worb5 crank

k so heres the set up. LML 150, pinasco top end ports matched and minor porting inlets flowed and exaust widened but not raised- simonini pipe- vortex 28 carb( for those of you who dont know about these they are a 24/24 opened up with a velocity stack built on top.) soon to have a cosa banded clutch and a new set of opened up boysen RAD dual stage style reeds and cage. the engine has 4000 miles on it and im thinking of a upgear so if the cases are split why not put in a new crank and bearings. I was looking at the Worb5 thats made for reed valves. any advice. most riding is high speed city and freeway. thanks in advance. Ty

ciao curare!!

thanks curare,
I know that I must extend the original inlet port but I wanted to know if it were necessary to create a kind of channel in the crankc for the immission of the fuel???

Thanks a lot Curare.
I thought the Worb crank would give a big improvement, but I see it is not like that on the engine I intend to do, I check the budget and see if I can afford it or just stick to the original crank (not longstroke)…

I know this is not my post but last thing…
is the longstroke better for travelling?


thanks curare and sorry for my bad english…(I’m Italian)
I will limit me to extend only the original inlet port!!

for Dark-Side,

since if you are using a special lip you could fit a reed block without any inlet port opening (the shoulder of the cranck that regulate the rotative immission is completely cut away). But give a look at the size of the original inlet port…

So the answer to your question is: yes you can mount a special lip and reed with no crank mod. , but it would not work at its best.

with a special lip I haven’t reported any advantages with the making of the inside fuel „channels“.


the Worb5 crancks special lip, are well made and balanced, but in a set up like the one you have you would not have a major improvement if you have already opened the inlet port wider then the crank half shoulder.
The Worb5 special lip gives you a noticeble improvement in engine that rev. high, like the Malossi or Polini with altered porting, or could give you something more only if you rise your barrel output port.

If you are after something more this is what you could do:

flat the top barrel base, so you will get out of the way the recessed sit for the pinasco head.
Put a Polini 177 head.
You could also use a Polini 177 piston and slight alter the port of your barrel rising the otput port of 1,5mm.
At this point you will have a Pinasco - Polini and should get about 2-3hp more that would not get just changing your crank.

If you do this job, it is very important you retard your time to 18 degree and to use the correct spark grade.

If you want a little more put also a PK flywheel modified for PX.

(this post only to receive notification…)

bump thanks

…sorry for my english,

I am Italian too.

for Geoturbo,

the longstroke is surely better for travelling. It allows you to use longer gearing, the engine will have more torque, so you will reach your cruising speed at lower rpm.

in the malossi website is written that when adopting these reed carburettor kit it is essential to modify the engine crankcase…
so if I use the Worb5 crancks special lip I must do the same job??

Hi typaco23,
It is a bummer when nobody replies,isn’t it?

Personally I don’t know ,but what I’ve read Worb 5 do kick ass engines so why don’t you email Dr.Worb himself he’s always answered my questions.

Cheers Paul

thanks. thats great info i’ve been thinking about doing that to the top end.

Original von curare: the Worb5 crancks special lip, are well made and balanced, but in a set up like the one you have you would not have a major improvement if you have already opened the inlet port wider then the crank half shoulder.

Hi, this thing is giving me some thoughts…
I’m planning to make a Polini 177 with reed intake and was thinking about the Worb 5 special lip (longstroke). Now, except for the longstroke, the performance\efficiency with the Worb 5 crank or the standard crank on a widened intake port is the same?!


hello geoturbo,

I said in a set up like the one typaco23 has, so we are talking about Pinasco 177.

The Polini 177 will feel minor improvement, more in the field of vibration that of power gain. If you are going to use a longstroke you don’t have a lot a choice except Mazzucchelli, but most of the time the worb special lip are better balanced and a better balanced cranck is always better to use.
The Polini 177 is already in its standard stroke version not a kit that develop its power curve in the high rpm, with the use of a longstroke the curve is going to be shifted a little back but since the better torque you are going to be able to use well the 23/65 gearing. With the 57mm stroke I find the 23/65 gearing a little too long expecially in combination with expansion exhausts.
Special lips cranks give noticeble differences in set up that rev higher. You could always alter the porting of your polini 177…