400cc 2 stroke heavily modified. Reed cages from a 250 single cylinder yamaha fitted (aprox 50% larger 6 petals vs 4!) 34mm Mikuni carbs replacing 28mm stockers, extensive porting raised exhaust port 10mm! Intake and transfer ports enlarged bridge in main intake knife edged and thinned down to nearly nothing. All intake ports finished with coarse sandblasting sand forced through for hours to airflow the port somewhat and leave the surface somewhat rough and still smooth. Exhaust port enlarged and mated to expansion chamber flanges then polished smooth.
Piston Intale skirt windows opened from 2-3/8th inch holes to huge 3/4 inch rectangukar windows (to aid intake from larger reeds and carbs. Windows lowered 5mm to open earlier.
Piston domes and head Combustion Chambers poished. Head milled .5mm raising compression nearly 1/2 point combined with ultra thin copper head gaskets.
K+N Air Filters replaced stock air box.
Spec 2 Expansion Chambers.
Boysen fiber reeds replacing stainless stock reeds.
All amounted to a massive increase in HP... from 31 stock to nearly 80HP! Amazingly it lost no drivability with the wild porting and huge carbs! It actually had a healthy boost off idle into a much stronger mid reange to a top end hit that was insane! If you ever rode a 2 stroke 125 motocrosser of late it was similar but times 4-5.... The little 400 is almost as fast as the 1297cc GSXR I have!!
Drivetrain:
Drivetrain mods were undercutting gears in transmission to help them engage and stay ingaged. other than that its stock. Yamaha makes some of the slickest gearboxes for bikes made!
Suspension - Factory Connection re valved forks and Progressive rear shocks. Older bikes suspension is pretty lacking in terms of modifiying... It was much better but nothing compared to modern bikes.
Notes:
Of all the 50+ bikes Ive owned none get the attention this one does. My only regrets was not keeping the color scheme stock. I let my painter friend talk me into the magenta and pearls it is. He taught me how to paint and gave me all the paint so I cant really say much.... Someday Ill repaint it...
It still gets peoples attention just from its sound, then they realize what they are looking at and so many say I had one of those when I was in collage!!!
I ride it 2 times a year, for the Toys for Tots Christmas Parade and the Saint Patricks Day Parade through Waikiki! Great Fun!!
my_711_naked_and_yellow.jpg 1381 hits | 75.46 KB | Posted: 5/31/05 The next project.... the 711 GSXR I built from parts I scrounged from all over! its done in this pic, well atleast till I painted it black with blue pearl and blue anodized aluminum chips all buried under a bunch of eurathane clear! It looked awesome...
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