Minarelli 50cc to 100cc Engine Upgrade & Tuning Project

[jonik]

Hi! Long time no see. I've been busy with car stuff, no time for scooters sadly. I've had my CPI Formula R for 12 years now with different setups. Here's newest videos with English subtitles:



It's pretty fast with 70cc sport setup but now I found cheap Minarelli 100cc engine taken from Yamaha Neos, everything still intact. Does someone have info of those? Very limited supply of tuning parts, not sure what to get. 124cc Malossi is biggest bore cylinder I've found but 120cc Airsal looks much better and comes with matching cylinder head. Tecnigas RS2 is the highest revving exhaust I've wound so far made for 100cc. Not sure would 70cc exhaust work with 120cc engine. I'm aiming for +10krpm and 120km/h (75mph) top speed. Stock 7000rpm and 90km/h (55mph) I've heard so it's definitely slower than my current setup.

Now it's winter in here so good time for some engine tuning and videos of course

Here's my variator modification video how I got my 50cc setups top speed from 80km/h (50mph) to 92km/h (57mph):


Greetings From Finland
JoniK

[aeroxbud]

Nice work.
We have the Neos 100 here, but not popular. I think it has the same engine as the 100cc Aerox. Not a lot of tuning parts but perhaps our Aerox 100 expert pete130 might have some ideas.

[jonik]

Hi!

Got the engine yesterday, Yamaha 4VP10




Now it's time for parts hunt. It looks like basic 50cc so almost everything should fit; variator, exhaust etc. Seller said the top speed was 80-90km/h so it's what I expected

[190mech]

Crankshaft flywheel taper is the same as a 90cc engine,variator splines are 90cc also,but 6mm longer,entire CVT is larger OD with a longer belt too..Piston pin is 13mm and cylinder stud pattern is wider than the 50/90cc stuff..
As said,pete130 has a build thread here with a good looking aluminum cylinder;
49ccscoot.proboards.com/thread/20450/132cc-bigbore-stroker-project

[jonik]

Okay, that helps a lot. Nice to know that the variator is better than on 50cc. Of course I have to modify it

I already have Keihin 28mm PWK carb so I'll use it and start with Yasuni C16 exhaust. I'm still thinking about the cylinder kit. Original cylinder head is very bad for power or at least needs massive modifying, easier to buy cylinder kit with head. Ignition is another thing, maybe stator rotating is enough.

[jonik]

Now I'm trying to choose which cylinder kit to get.

Naraku/China 113cc
+cheap
-without head

Cylinder kit Malossi 124cc
+124cc
-pricey
-without head

Airsal Sport 117cc
+aluminium
+with head

These are all I could find. So I think I'm going with Airsal because the original head is one of the worst I've seen with the odd wavy shape 😃

[190mech]

Yep,you will want a modern squish head or have the stock head TIG welded up and machined to proper dimensions($$$)..

[jonik]

Here's a live teardown video if someone is interested, quality is only 480p so not the best. Better videos coming soon..


What I found is that I would need to raise the cylinder 2-3mm and modify the head to make it usable. And it already had Malossi Multivar installed, looked identical to Malossi Overrange for 50cc engine so it's definitely oversized. But sadly rear pulley is same size as 50cc and that's why the belt is same too. Lyckily I still had my Malossi Overrange rear pylley and belt. So now I have full Overrange variator

[jonik]

New videos with English subtitles

28mm PWK install:


Malossi variator:

[jonik]

And ordered some missing pieces

753499 Intake funnel Polini connection 50,5mm for PWK carburettor
743614 Cylinder Airsal Sport 117ccm Yamaha BWs, Aerox 100 2-stroke reed valve assy racing for Minarelli horizontal
749068 clutch adjustable Evolution Racing 110mm for CPI, Keeway, Morini, Derbi, Minarelli 100

[jonik]

Parts arrived. Cylinder looks good, much better than original. Exhaust port timing is only about 170 degrees so I may have to do some magic with Dremel

[jonik]

New videos





Installed the cylinder after some modifying

[jonik]

I checked exhaust and transfer port durations:
Exhaust 187°
Transfers 123°
Blowdown: (187-123)/2 = 32°

Transfer duration is a bit low to my liking, exhaust is ok, blowdown is optimal. I'm going to raise the cylinder a bit with thicker rear gasket and lower the head 1-2mm. We will see how it goes

[jonik]

And now more videos

I fixed transfer duration with extra rear gasket and lowered the cylinder head


Then I advanced ignition timing by turning stator anticlockwise


And then I fitted Yasuni C16 City exhaust

[jonik]

And now it's running


Easily the fastest setup I've driven so far.

Had to buy speedo and tachometer for tuning purposes. I bought GPS speedometer from Ebay so I don't need to play with magnets or cable, works great. Found cheap tachometer with backlight as well, works like a charm