Vintage Dirt Bike Q & A

Hi guys, many years ago I fitted a 5mm spacer to the exhaust manifold of a Kx125 I had, this improved the bottom end throttle response. I recently came across an ad for a moose reed spacer to fit a honda and it claimed the same sort of benefits that the exhaust spacer provided. I was wondering if anyone has experience of using either exhaust or Inlet spacers on red rockets, what sizes were best, and what results were produced. Is the 78 or 79 model best suited to this sort of mod ?
I also came across an auction on ebay for a boost bottle kit for a rocket. Has anyone tried one of those and what results did that give.
I am looking for a mod that offers more low to middle grunt, without too big a loss at the upper end.

Increasing the tuned length of the intake and/or exhaust - spacers, longer pipes, and/or longer silencers - will promote low-end torque over top-end power. There are many variables at work and I would suggest the spacers will have a relatively small effect, but they are cheap. I have a "torque" pipe and silencer combo from Pro-Form and it is significantly longer overall than stock and it does increase mid-range, but also "signs off" quicker at the top-end. I have considered using the shorter-than-stock DG silencer with the PFR pipe to move a little back in the other direction. I think a boost bottle would be a cool addition, but I would not expect it to have a major impact. These appeared on YZs of the time, but then disappeared on later models. I suspect the performance increase did not warrant the extra cost of manufacture and assembly. My bottom line is two-stroke tuning is seriously interesting as an academic subject (get a download of Gordon Jennings book "Two-Stroke Tuning") but as a novice/intermediate rider there are no silver bullets performance-wise. Suspension, skill level, fitness etc. are far more influential.

http://rapidshare.com/files/235633898/Two-stroke_20Tuner_27s_20Handbook.pdf

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF