive to use the term “advanced past TDC”. Although we all know to what you are referring, the term “advanced” in this context suggests a crank position before TDC.
A suggestion is to say, ”continued in direction of normal rotation”.
Also are you sure you are on the compression stroke ?
Is the problem only on the intake valve/s ?
If the exhaust valves are reading ok, then it’s not a timing thing, because you only have one camshaft.
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How sure are you about TDC compression for each cylinder?
As long as there is any clearance at all, then the valve is closed. The compression value is immaterial, but if you are asking what stroke he is on, then ok.
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As long as there is any clearance at all, then the valve is closed. The compression value is immaterial, but if you are asking what stroke he is on, then ok.
:rolleyes:
What would you like to explain to me that's obvious next?
I'm not making any assumptions, but I'm also not trying to figure out ALL possibilities first.
So step 1 start with the most basic thing possible, assess the understanding of and certainty that the op actually has the motor at TDC compression each time.
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The marks on the flywheel (the lines ABOVE the D, right and S, left) are not always at full slack on the cam. So set the correct setting at the correct makes and it will be right. This is from Guzziology
I'm assuming yours is 0.22?
I just set the T5 last weekend, a set it to a tight 0.22 and seems good.
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:rolleyes:
What would you like to explain to me that's obvious next?
I'm not making any assumptions, but I'm also not trying to figure out ALL possibilities first.
So step 1 start with the most basic thing possible, assess the understanding of and certainty that the op actually has the motor at TDC compression each time.
Jeezuss Kev, please don’t start one of your things..
Your quaint one liner, whilst adequately descriptive to you as the author, was incomplete in its nature.
What does “how sure are you about compression” actually mean ?
PSI value ?
Equal on both sides ?
Were you enquiring as to whether he was on the correct stroke ?
People read what you say, not what you meant to say.
Please don’t pivot now and take the dialogue somewhere else and drift the thread.
Can we go back to the subject matter, no one’s lost an eye…yet.
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Jeezuss Kev, please don’t start one of your things..
Your quaint one liner, whilst adequately descriptive to you as the author, was incomplete in its nature.
What does “how sure are you about compression” actually mean ?
PSI value ?
Equal on both sides ?
Were you enquiring as to whether he was on the correct stroke ?
People read what you say, not what you meant to say.
Please don’t pivot now and take the dialogue somewhere else and drift the thread.
Can we go back to the subject matter, no one’s lost an eye…yet.
:rolleyes: :rolleyes: :rolleyes:
WTF would someone mean when asking about valve adjustments?
Sorry, my sentence lacked an "at" how sure he was about being AT TDC COMPRESSION....
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:rolleyes: :rolleyes: :rolleyes:
WTF would someone mean when asking about valve adjustments?
No need to be sorry Kev, I know you’re a rough and tumble type of guy, but if you proof read what you type, things will go better.
Also.
I offered several areas to start because no doubt some will be non applicable and some will have already been investigated. But if I run around long enough waving a weapon in the dark, eventually I’ll have to hit the mark.
As for your opening line …about valve adjustments ?
I go by what you say, not by what you meant to say.
Isn’t that your bread and butter..?
I know you’ll want to take another swipe, but I’ll stop if/when you do.
Can we get back to the bike ?
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No need to be sorry Kev, I know you’re a rough and tumble type of guy, but if you proof read what you type, things will go better.
Also.
I offered several areas to start because no doubt some will be non applicable and some will have already been investigated. But if I run around long enough waving a weapon in the dark, eventually I’ll have to hit the mark.
As for your opening line …about valve adjustments ?
I go by what you say, not by what you meant to say.
Isn’t that your bread and butter..?
I know you’ll want to take another swipe, but I’ll stop if/when you do.
Can we get back to the bike ?
:rolleyes:
Can't, still waiting on OP to provide more info.
Like answer the obvious....
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I can’t (easily) see how he could be at TDC if he was on the wrong stroke with those symptoms.
At the top of the exhaust stroke, winding the crank over, would close the inlet valve clearance since it’s opening the valve. He says it’s widening the clearance, so it’s closing the valve…
Also in that configuration, there would be zero clearance on the inlet rocker at TDC on the exhaust, because the cam would already have started opening the inlet valve due to the overlap at that point.
I think he’s winding the crank the wrong way and some slack in the timing chain is being taken up by the tensioner being flattened, thus putting the cam timing out by a few degrees.
Just a comment on the obvious… :popcorn:
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Just going to do a few more checks and will come back with what I find but bike is an 850T.
TDC was re-marked during overhaul as it was out a couple of degrees.
Cam timing was set using 1.50mm clearance on intake and was opening within a degree or two of spec.
Cam was in excellent condition and new stein dinse lifter. (Hope they and good quality? )
Unlikely Cam sprocket pin has shared considering the retaining nuts high tightening torque.
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QUOTE "Cam timing was set using 1.50mm clearance on intake and was opening within a degree or two of spec."
That's about 1/16 inch. I assume you meant 0.150 mm clearance which is about 6 thousanths of an inch.
You confirmed TDC mark matched flywheel mark with a straw in the spark plug hole just to confirm the flywheel isn't one bolt off on the bolt circle?
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To the op. Unless your cam timing is off, you are not at top dead center when you made your first adjustments. The fact that the Gap increased as you continue to turn the motor as proof that you were still on the cam.
Not sure how you're measuring for top dead center, but rule of thumb is to rotate the motor clockwise. Then immediately after the intake valves open and close, the Piston will begin climbing in the cylinder to reach TDC Best practice is to measure this way. You can use a straw in the spark plug hole and track the Piston till it reaches true top dead center. In this situation, the cam will be off both of the intake and exhaust valve and you can make your adjustments.
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I know it sounds strange but cam timing is checked with intake set at 1.50mm clearance.
Once confirmed its correct clearance is set at 0.22.
I watch intake open then close and use a soft rod to confirm when piston is at the top. D or S on flywheel will be close in the bell housing window.
So from TDC I turned engine in stages of about 8 degs. Intake clearance increased on both sides by about 0.15mm before closing while exhaust clearance was pretty stable before closing. Seems strange left and right are acting the same.
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I'm confused. I have an 850 T3 and there is never more than set clearance at TDC between the rocker and valve tip.
I once set up a BMW twin on the wrong cylinder timing position. Surprise, it ran but rocker clearance was very loose and noisy!
No reason for the clearance to open beyond set specifications unless the mechanical relationship between the crank and cam is in error when the setting is made. Possibly timing chain skipped a tooth? Key fell out of a sprocket at assembly? Timing marks between sprockets misaligned at assembly? Flywheel on wrong bolt pattern?
Clearance spec in the manual is 0.22 mm (or 0.00866 inches). No reason for it ever to open past that number. It would just make more noise.
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I'm confused. I have an 850 T3 and there is never more than set clearance at TDC between the rocker and valve tip.
I once set up a BMW twin on the wrong cylinder timing position. Surprise, it ran but rocker clearance was very loose and noisy!
No reason for the clearance to open beyond set specifications unless the mechanical relationship between the crank and cam is in error when the setting is made. Possibly timing chain skipped a tooth? Key fell out of a sprocket at assembly? Timing marks between sprockets misaligned at assembly? Flywheel on wrong bolt pattern?
Clearance spec in the manual is 0.22 mm (or 0.00866 inches). No reason for it ever to open past that number. It would just make more noise.
I agree he likely has the cam out of timing and probably off by one tooth on the sprocket.
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Was this motorcycle running well before you took it apart ?
Your method of checking valve timing sounds correct ( most cam manufacturers suggest around .050" to .060" valve clearance when checking cam timing)
Your removed the lifters and looked down the lifter bores to check the cam. Are you sure the cam had no wear around the ends of the base circles ?
Lastly , if you look in the intake ports , do you see heavy carbon deposits around the valve where it enters the valve guide ?
Keep us posted :thumb:
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I am with Bulldog9, and likely a few others, that cam timing is likely off.
Have you tried to check valve clearance on the inlet valve when the exhaust is fully open? Or checked the clearance of the inlet valves around the whole closed period, to see if clearance varies around the base circle? It should remain virtually the same other than at each end of the closed period; when it begins to get on the cam, where clearance will begin to reduce towards zero, and from where the valve just close until it is completely off the cam lobe, where clearance should go from zero to base circle value.
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Which brings us back to my original question.
How certain are you/have you verified that the motor is truly at TDC of the compression stroke for the cylinder in question. If cam timing is off, it is not.
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I'd put a skewer/straw in each plug hole, and make sure each cylinder
IS REALLY AT TDC, set the valves, and then one can go back and
check valve timing, etc..
As others have said, it's a good idea to make sure that the engine
is being rotated in the correct direction when lining up timing marks and so forth.
(I was gonna say, "the right way" when describing engine rotation above,
but, "in the correct direction" is far less ambiguous, and MIGHT protect me
from the grammar policeman..... :evil: :grin: :copcar: :thumb:)
-Stretch
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Ok, I'll get pedantic.
TDC = the physical position of the piston in the cylinder at the very top of travel. It happens at different times for each cylinder on a twin motor.
But it also is important to remember its relationship to the camshaft and how that controls valve timing
TDC Exhaust = piston top of travel on the exhaust stroke of the 4-stroke cycle (typically this means exhaust valve is open or in the process of closing and the intake is getting ready to open. In both cases there should be basically no lash)
TDC Compression = piston at top of travel on the compression stroke, meaning squeezing the gasses in the sealed combustion chamber. (For this both valves just be closed and intake especially shouldn't be getting ready to open for a while because that shouldn't occur until after the power stroke down and the exhaust stroke up).
But differences in camshaft lobe shape can mean slight differences in when some of the lash is starting to be taken up. And most importantly the timing chain/belt is what preserves the relationship between the crankshaft and camshaft to make these things happen at the right time.
Ok, I'm sorry. I do know that most of your understand these things, but I think some still don't put all the pieces together or forget parts at times (don't we all). But I wanted to spell it out so there was no more misunderstanding of meaning.
Now valve lash IS TYPICALLY checked at TDC OF COMPRESSION for the reasons stated. But honestly you CAN check lash anytime/anywhere in the 4-stroke cycle WHERE the base of the cam lobe is contracting the lifter/pushrod/follower etc.
For instance if the exhaust valve is wide open there's a good chance the intake is completely closed and vice versa.
The OP seems to have a problem where
he's not on TDC compression of the cylinder he's checking when he thinks he is. Whether that's bad camshaft timing, bad timing marks, or a misunderstanding on how to read them, I dunno.
So OP, what do you think it is? How will you check each possibility?
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Tappets move when engine runs, haven't heard if the engine actually runs or is it all bs & all Guzzi motors do this. I have seen tappets hit the valve covers, does that mean that motor has an issue? Are you going to say NO it can't do that? Food for thought on what you are talking about.
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So here are my results.
Made up a piston stop and checked TDC. Both sides are within the thickness of the line.
Specs for valve open/close are at 1.50mm valve clearance
IN OPEN 20 BTDC
IN CLOSE 52 ATDC
EX OPEN 52 BBDC
EX CLOSE 20 ATDC.
Only ever checked timing using the right hand cylinder but this time I checked both.
RH cylinder. IN 15 and 52. EX 51 and 20
LH cylinder. IN 12! and 51. EX 46! and 20.
Fired it up again and no loud tapping this time.
So valve clearance has never moved between checks
As I have never checked LH valve timing I can't say if its changed but funny how both IN and EX open are retarded the same amount pointing to manufacturing tolerance?
Will just keep riding it and scope cam next time sump is off.
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So here are my results.
Made up a piston stop and checked TDC. Both sides are within the thickness of the line.
Specs for valve open/close are at 1.50mm valve clearance
IN OPEN 20 BTDC
IN CLOSE 52 ATDC
EX OPEN 52 BBDC
EX CLOSE 20 ATDC.
