Bonneville America Forums Forums Technical Forums Performance Mods Question for Pat

Been pondering cam options for a while now, and once the weather turns i'll be doing the valve adjustment. So if i'm ever going to get cams that would be the time. The Tbike cams are expensive and the dynos show little to no gains till about 6k. Thats great and all, but below 6k is where i do all my riding with the few exceptions where i go wot thru the gears. Not something i do real often. maybe once or twice during a 200 miler. So while it would be nice, it's a lot of money considering the bike will run as it does now below 6k where i am 99% of the time.

so i want to know about the megacycle cams....do they give you low end benefits too, or is it all in the upper rpm's like the tbikes? Do they perform better all the way up the scale or if not where, and do you sacrifice anything at a certain point? Do they sell cams for our bikes or only mod your existing cam? Are there any other options for aftermarket cams besides those and the Tbikes? And finally, if there are answers where your findings may not me the same as mine due to the 865 vs the 790, please mention that where appropriate. If you decide to answer all this, and i don't blame you is you don't, thanks in advance.

Daz,
I got my cams from another member, therefore I did not have to send mine to them as they usually require. Yes, Megacycle re-works your cams. They grind the lobes off, then reweld new metal and regrind them to meet the profile you desire. I have spoken with them on the phone before and they know tons more that I pretend to know about cam timing, overlap and duration. Give them a call, they are very helpful and will most likely recommend the "Medium Street Grind" profile for you too. That is what mine are for, and they are also ground specifically for a wiseco 904cc/270º big bore, an added benefit.
The 865cc motors are a different animal from the factory. I have read recently where a lot of guys are getting better HP and maintaining the torque by simply advancing the exhaust cams by one tooth. Not to be done modestly if you don't know how the entire cam system works either.
Also, a lot of guys are running intake cams in teh exhaust to get better low end torque and maintain the HP levels across the board.
Also, I read where some folks have also used 790cc/270º cams in the 865cc/270º motors with good results.
In the 360º world, the Thruxton cams seem to be just the ticket.
Head hurt yet? Mine did when I did research on cams.
Now, don't get me wrong, Thunderbike has done a ton of research for your specific motor (865cc, 270º) and their cams do deliver what they say, but at a premium.
So, you gotta decide yourself:
A) Can I afford it?
B) What will I risk?
C) How much HP/Torque will I gain per $$ spent?

All good questions with no straight forward easy answer.

As far as the megacycle cams response: Well, my butt dyno says they gave me increased HP/torque across the board. I feel no loss anywhere, but gains everywhere.
Once I get them on a real dyno, I will know for sure.
I know lots of you are waiting for the results, but I need the time to get them done as I have been pretty busy and am in serious NorEast Rally mode now.

Patience grasshopper, I will post all dynos as soon as I have them.

I'd like to see that dyno compared to your stock cam dyno. If i do this it won't be for a while anyways. As to afforing the Tbikes, i'm not worried about that. I'm worried about the fact thier dynos show no improvment below 6K. I'm a bit leary about the thrux cams or advancing the ex cam. Not being experienced at this the last thing i wanna worry about is not having the stock guides when putting cams in. If i can't see the marks just as they are in the manual it's going to make me real nervous when starting it up for the first time. maybe if i have to remove the exaust cam i'll look at it and see if i wanna move it up a tooth, but that still worries me. I just wish i could buy a set of Tbike cams and get a linear power gain. as for megacycle, would they be able to tell what kind of gring to build for an 865 just by looking at my manual's cam specs?

I'm really at a place where i feel the bike needs that extra bit more to put it where i'll be satisfied. yeah, i know what you're thinking, and it's true i may never be fully satisfied with the maximum this bike is capable of w/o making it unreliable. But i don't expect my fantasy specs, just what i feel will relieve the spots where i feel the throttle just ain't giving me quite what i need, and i don't feel like it would take a lot more. the 10 HP and extra torque the Tbike cams afford i think would be easily enough if it weren't limited to just 1500 RPM's before redline up to the limiter which is 7500. Makes me wonder if there even IS a cam that would give me bother because the stockers are said to bring more torque than the 790 cams, so while you feel it thruout the range it may be because you didn't have that low orque to begin with. But mine may already be as good as it can get via cams, so therefore Tbikes was only able to tune thier cams to equal that and give more HP at the top.

Oem Manufactures do a lot of research on cams as well. Mostly they tune cams to give the best results over a broad rpm range. Most high performance cams produce more hp in the upper rpm range of a motor. There is always a trade off in cam profiles. Being your 865 motor was engineered to produce more torque on the low end, I doubt you will find a cam profile to give you much more in that regard. And thats where you say you do most of your riding.

Daz, ever think that you do most of your riding at low rev's cause that's where your bike makes power now? If you add the cams and get some more power up top I think you'll find yourself altering the way you ride, especially the way the cams like piling the revs on top of each other. The motor will be much more willing to rev, and it will reward you for the wait. Just a thought...

The only way to ride in the 6k and above area while still riding safely is a steady cruise speed. But who would want to cruise down the road at 45 MPH in whatever gear keeps you at 6k?! Other than that the only way to make use of the 6k and above area is to drive like a madman, and i save that for occasional moments. To ride in that range normally would be to die before long ! So no, i wouldn't be changing the way i ride.

you gotta downshift man! a 865 motor with as short of a stroke as we have ain't gonna have Rocket 3 roll-on power. These engines were built to rev and the stock cams totally rob that fun from us.

If you want roll on brute force you're on the wrong bike, no matter what you do to it.

The cam timing on the 865 engine seems to be intended more for emissions reduction than for performance. If you were to use a 790 exhaust cam, you would get close to the same power/torque curves that the T100 produces. They have about the same peak torque ( 1 ft/lb more) 1200 RPM faster, and 12 more HP.
An intake cam in place of the exhaust one will do a lot for you as well, but you are going to have to work out the timing because the intake timing marks will be a bit off. For street riding, I don't know whether there is enough gain to justify the extra time needed to work out the timing.

To do the cam swap with the intake in the exhaust, you can just use a dremel and make new marks for future alignments too. Just put them in place, mark with a sharpie, remove and grind the little dashes or dots as needed. That's what I would do.
Using the 790 cams would probably work best if you can get a good price for them. They come as complete assemblies for about $250 or just the cam for about a hundred less. But you then need to remove the backlash system form one set and put them on the others. Not a big deal to do though, you just need the backlash wrench.