175 Piston

[Doom Patrol]

The 175 option is something I'm considering. But where do you find a good piston that can be used in conjunction with a 60/110 crank?

[rosscla]

https://www.riminilambrettacentre.com/e ... celta.html

Or

http://www.scooterrestorations.com/lamb ... -assembly/

[Doom Patrol]

Isn't the conversion piston taller to account for the shorter rod on a standard set up? I genuinely get confused over this. I'd be thinking along the lines of a standard GP barrel taken out to 175.

[rosscla]

the conversion piston is designed to take a 150 out to 175 with a standard crank 57/107 you'd get a few extra cc with the 60/110 and need a 3mm packer to put the port timings back in the right place

Standard TV had a 57/116 crank so piston height different to compensate

[Doom Patrol]

Thanks Rosscia.

[hendy]

With a 60/110 and a gp 150 barrel bored to 175 you can pack it so that you have mid 120s transfers. Mine rides really nice like that, but I've also raised exhaust to 178 and inlet is something like 140.

[Doom Patrol]

With a 60/110 and a gp 150 barrel bored to 175 you can pack it so that you have mid 120s transfers. Mine rides really nice like that, but I've also raised exhaust to 178 and inlet is something like 140.

That's pretty much what I had in mind. I'm not actually sure what those timings mean, but I know a man that does. Thanks for the advice.

[Doom Patrol]

I went for this one in the end.

http://www.scooterrestorations.com/lamb ... ome-rings/

Just need to sort myself out a crank now.

[Doom Patrol]

Well, this one has come back to bit me on the bum a bit. I blame the virus.

I said I was going down the 175 route, and I did. I had a 60 x 110 crank, a conversion piston and a nice GP barrel to bore out to 175. I've thrown a spanner in the works of my own making really. Because nothing much has been happening I haven't been able to get the barrel bored out, for obvious reasons. However, I do have a proper 175 top end and thought that would do. It occurs to me now that I have a conversion piston and the wrong rod for a proper 175. So, my question is how will this set up work, or not?

[Warkton Tornado No.1]

If I understand the scenario, you have two 62 mm pistons, one being with the compression height (30 mm) to suit a 175, the other with a 'conversion' compression height of 39 mm.

If the newer 'conversion' piston is a good fit in the 'proper' 175 barrel, there's no reason for thinking that it could not be used. As it would have been intended for use with a 107 mm rod, you should need a base packer of a nominal 3 mm to bring the geometry right, but it's best to try & achieve the best squish in doing so.

The 'proper' 175 barrel could no doubt do with a hone, though & the ports chamfering. If you haven't already got a three leg sprung honing tool, they are well worth their money, but you have to be sensible with the stone grading selected & the drill being used. Although I have the option of a pillar drill & various variable speed mains drills, the best by far is the Milwaukee 18v brushless combi. The control of really low speeds without stalling enables a superb cross hatch finish.