Drawing two stroke engine in TikZ
I think this comes close to the shape you are looking for. I constructed this using arc with a fixed radius.
\documentclass[border=5pt,tikz]{standalone}
\usetikzlibrary{calc}
\begin{document}
\begin{tikzpicture}[every node/.style={font=\tiny\sffamily,inner sep=0pt}]
% Zylinder section
\begin{scope}[red]
\pgfmathsetmacro{\S}{0.105} %Segment radius
\draw[thick,xshift=.01cm] (-.25,1.75) coordinate (ZtopL) arc (180:0:\S) arc (0:180:-\S) arc (180:0:\S) arc (0:180:-\S) arc (180:0:\S) arc (0:180:-\S) arc (180:0:\S) coordinate (ZtopR);
\draw [thick] (ZtopR) arc (0:90:-\S) coordinate (ZR);
\draw [thick] (ZtopL) arc (0:-90:\S) coordinate (ZL);
\draw[thick,xshift=.01cm] (ZL) arc (-90:90:-\S) arc (90:-90:\S) arc (-90:90:-\S) arc (90:-90:\S) arc (-90:90:-\S) arc (90:-90:\S) coordinate (ZLbot) ;
\draw[thick,xshift=.01cm] (ZR) arc (90:-90:\S) arc (-90:90:-\S) arc (90:-90:\S) arc (-90:90:-\S) arc (90:-90:\S) arc (-90:90:-\S) coordinate (ZRbot) ;
\end{scope}
% Lines that connect to the Zylinder
\draw[thick] (ZLbot) --+ (-.2,0) arc(90:180:.1) --+ (0,-1.6) to[bend right=20] (-1,-1.5) --+ (0,-2) --+ (3,-2) --+ (3,0) to[bend right=20] (1.9,-1.3) --+ (0,.31) --+ (-.5,.31);
\draw[thick] (1,.2) --+ (.9,0) |- (ZRbot);
% \draw[red] (.5,-2.155) circle(1);
\draw[xshift=-.474cm,yshift=.03cm,rotate around={15:(0,0)},very thick] (-.25,-1.6) arc(130:476.6:1);
\draw[white,xshift=-.474cm,yshift=.03cm,rotate around={15:(0,0)},ultra thick] (-.25,-1.6) arc(130:465.5:1);
\draw[rotate around={30:(.3,-1.58)},xshift=.38cm,yshift=-1.6cm] (0,0) arc(180:270:.6) arc(0:-180:.7) arc(270:360:.6) arc(180:0:.1);
\fill[black,radius=.05] (.65,-2.25) circle;
\draw (0,0) -- (1,0) -- (1,1) to[bend right] (0,1) -- cycle;
\draw[fill=white] (.6,.45) arc(-10:190:.1) --+ (-.2,-2) arc(150:380:.1) -- cycle;
\fill[black,radius=.05] (.5,.45) circle;
\fill[black,radius=.05] (.29,-1.58) circle;
% \draw (.19,-1.6) arc(0:-90:.5) arc(180:370:.7) to[bend left=45] (.39,-1.6);
\draw[thick,rounded corners] (1,.2) -- (1,1.5) -- (0,1.5) -- (0,.4);
\draw[thick] (.013,.4) -- (-.2,.4) arc(90:180:.1) --+ (0,-1.9);
\draw[xshift=-.474cm,yshift=.03cm,rotate around={15:(0,0)},very thick] (-.25,-1.6) arc(130:406.5:1);
\draw[thick] ($([xshift=.5cm,yshift=-2.155cm]0,0)+(130:1)$) --+ (0,1.5) arc(-180:-270:.1) --+ (.04,0) -- ($([xshift=.5cm,yshift=-2.18cm]0,0)+(120:1)$);
\draw[thick] ($([xshift=.5cm,yshift=-2.155cm]0,0)+(60:1)$) --+ (0,.3) --+ (.5,.3);
\coordinate (h) at ($([xshift=.5cm,yshift=-2.155cm]0,0)+(60:1)$);
\coordinate (a) at ($(h)+(0,.3)+(.5,0)$);
