Minarelli high hp Setup mistake - how to resolve

[fips]

Aloha guys and greetings from germany

This is my planned minarelli setup:

Minarelli engine LC (running in a Aprilia SR50 LC like Stealth/Netscaper...)

Italkit 70ccm Alu 12mm(mainly because i had it when i was 16 and it ran perfect, and for nostalgic reasons)

5mm Spacer Polini Evo, with fitting studs

Yasuni C16 (no city, the real one)

Top Performance 85mm connecting rod and 44mm stroke

MVT DD ingnition

Top Performance Vforce membrane carbon

Stage6 spacer for carb over reat tire, 35mm adapter for carb, rewelded subframe for aerox

Keihin PWK 24mm Carb with open air filtre

Top Performance Variomatik

Top Performance Belt

Polini Evo 3G clutch 105mm , strong springs

Top Performance 24-28kg spring for converter

NGK EG9R Sparkplug

standard gears, standard converter, standard clutch bell, standard variomatik cover, Standart water pump

Since in germany it is not allowed to drive like this on the road, i will not drive with it for hours and only very randomly.

In the ~ 2000´s when i drove my scooter as teenager, I had a midrace setup very close to the one I´m planning on now.

Of course as teenager we never had the money or time to work on the scooter longer, because we needed it on a daily base (as we dont live in a city).

So my old setup was

Italkit 70ccm 10mm, Top Performance stroker crankshaft for AC Models 40mm stroke with 80mm connecting rod, 17,5mm dellorto PHBN, Airboxe opened with Malossi filter mat, Polini carbon membrane, Top Performance CDI Yellow with 3° adapter, Top Performance Nardo (basically stock) Vario, Polini 3G Clutch, Top Performance Belt, 15% Polini Spring for converter, Tecnigas Next (shortly Polini ForRace). (Stock ignition, stock gears, stock converter, stock water pump)

It ran absolutely fine with lots of torque compared to other scooters that relied more on rpm.

Anyhow... i think some of you already saw my fuqqup in the new setup.
At some point I guess I had too much whiskeys and though that the stock stroke of the minarelli is 43mm and with my 44mm crankshaft I would have a +1mm one.

Yesterday I watched Brents video about the MVT DD because I was wondering how to set it up for 44mm stroke.

When he said "so since the standard stroke of minarelli is 39mm..." I realized my fault....

Now to my problem:

I already bought all parts.The C16 is already used.

The case is already trenched and ported for the Italkit+Spacer.

The crankcase is drilled out to 76,5-77mm for the 44m stroke crankshaft.

How do i resolve this.

a) Trying to trade my 44/85mm crankshaft against the 40/85mm one. Run the Italkit+Spacer as planned.

BUT lose power due to 77mm crank-case volume change. Anyone any idea how bad that will be ?

b) Trying to trade my italkit (i don´t want to trade it actually, i love the brand), buy the TPR 86ccm and run it.

BUT will that even run good with a yasuni c16? I dont have money for another exhaust.

I heard the food of the cylinder is not as aggressive as the Italkit/Polini Evo, so my porting will be off.

I will have to create a chamfer or so, to not have a bad egde from block to cylinder.

What would you guys do?

And regarding the italkit. I don´t know if you know that brand or cylinder.
The Italkit cylinders are made by "Gilardoni" and the rumors says that the Italkit 70ccm is some kind of Polini Evo 1 clone.

I also like it becausee ~80% of all scooters I see run a Stage6 MK2 oder MK2 ported.

I think its boring to be another one of those, even if the cylinder may be a bit better (especially when ported).

[Lucass2T]

Gilardoni is a foundry where cylinders are cast. Polini and Italkit both are customers at the Gilardoni plant. You can see the letters EVG casted in the products that leave the Gilardoni plant. They are great products.

Not sure what your actual problem is regarding the crank/cylinder combo. But 43mm cranks work with the Gilardoni/Italkit 80cc cylinders, Athena 80cc kit and every other 43mm stroke cylinders. Swap in a standard stroke crank or buy a 43mm stroke cylinder. Since you're in Germany theres plenty and plenty of choice.

[fips]

Oct 17, 2022 0:04:37 GMT -5 Lucass2T said:

Not sure what your actual problem is regarding the crank/cylinder combo. But 43mm cranks work with the Gilardoni/Italkit 80cc cylinders, Athena 80cc kit and every other 43mm stroke cylinders. Swap in a standard stroke crank or buy a 43mm stroke cylinder. Since you're in Germany theres plenty and plenty of choice.

