Adjusting cam timing for best performance
(the "lost" web page........)
(under development)

When your cams are properly degreed, your bike will produce more power throughout the entire powerband.
There is no serious professional team that doesn't individually set EACH engine's cam timing for best power.

In 2005, Robert Jensen, using his own EC997's dynos, was commonly the fastest privateer in AMA 600 Supersport racing. He follows the below procedures and even measures power changes resulting from valve clearance changes (yes, valve clearance affects power).

WERA Nation #1 Endurance and and 4 #1 Sprint champions, Mark Junge's Vesrah Racing also have their own EC997's dynos

Just like fuel injection and carburetion - each and every engine individual engine requires it's own set of "optimum" cam timing numbers for best performance.

If anybody says differently?
Well, either their test equipment isn't up to the level of the EC997 (that would include
ANY dyno that relies on Sweep Tests for power), so the .5 hp increments that come and go are invisible to them or they haven't spent the time to learn or had enough experience, yet.

But, I'd take a guy who says "I don't know, I haven't tried that." over a guy who says "Just set it at blah de blah and that will(?) be perfect.".

Slotted Sprocket Sets  for the lucky owners of bikes that have bolt-on cam sprockets. Replace the original sprockets with new sprockets that have elongated mounting holes in the sprockets. The cams must then be adjusted, using dial indicators and degree wheel to the desired cam timing settings on the intake and exhaust.

Cam Sprocket Adapter Kits, for the applications that have stock, pressed on cam sprockets.

OK........  Sooooo.....

What are the "best" cam timing settings? Hmmm.... Call 10 different tuners and get 10 different answers or call 1 tuner and use those numbers or, look in our carb tuning sheets and check for suggested starting settings.
Up to you!


The Factory Pro Tuning Method is to derive the absolute, optimum timing settings for each engine.

Use an EC997 EGA eddy current dyno WITH integrated EGA or similar (that wouldn't be a simple inertia dyne or one with a huge eddy current brake hung on it) in order to make the fueling or carburetion a constant, as you are looking for less than .5 true hp changes and, changing the exhaust cam timing will affect the correct main jet (or equivalent by at least 1 size and therefore at least 1hp, masking the benefit or detriment of the tested cam timing.

For current sportbikes, let's assume that the intake cam timing is too retarded. Advance the intake cam until it just hurts the top-end power over the last 1000 rpm. Usually, set the intake so that the engine loses about 1%-2% power at redline as compared with the maximum power. Check in 2 degree increments.

but.........Be CAREFUL!
As you ADVANCE the intake cam, the INTAKE VALVE GETS CLOSER TO HITTING THE PISTON!!! Check the clearance - before you run the engine!!! SEVERE engine and personal damage (read: total destruction, injury and persistent permanent vacation ) can be caused by monkeying around with cam timing!! As if life wasn't already fraught with peril!!  :-)

Generally, advancing the intake cam increases the cranking compression - increasing power below 8k (assuming a sportbike), which is below the effects of intake tract tuning which GENERALLY becomes in phase at ~8k and above on current sportbikes.
Power improvements or non-improvements, 8k to redline, are due to optimally or non-optimally setting the intake valve closing point. That has to compliment the  intake valve closing, porting, valve seat angles and widths, intake port volume, velocity, length, velocity stack ID, angle of divergence, the exhaust system.... and that's just what cam to mind as I wrote this.... In fewer words, there are so many variables, that it's an act of mental m..... to assume that you can use a program to calculate best cam timing settings - I know all the above mentioned factors affect he optimal cam timing settings, but I haven't seen a formula that includes even more than 1-2 factors....

After you are satisfied that you have the intake cam lobe center where you want it.... (having that little drop-off in power at redline)

Retard the exhaust cam 2 degrees and check power and main jet/FI selection.  You'll find that, generally, moving the exhaust cam results in power changes that are about 1/3 the magnitude in power changes resulting from equal degree changes in the intake cam.
Example: if changing the intake cam 2 degrees, resulted in a 3% True hp change, then, typically, moving the exhaust cam 2 degrees will result in a 1% true hp change.
If you retard the exhaust 2 degrees and it loses power, then try advancing the exhaust cam 2 degrees.

