Re: Drilling Slides and Reversing the Process.

[Rey Kirkman]

I reversed my Dynojet slide holes by filling the holes with J.B. Weld.  I redrilled holes adjacent to the filled holes.  There was an article in Motorcycle Consumer News by Dave Searle, dated May 1996 a while back which addressed drilling of slides.  The bike they tested was Honda 650cc Hawk.  After drilling the slides and installing the rest of the components, throttle response was off.  Following are some interesting quotes from the article:       "Resigned that we must have done something wrong, we scratched the head of Joe Youkhan, the dyno operator, who'd had considerable experience with these kits.  Regarding the sluggish throttle response, he said that he doesn't ordinarily drill slides as suggested unless the bike  is really intended for the racetrack, because which throttle response at high rpm is enhanced, it is worsened at low rpm...Hmmm?  Back at the shop, we called Two Brothers Racing to see if they had any tips for us, assuming their extensive Hawk knowledge would provide the answer.  We were told, 'We don't sell the Dynojet kits, because nobody can get them to work.' "       "We called back the folks at K&N, which had provided the kit.  Acknowledging the company's reputation for quality and expressing satisfaction with other Dynojet installations we'd done, we gave them our results.  We also relayed the remarks we'd received from the dyno operator and Two Brothers.  They said their dyno comparison showed a gain of nearly five horsepower and offered to send another kit although our description of the needle dimensions seemed to indicate we had gotten the correct parts.  We were told however, as Joe suggested, that drilling the slides would hurt off-idle response but that the carbs would reach full throttle soon and therefore gave an acceleration advantage in spite of the derivability problem.  We were told the drilling does not actually influence horsepower, so we resolved to leave the slide holes alone on the next attempt.  Remember that the all-new GSX-R 750 has computer-controlled slide venting.  Our test indicates why.  Smaller vents will give better off-idle response, and larger vents give better response at high rpm.  Now we know why Suzuki went to all the bother.   MCN used a 0.109" drill to redrill the holes to stock size.   In November '96 in response to a query of a Yamaha FJ 1200 owner who wanted to undrill his slides, MCN called Yamaha.  There is no Yamaha spec for size of slide holes.  Yamaha suggested calling Mikuni, and Mikuni said the sizing had been worked out in Japan in concert with Yamaha engineers.  Dynojet's tech rep said they have information back to '91 models, but suggested most stock holes are in the neighborhood of 0.110".  A #35 drill is 0.110", and a 7/64 drill measures 0.1094"   Rey Kirkman ----- Original Message ----- From: P. Kuyper To: V-MAX TECH LIST Sent: Tuesday, March 07, 2000 8:08 AM Subject: RE: Going back to Stock Jets. If the slides are drilled out, it CAN be reversed.   Take some good 2-component glue. Close the hole with the glue and let it dry thoroughly. Drill in the original size holes again. However, at the moment I do not know the size. Anyone??   Patrick Kuyper Vmax Club Holland The Netherlands -----Original Message-----