50cc Cylinder and piston tunen

[Piet30Topic starterBerichten: 1082]

Hi,
I have tried to tune a 38,4mm original Vespa cycinder and a 38,4mm L-piston from JMPB.

Maybe you could share me some of your thoughts and opinions about the result and what I could improve. 😉

The beginning is drilling two holes in the piston between the piston ring slit

Then marking the positions of the piston holes to the cylinder

Drill a hole in the cylinder

And two small holes right and left side from cylinder screwing

Then milling the original channels deeper and two new channels

and grinding channels into the cylinder bore

Also milling the inner diameter of the outlet to 20mm

then opening the outlet window

reducing the cylinder hight by 1,5mm on top and using a 1,5mm thick cylinder feet gasket

The following angles were found out:

> Outlet timing —————-> 150°
> Channel timing—————-> 110°
> outlet open before channel—-> 20°
> outlet inner diameter———> 20mm
> outlet port map—————> 27mm X 17mm
> outlet hight to deck———-> 29mm

What are your thoughts?

[TimoO_DonateurBerichten: 3971]

Can you post some more pictures of your outlet channel? Then we can see what adjustments you made and could be made for better performance.

I think your outlet timing could be a bit higher (like 160), but my question is what kind of performance you’re looking at and what you’re going to do with the rest of the engine (like carburettor, transmission etc.)

[Piet30Topic starterBerichten: 1082]

it should not be a high performance cylinder for 1200 RPM or so.

Should run fast with much power on a standard tuned Vespa block with 13 carb and Gianelli City exhaust

http://www.jmpb.nl/store/index.php?act=viewProd&productId=1013

try to make some outlet pics later 😉

[tnerualBijdragerBerichten: 1189]

dude! ****well done****

Could you explain me how you did the exhaust port?

and a precise manual to make some booster ports???

nice dude!

[Piet30Topic starterBerichten: 1082]

ok, here a pic from the outlet

and the tools with what I did the outlet window in the bore.

The big diameter for the window width and the smaller one for the hight

[ronreniersBijdragerBerichten: 287]

nice job!!! it looks very good!!!
could you explain it more clearly how you did all those things?
if you do so it’s a bit easier for me (and others) to tune your way.
but again you did a very good job!!!

[tnerualBijdragerBerichten: 1189]

yes i agree with ronreniers.. Thanks a lot for extra pictures,

[Piet30Topic starterBerichten: 1082]

ok, have made some more detail pics.

start with the holes in the piston that is basic for the cylinder

start milling the holes

milling the channels

pre milling the outlet to 20mm in tube area. Open the inner curve with a big grinding stone

grinding rest of big channels

and grinding round and V-port channel

grind inner channels with a soft grinder in right diameter

that how to grind the outlat window

[ronreniersBijdragerBerichten: 287]

thank you for the details.

[tnerualBijdragerBerichten: 1189]

verdammt danke 😉

[Vespa Ciao!]

Kan iemand mij dit vertalen van wat piet30 heeft gepost, misschien snap ik het dan wat beter. Ik ben niet zo goed in engels

[tnerualBijdragerBerichten: 1189]

de overvloedige fotos zeggen meer dan genoeg 😉

[ritzeBijdragerBerichten: 3421]

haha you stole my idea 😛

it looks great man cant wait when it is on your vespa 😛

De budget beun tjoener: geen geld is te duur of het werkt nog niet
Link naar Mijn collectie / Projecten.

[pepkoDonateurBerichten: 2826]

can’t you make an “How To” of this? i think it will be very usefull 😛

[LeovinceBijdragerBerichten: 1148]

Since i have some dremel tools and an extra 38,2 original cilinder, i can do this by myself too:) A how-to will be nice to have…

[Gebruiker]

<i class="fa fa-comments-o" aria-hidden="true" style="font-size: 20px;"></i>