Modern Vespa

Did it need an upjet after?

How much was the squish clearance changed?

Haven't changed any jets yet (other than the main jet change to a 102 for the polinibox and drilled filter) but it was dark when I came back from the ride. We'll see over the next few days
Didnt measure the squish (You can never find solder when you want some lol,) but maths would suggest its squishier by .7mm?

Got some solder and the squish is 1.8mm, I have .4mm left on the head that I can sand off so I am going to do that this morning.
This reference says that 1.2mm is a good figure to aim for so should be good, watch this space.

So got sanding this morning, took squish down to 1.5, bolted it all up and was away 1st kick.
Adjusted tickover to about 940 and went for a gentle ride.
Gotta say sanding the head down was worth all the effort, pollinibox gave me more midrange (std 125 was gutless and needed reving to get going) sanding the head down, and shimming the barrel has given me, it appears more torque, from start to finish. Very happy,
Jetting may need a little more tweaking( occasionally v. slight hesitation in the midrange going from over run to acceleration, which wasnt there before the head and barrel mods).

To summarise mods so far:
Polinibox, worth its weight in torque, limits rpm to about 7500 but thats fine with a scoot that will be hauling a sidecar in the future
Jetting is standard apart from the main jet going from 96 to 102( suspect some more tweaking here).
Sanded down head by 1.8 mm using 40 grit taped to a sheet of glass then 'polished' with 120 grit. (Took about 2hrs in total broken up into 15min slots, so boring but cheap!)
Barrel packed up by .8mm (arbritary figure chosen by the gaskets I had 'in stock'.
Would more be better?
Cht temps are around the 240f mark

You should read up and study how to measure cylinder timing. Then measure what you have from factory. That can help answer what lifting cylinder will do. That will be a good skill to have when installing a new cylinder. Within limits, if you adjust by adding to bottom of barrel or raising it, results in increased power but moves that power higher into the rpm range.

Thanks for that insight Chris, this was/is just to play around with the 125 cylinder,( based on this article.https://www.scootering.com/scootering-classics-vespa-tech-part-2/) get used to taking it of and on and getting a bonus for next to nothing if I could, and it seems Ive hit a sweet spot in that, at the moment, I have improved torque all over the place, next is tweaking the jetting (suggestions are very welcome).
measuring the timing seems like a good idea if only to transfer my 'butt dyno' results into figures
Lokks like the search function on this site is going to get a hammering

One more experiment before I move onto a kit, thoughts on running without the air filter, leaving bellows to frame, good, bad, no change? You're experiences/expert advice please

That is a good article I've read it before and found it informative. Since your experimenting for experience, try your hand at exhaust porting as suggested in article. Cast iron is harder to mess up and will give you a feel for what it's like. I had a cast iron DR177 I used when experimenting.

This morning I ran it without the air filter, just bellows to frame, 102 jet not good so upped it to a 105 (next size up I had), it was better but probably needs more. testing cut short because the disc brake jammed on. (ongoing problem).

You are in seize territory, be really careful. I got spat off 30 years ago doing this at 50mph. So fast a seize no time to pull clutch in. The impact burned a hole in my leather jacket and fused it to my arm. Why take this risk and the crap going into engine too?

Hi Ferris wolf
There seems to be a concensus that A) it improves airflow and B) crap is minmised because the air is drawn from under the seat. And I like to experiment.
But I will take your cautionary tail to heart and replace the air filter, Thank you for your insight.

Hi so over the last few days I have been doing a bit more 'tuning' (its a bit addictive).Following this article (https://www.scootering.com/scootering-classics-vespa-tech-part-2/ I sanded down the head another .2 mm, total removed 2.0mm.Its as far as I can go on my head as I am now level with the fins.
Put a 1.5mm packer under the head( originally .2mm gasket then .8 mm packer)giving me a 1.3 rise over standard.
And I modded the exhaust port as per the article with the old dremmel.
Carb is standard apart from a main jet change from 96( std) to 102.
Squish is 1.2mm
I have just taken her out for a short shakedown run (8 miles or so)just to see how she goes.
I must say I am well pleased with the results, these further mods according to the old butt dyno have improved things again.
All the gears have become even more usuable ( I can potter around in 4th at less than 30mph and accelerate without changing down, couldnt do that with the standard 125.
And acceleration compared to the std 125 is like night and day.
Jetting I feel needs futher tweaking, it feels a little ( just a little) flat through out but especially low down.
So need to do some tuning runs to sort that out.
In short following that article has given me a much more useable and pleasureable machine to ride for not a lot of money.
How much? polini box cost me £125, box of jets £17. sandpaper £5 grinding bits £10.base packer £6
Total £163. Only other thing you need is a sheet of glass for rubbing down the head (borrowed mine from the fish tank ).

Maybe go up on the main 1 or 2 pts and tweak the pilot very slightly anti-clockwise to make slightly richer, maybe one eighth turn . You've increased performance so give it a bit more fuel. It can't harm it at all by doing so, I think you will find it better.

Thanks for your suggestions/guidance Ferriswolf, will give that a go and see what happens.

