[01 ] Removing the gas tank, airbox, air filter and the associated pieces are the first order of business.
[02 ] The throttle bodies are next on the list, but not without disconnecting the throttle cables, fuel lines and appropriate plugs.
[03 ] The frame is so tightly formed around the motor that the radiator must be moved forward in order to get a pair of hands inside the workspace.
[04 ] This is where the fun starts: with the removal of the valve cover.
[05 ] Welcome to the insides of an R6 motor. Here you can see the camshafts and the cam plates that hold them in place.
[06 ] A dial indicator is used to verify the stock cam specs are in order and to verify the new numbers when the adjustments are finished. After nearly 40,000 miles the cams showed some signs of wear, but nothing to be alarmed about.
 An indicator wheel is mounted to the stator rotor assembly, which is attached to the end of the crank. Top-dead center (TDC) and bottom-dead center (BDC) must be located before moving forward.
 With the stock cam timing specs sorted the cams are removed from the bike and the cam gears are split from the cams.
 While the West Coast GP Cycles cam-gear modifications couldn’t be photographed for secrecy’s sake, here’s a stock cam gear (left) next to an adjustable unit (right). Note the elongated holes at the top and bottom of the adjustable gear. This allows the gear to be adjusted to change timing where the circular holes on the OEM piece are locked at a set figure. Our R6 will have the stock holes elongated to exact lengths only West Coast GP Cycles knows.
 With everything back in spec the cams can be reinstalled and the rest of the bike put back together.
The cam chain was loose enough to nearly skip a tooth. The chain showed signs of wear but was still within spec so we turned our attention to the tensioner.
The OEM tensior had seen better days so an APE manual adjuster from Sudco International took its place. Problem fixed.
Unlike the typical gearhead who’s eager to share his knowledge and insider tricks with any like-minded rider, racers keep their secrets close to the vest. Ask most racers why their bikes are so fast and you’re lucky to get a smirk in return. When it comes to winning, most racers will do anything to succeed, even if it means fasting for days to drop weight or running some highly volatile race fuel their uncle Johnny brewed in his garage. So having a racer share insider secrets is like winning the lotto–it’s highly unlikely, but amazing when it happens.
Last month we kicked-off this build after seeing several AMA R6s run away from the pack during a race. It didn’t add up, how could an R6 that hasn’t seen an update in years be so fast? After lots of digging and a little prying we convinced several renowned race shops to share their tips about the power hidden inside every R6.
In the first installment a full Graves exhaust system and Bazzaz Z-FI QS uncorked the R6 in preparation for this month’s racer-only secrets. The free breathing pipes and trick-fueling computer unlocked 6.62 HP and 2.23 LB-FT at peak with equally impressive midrange increases.
This month we ventured under the valve cover and inside the motor for power mods most never knew existed. Along with other racer secrets like a thinner head gasket, a ported cylinder head and balanced/blueprinted lower end, cam timing is also another area tweaked for more power.
It’s all about timing
Without getting into an engineering dictation about engines, the internal combustion motor is essentially an air pump and the more air it can ingest the more power it can make. Furthering that notion, every reciprocating part inside a motor is interconnected and timed for a desired effect.
Cam timing in its most elementary form is the moment in which the intake and exhaust camshafts open and close in relation to the position of the crankshaft (and the pistons). It’s common knowledge that the intake valve is open during the intake stroke and the exhaust valve is open during the exhaust stroke, but the lesser-addressed area of the combustion process is called overlap. This is the points at which the intake and exhaust valves are both partially open at the same time. Take for instance the intake stroke: the valve is partially open just before and after its stroke because the valve must move from closed to open and then back (same goes for the exhaust stroke) as it follows the lobe of the cam. At the finishing point of either stroke one valve is closing as another is opening–this is overlap.
Overlap is important for the exhaust side because leaving the exhaust valve open during an intake stroke can help suck fresh air into the combustion chambers, but too little overlap doesn’t leave enough time for all of the spent gasses to leave the chambers–killing power and emissions. Consequently, if the intake valve is closed early it builds more cylinder pressure as the piston compresses the mixture, creating a bigger bang lower in the powerband. Generally this leads to more midrange power at the expense of top-end. However, closing the valve later develops less cylinder pressure in exchange for maintaining it higher in the powerband (more top-end power) because the engine doesn’t have to overcome pumping losses when compressing the mixture.
