Engine case modification. PX 200. Welding of cases for port modification

I am planing to build an engine for my PX 200. I would like to use either the polini 208 or the mallosi Long stroke. What I would like to know is how durable are the PX cases after welding and machining? I am going to be using the engine all day 5 days a week. Would I be better off just machining the cases?

A friend has pointed out that when the cases are manufactured they are cooled over a long period to maintain strength. 


I plan on using this engine all day 5 days a week for months on end and putting 30 or 40000km on it. 

Cast iron or aluminium?

Would I be better off using reed valve or keeping the standard oil injection. 

Sorry I know a lot of Questions.

If you only answer one part, please the welding and machining against simply machining.




if i was you i'd buy myself a newer vespa gts-like.

you'll be much faster with deliveries, specially if it's start-stop traffic.

no gear changing al day long, go for a variomatic scoot like the vespa gts 250 orso...

good luck with this ,




we have casings where the modis are allready done.








Hi dude


Just to make shure if i understood right the question ...


Do you talking about the porting of your casing reg the boostports of the racing cylinder or is there any problem with your engine case and you have to reweld it ?




I plan on doing around 300klm per day and using the scoot 5 days a week. The engine will not cool down and will be stop start all day, through the city. IE Not highway klm's.

Would using a 26mm carb with your t5, px 200 converted, piaggio exhaust affect reliability? Ie too much stress on the gears and clutch. 

I will be keeping my stock engine as a replacement should things go wrong.



Hi dude


What engine do you want to build ?

A tourer or a drag racer ?


If you need a reliable engine with more tourque it´s enough to port a stock engine case reg. the 208 Polini Cylinder boost ports.




No. I don't really like the autos. I test rode a 250GTs at the dealer before getting the px. The px is much more fun to ride.  If I upgrade, which is unlikely, I'll get a 600cc sports bike. Thanks for the advice anyway.

 The case I will be using will be brand new.

I have been looking at the services available from Worb 5. They weld up the original ports on the case and then grind new ports for the performance cylinder.