What pilot is in it now 50/120 ? Logic would suggest that as you have tuned your scoot and getting more grunt your HP is increased and so your main needs a jet up and if it's feeling flat low down maybe richen up the pilot. You're probably getting 1.5 bhp extra with the polini and air filter mod, 96 jet is standard , 4+ for polini , 1 for filter so 101/102. You've added maybe .5 to 1 hp, so maybe go 106 now and work down ? Such a science balancing main and pilot but the pilot being wrong is responsible for more seizes than the main. Richening up has no risk to you whereas the other way does. Out of interest what plug heat grade are you running . A 7 I would guess? A 7 plug is better for blasting around local whereas the 8 good for long runs. I keep both in toolbox and swap out depending on where I'm
Going and the weather. Remember too that when you hit winter your carb will run leaner so have the larger jet ready to swap out .

I've just come back from a run with a 105 in( weird set of jets it goes 100 ,102,105,108,110 and 112), so it revs to 8600 on the stand, 7600 wot in second and 6500 wot in third, up a slight hill.When it hits those numbers its like hitting a wall.
When changing down I think I am getting some 4 stroking( feels like its firing every third or 4th rev?
Temps 235f wot in 2nd for 3/4 mile slightly up hill.
Haven't pulled the plug yet ( family here) so thats to look at.
And yes I'm running a 7 plug.
Any thoughts?

Morning all.
So got out early to do a wot run before work.
3rd gear , slight uphill, 3/4 mile, revs 6800 and still rising(very slowly).
pulled plug and its black going to choc brown, so on the rich side I presume?
Is 3/4 mile at wot enough?
Then starting it to come home took 5 kicks and I had to catch it on the throttle ( normally its 1 or 2 kicks) does that indicate anything?
When I got home after about 2 miles, using no more than 1/2 throttle the plug was as black as your hat, again does that indicate anything?
Temp after the wot run was around 230-240 deg f.
Any input would be gratefully received.
For reference jet stack is 105mj, 140 air corrector be5 mixer with a 45/100slow running jet.

Give Tony a ring from vespa jets, he can get this right for you.
https://www.facebook.com/VespaJets/ UK based and really friendly and very knowledgeable. I think you might need to come down to a 103 MJ and possibly lean out your pilot with mixer, its such a delicate balance, the margins between pilot and main being in balance is tricky. He might suggest taking your pilot to 50/120, so you're going from 2.2 ratio presently (100 divide by 45) to a 2.4, the lower the number, the richer the jet. Although the 50/120 is standard pilot on a 24mm SI when bought new. Did you leave the engine running for a bit on stand before checking your plug? This is enough time to blacken it if pilot too rich.

Thanks for that heads up Ferriswolf I will contact him. The bike was on tickover for a bout 30 seconds before I shut off and pulled the plug, didnt realise it could make such a difference.( So much to learn , so little time). Your input has been invaluable, I owe you a pint or 2.
I'll let you know what he has to say.

Ferriswolf you were right with the idling call, did some more riding/testing yesterday, left the 105 in ( 102 too weak) and found the lower end is I believe weak, Plug too light for my liking.
Having a read on the forum, changing my air corrector from 140 to 120 and changing the be5 to a be4 might be wise move( 1 change at a time) and maybe if needed the pilot to 50/100( although the tickover seems good).
Any thoughts?
I must say I've learnt loads and I am enjoying the process of tuning these mods in. The butt dyno is a real thing, like flying by the seat of your pants , I'm getting a feel for my engine and what its trying to tell me.
For reference the scootering.com article changed to a 120 and changed the pilot to a 50/100 but then again leftt the main std??

Out of curiosity have you tried putting the original undrilled air filter back on then seeing how it drives, plug colour ? It will richen the mix up slightly, especially mid range . See how it performs . I put my polini box back on yesterday as my road 2 is so loud. Reminded me what a punchy exhaust it is, certainly up to 50mph it's far quicker than the road 2, but 5-6 mph top end slower. Most of my driving is local so it suits the restricted speed roads. Next step is clutch cog change as reckon I will get that 5mph top end back with a quieter and more comfortable drive. I have a 177

I drilled the filter but I can reseal it, worth a go.(It will have to wait a week I'm off to devon on holiday)

The polini is very punchy, along with the mods I've done 1st gear has almost become redundant and 4th will pull from27-28mph and I think that a cog change could give you the best of both worlds especially on your dr177.
Just need to find a Sidecar now.

Just an update on my trip down jetting lane.
I am now running a 100 main, be4 and a 120 air corrector and it feels close to where I need to be,throttle is responsive and temps dont go above 240 on my runleader temperature gauge. Will carry on tweaking as Im findingthis jetting lark to be very interesting.
Next stage is fitting a sidecar( I've found one )and putting a bigger jug on( probably a bgm)

And I've discovered that the idle jet is a 45/140 not a 45/100 (moral: dont believe everything the haynes bible tells you )

I don't believe any books, somebody may have been in there tinkering previously. You never know until you pull them and check.

yep rookie mistake for sure

Just upped the main jet to a 102 and the scoot feels brilliant.
If Im being picky the scoot returns close to tickover very quickly 1100 rpm then takes a few seconds to settle at 950 but i'll settle for that.
Have learned a lot from you lot and have really enjoyed setting up the jetting.
Thank you all.