The Problem is that the Italkit 70ccm, that I have bought, does not run with 44mm stroke (+5mm) and 85mm connecting rod (+5mm).

In total this combo would lift the Italkit 10mm away from the motorblock.

I think timings and everything else would be way off.

I never heared of a Italkit 80ccm. The only ones i could find are for AM6 Minarelli Mopeds (those cross bikes). I run a scooter (Aprilia SR50). I also dont find a 43mm crankshaft for my minarelli block. Can you send me links to that ?

I don´t want to buy a lot of additional parts, since I already put some money in the parts liing arround here.

I would love to hear from someone running a TPR 86 with a yasuni C16.

I would love to hear from someone who did a build with a standard crankshaft, after milling the motor block to 76,5-77mm for the big 44m crankshaft.How much negative impact has it on performance?

Sorry if its hard to understand, my english skillz are limited ;-)

[Lucass2T]

Timings would end up waaay too high.
Therefore switch to a stock stroke crank or look for a cylinder designed 43 or 44mm stroke. Gilardoni makes a 43mm stroke cylinder for minarelli horizontal. Athena too and Simonini carries a kit for 44mm stroke. Do some googling around and you'll find plenty of choices. The German and Dutch scooter scene and its availablity of aftermarket parts are very identical so it shouldnt be too hard.

[repherence2]

Oct 17, 2022 5:29:42 GMT -5 fips said:

Oct 17, 2022 0:04:37 GMT -5 Lucass2T said:

The Problem is that the Italkit 70ccm, that I have bought, does not run with 44mm stroke (+5mm) and 85mm connecting rod (+5mm).

In total this combo would lift the Italkit 10mm away from the motorblock.

I think timings and everything else would be way off.

the way i see it, if you were willing to put in the work, that would be a KILLER full stroker engine.  it would be just a tad over "Square Bore", which some have said is optimal.  it would be 47mm bore x 49mm stroke.

"...timings and everything else would be way off,"  that is true, but if you have the skill and will, you could modify the ports.

i would imagine that you set the bore to a height where the transfer port duration is good.  from there i would port the exhaust port upward to a suitable/target RPM range, and port the transfer ports downward.  i think porting downward on transfer ports do less harm that porting upward on transfer ports because you do not change the roof angle.  get one more of those "5mm Spacer Polini Evo,"  that you have on your list and you could have it machined/milled down to the height that is appropriate for the transfer port duration that you seek to make the Italkit perform how you like it (Blowdown).  it may involve stacking some head gaskets too or making a custom head gasket.

my imagination could be totally wrong, but the way i see it, instead of being "boring" like the ported stage6 bores you describe, a square bore full stroker minarelli would be very intense with your c16.

if i were you, i would put in the work to mock it up.  you will never know if it is workable until you put a degree wheel (or 360* protractor taped to cooling fan) on it to check the durations of the ports.  but that's just me, i do not like "boring" too.

here in Hawaii, guys run "ministroker" cranks with Polini Corsa bores on the Honda based 2 stroke engines.  ministrokers are simply cranks that have a longer stroke than the stock crank and most do not require machining of the case.  they stack base gaskets to make it work and achieve the port timings.

[titiz67]

very interesting topic,
Lower stroke than mounted bore in fast revs promotes power
Stroke equal to the bore compromise between mounted in max revs and max torque.
Longer stroke at bore leverage promotes torque.
We can by modifying the diagrams change its behavior
If you keep the parts you have:
47 bore and 50 stroke (86cc) with power oriented diagrams.
We can have a naturally torquey engine and some elongation.
Or normally we have:
Bore 47stroke of 40 (69cc) we are power oriented which are generally already for our small very torquey machines.
And I just thought about your problem of 10mm too high,
you can play on the piston, I'm thinking of a piston from a Peugeot speedake in 47.
I would take a photo because the axis is 12 but different heights, it is lower but I don't know how much.
If the piston solution works, you wouldn't have to put a 10 mm wedge.
I like that idea, but it involves a bit of metrology and testing and informations sourcing.

[titiz67]

I measured the pistons and I would like to inform you that these are 40 mm diameter pistons, therefore original. And between the piston pin and the top of the piston and 4 mm. It also makes me want to do a hybrid editing of the genre.

[titiz67]

Easier the piston of this kit: Simonini 80cc 47.5 x 44 .
or this one Airsal 80cc 47.5x45.

