flywheel without timing markers

[ironborn65]

Hi everyone and Happy New 2024

I need to tune the ignition of my 850 T3, but the flywheel, besides the 'D', the 'S' and the '-' for the PSM, I see no other marks.
I was expecting another dash line before the PSM to represent the 2° ignition.
I'm confused because in the service manual the letter D and S should have a dash in the middle to represent exactly the PSM, but the only dash I have is a little bit before and so I assume it's the PSM, the letters should be just a generic label to indicate that the proceeding dash is the PSM. There are no bullets or markers as I see in some pictures over the web. Some guy is setting the markers themself using the goniometer, but the gearbox has been removed, new flywheels have no markers, I assume.

So, if I don't have any, I could do an approximation given that each tooth is 3,78° or calculate the distance given the circumference, ... unless the 'D' and 'S' are the PSM and the '-' the 2° of the anticipo.

Any advice?

I hope I'm clear though
thanks




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[Frenchfrog]

Best thing in my opinion is to check with a graduated disc and then mark the flywheel according to that.It won't take all that long and you then know that the flywheel is correct.

[chuck peterson]

Timing wheels…the only way to fly

https://youtu.be/tW3YBr1_MBA?si=lzh4SKhNqj9G-Uky


OR….

Measure flywheel circumference…

Divide by 360…..

The result is the distance for each degree..

Measure/mark for what you need, static or advanced BEFORE tdcenter..don’t know what the T3 needs..

[Tom H]

If you think there may be a TDC mark. Pull the spark plugs. Pull a rocker cover. Pull alternator cover. Turn engine with a wrench or socket on the nose end of the crank shaft. From the front of the bike, standing next to the front wheel looking at the front of the engine, the crank shaft turns clockwise.

Turn engine by hand. Look for the exhaust valve to open and close, then look for the intake valve to open then close. Now with a drinking straw or the like, pit it gently into the spark plug hole and continue to rotate the engine. The straw will rise out of the hole. It may bind, you may need to adjust the angle. When the straw stops rising, that should be TDC on the compression stroke. You may need to turn the crank shaft back and forth a few times to make sure your at the very top of the stroke.

Now you can look in the timing hole and see what mark is showing there. Make note of which cylinder you used and what letter is showing in the window. In riding/seated position, the LH or RH cylinder. At least now you have TDC. Then you can estimate the marks for degrees.

Hope this helps a bit.
Tom

[blackcat]

I just went through this on my CX as it has a lightened flywheel which did not have timing marks. Years ago(like 12-15 years) when I got the flywheel, I set it up with a degree wheel, installed the Dyna ignition and of course forgot to mark the flywheel. When the bike was recently apart for frame painting, etc. the bike sat for about a year and the Dyna box went bad(old, cracked) so I had to start all over again.   Anyway, as others have said, buy or print out a degree wheel and buy or make a piston stop.
 
“You don’t push against the piston stop, just use it so that the piston stops gently against it.  Note the degree wheel reading and then roll the piston back down and through until it hits the stop again.  Note the degrees.  The midpoint between the two readings is tdc.  Remove the piston stop, rotate the engine to that midpoint and you are at tdc. Set the degree wheel at zero and then start setting your marks.”

[Moparnut72]

Anyway, as others have said, buy or print out a degree wheel and buy or make a piston stop.
 
“You don’t push against the piston stop, just use it so that the piston stops gently against it.  Note the degree wheel reading and then roll the piston back down and through until it hits the stop again.  Note the degrees.  The midpoint between the two readings is tdc.  Remove the piston stop, rotate the engine to that midpoint and you are at tdc. Set the degree wheel at zero and then start setting your marks.”

This is the best way, easy to do and quite accurate. I used this method when I was racing outboards. Most older outboards didn't come with decent timing marks.
kk

[pehayes]

One could also count the number of teeth on the perimeter of the flywheel ring gear. Divide that into 360 to determine the number of rotation degrees represented by each tooth.  I think I have seen this number posted before, but there may be different sized ring gears for different models.  Best to count on this particular wheel.  Easiest if the clutch is disassembled, but it can be done carefully through the inspection hole shown above.

I found this quote:  "It's 3.75 degrees per tooth: 360 degrees divided by 96 teeth."

As referenced in this lengthy post:  https://wildguzzi.com/forum/index.php?topic=107671.0

Patrick Hayes
Fremont CA

[John A]

In my experience it is more common to have inaccurate timing marks in relation to true TDC from the factory. The accuracy of the marks in relation to each other is fine . There can also be a parallax error when viewing the mark at an angle. Some fabricate a marker that is bolted to the inside of the bellhousing and provides a flat surface to sight along and adjust it to reflect true TDC. I do that on a non injected Guzzi for those you can supertune the timing. From the factory there is the possibility of accumulated acceptable tolerances especially with the stationary marks being on the transmission. On my Bassa true tdc was off by a couple teeth but I didn’t need to check timing on that but my CAL2 I did for it has points. It was off by about a tooth so l made a stationary marker out of aluminum that I bolted to the engine side inside the bellhousing. The bigger the degree wheel the more accurate it is but you can only go so large because otherwise you have to take the head pipes off to fit it to the crank. I think about a ten inch is the biggest you can fit unless you pop the head pipes off.

