Polini 210 squish

[Eibar]

No head gasket 1.5 squish. Just curious others settings (standard dowelled polini head that came with kit)

[H,POOL GADGE]

am running a polini 220, 1.5 packer, 1.4 squish

[joeythescooterboy]

Read an article from Scooter Centre today saying that you need as much as a 2.2 squish on the Polini kit with a 60mm crank for it to rev out.
Heard this before on another site????

[H,POOL GADGE]

interesting, In the 80's first thing we did woz skim the head, to god knows wot squish! now there's a science behind squish 'n' compression....to be honest av never heard of squish allowing an engine to rev out, a pipe maybe and run cooler!!! I would'n argue against ye joey, coz am unsure on that, like!!! maybe a tuning Guru can shed an Encyclopedia'n explanation on this!!!!

[Norrie Bodge]

1.2 squish on my malossi-220
Pinks with anything above 1.5 squish
Using one of these -> https://www.pmtuning.co.uk/pm-tuning-hi ... ossi-210cc

[joeythescooterboy]

https://blog.scooter-center.com/en/deta ... ke-cranks/

[H,POOL GADGE]

Nice read that gadge...they certainly pushing scooters into modern day speeds, a think economy cruisings out the window, like! 28mm carb,,,, 120kph/74.5mph and 20bhp @ that speed, awesome, probs get 60 mile to the tank! and getting a speeding fine on a motorway on a vespa, hahaha! be on national news, haha!!!!! But joey'Boy, I did'n see it saying 2.2 squish allows it to rev out!!! but 2.2 squish would allow the engine to run cooler, maybe the squish is greater because the compression is high, I believe the compression on my 220 to be 10:1, dunno me like?????

[joeythescooterboy]

Me neither
Wasn't SSC blog mentioning big squish helping it to rev out, read that somewhere else but can't remember where.
I'm just wondering how much truth is in it, I believe Harry Barlow is a fan of the big squish?
I'm on a Polini 213 with MMW head running 1.2 and Kytronic.
Still get a smidge of pinking mid range but think it's more to do with jetting at the minute.

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[Jack221]

Malossi 221 with 0.9mm squish and Kytronic

To give you something to think about. I do think there is no 'one size fits all' when it comes to squish. From what I have picked up over the decades, I have formed an opinion, that squish is all about the rpm that peak power is made at.
The higher the rpm at peak power the tighter the squish should be to get the most out of it.
Mine currently makes peak power at about 8,300 rpm so needs a tight squish to stop the pinking (more turbulence and less volume = less detonation) and needs the Kytronic to back the timing right off at the same point (increased turbulence acts like advanced timing).
A scooter making peak power at 7,000 or so might benefit from lets say a 1.2 squish and 6,000rpm maybe a 1.5mm. But as timing, porting head type and compression all affect each other, when adding squish as another variable we need some way to rationalise it and I think this might be as good a way as any.