\draw[thick] ([yshift=.2cm]a) --+ (-.5,0) --+ (-.5,.8) --+ (.4,.8) --+ (.4,.6) --+ (-.2,.6) arc(90:270:.2) --+ (.6,0) --+ (.6,-.2) -- cycle;
\draw[xshift=.4cm,yshift=1.5cm,rounded corners=2pt,fill=white] (0,0) rectangle (.2,.3);
% \draw[xshift=.4cm,yshift=1.77cm] (0,0) parabola[parabola height=.4cm] (.2,0);
\draw[xshift=.4cm,yshift=1.77cm] (.2,0) --+ (-.05,.4) arc(0:180:.05) -- (0,0);
\draw[fill=white,xshift=.4cm,yshift=1.77cm] (-.05,0) rectangle (.25,.15);
\draw[rounded corners=1pt,xshift=.45cm,yshift=1.5cm] (0,0) --+ (0,-.05) --+ (.1,-.05);
\node (a) at (2.7,.1) {Auspuffkanal};
\draw (a.west) --+ (-.4,0);
\node (a) at ([yshift=-1cm]2.7,.1) {Ansaugkanal};
\draw (a.west) --+ (-.4,0);
\node (a) at ([yshift=-2.5cm]2.7,.1) {Kurbelwelle};
\draw (a.west) --+ (-1.3,0);
\node (b) at (1.8,1) {Kolben};
\draw (b.west) --+ (-.8,-.3);
\node (c) at (1.3,2.1) {Z\"{u}ndkerze};
\draw (c.west) --+ (-.4,0);
\node (n) at (-2,-2.4) {Kurbelgeh\"{a}use};
\draw (n.east) --+ (1.2,0);
\node (n) at ([yshift=1.5cm]-2,-2.4) {Pleuelstange};
\draw (n.east) --+ (1.9,0);
\node (n) at ([yshift=2.3cm]-2,-2.4) {\"{U}berstr\"{o}mkanal};
\draw (n.east) --+ (1.15,0);
\node (e) at (-1.5,1.25) {Zylinder};
\draw (e) --+ (1.2,0);
\end{tikzpicture}
\end{document}
I think you need to draw a continuous path and probably to avoid decorations. The easiest way I'm aware of is to use hobby. Then you can just specify the points you need.
\documentclass[border=5pt,tikz]{standalone}
\usepackage[utf8]{inputenc}
\usetikzlibrary{calc,hobby}
\begin{document}
\begin{tikzpicture}[every node/.style={font=\tiny\sffamily,inner sep=0pt}]
\draw[xshift=-.474cm,yshift=.03cm,rotate around={15:(0,0)},very thick] (-.25,-1.6) arc(130:476.6:1);
\draw[white,xshift=-.474cm,yshift=.03cm,rotate around={15:(0,0)},ultra thick] (-.25,-1.6) arc(130:465.5:1);
\draw[rotate around={30:(.3,-1.58)},xshift=.38cm,yshift=-1.6cm] (0,0) arc(180:270:.6) arc(0:-180:.7) arc(270:360:.6) arc(180:0:.1);
\fill[black,radius=.05] (.65,-2.25) circle;
\draw (0,0) -- (1,0) -- (1,1) to[bend right] (0,1) -- cycle;
\draw[fill=white] (.6,.45) arc(-10:190:.1) --+ (-.2,-2) arc(150:380:.1) -- cycle;
\fill[black,radius=.05] (.5,.45) circle;
\fill[black,radius=.05] (.29,-1.58) circle;
% \draw (.19,-1.6) arc(0:-90:.5) arc(180:370:.7) to[bend left=45] (.39,-1.6);
\draw[thick,rounded corners] (1,.2) -- (1,1.5) -- (0,1.5) -- (0,.4);
\draw[thick] (.013,.4) -- (-.2,.4) arc(90:180:.1) --+ (0,-1.9);
\draw[xshift=-.474cm,yshift=.03cm,rotate around={15:(0,0)},very thick] (-.25,-1.6) arc(130:406.5:1);
\draw[thick] ($([xshift=.5cm,yshift=-2.155cm]0,0)+(130:1)$) --+ (0,1.5) arc(-180:-270:.1) --+ (.04,0) -- ($([xshift=.5cm,yshift=-2.18cm]0,0)+(120:1)$);
