Author Topic: Why TDC to adjust Guzzi valves?  (Read 4616 times)

Rough Edge racing

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Why TDC to adjust Guzzi valves?
« on: November 04, 2018, 06:35:11 AM »
 Asking this after reading the chopstick in the engine thread.....I had a cafe Cali 2...adjust the valves the usual way I've always done on  dozens of auto and bike engines without needing to find TDC...It ran well ,sounded like a Guzzi, sold the bike to Petrus Rocks on this site and he has ridden it hard for several years without adjusting the valves...
 So why the need to find TDC??

Offline kballowe

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Re: Why TDC to adjust Guzzi valves?
« Reply #1 on: November 04, 2018, 06:40:28 AM »
We all know that we can adjust the valves, once the tension is off.
But, I like to use the "TDC" method.  It seems more technical.  Makes me feel like a professional mechanic.

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Offline PeteS

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Re: Why TDC to adjust Guzzi valves?
« Reply #2 on: November 04, 2018, 06:48:29 AM »
TDC is the reference point. On the two Guzzis I have/had the 850LM and EV, TDC is not at the base circle of the cam. If you use the point of greatest clearance, that is actually on the base circle it will be too tight at TDC on at least intake or exhaust.
Maybe the newer bikes are different but that was case on mine. Next time you have an older Guzzi in the shop you can check it for yourself. I have not seen this on any other bike I have set the valves on, only Guzzis.

Pete

Offline Kiwi_Roy

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Re: Why TDC to adjust Guzzi valves?
« Reply #3 on: November 04, 2018, 07:26:13 AM »
I think after the chopstick in the engine a lot of guys will be doing it differently.

The method I sometimes use is rotate the engine until the exhaust valve opens then closes to the point both valves are open, that's TDC on the exhaust stroke then rotate it one full circle and set the valves.
Its also a quick check when replacing the cam chain or gears, the valves rock at TDC.
If you move the tappet more than a thou or two you know you have done something wrong.
« Last Edit: November 04, 2018, 07:33:16 AM by Kiwi_Roy »
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Re: Why TDC to adjust Guzzi valves?
« Reply #3 on: November 04, 2018, 07:26:13 AM »

Offline Lannis

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Re: Why TDC to adjust Guzzi valves?
« Reply #4 on: November 04, 2018, 07:29:12 AM »
Asking this after reading the chopstick in the engine thread.....I had a cafe Cali 2...adjust the valves the usual way I've always done on  dozens of auto and bike engines without needing to find TDC...It ran well ,sounded like a Guzzi, sold the bike to Petrus Rocks on this site and he has ridden it hard for several years without adjusting the valves...
 So why the need to find TDC??

I know you know bike engines intimately ... so where do YOU position the crank to set the valves on a V-twin as opposed to, say a 360 degree parallel twin?   Does it matter whether the tappet is JUST about to contact the cam for that pushrod, or whether the tappet is on the base circle directly opposite the point of highest lift .... ?

Trying to understand the reason for the question ... ?   :bow:

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Offline wirespokes

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Re: Why TDC to adjust Guzzi valves?
« Reply #5 on: November 04, 2018, 08:04:14 AM »
Yeah - I'm curious how you do it. What's your procedure?

I know with cars there are different ways of getting the job done. I recall trying to sort out a Volvo P1800ES that didn't want to run right over 3500 RPM. Ran ok below 3500, but wouldn't above that.  Two shops diagnosed it as engine needing a rebuild, but I knew that wasn't the case. I adjusted the valves a couple of times just to ensure everything was correct using the TDC method. Nothing made any difference, and I looked into a lot of different things for three or four days. Finally I tried adjusting the valves using a method detailed in the manual which went something like - when X valve closes, adjust Y, I noticed three valves weren't actuating. Bad cam!

Other than that time, I've always used TDC when adjusting valves.

