Confirming TDC with new flywheel installed

[mznyc]

Having to remove old flywheel on clutch replacement,Ive lost my TDC marks.Uh yes would have been much easier to mark old flywheel TDC marks to case but I'm learnin here.

I'll guess the best way will be to rotate crank with alternator nut observe when both rockers have play on one side, install flywheel and align appropriate mark,S-left,D-right.Do this several times to confirm they do this repeatedly on both sides as they should.

Make sense?

[motoguzznix]

Having to remove old flywheel on clutch replacement,Ive lost my TDC marks.Uh yes would have been much easier to mark old flywheel TDC marks to case but I'm learnin here.

I'll guess the best way will be to rotate crank with alternator nut observe when both rockers have play on one side, install flywheel and align appropriate mark,S-left,D-right.Do this several times to confirm they do this repeatedly on both sides as they should.

Make sense?

There should be a white paint mark on the inner side of the flywheel corresponding with the same mark on the crank.

For the flywheel mounting it does not matter which TDC is adjusted. You will be right either on overlap or on compression TDC.

[mznyc]

Thanks motoguzznix

I think I solved it by lining up mark on flywheel to case "tit". Rotated till I saw cylinder at top of case and S or D mark,(depending on which side I was checking), where sight hole would be.Did this several times to confirm I wasnt on overlap.Adjusted valves and had rocker play when correct flywheel mark was in sight window.

Sound correct?

[mznyc]

So finally gettin back into this week as Ive been wiating for hub from dealer for over two months.

 

Still questioning whether I got this right.

I got one side(believe it was left) to line up perfectly at TDC but the other side's flywheel mark would be an inch or two from the sight window at that cylinder's TDC.Is this common/acceptable,bike had been running perfectly before tearing apart and kinda remember that it was like that on last valve adjustment with the original flywheel.

Is this a case of the marks not being an exact science and a Guzzi quirk? Just get it close when you have TDC?

Thanks

Michael

[68C]

Get an old spark plug and a degree disc.

 

Stick the degree disc to the front of the alternater with a blob of BluTack (used by kids to stick posters to their bedroom walls).

 

Smash the ceramic out of the spark plug and weld in a bar pointing out the threaded end about one inch, round it off.

 

Make sure the piston is not near top dead centre and screw in the plug.

 

Slowly turn engine until the piston just touches the plug tool. Make a note of the degree disc angle.

 

Slowly turn the engine the other way until the piston again contacts the tool. Make a note of the reading.

 

Top Dead Centre will be exactly halfway between those two readings. Make a note of that angle.

 

Remove plug tool and turn engine until the degree disc is at the angle noted in the previous step.

 

That is TDC. Repeat for the other cylinder

 

 

 

I leave it to your imagination the result should you use the starter motor to turn the engine during this procedure!

[Kiwi_Roy]

I have never used flywheel marks for timing or setting valves.

With the rocker cover off rotate the engine feeling for TDC with a dowel or something soft.

at that point both valves are either open or closed, if the valves are open rotate 360 until they are closed then set valve clearence.

Most of the old bikes I worked on set the ignition a distance before TDC e.g. 1/2"

I don't believe you can adjust the firing angle on the Vll Sport, tht's an ECU function based on the camshaft pickup, not something you adjust mechanically. The only use for the timing marks is for using a strobe light.

 

Tell me I'm wrong

 

Roy

[docc]

I have never used flywheel marks for timing or setting valves.

With the rocker cover off rotate the engine feeling for TDC with a dowel or something soft.

at that point both valves are either open or closed, if the valves are open rotate 360 until they are closed then set valve clearence.

Most of the old bikes I worked on set the ignition a distance before TDC e.g. 1/2"

I don't believe you can adjust the firing angle on the Vll Sport, tht's an ECU function based on the camshaft pickup, not something you adjust mechanically. The only use for the timing marks is for using a strobe light.

 

Tell me I'm wrong

 

Roy

Well, there is a "shim" on the timing sensor that can be "adjusted."

 

Closer = earlier BTDC? Thicker = later BTDC? (idk)

 

Just in case the weather turns off bad and you need something more to tinker around with . . .

[gstallons]

The shim for the crank sensor only determines "air gap" between the sensor and the teeth of the gear. It will not affect timing since it is adjusting a perpendicular distance.

[mznyc]

Get an old spark plug and a degree disc.

 

Stick the degree disc to the front of the alternater with a blob of BluTack (used by kids to stick posters to their bedroom walls).

 

Smash the ceramic out of the spark plug and weld in a bar pointing out the threaded end about one inch, round it off.

 

Make sure the piston is not near top dead centre and screw in the plug.

 

Slowly turn engine until the piston just touches the plug tool. Make a note of the degree disc angle.

 

Slowly turn the engine the other way until the piston again contacts the tool. Make a note of the reading.

 

Top Dead Centre will be exactly halfway between those two readings. Make a note of that angle.

 

Remove plug tool and turn engine until the degree disc is at the angle noted in the previous step.

 

That is TDC. Repeat for the other cylinder

 

 

 

I leave it to your imagination the result should you use the starter motor to turn the engine during this procedure!

Thanks 68.any reason I couldnt a bolt the same size as the spark plug,but and inch longer as a positive stop device as I dont have access to a welder?Put something on the end that wont damage the piston and wont come off. Is the exact length crucial? Assuming the important thing is the relationship/measurement of when the contact from both rotations as the reference?

