Modern Vespa

im looking to put some "pizaz" into my 83 pk50 s.

what do you guys think my BEST options for the value and what can i expect from them?

i dont mind spending a few hundred to get the bits i need.

thanks in advance.

J.A.T.O.

Tonysmallframe would know.

I would say route #1 would be getting new cases and building up a new engine to go into the frame, and handpicking the best parts that will work together

and route #2 is the more limited and restrictive route of keeping the existing PK 50 cases, and gutting out and replacing what you must to give you an engine as far as you can get with what bits you're starting with.

the nice thing about route #1, is that despite it costing more, you have a spare engine you can always throw back in there should you want to get a new bike ...or should your fast engine take a shit.

i have heard of people putting px engines into smallframes.

apparently it just makes working on them afterwards complicated due to lack of space.

anyone think that might be a decent way to go?

PX motors are shit. Heavy, off balance, and you'll never get much power out of them as the design is pants compared to a smallframe.

PK50 - first off I would find a breakers and get the gears from a PK125 - or the whole motor if necessary for parts.

For a decent route with not alot of outlay, I would do a Malossi 136 with a bit of port work on the cases. (If you have a friend handy with porting, do Polini 130 kit. Not as much of a bolt on as the Malossi, but you can coax a bunch of power out of the base kit) You will have to change out cranks, a mazz full circle would work with reed induction and a TM24, or you could run a mazz race cut crank, stock type induction, and a smaller or similar carb. There are a bunch of good exhausts for smallframes - would a curly pipe fit on PK? If so, PM40 is a really decent roadgoing pipe.

there is a picture of my current exhaust on the project report gallery.

what do you think doing all that would cost me and what sort of speeds could i expect from it?

am i going to be a lot happier with that as opposed to just getting a kit?

Awesome Avatar!

Just a reminder that 50cc engines don't need new cases to be made into 135cc, just a longer crank and taller primary gear. Often, they are excellent starting points because they see so little wear on the internals.

I just did a 102 kit, Polini right hand pipe and a 19mm carb on a 50 special. it now slips the clutch at 1/2 throttle. Really like it so far but plan to put in a 90 primary and 4 plate clutch.

As it is it has more power at 1/4 throttle now than it ever had before. Only took an afternoon get it to where it is now.

like patrick already said, the 102 is a viable option. add a pipe and carb and you'll be in the game for cheap.

if you up the ante to a 130 or better kit, you'll need a crank, carb and primary. factor these and the price to build if you don't do your own work into the cost.

anyway, PKs are fun... best handling smallie with a great building block for a motor.

best,
-greasy

do not put a PX motor into your smallie. that would ruin it.

best,
-greasy

judging from that photo, your exhaust will support a beast of a kit...

go big or go home...

best,
-greasy

I have a fity special which i used v100 casings with 50 gears(4 speed) primi primary and clutch and a 20mm carb dr 135 kit .I used the elctrics from a pk 50 to give electronic ignition.My wife drives the scoot and goes well keeping up when going to rallies 50-60 mph and no problems so far
Your 50 engine has lots of usable bits but i would suspect that the inlet port from the carb would be rather small and you would be better with 125 casings also i think the crank on the 50s is tiny and as mentioned previously would have to go if you wanted to use a kit
I have seen lots of casings and internals tiurning up on ebay in the uk
If i can help source you some bits let me know.
(Im not a dealer just a scooetr nut)

I also have a fifty special, and have stuck with the original casings with 110 Mallossi kit, Maz race cut crank, standard gearbox, but with Polini 4 plate clutch and gear up kit, Leo Vinci pipe, and 19/19 carb.

I am still messing about with the ignition at the moment, but I am getting close to just bunging the old points back on.

The PK casings are an improvement on the earlier V range, with a different crank, electronic ignition etc, and should take the 136 kit no problem. Or if you have money to spent one of the offerings from Falc or Quattrini!

rip out the lump and pop a rotax in

http://www.lambrettainnovation.co.uk/view_page.php?pid=23

50 cases are the same as 90, 100, and 125 cases. Only the crank and primary gears differ on the 50 from the rest. With a crank for a 90-125cc, you can put a 136cc on 50 cases.

Yes all the PK cases are the same, the earlier V50's like mine have a different crank (and the V70's). All the PK cases will enjoy the 136 kit, and even bigger. My next upgrade will be some PK cases, I just wanted to tune up the original motor for the fun of it. Mazzucchelli list a separate race crank for the V50 (AMT158), so it would be rude not to.

What's better about the PK cases aside from the 3-stud manifold allowing more porting and fewer air leaks? Aside from the ETS motor, I thought they were all the same.

The crank oil seal is 19mm on the V50, prim, and ET3, with a 20mm bearing. The PK's have a 20mm oil seal. The XL and ETS have 24mm oils seals and 25mm bearings.

Conversion seals and bearings are now available to put any crank into any set of casings, but they weren't when I built my motor. I could have put a prim crank into it, but at the time the only race ones were full circle for reed induction.

Interestingly all the extreme 54mm long stroke cranks for 140cc+ motors, are only available with 24/25 cones, ideally for use with the later casings.

I bought all my tuning parts in one go from Kegra racing years ago, and they were the best available for the V50 at the time. Smallframe tuning has come on a long way since then, and if I did it all again I would start with a set of PK XL cases.

You do know that there's bearings and seals are readily available to convert the standard smally cases to fit a ETS crank right? Bearing number is 6005 C3.

I'm pretty sure the XL cases are still 20/20. Standard PK cases are 20/19, and the XL2 and ETS are 25/24.

yep. that's why the only scoot to make it through the Dakar is PX

PX engine is the most thoroughly licked like cat's balls largeframe engine ever.
All in all px is the most convenient bike when speaking of easy-to-reach engine and areas, unlike pk and primmy where you have to be a skinny mod with bony arms to get to the carb for instance...

and btw pk50 engine is only 4 kilo lighter than px150

well end up with the lyrics))

the best and the most economic way to pimp up a 50 is a 102 kit
and a tuned exhaust, polini for smallframes par example

but in my not so humble opinion - 50cc tuning is a waste of money
that could be spent on buying...whatever

How silly of me, your right Max, all the pre XL PK50's are 19/20. Which would work with the Mazzucchelli AMT182 ET3 race crank.

Nothing wrong with the PX engine, but not in a smallframe.

The smallframe is a much better handling beast than the PX, which is why some many racers in europe tune them up. Bodging PX motors into smallframe should stay back in the eighties!

Thats put the cat among the pidgeons!

once nearly bought a smally with a 200 lump in it ...
took it for a blast but it braked (rear) when it went round a corner .. thought it must have had the cable snagged but when i pulled it it was loose..
took it back and undid the cable then tried again and it still did it .. very wierd

i know it has nowt to do with tuning but i thought id share ... id like to try another just to see how it handles