As beneficial as custom cam-timing adjustments can be, maladjusted cam timing can lead to catastrophic engine failure in the form of piston-to-valve (PTV) interference. If cam timing is out of spec with the crankshaft a valve can hang open long enough to contact a piston. In the event of PTV issues carnage quickly ensues.
With a basic understanding of cam timing we paid a visit to West Coast GP Cycles, a local shop known for its ultra fast R6 race bikes. Although the team wouldn’t reveal exactly what specs the cams were timed to, they did admit that the R6 is unique in that closing the overlap doesn’t kill top-end power. Instead, the mighty R6 sees gains across the board.
For the mechanically inclined this might not be out of the question, but for everyone else this task is better left to the pros at West Coast GP Cycles, who for a few hundred dollars over a valve adjustment will modify the stock cam gears and set the cam timing to their top-secret specs.
As for the actual process, the tank, airbox and throttle-bodies hit the workbench first followed by the valve cover and the cams. The techs then shared an inside trick about slotting the factory cam gears.
“Adjustable cam gears are nice, but if the adjustment bolts slip the cam timing can come out enough that you’ll have piston to valve clearance issues. We slot the factory cam gears in the direction the cams need to be timed so in the event a bolt comes loose, the cam will revert back to the factory setting with the only adverse effects being a loss of the newfound power,” Andy Palmer of West Coast GP Cycles said.
With the cams out and the cam chain held in place the cam gears are slotted to the top-secret specs and the valvetrain is again installed. First the cam timing is double checked to make sure the cam gears were slotted to the exact spec. Then the valve clearances and the PTV clearances are checked to make sure the valves are in spec and the valvetrain is free of interference.
After everything is cleared for takeoff the bike is reassembled and ready for another custom fuel map. The newly modded motor will undoubtedly need more fuel to match the larger amounts of ingested air.
After tweaking the AFR with the Bazzaz, the new dyno numbers were impressive. Considering our 2006 R6 had nearly 40,000 miles on the clock and consequently had lost a step or two in its old age, it still hammered down 113.66 HP and 43.11 LB-FT at peak. The cam-timing mods were worth 5.28 HP and just under 1 LB-FT over the previously installed Graves full system and Bazzaz fueling computer. But more impressive were the gains over the slip-on only baseline where the R6 jumped from 101.76 HP and 39.93 LB-FT to the aforementioned 113.66 HP and 43.11 LB-FT for total gains of 11.9 HP and 3.18 LB-FT at peak.
For those interested in more than just peak numbers it’s important to note that from 6,000 RPM onward the power is far stronger with the timing, exhaust and fueling mods. Not only has the midrange been increased but the real fun begins over 11,000 RPM where the free-breathing combination really opens its lungs.
Although our high-mileage R6 was in good working order, had we used a newer motor with lower mileage the final tally would have been closer to 118 HP according to Andy at West Coast GP Cycles.
“Considering the bike had nearly 40,000 miles on the clock it did well. Comparing the numbers to low-mileage examples I’d say there’s about a 4 HP discrepancy, which isn’t bad at all, but we usually see closer to 118 HP–right in the hunt with a GSX-R750,” he explained.
Much to our disbelief the seasoned R6 went from barely traversing the 100 HP mark to knocking on 115 HP with a few simple mods. Riding impressions were eye opening to say the least. Where the stock bike felt weak in the midrange and adequate near redline, the modded example had massive amounts in the middle and so much top-end you’d swear there was a 750 bolted between the rails. This folks, is the real deal and anyone with an R6 that’s already sporting a full system and fueling computer should consider this a must-do mod. As for the kicker, there’s no reliability concerns either, so it truly is having your R6 cake and eating it too.
We borrowed our high-mileage R6 from an SSB local who had recently purchased the seasoned steed from the original owner. Much to our dismay the bike had some cam-chain noise on fire-up that would subside as the tensioner built up oil-pressure. Once inside the motor we were treated to a stretched cam chain and a roached cam- chain tensioner.