Author Topic: Performance Tuning  (Read 17346 times)


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Performance Tuning
« on: October 20, 2013, 04:04:56 pm »
The basic concept ot the RC31 race engine was Velasco's, based upon his years of work at Honda Racing. The heads were ported by a respected Canadian, Rick Tomacic, and according to Erion, flow better than factory VFR heads. The RC31's heads were fitted with 1mm oversize Del West titanium valves, which weigh only 60 percent as much as steel valves. Light titaniurn valves continue to follow a cam contour long after steel valves would have floated. Velasco selected a Megacycle cam, based on what had worked in VT500 Ascots. Three-milimeter-oversize Wiseco domed pistons (82mm) were installed, increasing the displacement to 700cc with a compression ratio of 12:1. Con rods were cut from titanium billet by Crowers "really big, and 60 to 70 grams lighter than stock," says Erion.
The downdraft intake system was topped by two 39mm racing CV carburators taken from an RC30 race kit. Ignition came from a Honda RS750 dirt-tracker, providing 36 degrees advance by about 3000 rpm for optimum performance with higher compression. The new ignition system extended the rev limit to 12,000 RPM and eliminated the requirement for a battery. The Exhaust system dimentions were copied straight from the RS750. Kerker fabricated the two-into-one exhaust pipe in stainless, feeding an RS-style canister and muffler section.
Engine longevity was increased by the installation of an RC30 radiator and another sourced from a VFR750. Coolant from the bottom radiator was pumped to both cylinders in parallel, eliminating the issue of rear cylinder overheat experienced with O.E.M. sequential routing.
A complete road-race front end was lent by Honda, taken from a ex-Joey Dunlop Isle of Man TT1 bike. Twin 323mm disk brakes, machined-from-solid calipers with Nisin pads, delivered more than double the original stopping power. A Fox shock controled the rear suspension. The 17-inch rims were 3.5/4.5-inch, shod with bias-ply front/radail rear mchelin 250 GP slicks.
                                                             Bore                           Stroke                    cc
VT500                                                             491
Trnsalp600,Shadow, Bros, Revere                  75                               66                      583
Trasalp650,XRV650, ,GT,Bros,Deauville     79                        66         647
Transalp700, Deauville                                81                        66                 680
XRV750                                                             81                        72        742
« Last Edit: October 23, 2013, 12:46:10 pm by Dougie »