Evolution SR2

[fsvaasam]

Did some boost ports too, like reed valve engines have. Cannot make them very big or can puncture cylinder wall.

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[mifatwin]

Das englische ist mir gerade zu kompliziert.
Aber die Bilder sprechen für sich! Gute Arbeit!

[Paulisch]

Meine fresse ist das eine Waffe

[SR2_Berlin]

This is by far the most advanced SR2 modification i have ever seen!
I like it also original, but i like also modifications like these very much.
How much has the performance improved?

[fsvaasam]

It goes 53-54 Km/h on flat surface and 14 front sprocket. Its enough speed with this original engine. All modifications aiming for good torque, which you have to have with only two speed gearbox.
It feels very strong when cold/half warm engine, but now im losing torque when engine is hot. Especially after some flat out running.
I think i have too much compression ratio and im planning to drop some and also noticed i have blow by thru piston rings. It warms up intake air in cranckcase. Pistonrings feels like not compressing enough, so im looking some replacement piston for this aplication. Any hints for this? Thinner pistonrings preferred. Like new engines have.
Here you can see sign of blow by behind piston rings. Is it normal with stock engines?

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[fsvaasam]

You can see also from piston crown that its catching cylinder wall. Too much heat expansion here.

[SR2_Berlin]

I thought Finland is almost completely flat
So i expected you will use a 16 or 17 front sprocket! Except you like acceleration more than speed...
Blow by behind the piston rings happens. With my previous used engine i drove long time with this minimal blow by.
If you want to reduce the compression you could try a Gasket like this. Originally there is no gasket, but a gasket will lower the compression a little bit.

[fsvaasam]

I think +50Km/h is good speed for otherwise standard moped. Like to keep up with traffic in town driving. With two speeds and low torq it feels like someone drives you over from behind when you are leaving traffic lights
You are right with this gasket, i might try it. Ive been also thinking to make 1mm gasket between block and cylinder. It lowers compression ratio and it also changes port timing, so it would be interesting to see what happends with this engine when do so.
Usually it makes engine produce power some higher rpm, so i dont thing its too good idea when aiming for torque.
My other SR2 with Minarelli engine, its different kind of animal. Fairly deacent modifications this engine you can run +80Km/h easily. Power band is high, but you can get away from bad torque with six speeds.

[fsvaasam]

Im sorry to input simson unrelated pics here on this site, but as some one here said you like pics, i send some more my projects. Colour theme is ispired from SR2 so it will fit in this continue, i guess Brush painted budget trainee bike for kids.

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[fsvaasam]

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[fsvaasam]

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[fsvaasam]

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[fsvaasam]

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[Otto]

Looks like you spend lots of time in your bike projects in long cool dark winter nights up in the north.

[fsvaasam]

You are right Otto. Winters for building and short summer for riding