Here's a seed for a good technical discussion thread.
Camshafts; Triumph Hinckley Bonneville (or others!).
I've read ton's of posts and threads around the "misinformation byway" about cams for these venerable Triumph's, and how 'this n' that' Camshaft is... the "best".
But a few things always bother me.
1.) Mainly, there are no "specs" ever available for any aftermarket Triumph Cams, nor apparently has anyone ever taken the time to measure vital things like lift, intake opening / closing, exhaust opening / closing, duration, etc. The next time someone buys a set of aftermarekt cams, how about measuring and recording some of this info? A micrometer and a Timing Wheel would do the trick!
2.) "All I know is, I installed it in my bike,,, and it's fantastic..." is not an objective, scientific analysis. The $$$ spent 'Placebo' effect swings almost always one way on these Internet Forums. When is the last time you heard someone on a Bike Forum say:"I paid $900 for
xxxxx, and now my bike runs like crap!". Never, ever happens.
3.) Although the newer Triumph 865cc models (2007 onwards) displayed a slightly better 1/4 mile elapsed time over the former 790cc offers (Motorcyclist Magazine website), many 790 owners insist that the 865 cam is "crap", and the 790 cam is... "better". Say wha'?
Motorcycle Performance Data and Specifications - Motorcyclist Magazine From the April, 2009 issue of Motorcyclist motorcycle measured hp (@ rpm) measured torque (lb. - ft. @ rpm) corrected quarter-mile* (sec. @ mph) Bonneville ('01) 56.8 @ 7250 42.1 @ 7000 13.57 @ 96.4 Thruxton 900 ('07) 58.6 @ 7250 47.0 @ 3250 13.48 @ 100.18 motorcycle top-gear roll-ons 60-80 mph* (sec.) wet weight (lb.) ergos** last tested Bonneville ('01) 6.89 499 7/01 Thruxton 900 ('07) 6.29 497 28.1/18.6/4.9 1/07
There is also a cam to cam comparison done by an objective modder on a popular Triumph site that by means of back to back Dyno runs illustrated extremely little difference, only a very slight (1-2 HP) trade of of low end torque for high end HP on the 790 Cam, which explains the slightly better E.T, (low end launch) results for the 865. Regardless, some folks remain convinced (and livid!) of one being superior to the other? Most other dyno's with references to cams are a mixture or combination of numerous mods, so there's no real "telling" or specifics of what did what.
Note that the
"Blue" lines are the stock 865 cams in a 360 degree Bonneville. The
"Red" lines are results of a 790 cam installed in the same bike. You 'rob Peter to pay Paul', losing some lower RPM power, and gaining way at the top. Note the nice HP and Torque curves of the Stock Bike, Vs, the "dip" from 3000 to 5500 RPM experienced with the cam swap. Know where your riding RPM range actually is (you might be surpised!) before you mess with this type of "mod". Great for "Dyno Racing", poor for street performance.
On a street bike - and actually for most riding intents and purposes - the HP curve should be slightly "convex" or slightly humpbacked, not seen like a crescent moon. It should never have any sudden dips or valleys.
The torque "curve" should be as flat and straight as possible, with no dips or valleys. This results in the most pleasurable and predictable style bike.
The a/f curve will depend on the a/f ratio that results in the best performance. This is not necessarily "flat" all the way across the chart, nor is 13.1:1 a guarantee of anything. All motor set-ups and responses are slighlty different.
On that same subject, it is also impossible for anyone to provide an effective Ignition Advance Curve from afar. It's impossible to guarantee optimal power from a module ordered over the internet. This is something that must be done on a Dyno, or with the proper Tuning equipment,
in situ. Also note that the more you improve your engines VE, and A/F burn efficiency, which 99.9% of "Mod's" should be doing, the fact is that you would then need LESS Ignition advance, not more. Think about it.
4.) When comparing one year Bonneville and engine to another, posters always seem to miss the fact that with few exceptions, the peak torque, and peak horsepower RPM numbers changed annually, as did obviously the resultant Powerband, so the "drivability" and so on changed annually as well. Someone in the Triumph design department was experimenting... but for what end?
Also note the differing characteristics and intended end use between the 270 degree Scrambler, and the 360 degree Bonnevilles - all with different powerbands as well. A confusing, but thought provoking puzzle.
5.) As we all know, no single camshaft could EVER satisfy the almost infinite variety of riding styles and purposes, therefore how could one brand name ever be so broadbrush recommended? What does one want? Lot's of low end grunt?, High speed passing capability? 1/4 Mile E.T. improvement? Best economy? Least harmful emissions? Mid-Range power bursts? Alert modders know that there is unfortunately no "one size fits all" solution with respect to cams. The spawn of "Variable Valve Timing".
All that said, without knowing what the specifications are on a set of cams, it's absolutely impossible to state factually that one is better than the other. Note as well that virtually ALL automobile aftermarket Cam manufacturers readily publish their specs, and offer various types of cam profiles to suit different hot-rodding styles. So why not bike cam makers? Why again, has no one ever bothered to measure the cams and settings during an installation... or HAS someone? Speak up!
In the end, the vague word "Improvement" could also be debated, as "improvement" of a few measly HP on a paper Dyno graph might be one thing, but how does that translate respectively to the street or track? Is it what the end user actually wanted or required? I believe these are all valid questions, which - to my limited knowledge - have no valid answers yet.
The proclamation "It transformed my bike..", leaves a lot of open space for speculation, and tends to be subjective. Transformed in what specific way? Compared to what?
These aftermarket camshaft sets tend to be expensive, so say $800 bucks for 1-2 HP translates to say $400/HP, a horrible transaction. Should be no more than around $100/HP, or you may want to strongly consider trading up to a different / higher performance stock bike as a base to work from. Otherwise, you'' eventually end up with an $18,000 bike... worth $5,000 on the second hand market
. Potential buyers considering spending that amount of money above and beyond the bikes original MSRP would prefer to purchase personally chosen mod's themselves. Unless of course you proclaim you're gonna keep the bike forever... which unfortunately almost no one ever really does.
Anyone have any good Technical / Specification Information / Objective material on any of these aftermarket cams?
Added later:
"Supposed" specs on Thunderbike cams (New Zealand)
Thunderbike Cam Specs
Intake:
Open 18* BTDC
Close 45* ABDC - Lobe 106
Exhaust:
Open:46* BBDC
Close: 18* ATDC - Lobe 105
Overlap of 36.00 degrees and has in Intake Duration of 243.00 degrees. The Exhaust Duration is 244.00 degrees. The Inlet Cam has an Installed Centerline of 103.50 degrees ATDC. The exhaust cam has an Installed Centerline of 104.00 degrees BTDC.
I can't vouch for these, but it's all i could find on the misinformation byway!
Ride Safe (and suitably cammed)!
Bob
Re: Camshaft Chronicles 
