Gori 175 piston to bore clearance, should I worry?

[rogscoot]

Hi,

My Gori 175 cast iron kit arrived today, looks nicely finished but I am a bit concerned about the piston to bore clearance - I know in Sticky's kit book the Gori 200 he tested had 0.13mm of clearance so maybe it's normal for these kits.

My rudimentary test of using 2x feeler gauges at the piston skirt with the piston at the top of the barrel gives me around 0.15mm of clearance, that is with the gauges pretty tight on either side of the piston.

0.15mm seems to be the wear limit on most standard Lambretta cast iron barrels, however in the Vespa world 0.14/15mm is clearance on assembly for most largeframes so perhaps Mr Gori has followed this rule?

The ring gap is approx 0.30mm.

I just wanted to check before I fitted it, grateful for any advice especially those who have already used this kit!

Cheers,
Rogscoot

[GExS]

I’ve used the kit and the clearances are okay. I’ve just bought another one and it has an improved cylinder head with a weird ring that goes between the barrel and the head.
You’ll love it, I’m sure.

[rogscoot]

Thanks for the reply, I have the kit with the new head and spacer and just a quick note...

The spacer on mine was machined slightly off centre so when the piston was at TDC it would touch the spacer on one side.
Gori are sending me a replacement cylinder and spacer so fingers crossed everything will be fine with this one.

Cheers,
Rog

[vegansydney]

Interesting that is one of the new versions with the unique 'Super Cool' head. Strange that they'd redesign the head, update the piston but leave the bore size the same

Can you please post the measurements once you receive the replacement item? I've been interested in the '200 Sport' version after looking at the dyno graphs in the Lambretta kit book. It's far from ideal, especially on a brand new kit but I'd personally buy an first oversize piston and get it rebored, or get the piston skirt coated with PC-9 or similar dry lubricant. The company that coats all my piston skirts can coat up to 0.1mm thick.

Good luck and please keep us posted on the replacement kit.