Don't you mean ABDC
AND the unstated obvious is that you're talking:
IN OPEN 20 BTDC of the EXHAUST STROKE
IN CLOSE 52 ABDC of the INTAKE STROKE
EX OPEN 52 BBDC of the POWER STROKE
EX CLOSE 20 ATDC of the EXHAUST STROKE
So the intake valve doesn't "close more" ATDC of the compression stroke.
So I'm still confused how you could see more clearance at the intake slight after either.
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Seems to me you're making it over complicated.
If you truly have the Piston at top dead center on the compression stroke And as you turn the motor past top dead center clearance opens or widens then your cam is not in sync with the crank.
The only changing clearance that should happen as the motor turns past top dead center is that your clearances should close as the cam rotates to open either the intake or the exhaust valves.
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All I have show is that all valve closing to within 1 degree of spec and there is no way to change timing without throwing these out of spec. So I am guessing it is poor manufacturing tolerance or extreme wear and its hard to imagine that the base circle has worn so leaning toward poor manufacturing.
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chain wear, slight inaccuracy when measuring.
The kind of difference that you have found is minimal as far as I'm concerned, especially for a road going bike with mileage.
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Just drive it with the clearance set to spec at top dead center. My T3 has has had more valve clearance past top dead center for the 47 years I have owned it
and the engine runs just fine.
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Thanks for reply Acogoff, that's exactly what I'm going to do.
As clearance never seems to change I think it is what it is.
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The masters that cams are ground from get worn and as they age the discrepancy gets larger. P3 cams and Norris cams are noted for this. I learned by precisely timing performance cams in Guzzi’s when timing using the intake centerline method that the other lobes do not necessarily land in the same position according to the timing card. I talked to cam grinders who told me that the master cams become worn so I should either ignore the discrepancy or average it out and I would not be able to notice it. Some tuners use a fixture to map a cam before installing it in engines used for competition where a tenth of a second can result in a win or loss. I was on a funny car team and found a bad intake lobe on the cam when I was setting the valve clearance between runs. We didn’t have time to change it so we ran with it and set a track record and won the round because the track was slippery enough to make cars with slightly less power run faster.
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I wonder if valve bounce from too high rpm could cause additional wear of the cam base circle in spots?
Anyway, the primary reason for valve clearance is to give the valve seats enough time to cool, especially the exhaust valves. Plus sufficient compression. The factory will give values that ensure that there is always enough valve/-seat contact to prevent burned valves as well as good compression. For normal use, clearance is not super-critical; a bit extra clearance will give a bit more noise and a little more low-rpm power, while a little less clearance will give less noise and a little more top-end power. If valve clearance vary a little during the closed phase, noting will happen as there is no load on the valve lifter or cam base circle.
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Tappy valves are happy valves.
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Thanks for reply Acogoff, that's exactly what I'm going to do.
As clearance never seems to change I think it is what it is.
I'd be curious to know how much the clearance opened after TDC. I believe that was your initial concern.
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I prefer the minimum clearance spec, not because of noise, but what the noise represents. The more clearance, the more the tappets are getting hammered. I'd like to keep that to a minimum. Pete Roper recommended .004 and .006 for square fins and a thousandth more for round fins and that's what I've been running.
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The old Volvo OHV engines said 0.45mm of clearance, which is 1/64 or 18 thou. Presumably, they had "tamer" cam profiles, which would ease how the clearance was taken up before lifting of the valve began, but it is still a substantial clearance. Yet these engines would last "forever". Kawasaki, on the old Z1, listed clearance to be set between 0.05 and 0.20 mm IIRC, indicating that clearance is not critical in that engine. These engines also lasted a long time.
In my simple head, you would typically want more valve clearance with long duration cams in order to ensure that the valves stay close long enough. The cams on most Guzzis have quite short duration, though, so running the engine around the minimum recommended clearance should not hurt. Personally, I have stopped fretting about valve clearances; if the engine starts fine, idles fine, pulls well from low rpm AND does not clatter loudly, I do not bother to check the clearances. I do not run my engines hard, nor do we experience hot weathers, meaning the valve seats live a fairly sedate life. YMMV.