How to made a 30hp Kreidler 90cc dragrace cylinder, read below the tuning information

This is how it runs    • In 3,85 sec to 100km/h. Dutch Prostoc...  

Read here the history about the symmetric twostroke engine:
https://www.kiwibiker.co.nz/forums/sh...

Ofcourse the cylinder is a very important part in tuning, but not the only one. The whole set-up has to be in the right balance, so every part has to be dedicated for exactly the same rpm range.

Read all 2stroke tuning information in my notes: https://www.facebook.com/luc.foekema/...

This is how I made my 30hp dragrace cylinder in 2006.
This is the only cylinder I made for the 90cc dragracer, never made a second one. I used this cylinder from 2006 - 2015
All pictures in this video are from the year 2006
The first runs were made with a 4 gears engine and 28mm carburettor. The power at the start was about 22hp at 12000rpm, which result in:
2006: 150m time 7.35 sec endspeed 115km/h

After 2006 there were made small changes and with 30mm carburettor the power was 23.9hp at 13.800rpm, result:
2007: 150m time 6.91 endspeed 119km/h

After 2010 still some little changes were made, all ports were made to the limit and with new pipe and 34mm carburettor the power ent up to about 30hp at 14.000rpm,
2011: 150m time 6.64 sec 125km/h
2015: 150m time 6.53 sec 122km/h

Engine specifications now:
Bore / stroke 53.7 / 39,7mm
UCR 14:1
Crankcase pressure ratio 1.41:1 (which is to high)
Timing 198 - 133 - 236 Rotary intake 146/82
Ignition UltraSap Curve Curve 4/1000rpm 180mJ
Power backwheel 30hp 14.000rpm

Initially I thought in 2005 it will never work well, with such a heavily oversquare engine bore 53.7 mm stroke 39.7mm. Oversquare gives less cilinderfilling, so not advisable when tuning for max power.
Also the piston was much heavier so that the crankshaft balancing would come under heavy pressure with a balance factor of 23%.
The transfers don't have a good radius, because Kreidler cylinders has no space for it.

Why made this cylinder? Because I want it simply and with the use of a Kreidler look as original as possible.
It all turned out to be particularly noticeable and drove well above expectation very soon I drove one record after another.
But also with higher power the problems became more clear, the crankcase room was to small, so the prepressure become to high with 1.41:1
This was first discovered end 2014.

I hope
In the new 100cc version for 2019 this will be corrected, incl. a stroke of 44mm, a 38mm carburettor, a new dedicated pipe and cylinderhead.
22 dec 2021 still not ready after 1 year cancer and 2 years covid problems.

Calculations
Still working on 2t program which will show very easy the engine capacity.
I stopped to made calculation for third parties (cost to much time).
I want to have more time for many special projects, not only 2t.

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