Next project for spring, to zerodeck or not!

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Next project for spring, to zerodeck or not!

Postby rob h » Fri Mar 02, 2018 6:54 pm

The pinasco alloy 177 has instructions to take 1mm off the head to improve performance, and you can raise the exhaust port 1mm to give more revs. After reading the article in "scootering" about tuning a basic restricted vespa., I liked the idea of fitting a zero decked or 0 squish cylinder head. then fitting a 1.5 mm base gasket, with bolt compression of the head it gives 1.3 mm squish and raises the exhaust port by the same.
As the pinasco 177 ports are quite conservative, i was thinking of replicating the upgrade. I have the zero head already available, bought it for £20 off e bay.
I also have a polini head, which is supposed to give the pinasco 177 a big jump in compression, as the standard head is around 2.3. anyone one tried either of these modifications? Or any thoughts.! Cheers Rob.
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Re: Next project for spring, to zerodeck or not!

Postby Leigh » Mon Mar 05, 2018 12:11 pm

Hi Rob,

Whilst I haven't done this with a Pinasco, I have played around with compression when fitting 60mm cranks to other kits. Raising the compression will improve performance, but will also raise the temperature at which the engine operates, so you need to be careful.

Generally raising the exhaust port increases top end rpm, but reduces torque in the lower rev ranges. The best way to think of it is a Polini would be more like a malossi if you raised the ports with a barrel packer. When putting a 60mm crank onto a kit the rule is that a packer under the head gives the engine more torque, a packer under the barrel gives higher rpm.

It sounds like what you are suggesting is trying to compensate by the lost torque by increasing the compression of the cylinder. It'd be interesting to see how that works out, so keep us updated!!

Cheers,

Leigh.
Another fine tip stole from Mick Maidment!!!!
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Re: Next project for spring, to zerodeck or not!

Postby rob h » Mon Mar 05, 2018 7:16 pm

Thanks for that. Might try polini head first, i have a cht guage somewhere i will fit that as well. So a lower squish would increase compression, would this give just more torque?
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Re: Next project for spring, to zerodeck or not!

Postby Leigh » Tue Mar 06, 2018 1:25 pm

Yeah, torque is where you will notice most difference.
Another fine tip stole from Mick Maidment!!!!
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Re: Next project for spring, to zerodeck or not!

Postby rob h » Mon May 21, 2018 8:06 pm

Ok, tried fitting a polini head to a alloy 177 pinasco kit. Results are mixed, had to change the atomiser back to be3 from be5. Took it on my normal test route, but a little gusty. found mid range acceleration way better, engine was noticably revvier. low down needed more revs, but from 45 to 60 in 4th was a constant steady moving increase, easily better than the pinasco head. On 22t gearing, seemed to flat out around 60 mph( around 65 on clock), I think I got more eventually with the pinasco head but I love the mid range acceleration. Options are to fit a DRT 23 cog if I want 70 MPH. However I think I am happy to sit around 60mph nowadays, mainly a b road rider.
The actual cylinder heads are quite different in design, more of the polini bowl area in use and deeper, I may go for a different exhaust as well. This sound right to you guys.
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Re: Next project for spring, to zerodeck or not!

Postby rob h » Sun May 27, 2018 6:50 pm

Ok just to update, I fiited a Polini head to a new style pinasco large port alloy 177 cylinder. I have just took it for a good run. The revs have literally doubled, acceleration improved by a third. The speedo will rise constantly from 45 to 60 mph. However my top end is slightly lower, 63 mph, will sit at 60mph no worries in gusts etc.. I have lost about 5 mph. I think I need an expansion unit to take advantage of the new rev range. Love the acceleration!!
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