I wouldn't be as enthusiastic as to change the timing by a full tooth!
... as this affects both inlet AND exhaust timing in the same direction!
I did it by profiling the rocker face, (where it contacts the cam
. I used a dial guage on a loosely tightened head to check cam phasing, (before and after
), and a small blob of plasticine on top of the piston to check piston to head and valve to piston clearances
. I had a degree wheel, (fabricated from a 360 deg. protractor attached to the flywheel
Check out the link ; https://forums.off-road.com/dirtbike-...sprockets.html
As the 230's have a cam with constant lobe centers and cam duration, advancing the cam in its entirety, (between 1 and 6 degrees MAX
!), would improve low and medium rpm torque
, with a SLIGHT reduction in peak power, (with imperceptible changes in emissions, idle and fuel consumption, ie. no change in jetting required
(I wouldn't recommend exceeding 6 degrees
Retarding the cam in it's entirety on the other hand moves the intake / exhaust timing events to a point later in the TDC of the ascending piston, which shifts torque from lower rpm to a higher-speed range. Overall, the advance/retard scheme creates a torque shift.
Profiling on the other hand can be done to a single lobe / single valve
, ie. either the inlet or exhaust or .... both as I have done ... as retarding the intake and advancing the exhaust, “spreading the centers
”, decreases overlap and results in a wider power band
Bearing in mind that TORQUE, (the twisting power of a motor
), is the increase that you're after
, and that even in racing, the name of the game is acceleration
, (ie. a wide torgue band from the mid to top end range
) ... so you may also want to experiment with intake diameter and length as well?
My current testing shows and increase of bottom end torque, again with a slight reduction in top end by extending the intake length, (clearly the converse also applies
I can tell you that after all my modifications ... I have a slight, (some 5%
), top end power increase ... however, I have a substantual
bottom and mid range boost
, (of which I put this to good use with a sprocket change from a 13T front to a 15T
... to the extent that the 230's now almost
feel like the WR450 did when it was new, (with it's 1/2 throttle and other crappy restrictions
), except the 230's are considerably lighter and more manouverable!
Before embarking on any modifications however, I would advise thinking them through,
(unless you're like me and just want to experiment
. Decide on exactly what it is that you want to achieve, and what the cost is,
(financial as well as a trade of of bottom end to give top end, noise, etc
and have fun ...