Vespa 210 long stroke

Hi evryone Ive aquired a long stroke crank and have a spare malossi 210 kit so thought i’d build a motor. Never done a long stroke motor before so any advice/pitfalls most welcome. Curare I know you are experienced with these so your knowledge is most welcome!

I’m in the same boat,I’m intrested in doing this in the future.

However,I’m told the Mazz crank’s are a bit shite and really need splitting and fitting with a decent bearing to be of real use.

I admit this is hearsay as I’ve never used a Mazz personally but that did come from someone I respect and trust.

No connection but…

…I read Harry is doing a 170 conversion for the Polini T5 kit,do you know what piston he uses Diablo?

Yeah Diablo,that’s me.

A bloody amature.;D

Cheers Nicey,was that the T5?

In answer to you Juan I don’t think the pistons are that expensive. Like I say Harry gets them working really well but I don’t think better than the malossi. If youv’e got old kits its definitely woth doing. Harry is a top bloke who I bother with stupid questions all the time. He’s forgotton more than I will ever know but is very free with information and advice. He operates out of Grand Prix now and can be contacted there if your thinking of doing a 170.

Cheers Diablo.[H]

What I think Curare means(and please correct me if I’m wrong) is the combustion chamber need’s increased to accomadate the longer stroke-i.e.;milled out,but the actual squish will still be around the 1.3-1.1 area.

But that’s a total guess.[:D]

Yeah mazz are shite. I get all my cranks done by Harry Barlow. He recomends at least welding the pin but i think I want to source a rod and bearing. Harry has also supplied me with a packer for the base but I’m also unsure if this way is best.


The only reason I’m asking is because I have a shagged Polini and standard barrel in the garage and am considering my option’s for them.Normally I’d just go Malossi.

It sounded like Harry’s conversion performed well at the Nuremburg ring but a Wisco piston is likely to cost more than a full Malossi kit anyway.[?[]

No problem,when we get the detail’s for next year I’ll post them up here.

Or ask FB on scooterboy world if you can join the gang.The details are in the protected forum.[;)]

sure will do

Yeah it was a T5 but not the 170 conversion just the 152. To be honest I’ve not heard a sausage about the 170, he’s never mentioned it. I know he did a T5 200 and a 225 in his sprinter but no 170.

… and this despite the problems, since obviusly there are some problems using longstroke with barrels which porting are optimized for a different stroke.

The piston will go lower and this, expecially related to the low lip of the exhaust port will expose to or increase the risk of
short circuit. It means that part of the fresh gases will by pass or will pass over the burned ones going directly out from the exhaust port. This will give you the impression you are running rich when you are running right, and to set the carb right is more difficult.
And of course it is not good for efficiency.
And the cilinder will not be cleaned as it should.

You could cure this if you give more angle to the lateral ports

Another thing is that it will change the Blow down time. The pressure inside the cilinder will increase (increase the power stroke)but not in the cranckcase. (The optimum is when the two pressure are almost equivalent). This will cause the cilinder to suck more mix then is pushed and then it won’t get filled as it should.
This could be cured to but again from who has experience.

For this reasons, and others(that is long to explain here), it is almost necessary the use of reeds with longstroke if not it will be very difficult to set it up.

For the squish:

with the increase of stroke you should use an head gasket of 1,5mm, or you can have it machined in a way that the head gasket is „included in the squish“ so the squish that you have (at least 1mm + another 1,5mm for the extra piston travel)
I hope I made myself understood.

[:D] No problem Curare,sorry.

I had a Polini done by Harry, standard carb and huge main jet, runs a bit rich and the carbon build up is horrendous but not a problem.
So far its done over 4000 miles including Holland twice and not even a hint of a seize or breakdown despite being thrashed.

(Apart from when my stator stopped working!)

He used a Suzuki piston in mine btw.

So why do you need to use such a large squish. I know this to be true just don’t know why.

I’d also be intrested in knowing if a spacer under the barrel or a machined out 'head is the best way to go?

Curare,our Italian friend,throw some light onto this for us please.

Thanks lads much food for thought. It will be a spare engine so plenty of time to experiment. Juank are you the same geeza as on scooterboyworld forum?

Cool pleased to meet ya. Was hoping to do the cannonball this year but it hasn’t worked out. Defo for next year though

Cheers Diablo.[H]