Offline LowRyter

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Re: Why TDC to adjust Guzzi valves?
« Reply #6 on: November 04, 2018, 08:05:02 AM »
Take off the front cover, rotate alternator with socket, find "D" on the flywheel, then mark the alternator fin at 12 o'clock with a marker.  The "S" will be at 3 o'clock (after a complete turn).  If the valves are tight, give it one more complete turn for the compression stroke.

Makes it very easy after you mark it. 
John L 
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Offline Chuck in Indiana

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Re: Why TDC to adjust Guzzi valves?
« Reply #7 on: November 04, 2018, 08:33:35 AM »
I routinely do a leakdown test when I adjust the valves.. you *have* to be right at TDC to do this. Why do a leakdown? Because I'm anal..  :smiley: It only adds a couple of minutes to the valve adjust procedure, and you *know* what condition the valves and rings are in. If you keep a log over the years (anal again) you can follow the condition of the engine. I've been doing it on airplanes for..uhh.. 45 years (gulp) and Guzzi engines are just two cylinder radials.. :grin:
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Rough Edge racing

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Re: Why TDC to adjust Guzzi valves?
« Reply #8 on: November 04, 2018, 08:39:30 AM »
I know you know bike engines intimately ... so where do YOU position the crank to set the valves on a V-twin as opposed to, say a 360 degree parallel twin?   Does it matter whether the tappet is JUST about to contact the cam for that pushrod, or whether the tappet is on the base circle directly opposite the point of highest lift .... ?

Trying to understand the reason for the question ... ?   :bow:

Lannis

 Well, I do know old Triumphs as far as making them go fast in a straight line.... I don't do adjustment by crank position, I do it by valve position... I have been using the following method for many years as recommended by  USA high performance auto cam manufacturers..

 To adjust the intake, rotate the engine in the normal direction until the exhaust valve on that cylinder starts to open, now adjust intake... To adjust the exhaust, rotate the engine until the intake on that cylinder cycles until just about closed, now adjust exhaust
 This has worked on Chevy V-8's, vintage Triumphs, Guzzi, OHC Honda's and Ducati...
   I'm not saying there's anything wrong with using TDC, I just prefer this way...Try it, and see if it works fr you and save the chop sticks for Kung Pao Chicken...
 On the Guzzi 950 I rotated the engine using a screwdriver in the timing hole ....

Offline PeteS

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Re: Why TDC to adjust Guzzi valves?
« Reply #9 on: November 04, 2018, 08:57:28 AM »
Guzzi cams are different, at least their relationship to the crank is Rough, just saying.
On all my other bikes I can put a pencil in the spark plug hole, rotate the crank until the pencil is fully out, check the lash and move the crank a few degrees either way and the clearance stays the same
Do that with Peters 950 and moving the crank one way the lash tightens, the other way it loosens. TDC is on the ramp not on the base circle.
Your way may have worked if Peter's 950 hasn't burnt a valve but that may only be luck.

Pete

Offline Tusayan

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Re: Why TDC to adjust Guzzi valves?
« Reply #10 on: November 04, 2018, 09:13:10 AM »
Guzzi cams are different, at least their relationship to the crank is Rough, just saying.
On all my other bikes I can put a pencil in the spark plug hole, rotate the crank until the pencil is fully out, check the lash and move the crank a few degrees either way and the clearance stays the same
Do that with Peters 950 and moving the crank one way the lash tightens, the other way it loosens. TDC is on the ramp not on the base circle.
Your way may have worked if Peter's 950 hasn't burnt a valve but that may only be luck.

Pete

Yes, that is also my experience.  I imagine the procedure for setting both valves at TDC results from it being simpler to set the piston only once to adjust both valves on a given cylinder.  It makes no difference to the clearance in the system as long as the valve lash is specified for the piston position used for adjustment.

Offline yogidozer

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Re: Why TDC to adjust Guzzi valves?
« Reply #11 on: November 04, 2018, 09:46:19 AM »
So why the need to find TDC??
Why not just do this?