 

I have never used flywheel marks for timing or setting valves.

With the rocker cover off rotate the engine feeling for TDC with a dowel or something soft.

at that point both valves are either open or closed, if the valves are open rotate 360 until they are closed then set valve clearence.

Most of the old bikes I worked on set the ignition a distance before TDC e.g. 1/2"

I don't believe you can adjust the firing angle on the Vll Sport, tht's an ECU function based on the camshaft pickup, not something you adjust mechanically. The only use for the timing marks is for using a strobe light.

 

Tell me I'm wrong

 

Roy

Thanks Roy.This is the method I use for adjusting the valves.I use a wood chopstick as a probe.

 

Trying to find out if those flywheel marks are crucial or just Guzzi's "Atza closa nuff" engineering.From memory I thought they werent exact from the first adjust I did,but not a 100% sure,.... Finding what I believe TDC is not the problem.Piston at the top of it's travel,no pressure on rocker arms.

I dont know what adjusting the firing angle means.I didnt mention that so you kinda lost me there as to why you bring it up,...

[jrt]

Mike, the marks on the flywheel are approximate. You only have a few orientations of the flywheel based on the bolt-up pattern, so get as close as you can and that's it.

 

The spark plug idea is good, but you can do the same thing on the ultra-cheap- even using a chopstick. Just spin the motor on compression and stop at any point before TDC. Put a chopstick in the sparkplug hole and mark it with a pen - level to the head or some other point. Read the degree wheel. Now spin the motor the other direction until it pushes up the chopstick to where the mark aligns with the head again. Read the degree wheel and split the difference- that's TDC. The critical thing is being able to measure the piston height at forward/reverse spin- how you do that is open to interpretation.

[mznyc]

Mike, the marks on the flywheel are approximate. You only have a few orientations of the flywheel based on the bolt-up pattern, so get as close as you can and that's it.

 

The spark plug idea is good, but you can do the same thing on the ultra-cheap- even using a chopstick. Just spin the motor on compression and stop at any point before TDC. Put a chopstick in the sparkplug hole and mark it with a pen - level to the head or some other point. Read the degree wheel. Now spin the motor the other direction until it pushes up the chopstick to where the mark aligns with the head again. Read the degree wheel and split the difference- that's TDC. The critical thing is being able to measure the piston height at forward/reverse spin- how you do that is open to interpretation.

Thanks Jason.The important question here was "Are those marks exact?"Which your saying they are not.This is what I assumed as I havent touched the timing in any way and the bike has run perfect before removal,just separated motor from transmission and pulled clutch.In theory if I get new flywheel marks to show in the window ,or thereabouts while at TDC on each side, I should be good to go.The first thing I noticed as you mentioned is with the bolt pattern in only one position will those marks be close.Left is dead-on, right mark is and inch or so from window,so I believe I'm good, even without using a degree wheel,haven't been able to find one locally.

Please feel free to throw in your 2cents if anyone disagrees.

[Baldini]

It's a Griso flywheel?

They're both 90deg twins - why would TDC marks be different to V11? Maybe I'm thick... but I don't understand.

 

I'd put correct TDC marks on flywheel anyhow, just cos you might as well!

 

KB

[mznyc]

It's a Griso flywheel?

They're both 90deg twins - why would TDC marks be different to V11? Maybe I'm thick... but I don't understand.

 

I'd put correct TDC marks on flywheel anyhow, just cos you might as well!

 

KB

Hi Keith

Yes it's a Griso.I'm not sure, but I thought the original Scura marks wern't exact.So I'm not saying they're different,just asking if other people have experienced this,inaccurate flywheel marks,albeit very close.Suggesting making an accurate mark on new flywheel sounds like a good idea.

Cheers

Michael

[68C]

Hi mznyc,

 

 

Sorry for delay in replying - summer suddenly arrived so went camping. As several folk have posted anything that fits the thread would do. With the old 1970's two strokes we used a Dial Test Indicator screwed into the plughole to set the ignition timing as most had spark plugs in the middle of the head. You could either find TDC by rocking a measured distance either side of TDC and making two marks on the flywheel and again halving it or if you were lucky the manuacturer gave timing in both degrees advance and piston distance from TDC.

 

 

Perhaps an aside, I have just made a Cliff Jefferies MyEcu kit (second attempt!) and having great fun starting the tuning process, it is already crisper than the OEM ECU although a bit hesistant at low throttle openings. Even us older buzzards try and keep up with the times.

[jrt]

Thanks Jason.The important question here was "Are those marks exact?"Which your saying they are not.This is what I assumed as I havent touched the timing in any way and the bike has run perfect before removal,just separated motor from transmission and pulled clutch.In theory if I get new flywheel marks to show in the window ,or thereabouts while at TDC on each side, I should be good to go.The first thing I noticed as you mentioned is with the bolt pattern in only one position will those marks be close.Left is dead-on, right mark is and inch or so from window,so I believe I'm good, even without using a degree wheel,haven't been able to find one locally.

Please feel free to throw in your 2cents if anyone disagrees.

 

I agree with you insofar as there is only one reasonable alignment of the flywheel. I think sometimes- or some bikes- the marks align and on others they don't. I have never worried too much about it- I don't use the alignment marks. I use a chopstick whenever I set the valves. As long as I am pretty close, then the valve adjustment is going to be fine. And it's quick.