\draw[thick] ($([xshift=.5cm,yshift=-2.155cm]0,0)+(60:1)$) --+ (0,.3) --+ (.5,.3);
\coordinate (h) at ($([xshift=.5cm,yshift=-2.155cm]0,0)+(60:1)$);
\coordinate (a) at ($(h)+(0,.3)+(.5,0)$);
\draw[thick] ([yshift=.2cm]a) --+ (-.5,0) --+ (-.5,.8) --+ (.4,.8) --+ (.4,.6) --+ (-.2,.6) arc(90:270:.2) --+ (.6,0) --+ (.6,-.2) -- cycle;
\draw[thick] (1,.2) --+ (.9,0) --+ (.9,.2) --+ (.2,.2);
\draw [thick,magenta] (1.2,.4) to [quick curve through={ ++(-.1,.2) ++(.2,.2) ++(-.2,.2) ++(.2,.2) ++(-.2,.2) ++(.2,.2) ++(-.2,.2) (1.2,1.845) ++(-.15,.15) ++(-.15,-.15) ++(-.15,.15) (.69,1.845) }] (.65,1.845) (.35,1.845) to [quick curve through={ (.31,1.845) ++(-.15,.15) ++(-.15,-.15) ++(-.15,.15) ++(-.15,-.15) ++(-.15,.15) ++(-.2,-.15) (-.6,1.845) ++(.1,-.1) ++(-.2,-.2) ++(.2,-.2) ++(-.2,-.2) ++(.2,-.2) ++(-.2,-.2) ++(.2,-.2)}] (-.6,.4);
\draw[thick] (-.6,.405) --+ (-.2,0) arc(90:180:.1) --+ (0,-1.6) to[bend right=20] (-1,-1.5) --+ (0,-2) --+ (3,-2) --+ (3,0) to[bend right=20] (1.9,-1.3) --+ (0,.31) --+ (-.5,.31);
\draw[xshift=.4cm,yshift=1.5cm,rounded corners=2pt] (0,0) rectangle (.2,.3);
\draw[xshift=.4cm,yshift=1.77cm] (.2,0) --+ (-.05,.4) arc(0:180:.05) -- (0,0);
\draw[fill=white] (.35,1.77) rectangle (.65,1.92);
\draw[rounded corners=1pt,xshift=.45cm,yshift=1.5cm] (0,0) --+ (0,-.05) --+ (.1,-.05);
\node (a) at (2.7,.1) {Auspuffkanal};
\draw (a.west) --+ (-.4,0);
\node (a) at ([yshift=-1cm]2.7,.1) {Ansaugkanal};
\draw (a.west) --+ (-.4,0);
\node (a) at ([yshift=-2.5cm]2.7,.1) {Kurbelwelle};
\draw (a.west) --+ (-1.3,0);
\node (b) at (1.8,1) {Kolben};
\draw (b.west) --+ (-.8,-.3);
\node (c) at (1.3,2.1) {Zündkerze};
\draw (c.west) --+ (-.4,0);
\node (n) at (-2,-2.4) {Kurbelgehäuse};
\draw (n.east) --+ (1.2,0);
\node (n) at ([yshift=1.5cm]-2,-2.4) {Pleuelstange};
\draw (n.east) --+ (1.9,0);
\node (n) at ([yshift=2.3cm]-2,-2.4) {Überströmkanal};
\draw (n.east) --+ (1.15,0);
\node (e) at (-1.5,1.25) {Zylinder};
\draw (e) --+ (1.2,0);
\end{tikzpicture}
\end{document}
Obviously, you'll want to tweak it a bit and presumably won't want magenta, but, hopefully, this should get you started.
Personally, I would avoid all the shifts on paths in the code. These just confuse me, since apparently absolute coordinates are somewhere else and for no obvious reason. However, that may just be a matter of taste, so I only changed the ones I actually needed to understand.
Not a matter of taste: \sf is decades obsolete. It ought not be used in LaTeX 2e. (And some classes no longer support it period.)
snakes is also deprecated, though much more recently so.