Polini head options

Thanks Curare, those settings are pretty much what I expected. I’ve just measured the piston clearance on the kit. is 0.003. I plan to hone to improve clearance to 0.004-0.0045… I have heard this will help reduce the chance of siezing?

Cheers nicegold90

…sorry the link for the photo is

…I must have made an error tipping ?¨!

Hi Curare, great picture, this is very nice as we can imagine more easily what you are doing or writing and what we need to do!!

This is really to continue


Thanks for the pictures Curare, very interesting. There sure is a big difference between the two heads. Do either of them require a 1.5mm gasket for use with the 60mm crank?

What sort of performance do the makers claim?

Cheers Nicegold90

I’ll run this set-up until the engine is run in, and then start to experiment.

From your advise I will try the W5 longstroke head, any maybe, while I wait for them to be available, the 2-2.5mm head gasket.



I am building a 207 polini engine with reed and longstroke.
I have PM head, SFK head, one head from Stoffi, and one Worb for longstroke, and also a Pinasco 213 head.
I am planning to try all these head wich some have very different shape (Stoffi in comparison with SFK for expample).
The engine is not ready yet, I think It will be finished in about a month. If you are not pressed live me your e-mail and I will contact you or write again in the forum.
I am not honing this one, I want personally experience in which percentage all the problem reported about this barrel are real or due to approximative set up.
Same problem people reported for the polini 177 kit that I didn’t personally experienced in my one, and it is not just bolt on. So let’s see…
I have just finished porting the cases if you are interested I could send pictures…

Hi Curare, you’re right, polini kits are cheap!

As for my question over the head gasket, sorry I was not clear, the head has been milled for a polini 208 WITH a 60mm crank, and, as I said, the advice of worb5 is that it will offfer 1.2mm of squish if fitted with no head gasket, and 1.7mm with a 5mm head gasket.

Sorry to have not been clear, can you now advise me on which squish clearance I should go for?

thanks for all your help, Nicegold90

By the way, I can see why you’re not keen to get outside. I was in europe for 2 weeks last month and could not belive how cold it was. I’m in New Zealand, where we can ride scooters all year round!

Can you get a double ticket???

Thanks Curare, very interesting to hear your experinece with the heads.

I will pass on your findings to the guys I know who run malossi. Where can someone buy a stoffi head?

I would also be interested to hear the result if you run the pinasco head on the polini.

I will have to wait until the worb5 longstroke heads come back into stock!

Meanwhile I finally got my engine back into the frame late last night, so will be heading home for first test ride at lunchtime.

I used the worb5 head for standard stroke, and added a 1.5mm gasket under the barrel. I also used a .5mm gasket under the head, just to be sure.

As for the flywheel. I used a standarrd PX elec start one, but removed the ring gear and had the flywheel machined to remove weight.

I’ll let you know how it runs.




thanks Mikke I am glad it could be of some use. As I said before it was not easy for me I am an electronic dinosaur.
I am trying to improve, to make it cleaner and posted the pictures on another address.


For Nicegold I added a picture where you can see two different head for P200. As you can see the shapes are really different.

Everynow and then I will add some other picture and when needed as Mikke said will be easierto show in a picture whenever it will be possible.

hello Nicegold,

yes I used the RZ right hand with different configurations, so I share my personal ridind experience not theoric.

In your case I would either alter the exhaust port, 2mm larger right and left and 1mm
higher and use the RZ right hand, or use a SIP exhaust or the RZ 2000 exhaust with standard barrell porting. Both of them are a little less loud then the RZ right.
Grounding, yes you will tend to touch the ground with a left exhaust but this will be an issue when riding fast cornering in two, but alone, with stiffer spring that you will need for track, it will be OK.

In your case, and for your need I would use with no doubt the follow:
Barrel porting standard, short 4th gear and SIP EVO.
And consider either a Mikuni or Keihin carb.

hello Nicegold,

not really much difference between EVO and Performance, but I will go for the Evo since not stainless and will last longer.

All the other attention are very OK but… I wouldn’t waste that money apart for honing. In case of need just a spare barrel would cost you more or less the same ammount.

As far as concern the carb size you could ear and read many different opinion and opposite opinion each one supported by the correct theory, but… for me go for a Keihin 28 or a Mikuni TMX 30. It is important. I tried I tried and tried to make the 24 or 26 better then the last two but… maybe I need the right theory but in pratical therm…goodbye baby, see you never again.


for the head you have bought you said is the worb5 for standard stroke. If you use .5 gasket is just to have less compression with 57mm stroke, but you are using longstroke so you have to use 1.5mm gasket.


it was not easy for me net.idiot to send some picture but at the end with the help of my lady SHE managed to do it.
You can see them at

This is an engine project for daily use so the engine won’t need to search the power at high rev, so absolutely power will be sacrified for engine tractability and caracter.
Notice that the inlet port for this kind of engine is way too large I could have made a smaller inlet for a different manifold but this one is to accomodate the new MMW2 manifold.

I hope these photo will be of some help.

Next one , within few month a no - compromise racing engine.

hello Nicegold,

I am glad the pictures have been of some help. I will post some others when I think I have something interesting or if somebody asks.
As far as concern the RZ right hand is one of the best exhaust out there in the market that I have tried. (Still not tried the vespadoctor beerace one, but time will come.)

But, I will try to be clear in few words:

Your set up : you are using a longstroke.
The power range with longstroke is effected and you will have a back shift of power pick (I hope it means something). So you will have more low- mid, mid. You won’t have more power, but that power will be avalable in another rpm range. Low-mid, mid range better, mid high more or less the same but high rpm and over rev will suffer in comparison with standard stroke.
The RZ right hand will do the same thing.
The combining result, (every engine is a combination of things, one good thing for one for another engine will not so good,) will be that you will have a very full engine that will pull like a train up to mid-high rev and that will run flat at high rev and with very little over- rev. To exagerate it will feel like there is a kind of high rev limiter.
So for your set up a better choice will be the RZ2000, or SIP either in EVO or in Performance guise. ( I know they are left hand) .

Of course you could alter the port of the barrel, but then low rpm will suffer etc…then with altered ports you could consider the use of the RZ right hand…you see you change one thing…

…I personally don’t like the option you are using: 1,5mm base gasket + 1mm head gasket for Polini 207…but try maybe you like it. It makes the polini more like a Malossi but at that point with this kind of power curve the Malossi 210 is better no doubt.

I prefer 2,5mm head gasket with an exhaust like SIP, we talked about it in comp. with RZ rh. (or worb5 head for longstroke).

The Stoffi head you can buy at Stoffi’s garage. You can search their net address on yahoo.

Yes next I will try, just for the hell of it, the Pinasco head.