Rough Edge racing

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Re: Why TDC to adjust Guzzi valves?
« Reply #12 on: November 04, 2018, 09:47:00 AM »
Guzzi cams are different, at least their relationship to the crank is Rough, just saying.
On all my other bikes I can put a pencil in the spark plug hole, rotate the crank until the pencil is fully out, check the lash and move the crank a few degrees either way and the clearance stays the same
Do that with Peters 950 and moving the crank one way the lash tightens, the other way it loosens. TDC is on the ramp not on the base circle.
Your way may have worked if Peter's 950 hasn't burnt a valve but that may only be luck.

Pete

 Perhaps...There has to to be some lash when the cam is not on the ramps as I understand cam theory...I suspect, maybe wrong, a stock Guzzi 2 valve has long gradual clearance ramps for longer valvetrain life....At TDC both valves are closed and likely off the ramps...Intake closes  a bit after BDC...Ignition starts about 36 degrees before TDC and should be finished about 12 degrees ATDC, and then the exhaust starts to open just before BDC....
 Pete's 950 has the usual Guzzi gentlu valve clatter ...I don't know because I don't have have knpwledge of Guzzi valve timing events without using a degree wheel and dial indicator

 At any rate,after adjusting the valves when I owned the bike , it was timed at 117-118 MPH at the Ohio standing start one mile track in four runs, ans Pete has run it hard for extended periods....So It's my Italian /Russian luck  :laugh:

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Re: Why TDC to adjust Guzzi valves?
« Reply #13 on: November 04, 2018, 11:26:29 AM »
Asking this after reading the chopstick in the engine thread.....I had a cafe Cali 2...adjust the valves the usual way I've always done on  dozens of auto and bike engines without needing to find TDC...It ran well ,sounded like a Guzzi, sold the bike to Petrus Rocks on this site and he has ridden it hard for several years without adjusting the valves...
 So why the need to find TDC??

Because the engineer that designed it says so.

V1000 Service Manual page 30
"After the first 500-1000 km (3--600 miles) and later on every 3000 km (abt. 2000 miles) or any time valve operation
is too noisy, check the rocker clearance. Do this adjustment on a cold engine with piston at TDC at the end of the compression stroke (valves fully closed)"
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Offline John Croucher

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Re: Why TDC to adjust Guzzi valves?
« Reply #14 on: November 04, 2018, 12:15:16 PM »
The bigger question, why are the valves getting tight or loose? 

On the MG's I owned with solid lifters, I turned the engine over until the valve I was working on was loose, tightened it to the point that it still moved, but was not tight.  No feeler gage. 

On a Convert, I could not get the ticking to go away.  One day, a guy came up to me and said, "you need to fix the small end bearing on the rod and the ticking will go away.  He was exactly right.  It wasn't the valves, but the small end bearing was worn. 

Offline Stevex

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Re: Why TDC to adjust Guzzi valves?
« Reply #15 on: November 04, 2018, 12:19:36 PM »
Most Guzzi flywheel markers are a couple of degrees out anyway, so it's all relative.

Offline earemike

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Re: Why TDC to adjust Guzzi valves?
« Reply #16 on: November 05, 2018, 06:14:20 AM »
Damn, as a kid I was taught to look for where the cam rocks, both valves closed around tdc.

As the rods spin loosely there I’m good, tbh I’ve never looked for flywheel markings but have confirmed piston location.
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Offline John A

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Re: Why TDC to adjust Guzzi valves?
« Reply #17 on: November 05, 2018, 07:04:53 AM »


That's because centering the S and D marks is not TDC for valve setting, the horizontal lines next to each are and they are a degree or so off from the letters.

Center the lines in the timing hole, mine are faint and hard to see so I put paint on them.

I doubt it will make much difference if any but its the proper procedure.


