Building another Suzuki GP100 NSR 110 hybrid using a re plated but standard NSR250 cylinder.
Stroke 48mm Bore 54mm for 110cc ... (an NSR is 54 x 54).
Inlet opens 140 BTDC closes 80 ATDC
Exhaust opens 80 ATDC
Transfers open 114 ATDC
The shorter stroke gives me a very useful increase in blow down time area without having to do any porting at all.
The cylinder sits on a 12.5mm spacer plate, the head is spigot ed 2.5mm into the cylinder and the cylinder also has 2.5mm skimmed from the top, 0.65mm squish.
Using the standard head gasket so as to control the water flow around the cylinder.
Yamaha RD400 2T2 rod with solid pin and flat big end bearing cage. The balance factor turned out to be 55%. I was looking for 50% so next time I will use a smaller Mallory slug opposite the bigend.
The whole motivation for this engine is to have a smaller diameter inlet tract.
So I am leaving the original 24mm inlet tract un touched. Previously I would have made this as large as I could get away with. but an earlier dyno test with the variable inlet valve suggested there was not much top end in it and a noticeable difficulty in getting the carburation right at the lower end of the torqe curve just as the engine was coming onto the pipe.
This is the dyno graph that has inspired me to try a smaller inlet tract. Red is the variable inlet open and equivalent to about 32mm and Blue is closed and about equivalent to a 24mm inlet tract. Top end is much the same, the difference seems to be just a little over rev.
Below are some links to the earlier Suzuki six speed, water cooled, drysump GP100/NSR hybrid.
The VeTec or variable inlet area story. Follow the links back to see the pictures.
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