Hi, I’m considering building an engine suitable for reliable touring, hopefully with quite a high crusing speed, however externally I want the engine to look standard.
I have some experience with two stroke tuning (but not with Vespas) and so I’m asking for help with what works and what doesn’t.
I’m considering kit barrell, mallossi, polini (using GS piston) or pinasco, not sure?
Maybe casings welded for bigger transfers (I can do this myself so cost isn’t a question).
Possibly stroked out to 60mm (maybe more!)
Using premix system. With 24mm maybe 26mm carb.
However I want to use the standard exhaust system.
Can anyone guide me in the right direction.
so I think it is about a 200 engine.
I love the Polini, but it is true that many had piston problem with it.
With longstroke and a Worb5 head with 2,5mm squish it works beautifully.
But I have to say that with a Pinasco you can make a fast touring thing too.
With a longstroke and worked head or 1,5mm head gasket, an rh2000 exhaust, PK flywheel and 23/65 you can see the tacho go after 120. (no short 4th needed.)
26 juank told you what is all about,
but be carefull with the 24/24 too. It seams to be around many that will give you problems. So if you buy one and the carb set up is not responding think the carb could be the cause EVEN THOUGH IT IS NEW.
The main problem is the float needl not working as should even though it looks in perfect working state.
I will try to discover why when have some spare time.
Curare has loads more experience than me with long stroke motors but if you want high speed touring I would put the packer at the base. This should allow the motor to make power at higher revs. With the set up you should also consider up gearing. My bike seems to be making peak power at around 6000rpm. the std exhaust creates power lower down which will limit the revs the bike can make as well. If it was me I wouldn’t use the 60mm crank simply because the mazzechelis are not as strong as the genuine Vespa cranks and touring is all about reliabilty.
Oh yeah,forgot to add that Spaco 26’s are complete crap.Stick with your standard carb.
I’m guessing that’ll be just a little less reliable than the Mazzuccelli crank!
So am I best to cut and stroke the standard crank?
If so who sells the best eccentric pin conversion, and what sort of inlet timing would be recomended?
I don’t think you need to stroke the crank. Others may disagree but the best reason for stroking the crank is extra torque which the polini has bundles of any way. You will need to alter the crank web for inlet timing but if it was me I’d keep the std rod.
things are becoming clearer now.
So it looks as if I will be using standard carb and exhaust.
I’m now torn between using a mallossi barrel, stroked or a polini as I’d like to make full use of the available transfer area, however I’m not keen on the gransport single ring for touring.
Do I try the mallossi barrel shortened in the search for lower down power?
Can I bore out my dellorto 24 to 26mm?
Is there any advantage in welding up the crank case to enlarge the transfer ports further?
What do you think??
I know thats no help but i couldn’t resist posting it[:D]
Thankyou all, this is getting interesting!!
from what you have said this looks to be the spec I will follow:
P200 crankcasing ported to match the kit transfers, as no one seems to rate the need for larger ports.
A 60mm off the shelf crankshaft, as no one has mentioned any larger strokes.
A pollini 207 barrel mated with either a GS or possibly Mallossi piston, more research to do there I think. Exhaust port will be widened according to the spec of the piston I go for and the whole engine will be gas flowed.
Standard exhaust as originally planned.
Standard 24/24 carb though I suspect that an original Dellorto one rather than a new Spaco version (or has this always been a problem with this carb Curare?).
Head wise I think that a large combustion chamber with a tighter squish band makes best sense (about 1.5mm) or has this been shown not to work?
All this throws up two more questions related to the long stroke crank:
Is there no need to cut any further from the inlet timing, with the Mazzuchelli 60mm crank?
And as I’m expecting to need a packing plate at either top or bottom of the cylinder which will show greatest improvement!
Thanks again for your help.
Ive done 2000 miles on my polini with the gs piston. I’ve had no problems so far. I intend to check ring wear this week but there are no indications that it has worn excessively. If you use this kit with a std exhaust I would suggest up gearing it for high spped touring(23/64) and then I think it will work pretty well. There is an amazing amount of useable torque right where you need it which means problems with headwinds hills etc are a thing of the past. You will have to do a massive amount of work to a malossi to make it a decent tourer and as Juan says its not designed for that any way. He is also right about the 26mm carbs-steer well clear. The polini does need a bit of work to start with. You need to run a huge piston to bore clearance mine was .006" and a low comp head. Mine measures 34ml with the squish. Mine also has a wider exhaust port and generally all the sharp edges tidied up. Done lots of motorway miles now and is quite happy being held at full throttle for long periods between fuel stops. I’m running a reedvalve on mine(it used to be a malossi) but I would recommend if its serious touring to get a long range tank with fuel pump and premix. You can run autolube but I was using a 4% mixture for fast motorway use. Hope this is of use
Just to throw another option into the equasion you could try this if you’re unsure about the single ring set up.
Yes,it is very expensive but the Malossi piston is as tough as old boots and the Polossi conversion is very popular in Germany and seems to be finding more fans by the week elsewhere.
Other than that seek out a siezed 207 kit and buy your own Malossi piston and seek advice from Diablo and Curare who’ve forgotten more than I’ll ever know.
Firstly the Malossi is not a touring kit,it makes it’s power too far up to be considered as one.However,it may be more suitable with a 60mm crank and a machined 'head.I haven’t treied it though.
Initial reports on the Grand Sport Polini are very favourable.I’ll be building one the next time around.
The Pinasco is a fine,grunty kit especially in long stroke form but feeds a single transfer as per the standard 200 so it’ll always be limited.
You pays your money…