The marks on every Guzzi engine I've checked are not at all accurate in relation to true TDC and their degree from it. Then you have the parallax of where your eye is. Sometimes on hot roded Guzzis you will see a proper marker in the hole. The degrees marks are usually fairly accurate in relation to each other, it's in relation to the engine that the problem comes.
« Last Edit: November 05, 2018, 07:13:43 AM by John A »
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Offline mechanicsavant

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Re: Why TDC to adjust Guzzi valves?
« Reply #18 on: November 05, 2018, 07:20:17 AM »
I'm not sure about Guzzi . But it has been my experience that some Mfgr.want valves adjusted @ tdc. Because the heel of the lobe is not prescision ground , only ramps  & lifting area.Feel free to criticize at will

Offline Chuck in Indiana

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Re: Why TDC to adjust Guzzi valves?
« Reply #19 on: November 05, 2018, 08:33:59 AM »
I'm not sure about Guzzi . But it has been my experience that some Mfgr.want valves adjusted @ tdc. Because the heel of the lobe is not prescision ground , only ramps  & lifting area.Feel free to criticize at will

Ok. I've never seen a cam where the heel is *not* ground. The wheel on a cam grinding machine is fixed, and the cam lobe is formed by the cross slide moving in and out as the cam rotates.
That's not to say that I've seen every cam in the world,  :grin: but that's my experience.
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Offline lti_57

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Re: Why TDC to adjust Guzzi valves?
« Reply #20 on: November 05, 2018, 09:54:32 AM »
Damn, as a kid I was taught to look for where the cam rocks, both valves closed around tdc.

As the rods spin loosely there I’m good, tbh I’ve never looked for flywheel markings but have confirmed piston location.

Thats     how i set mine no issues ever
I do my BMW 325 that way  just work my way down all 6 cylinders and do both the intake and exhaust at the same time
« Last Edit: November 05, 2018, 11:49:07 AM by lti_57 »
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Offline Kiwi_Roy

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Re: Why TDC to adjust Guzzi valves?
« Reply #21 on: November 05, 2018, 10:30:44 AM »
Well, I do know old Triumphs as far as making them go fast in a straight line.... I don't do adjustment by crank position, I do it by valve position... I have been using the following method for many years as recommended by  USA high performance auto cam manufacturers..

 To adjust the intake, rotate the engine in the normal direction until the exhaust valve on that cylinder starts to open, now adjust intake... To adjust the exhaust, rotate the engine until the intake on that cylinder cycles until just about closed, now adjust exhaust
 This has worked on Chevy V-8's, vintage Triumphs, Guzzi, OHC Honda's and Ducati...
   I'm not saying there's anything wrong with using TDC, I just prefer this way...Try it, and see if it works fr you and save the chop sticks for Kung Pao Chicken...
 On the Guzzi 950 I rotated the engine using a screwdriver in the timing hole ....
That makes a lot of sense, especially for a large multi cylinder auto engines where it's very difficult to rotate.
I just need to remember it, that's the hard part.
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Offline mechanicsavant

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Re: Why TDC to adjust Guzzi valves?
« Reply #22 on: November 05, 2018, 01:38:25 PM »
The motor that comes to mind was the  A series Renault  (1.4l),I suggested just set the lash on the heal of the lobe ,the factory rep said you wouldn't be accurate enough because of the procedure used by Renault! So when everyone went to lunch I played with the mule we we're learning on and Dang if the difference in clearance didn't differ a few thou from lobe to lobe!

Offline Chuck in Indiana

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Re: Why TDC to adjust Guzzi valves?
« Reply #23 on: November 05, 2018, 01:43:38 PM »
It's French. That explains everything..  :grin: :boozing:
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Offline John A

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Re: Why TDC to adjust Guzzi valves?
« Reply #24 on: November 05, 2018, 03:33:20 PM »
It's French. That explains everything..  :grin: :boozing:


I was working on a French helicopter. In the maintenance manual where it was to describe putting the interior furnishings back in, it said I was to "offer up the stuffing" so I completely agree with Chuck :evil: :boozing: :grin:
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