The power change with the exhaust cam will be a more "global" change - increasing power, pretty much across the powerband - You aren't really looking for any power drop-off at high rpm, though, if there is, it's up to you, the tuner, to make a choice of what's important.

Generally, I try to improve power from 8000 rpm to a skosh below redline - as that's what used on a racetrack. I use the same on most streetbikes.

Cruiser stuff works the same way - a 100 hp bike that redlines at 6000 rpm feels better when the peak power is optimized for 5250 rpm, as compared to a bike that make 101hp at the rev limiter (and less power below than the other bike). I grimace when a guy comes in with a 1340 Harley and has a cam set that is too big and now he wants to rev the engine till 8000 rpm. Sure, the lowend stinks, and the bikes not as fun to ride...... It's not fun to tell the guy that that's a bad idea and that he should use a smaller camset - and lowend would jump up and peak would probably improve, too. There's no market so goofy as the metric cruiser market - most stuff is dj dyno developed and some companies make these utterly ludicrous power claims.....

In 30 years of doing this - I haven't been able to predict which way an exhaust cam needs to go - advance or retard. I've asked others that have good dynos and good test procedures and the only answer I've gotten from anybody that I trust is "I don't know, either...." From some of the Sweep Test dyno guys, I get confident answers, though.... but..... few specs developed under Sweep Test conditions stand up to a Steady State or Loaded power test optimally.

If power had increased in the desired rpm band by retarding the exhaust cam, go another 2 degrees. As you RETARD the exhaust cam, the EXHAUST VALVE GETS CLOSER TO HITTING THE PISTON!!! Check the clearance - before you run the engine!!! SEVERE engine and personal damage.....

After you have re-optimized the FI or main jet (if you are using an inertia dyne, you will have to change main jets to see if power increases with different  main jets - with the EC997 EGA, you could check CO%, HC and CO2 readings to see if the optimum readings had changed, perhaps negating the requirement of changing main jets again - saving an hour or so of labor at each change.

If power decreased when you retarded the exhaust cam, try advancing the exhaust cam - in 2 degree increments. Basically, put the exhaust cam where it produces the best power.

Oddly, very often, testing on pre 2000 Suzuki 750's and Yamaha 750's done on inertia dynes seems to indicate a 105 lobe center setting on the exhaust. I'm not sure why, but most commonly, often, on the same applications, I end up with 101-102 lobe center, opening the exhaust valve later (a longer power stroke) as compared to 105 lobe center, which opens the exhaust valve earlier (shortening the power stroke). On the EC997, there is about a 1.5hp to 2.5hp difference between the 2 settings (that can be felt on the street or track). With a stock cylinder head on the GSX-R and YZF, 105 is not correct! (o - THAT'S pretty old!)

Factory's Cam Sprocket Adapter Kit
- specially designed adapters replace the original, pressed on stock cam sprocket assembly, allowing adjustments to cam timing.

Available through FACTORY or qualified local source.

application model year

Slotted Sprocket

Kits contain:

1pr. replacement slotted cam sprockets

Cam Sprocket Adapter Kit

Kits contain:
1pr. slotted cam sprocket set
1pr.  cam sprocket mounts
1 set cam sprocket bolt set

Honda CBR600 91-99 x  
  CBR900 92-99 x  
Kawasaki ZX-6R 95-99   ra-camspkt-k59
  ZX-7 93-99   ra-camspkt-k31
  ZX-9 94-97   x
Suzuki GSX600F Katana 88-> x  
  GSX-R600 92-93 x  
  GSX-R600 97-99   x
  GSX-R750 86-87 x  
  GSX-R750 88-89 x  
  GSX-R750 90-92 x  
  GSX-R750 93-95 x  
  GSX-R750 96-99   ra-cmspkt-s37
  GSX-R1100 87-89    
  GSX-R1100 90-92 x  
  GSX-R1100 93-98 x  
Yamaha FZR400 88-90 x  
  FZR600 88-98 x  
  FZR600   x  
  FZ750   x  
  FZR1000 89-94 x  
  YZF1000 96-97 x  
  FJ1200   x  



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