Bonneville America Forums Forums Technical Forums Performance Mods Finally got my Camshaft Timing Specs

Got my camshaft timing specs faxed to me by my dealership. They took a little bit of deciphering, because the fax wasn't 100% legible, but I used the MegaCycle cam specs that Dinqua posted to figure out what value each number represented. So anyways:

INTAKE (Measured at .006" cold lash)

105 Degree Lobe Center
9.398mm Valve Lift
274 Degrees of Total Duration
244 Degrees of Duration @ .050" Lift
Opens at 17 Degrees before TDC (@ .050" Lift)
Closes at 47 Degrees after BDC (@ .050" Lift)

EXHAUST (Measured at .009" Cold Lash)

103 Degree Lobe Center
9.626mm Valve Lift
284 Degrees of Total Duration
254 Degrees of Duration @ .050" Lift
Opens @ 50 Degrees Before BDC (@ .050" Lift)
Closes @ 24 Degrees After TDC (@ .050" Lift)

Overlap (if I did the math right) is 41 Degrees around TDC.

The only other grind I can compare to, is the MegaCycle grind that Dinqua is using. If I got the math right, Dinqua's cams give him 42 degrees of overlap, my exhaust cam gives more duration, but less lift than his does, and his intake cam gives a heck of a lot more lift and duration than my intake does. I tried comparing my cam specs to the specs for the Stock 790cc and 865cc cams listed in the service manual, and their numbers don't concur between duration and valve open and valve close. (again, unless I got the math wrong)

For whatever its worth!

But the MC cams didn't give me much more. 2 HP and 4 less ft/lbs of torque. I did dyno them and will be able to psot a picture of the printout once I get another cable to connect my new camera to computer. I posted this info in the old Megacycle cam thread as well.

I need to do some more research to maybe figure out what the desired outcome of these cams were. My cam specs are one of the few that I've come across where the exhaust cam is more aggressive than the intake cam. They do resemble the specs for the 865cc cams, but with more duration and overlap.

Dinqua, I wrote this in reply to your post, on the Megacycle thread, about your dyno results with your megacycle cams, don't know if you saw it;
____________________________________________________________
Dinqua,
A quick and easy fix to get back your torque and more power with these megacycle cams you have installed, is to advance the megacycle exhaust cam 1 tooth, thereby opening & closing the exhaust earlier, reducing the overlap from 42 degrees to 27 degrees.
I advanced the Bonneville exhaust cam by 1 tooth that I had fitted to my Thruxton engine.
Trust me it works, got my bottom and midrange back and more.
I have a dyno simulation program and inputed the 790 SM cam specs, 790 SM intake retarded only & 790 SM exhaust, megacycle cam specs, megacycle intake & advanced megacycle exhaust.
The megacycle cams make about the same hp as the 790 SM cams but with a loss of torque. The retarded intake 790 SM, 790 SM exhaust makes similar torque and hp as the megacycle cams with the exhaust advanced.

Cheers..........Agro
____________________________________________________________

Did a simulation with your cams and Dinqua cams, your cams have alitle bit more torque in the low and midrange compared to Dinqua's cams. Both these megacycle cams sets make almost the same hp as the stock 790 cams but lose a bunch of low and midrange torque compared to the 790 cams.

Both you guys, Roundslide and Dinqua, can regain lost torque and more horsepower by advancing the exhaust cam 1 tooth which is 15 degrees, it works!

Cheers.............Agro

Agro, thanks for running that sim with my cam numbers! I may give that a whirl.

How's your thrux running?

Thrux is running good, easily pulls 19/43 gearing and 160/70-17 tire to 7000rpm in top gear.

You said in RAT;
<< Agro ran my cam specs through a simulation program, and told me that my cams would tend to emphasize the low and mid range torque, which seems consistent with how the bike pulls >>

I said in a reply post to you;
<< Both these megacycle cams sets(yours and Dinqua's) make almost the same hp as the stock 790 cams but lose a bunch of low and midrange torque compared to the 790 cams. >>

In fact you would have been better off with the stock 790 cams, but if you advance the megacycle exhaust cam, you'll get back the bottom and midrange torque similar to the 790 cams, with real strong top end power compared to the stock 790 cams. Plus reducing the overlap from 41 deg to 26 degrees.

Cheers.........Agro

Agro, thanks for clarifying what I obviously misunderstood, and thanks for replying to SalMaglie about the cam rotation! Have fun with the thrux!