Engine support structure in motorcycle

1. An engine support structure for a motorcycle, which comprises:

a first main frame segment extending rearwardly from a head pipe to support a front wheel;

a second main frame segment to pivotally support a swingarm to support a rear wheel; and

an engine casing interposed between the head pipe and the swingarm;

wherein the engine casing includes a crankcase section to support a crankshaft, a cylinder forming section protruding upwardly from a front portion of the crankcase section and a transmission casing section disposed rearwardly of the crankcase section;

wherein the first main frame segment includes a first mount portion, which is connected with a front portion of the cylinder forming section, and a second mount portion which is connected with a rear portion of the cylinder forming section; and

wherein the second main frame segment includes a third mount portion which is connected with a rear portion of the transmission casing section.

2. The engine support structure for the motorcycle as claimed in claim 1 , wherein the second mount portion is disposed above the first mount portion.

3. The engine support structure for the motorcycle as claimed in claim 2 , wherein the cylinder forming section includes a cylinder part, which is disposed above the crankcase section, and a cylinder head part disposed above the cylinder part, and

wherein the first mount portion is connected with the cylinder part and the second mount portion is connected with the cylinder head part.

4. The engine support structure for the motorcycle as claimed in claim 1 , wherein the first mount portion is connected with the cylinder forming section on one side below an exhaust port, and

wherein the second mount portion is connected with the cylinder fonning section on one side where an air intake port is formed.

5. The engine support structure for the motorcycle as claimed in claim 4 , wherein the second mount portion is connected with the cylinder forming section on an outer side of the air intake port at a position level with the air intake port.

6. The engine support structure for the motorcycle as claimed in claim 1 , wherein the first and second mount portions are each formed in a pair on left and right sides of the engine casing.

7. The engine support structure for the motorcycle as claimed in claim 1 , wherein the third mount portion is formed at a plurality of sites spaced one above the other in an upward and downward direction.

8. The engine support structure for the motorcycle as claimed in claim 7 , wherein the plurality of the third mount portions are formed in a pair in side-by-side relation in a leftward and rightward direction.

9. The engine support structure for the motorcycle as claimed in claim 1 , wherein the cylinder forming section includes a cylinder part, which is disposed upwardly of the crankcase section, and a cylinder head part which is disposed upwardly of the cylinder part, and

wherein the crankcase section and the cylinder part are formed integrally with each other by means of die forming.

10. The engine support structure for the motorcycle as claimed in claim 1 , wherein the first main frame segment includes a lower first tube, an upper second tube, which are arranged in an upward and downward direction, and a connecting tube connecting the first tube and the second tube with each other, and

wherein the first mount portion is formed in a rear end of the first tube and the second mount portion is formed in a rear end of the second tube.