[ray bear]

sometimes the marks are  there but you really have to look hard with a bright light and you may pick up a faint electronic pencil  line , on my V7 sport I didnt see the marks until I was setting it up with the degree wheel and they were hardly visible until I knew where to look ,

[Scout63]

Whenever I have one apart I check timing with a degree wheel and a dial indicator or piston stop, and if necessary cut new timing marks with a small triangular file and paint the marks. It just seems like the right thing to do.

[ironborn65]

thank you all, it was very useful.
Using a plastic straw to find the PSM in the spark-plug hole is quite hard, especially if we need to be precise. In the last few degrees the piston is barely moving, that's why it is called PSM, Punto Morto Superiore = topmost dead point.
A very close inspection of the flywheel, after cleaning, showed no sign or mark. This T3 was a former Police vehicle, maybe it means something ....

I'm opting for the goniometer and the piston stop, because I can not trust the 'S'/'D' label or the dash line. I will mark the flywheel for the future generations to avoid all this hassle.

[pehayes]

I made my own piston stop by smashing out the central portion of an old spark plug.  The threaded rod has to have a hole up through the center in order to bleed off any air and avoid compression.  The advantage of the piston stop is that you get to accurately and rigidly stop the piston in a portion of travel where it is moving vertically quite a bit in relation to rotation.  Stop it in one direction and then stop it again in the other direction.  The TDC point is exactly halfway between your two stop marks.

Patrick Hayes
Fremont CA

[Tom H]

Yes, a degree wheel and a piston stop are most likely to be the best tools to find The "True TDC". JMHO there is a point that the piston at TDC does not move, but the crank still moves a few degrees.

I gave my "easy way" to find TDC for the easy way. "I" use a Phillips head screw driver and BE VERY CAREFUL to not let it bind as I turn the crank when I adjust the valves.

Now, if you want to add more to the flywheel timing marks issue. You have TDC's the crank shaft to EXACT TDC.........

Now you install the flywheel without moving the crankshaft......... ...

With the flywheel bolts installed but not snugged or tightened..... You can move the flywheel a few degrees either way from the TDC mark arrow inside the bell housing and likely the degree wheel.

Tom

[ironborn65]

An update, that can be of help for others.

I used the piston-stop and I can inform that in my flywheel the letters 'S' and the 'R' marks indicate the PMS, the letter is centrally aligned with the mark on the engine body.
The line mark just before corresponds to the timing advance, about 2°.
So, I'm set now.

thanks for the suggestions.

[Frenchfrog]

Well done !!!!

[Antietam Classic Cycle]

An update, that can be of help for others.

I used the piston-stop and I can inform that in my flywheel the letters 'S' and the 'R' marks indicate the PMS, the letter is centrally aligned with the mark on the engine body.
The line mark just before corresponds to the timing advance, about 2°.
So, I'm set now.

thanks for the suggestions.

Shouldn't "R" be "D" (for Destra).

[Chuck in Indiana]

Yes, "Dis side, and Snot dis side." 

[guzziart]

thank you all, it was very useful.
Using a plastic straw to find the PSM in the spark-plug hole is quite hard, especially if we need to be precise. In the last few degrees the piston is barely moving, that's why it is called PSM, Punto Morto Superiore = topmost dead point.
A very close inspection of the flywheel, after cleaning, showed no sign or mark. This T3 was a former Police vehicle, maybe it means something ....

I'm opting for the goniometer and the piston stop, because I can not trust the 'S'/'D' label or the dash line. I will mark the flywheel for the future generations to avoid all this hassle.

Ok, thanks for your explanation of PSM, I have never heard the acronym before with regard to motorcycles...Googl e was absolutely no help with this one.
Art

[guzziart]

Yes, "Dis side, and Snot dis side." 

  Good one Chuck!

[Howard R]

Yes, "Dis side, and Snot dis side." 

Easy Italian -> English:
D = Driveshaft side
S = Starter side

[ironborn65]

Shouldn't "R" be "D" (for Destra).

a nitpicker, ah? ;)

:D

it's ok if I bring some fun here

In turkish there would be no problem, they both start with the letter 'S' (sağ - sol).

all the best

[John A]

D is right!
Why does Guzzi deviate from the accepted practice of numbering cylinders or engines from left to right as viewed from the operators station?  It always puzzeld me until I realized they followed the other accepted practice , they numbered them from front to back, which is why the left is #2 and the right is #1,

[Moparnut72]

The forward most cylinder is usually #1 as the accepted practice.
kk

[John A]

The forward most cylinder is usually #1 as the accepted practice.
kk

Isn’t that what I said? My apologies for not being clear.
Edit, I should have split the sentence up

[Moparnut72]

Not being critical, just clarifying a bit.
kk