[brappotuning]

Oct 16, 2022 5:51:39 GMT -5 fips said:

Aloha guys and greetings from germany

This is my planned minarelli setup:

Minarelli engine LC (running in a Aprilia SR50 LC like Stealth/Netscaper...)

Italkit 70ccm Alu 12mm(mainly because i had it when i was 16 and it ran perfect, and for nostalgic reasons)

5mm Spacer Polini Evo, with fitting studs

Yasuni C16 (no city, the real one)

Top Performance 85mm connecting rod and 44mm stroke

MVT DD ingnition

Top Performance Vforce membrane carbon

Stage6 spacer for carb over reat tire, 35mm adapter for carb, rewelded subframe for aerox

Keihin PWK 24mm Carb with open air filtre

Top Performance Variomatik

Top Performance Belt

Polini Evo 3G clutch 105mm , strong springs

Top Performance 24-28kg spring for converter

NGK EG9R Sparkplug

standard gears, standard converter, standard clutch bell, standard variomatik cover, Standart water pump

Since in germany it is not allowed to drive like this on the road, i will not drive with it for hours and only very randomly.

In the ~ 2000´s when i drove my scooter as teenager, I had a midrace setup very close to the one I´m planning on now.

Of course as teenager we never had the money or time to work on the scooter longer, because we needed it on a daily base (as we dont live in a city).

So my old setup was

Italkit 70ccm 10mm, Top Performance stroker crankshaft for AC Models 40mm stroke with 80mm connecting rod, 17,5mm dellorto PHBN, Airboxe opened with Malossi filter mat, Polini carbon membrane, Top Performance CDI Yellow with 3° adapter, Top Performance Nardo (basically stock) Vario, Polini 3G Clutch, Top Performance Belt, 15% Polini Spring for converter, Tecnigas Next (shortly Polini ForRace). (Stock ignition, stock gears, stock converter, stock water pump)

It ran absolutely fine with lots of torque compared to other scooters that relied more on rpm.

Anyhow... i think some of you already saw my fuqqup in the new setup.
At some point I guess I had too much whiskeys and though that the stock stroke of the minarelli is 43mm and with my 44mm crankshaft I would have a +1mm one.

Yesterday I watched Brents video about the MVT DD because I was wondering how to set it up for 44mm stroke.

When he said "so since the standard stroke of minarelli is 39mm..." I realized my fault....

Now to my problem:

I already bought all parts.The C16 is already used.

The case is already trenched and ported for the Italkit+Spacer.

The crankcase is drilled out to 76,5-77mm for the 44m stroke crankshaft.

How do i resolve this.

a) Trying to trade my 44/85mm crankshaft against the 40/85mm one. Run the Italkit+Spacer as planned.

BUT lose power due to 77mm crank-case volume change. Anyone any idea how bad that will be ?

b) Trying to trade my italkit (i don´t want to trade it actually, i love the brand), buy the TPR 86ccm and run it.

BUT will that even run good with a yasuni c16? I dont have money for another exhaust.

I heard the food of the cylinder is not as aggressive as the Italkit/Polini Evo, so my porting will be off.

I will have to create a chamfer or so, to not have a bad egde from block to cylinder.

What would you guys do?

And regarding the italkit. I don´t know if you know that brand or cylinder.
The Italkit cylinders are made by "Gilardoni" and the rumors says that the Italkit 70ccm is some kind of Polini Evo 1 clone.

I also like it becausee ~80% of all scooters I see run a Stage6 MK2 oder MK2 ported.

I think its boring to be another one of those, even if the cylinder may be a bit better (especially when ported).

Hello , i am kinda new to this forum (even tho i am registered for some time already)

How is it going with the italkit?
Is the cylinder worth it ?

Cause i bought the italkit pack witch contains:
Italkit cylinder [47.6] 2 part head
Crankshaft [stroke 43] [conrod 85mm]
(Which has to be used with 5mm spacer)

Thanks

I am gonna run it with :
Ported crankcase
Stage6 vhst 28
Malossi e15 airfilter
Stage6 intake manifold
Malossi vl14
Malossi 5mm reed valve spacer
Roost 77 exhaust
MVT DD inner rotor ignition
Stage6 oversize variator
Stage6 torque control mk2 clutch
Stage6 wing cooler clutch bell
Malossi 13/44 primary gears
I also have Malossi 14/43 gears if needed
Polini gearbox cover
Polini variator cover
Probably electric water pump, for now i have the Stage6 SSP one
RPG radiator