Page 2 of 3

Re: Polini 165 install

PostPosted: Tue Apr 14, 2015 11:19 pm
by Hoolio
Alright boyos! The 165 is in, the GPR pipe is on. Will post pics. Scoot feels great - still running in so haven't let rip, but it's backfiring like a bugger every time I'm engine braking, and even when changing gears unless I'm very quick with the clutch lever. I guess I'm running lean - went up to #17.5 one the idle (stock on the Polini carb is #15) but still backfiring. Am on 92 for the main so will try going up on that.

Re: Polini 165 install

PostPosted: Mon Apr 20, 2015 7:54 pm
by Neurotic-Hapi-Snak
For reducing compression, I'd suggest having your head or piston milled instead of using a spacer. A spacer will mess up your squish and make your engine run less efficiently. Also, if you're still using the 125 head, switch to the 150 head, it's a bit of cash, but it will reduce compression, increase combustion chamber volume, I believe it has larger valves, and will keep your squish nice and tight for optimum mix turbulence and combustion. Port your head, too, the stock intake port ID is several mm smaller than the ID of the Polini intake manifold. That should increase both low and top end by decreasing intake resistance and creating a "funnel" to increase intake velocity past the valve.

Here are the measurements for the intake and port:
Polini intake manifold ID 25mm, cross sectional area 1963.5mm2
Head intake port ID 21mm, cross sectional area 1385.5mm2
That's quite a difference and if you have just a step down in diameter where the manifold meets the port, that's going to cause a lot of turbulence in the intake airflow.

You'll also need a new intake spacer/insulator, one off a GY6 with a ID of 23mm and bolt spacing of 45mm should work if you open it up to 25mm. There's ones on eBay for not too much.
http://www.ebay.com/itm/121487279162?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Re: Polini 165 install

PostPosted: Tue Apr 21, 2015 1:03 pm
by Hoolio
Cheers for the reply. For the intake spacer/insulator I dremelled out the original one that came with the carb because the inner diameter was smaller than the carb outlet/manifold inlet. I think you mentioned that in a previous post. I opened out the diameter to be to be a diameter in-between the two.

I'd also come to the conclusion that the 150 cc head is the way to go. I could not get the spacer to work (I tried with 1.5 mm aluminium) because it felt like too much tension was on the timing chain. Actually I could not get the timing sprocket back on its shaft with the spacer in.

Re: Polini 165 install

PostPosted: Tue Apr 21, 2015 2:51 pm
by Neurotic-Hapi-Snak
Yes, get the 150 head. The 4T has what's called a Huron head which is designed for squish, and relies primarily on squish for proper mix turbulence, which keeps the fuel/air mix mixed in the combustion chamber, which leads to more efficient combustion, which equals more power and less fuel consumption. If you want to get really good results, you should check the squish band with solid solder stuck to the piston, IIRC it should be .040-.060". Just Google squish clearance measuring.

Re: Polini 165 install

PostPosted: Tue Apr 21, 2015 3:44 pm
by Hoolio
Great detail thanks. Couldn't find any refs to 'Huron head' but just found 'Heron head' which looks like what you mean.

Just attaching some pics of the GPR pipe which is ... aah, just a thing of engineering beauty.

Re: Polini 165 install

PostPosted: Tue Apr 21, 2015 4:02 pm
by tipper
That GPR pipe is a thing of beauty I wish they made one for the 200.

Re: Polini 165 install

PostPosted: Tue Apr 21, 2015 4:48 pm
by Hoolio
here's how it sounds:
http://youtu.be/gRw4wW9P9Vw

Re: Polini 165 install

PostPosted: Tue Apr 21, 2015 4:58 pm
by tipper
I emailed them a while back asking if they were developing one for the 200. They said they would if they had a scooter to use during the development,might have to make trip to Italy at some point this year.

Re: Polini 165 install

PostPosted: Tue Apr 21, 2015 6:50 pm
by NICK
Matt you could nip back that way on your return from America, and also call in at Rimmini Lambretta and say hello to Dean for me ,who hails from Bodmin Cornwall origionally.Cheers

Re: Polini 165 install

PostPosted: Tue Apr 21, 2015 8:46 pm
by Hoolio
a trip to Italy on a scooter - the stuff of dreams!
:)

Re: Polini 165 install

PostPosted: Tue Apr 21, 2015 9:48 pm
by Neurotic-Hapi-Snak
Too bad that GPR exhaust won't stay nice and shiny. On mine the header and outlet pipe turned brown.

Yes, it is a Heron head, not Huron.

Re: Polini 165 install

PostPosted: Tue Apr 21, 2015 11:25 pm
by Hoolio
Hmm good point - already looking a bit brownish at top of header pipe. Wonder if some VHT Satin Clear would hold up to the temps.

Re: Polini 165 install

PostPosted: Thu Apr 30, 2015 2:50 pm
by Hoolio
Just writing to confirm the gasket for the Mikuni VM22 fits the Polini carb:
http://www.ebay.co.uk/itm/291415551537

Saves waiting for the original one to dry back to its original size when you're fiddling with jets.

Interestingly you can pick up a Mikuni VM22 on ebay for about 30 quid - I wonder how Polini get that up to 115 quid! This one looks very similar but with choke knob instead of cable:
http://www.ebay.co.uk/itm/26mm-PIT-DIRT ... 20f2b60fd8

I guess the problem would be getting a manifold to fit.

Re: Polini 165 install

PostPosted: Thu Apr 30, 2015 2:56 pm
by Hoolio
Now I have over 100 posts could someone ping me the code for Tasso please? Gonna bite the bullet on the 150 cylinder head
In for penny eh?

Re: Polini 165 install

PostPosted: Wed May 06, 2015 8:29 pm
by Hoolio
Guys (and gals?) - I've recently received some info that would suggest it is imperative to get a 150 head for this kit.
So... anyone got a members discount code for Tasso they could let me have?

Re: Polini 165 install

PostPosted: Fri May 08, 2015 8:46 am
by Hoolio
No reply from Tasso although got the code (thanks Howscoot). As a long shot I have been in touch with a pal in New Delhi to see if he can ship me one over directly.

Re: Polini 165 install

PostPosted: Sun May 10, 2015 5:38 pm
by Hoolio
Hi guys - anyone know whether part no. SF510-0043 would be OK for the cylinder head? Looks like it may be a cylinder head off a Speedy

Re: Polini 165 install

PostPosted: Sun May 10, 2015 6:29 pm
by Neurotic-Hapi-Snak
That's the same part number as the head for the Stella 4T.

Re: Polini 165 install

PostPosted: Sun May 10, 2015 9:57 pm
by Hoolio
Happy days! Thanks mate!

Re: Polini 165 install

PostPosted: Mon May 11, 2015 6:45 am
by Neurotic-Hapi-Snak
Be aware the Stella doesn't have a SAS or any of that garbage.