ring ends in ports

[lofty]

Hi all,

I have a barrel that I want to put a couple of boost ports, however the piston I have has the ring pegs situated where the boost port should logically go..

My original feeling is that this is a no-no..

however I have seen some information on the internet that makes me think its not quite that bad..

If the piston and rings are of a suitable modern spec (wiseco) and the ports are not too wide and are tapered does that make it acceptable.. when I say acceptable I mean it wont be likely to trap a ring and wreck the piston and barrel when im hooning down an A road..

any knowledge or experiences with this in Lambretta land?

[Warkton Tornado No.1]

There’ll surely be other, better advice to come along but....

Like you say, I can recall seeing information where the tuner had resorted to ring pegs traversing ports & stating the methods by which easing that traversing should be achieved.

However, if it were me, I’d sooner select another piston (such as the OEM) if the pegs are in a better place or re-peg the Wiseco.

My reasoning is that I’d still fear a snag, but the ring peg wear will undoubtedly be accelerated due to the springing of the rings into the port.

[Adam_Winstone]

The only Lambretta reference I know of is the very respected WCLW humiliator kit, .which had ring pegs
exposed by the boost port. This was extremely reliable!

[lofty]

thanks.. I saw the WCLW reference too..
also one about early RB pistons having a similar situation with ring gaps and boost ports.. again no issues reported..

[Warkton Tornado No.1]

Post by lofty » Wed Sep 07, 2016 11:28 am

thanks.. I saw the WCLW reference too..
also one about early RB pistons having a similar situation with ring gaps and boost ports.. again no issues reported..

Adding ports to an existing cylinder, utilising pistons intended for completely different engines will inevitably mean some compromises.

Tuners in the UK have been adding boost ports to Lambretta cylinders for many years & I believe their preference is to emulate the OEM geometry of modern two stroke designs & avoid ring pegs traversing ports.

I have seen two parallel boost ports where there logically may have been one, wider port, but for the fact that the Tuner wanted to support the ring ends.

Ultimately, it is your choice what compromises you consider acceptable.

Good Luck with whatever choice you make.