LCGB Forums

I need a re-plate on a TS1 and was hoping to maximize CC.
Boring out to 72mm would leave the spigot 1.4mm thick.
Is this too thin and could it break in the motor?

Anyone had any experience?

IMO Yes it is too thin and yes it will flex and break. I would not go beyond 71 mm on a standard spigot, and even then would shorten it.

Thanks Bernie, I thought I was being a bit optimistic.

I think AF's can steel liner it & use a RB/Rapido250 piston, with a couple of oversizes, I'm sure they did that for a mate of mine

I spoke to Paul at PJME in Wolverhampton who have iron lined a few barrels for me about the possibility of running 72 mm on an iron lined with standard spigot diameter. I thought it might be strong enough to cope. He advised against it and thought that it would fail. Having had a spigot fail on me before I didn't want to risk it.

If you are looking for an increase in capacity, with a two stroke, an increase in the stroke is theoretically better as most of us already have engines oversquare. Two stroke MX engines are undersquare. It is also a practicable proposition these days for Lambrettas, & one I would advocate.

However, there is mention of the Rapido 250 & I just wanted to say that I believe the spigot on those barrels is larger, necessitating modification of the crankcase mouth.

Ive got a steel linered rb thats 72mm , std spigot (75mm).....done by pjme to 71 mm, did over 10k miles on it ....I had it rebored over the winter to 72 mm , done over 2k miles so far , no problems yet .....with the spigot .
Russ