Porting and Polishing
Sean Lukan
Anyone have any tips on porting and polishing the head on my 900rr? Want
some extra bang on the straights? Tips on books to read etc would be
much appreciated.
Sean
Randle Bain
This is probably best handled by someone who ports heads for a living.
You have to be very careful modifying today's motorcycles. Its very
easy to screw up a good thing. I recently found a really good book "The
Racing motorcycle" by John Bradley. It is available from Euro Spares
(race...@eurospares.com). I haven't had time to sit down for a good
read yet but it looks very well done.
The book deals more with bike setup than with engine development.
Gordon Jennings put out a book on tuning a few years back, but I can't
remember the name for the life of me. Anyway check with Euro Spares,
they could probably recommend a good engine book too.
Best advice? Pay someone who has a know reputation with a 900RR. And
remember the porting, cams, carbs, and pipe have to work together. The
induction/exhaust system is a system, altering one component can destroy
efficiency. So you can make the head flow like crazy and experience a
drop in horsepower if everything else doesn't "like" the new head
configuration.
Randy
Fred Farzanegan
In article <34BF767D...@cadvision.com>, Sean Lukan <luk...@cadvision.com> writes:
|> Anyone have any tips on porting and polishing the head on my 900rr? Want
I agree with the other poster: there's a lot you can do wrong.
Even the best tuners these days don't do much porting- the factory
port shape is pretty darn good. The only area for improvement
is because of how the head is cast. Since the head is mass-produced,
there are imperfections that can be carefully blended back. The
intake area should be a satin finish (to help larger fuel molecules
vaporize) and the exhaust can be mirrored.
But, honestly, if you're looking for more power, there are much
less costly (and less labor intensive) ways of getting it. The factories
spend a lot of research to make big HP right out of the box-
the correct port shape comes with that.
The big $$ porting jobs are for _heavily_ modified superbikes.
They've already done all the other motorwork, (oversize valves,
hot cams, overbore, full-radius, etc.) and need better/modified
flow to get the most out of the motor.
Good luck,
-fred