Modern Vespa

Sorry for such a basic question to something that has been talked about on here endlessly but here goes.
I read a thread last night about finding TDC and using a degree wheel and others chiming in with their advanced Nasa calculations to get to where you want to be. My head was pounding and I was getting more confused by the nanosecond . Then, not far into the responses came a post by ( his name escapes me right now) that read,

"I know you already figured it out Astro, and nice post Jim.. but for any of you who are like me and can't read formulas and can only add, subtract and divide by 2:

What you'll need:
* Degree wheel
* Pointer (wire / coat hanger)
* Piston stopper
* Something to mark the cae and flywheel with (Sharpie / tiny paint brush / file etc.)


1 - Put the degree wheel on your crank / flywheel.

2 - Set up a pointer (piece of wire or coat hanger) on a flywheel cover screw.

3 - Put a piston stopper in the sparkplug hole.

4 - Roate the crank CLOCKWISE until the crown of the piston hits the stopper and it stops.

5 - Set the degree wheel to 0 (with the pointer) (Be careful not to move the degree wheel independantly of the flywheel when you're rotating the flywheel)

6 - Rotate the crank / flywheel COUNTER CLOCKWISE until it stops.

7 - Write this number down (we'll call this "number 1")

8 - Subtract "number 1"from 360 (the result will be "number 2")

9) Divide "number 2" by 2 (the result will be "number 3")

10 - Add "number 3" to "number 1" (the result will be "number 4")

11 - Remove the piston stopper.

12 - Continue to rotate the crank past where you stopped COUNTER CLOCKWISE until your degree wheel reads "number 4" at the pointer you've made out of a wire)

13 - Mark your flywheel and case here.. this is TDC..

Done!... It's that easy!



To get to say 18 degrees BTDC for example, rotate the flywheel COUNTER CLOCKWISE 18 degrees from your new TDC mark... Mark the flyweel.. this number will be to the RIGHT of your TDC mark on the flywheel. "



Great, something i can almost figure out! My problem is I cant get past the thought of it being even simpler. Probably because that's my limit, I dont know, but if you put a piston stop in and turned it clockwise until it stopped and you made a mark on the flywheel and engine case then rotated CCW until it stopped and you then marked the engine case again to line up with your original flywheel mark and measured between the two marks on your engine case and split it in half, that would be where you marked TDC? Then throw on your Degree wheel with 0 being at TDC and make a mark , in my case 18 degrees BTDC and you'd have your firing point?

Its one of those things that I know I'm missing something in my view of it and I just cant understand all the bextra motion involved..

Please help guide the miss guided so I can get it right and check of bad timing as one of my problems with my Scooter...

Spot on.

Mark it 8 Dude!

Sounds about right but visualization may help, too. Watch Robot set timing in this video. Starts at the 3:50 mark.

You can also find the TDC the hard way which is removing the cylinder head which is not too bad either.

P125X with Malossi 166 kit, Si 24 24 and a Sip Road performance exhaust.

That is what I have but on a sito plus. I can send you a picture on where my marking is at.

Do you have the original stator on it or the newer version with Green, red, white, black and blue wires?. The newer version will have the marking A and IT. You will be closer to the A(lefty one) by the time the timing is done.

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Sounds about right but visualization may help, too. Watch Robot set timing in this video. Starts at the 3:50 mark.

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But i dont understand the need for the Pointer wire. It seems over confusing and that example I gave by name unknown still is the simplest I've found.

So I should be spot on? And when I strobe light my timing I want my Flywheel TDC mark lined up with engine case !8 degree mark correct?

The pointer is so that you have a reference. It is like the old school watches when you want to "zero it" you move the crown of the watch to counts the seconds from zero.

Well I did that after because I was scareded and my TDC was spot on but i was convinced my simple way of marking 18 BTDC must be wrong. I did have to rotate the Stator plate A little to get my18 BTDC case mark to line up with my flywheel TDC mark while strobing!

I bought this scooter as is. Im looking at the Stator right now, it has green,red,purple,black and yellow wires. No A and IT marks just a factory v groove on oter edge with a raised rectangle next to it if that makes sense? Both look to be in the casting..

I bought this scooter as is regarding the motor setup, I did break it down and attempted to paint it and pulled a new harness and cable housings.

"Then, not far into the responses came a post by ( his name escapes me right now) that read,"

Thank you as well VADER19!!!!
I knew it would come to me

I kid you not, finding the TDC and setting the timing where it needs to be is so simple that it's somewhat complicated.


...at least that's my thoughts on it.

Dunno what problem is here...
A; check timing BEFORE fitting the head & all sorted.
B; poke a micrometer down plug hole, watch for needle to move (also vernier/calipers can be used)
C: pull off flywheel and look for the scratch marks from prior attempts at timing, then work out which are; the shiniest ones (possibly these are the latest prior attempt) or the newest looking ones or the ones that match the other numerous scratches & marks on the stator plate)
THEN
go with C (or possibly A, maybe B)
THEN
fang-it up n down that nice quiet residential street a few times...
IF it sounds good, then sorted, get a beer!
If it runs like a bag o shite, try one of the other marks & repeat.
Then on about the 4th attempt (& likely after 4 beers to alleviate the frustration & a few bongs for inspiration) ...
THEN
Check the WIRING, as most carb issues are caused by the wiring & it did seem to fire that time a few hours ago when you sprayed heaps of ether down the carb & had foot on brake (so brakelight was on), it must be that!

If it is POINTS:
Get multimeter out & find the wires that create a circuit across the points (this is yet again a mysterious combination), attempt to set points & slowly spin flywheel to see when (actually IF is more likely) it circuit breaks & guess that as it now actually opens & closes it should be close enough to get it started (with a healthy dose of ether!)
THEN
fang-it up n down that nice quiet residential street a few times...
IF it sounds good, then sorted, get a beer!
If it runs like a bag o shite, try adjusting them a beesdick & repeat.
Then on about the 4th attempt (& likely after 4 beers to alleviate the frustration & a few bongs for inspiration) ...
THEN
Check the CARB, as you ALREADY know that for once it's NOT the wiring! Later on check the condenser thingee & just replace it with the one you found in the glovebox (coz, for sure it is better than the one that is in there, why else would it be in the glovebox aye?)

IF you're stuck at work & it won't work & boss needed to be home an hour ago (this may, or may not be from experience) & you have a non-battery VBC & know that the points are opening & closing, hook up a 12v battery across them, then that mofo WILL have spark!

After all that & you are packing up & sweeping the floor you spot the woodruff key in the grime...

Repeat...............


I fukn love these simple machines!

If the flywheel fits the crank taper properly you don't need the woodruff key anyway.

So Im "Not the only asshole in the room"?
Just got done listening to Volbeat and its pretty much the same, I'm not the first or the last.
Good writeup!
Have a good one

Thanks everyone

It's not hard! Good chance to have a look at things too.
No wheels or math. A certain TDC to mark.

I understand that a good fitment on a conical shape crankshaft (male) to the conical shape flywheel(female) might seems like a good fit but you have to use the woodruff key to avoid slipping.

The flywheel might go in all the way but there is a chance of slipping. The woodruff key would completely eliminate the chance of rotating. Are you running your scooters with no woodruff key? I am not saying that is imposible, nor I am saying it wouldn't work but eventually it will come loose.

I'm not but I did read i little something about doing that recently. I didn't finish the article because its something that doesn't interest me as I need to get the basics down first, lol.
Wouldn't a conical fit be so precise that galling wood occure? Like a mf to get apart after any length of time?

Scooter help.com has a simple, easy to understand text for setting this. I remember reading few different ways from various members here. I distinctly remember one method described by a member here that was so ridiculously confusing that I thought I would have to hire a tutor for algebra and another for some origami lessons.
There were others much easier to follow.

I do agree with the original poster that there must be a very simple method somewhere out there. I've gone with a degree wheel, a piston stop, and a piece of wire with good luck so far.

It helps to wrap your head around what you're measuring.

When you put a piston stop in the spark plug hole, you're stopping the piston a certain distance before it reaches top dead center. You're trying to measure that distance.

The piston stop keeps the flywheel from making a complete 360° rotation. So the distance to top TDC is the middle point between 360° and however many degrees the flywheel turns before it stops.

Let's say with the piston stop in, the flywheel only rotates 300°. That means the stop is blocking 60° rotation. So TDC is going to be 30° (360° - 300° divided by 2) from the point the flywheel was blocked by the piston stop.

After you done it a couple times it becomes clear.

^^^^^that!

So that means the way I do it is correct. Correct?

Yeah, you got it. The clockwise /counterclockwise turning is what confuses people though. It's basically irrelevant which way you turn the flywheel. Just remember to add that half difference in degrees to whatever direction you're turning it.

It is satisfying when this is accomplished successfully. For me having the appropriate tools is fundamental to the results, good quality accurate degree wheel, degree wheel holder, pointer, piston stop or dial indicator and strobe light.

Thats just it! Thats why im still confused. I dont use the ' pointer' because i dont understand why I need another element added to , rotate right, hit piston stop, make mark, rotate left, hit piston stop, make mark.
measure between the two marks, cut that in half and make that your TDC on engine case.
Match flywheel mark to TDC mark, throw on degree wheel at 0 on TDC , look to your left for your degree mark for your scooter and make a mark!

See thats why im worried im doing it wrong...

Pointer provides more accuracy.
You could also pull the spark plug and aim a flashlight to verify the piston is truly TDC at your mark, more or less.

Along the circumference of the case that meets the flywheel, timing can also be confirmed somewhat via a tailor's (metric) tape measure. 1.48mm = 1 degree.
Along the circumference of the stator, 1mm = 1 degree.

If you're verifying a points ignition you'll need a timing light, btw.

Yes I did the measurining tape just to make sure I had my 18 degree BTDC and Ive strobed it about 10 times aswell convinced I'm doing something wrong, lol.
I guess I just got confused when I read those other posts that have those f ing formulas. Not sure why they have them if its this easy.
Thanks for the advice!

So, I need a short thread piston stopper for short thread spark plugs and long stopper for long thread plugs?

For Pinasco 177, I need short thread stopper and plug right?

Nope, you only need one size. One size of piston stop will work for any cylinder head out there.

"This SIP Piston Stopper is manufactured using a high quality black coated steel and is available in two sizes-Short, for the Smallframe motors and extra long for the Largeframes"

This is what I see in SIP website. Just wondering what size do i need for Pinasco 177. Thanks

Either will work. The larger one is just going to give you larger numerical values than the shorter one. Your math will still turn out the same.