The Prophet

In no particular order, and very certainly open for polite debate, a suggested Top Ten List of surefire ways to ruin an otherwise decent Streetbike.

1.) "Swiss-Cheesing", or totally removing the Airbox. Particularly on any post 1995 or later EFI bike, this is a very bad idea. Note that not ALL bikes have an airbox, some are merely sound reducers to comply with legislation, etc. Find out which it is before you drag out the ol' holesaw or the reciprocating sawsall. All that you will accomplish is moving the Powerband upwards, and producing a dip in the torque band. It's best to always remember that it is the power you can actually USE, not the peak HP, that counts.

2.) Choosing an incorrect aftermarket exhaust system. "Shorty" drag pipes being the worst. Loud pipes do not always translate to increased performance - think "Placebo". If your bike is say 2 or 3 years old, chances are it is extremely difficult to beat what is on there from the factory - for the street. Naturally, not all aftermarket offers are bad, but yes, some are horrid. Know what a cross-over pipe does, and use a pressure guage correctly to confirm if the backpressure is actually excessive. Guages don't lie. Choose wisely Grasshopper... most just make it louder and force increased noise legislation against all riders.

3.) Making a modern bike into a Hard-Tail. No explanation needed.

4.) Subscribing far too deeply, and literally to the very tired old adage that the engine is 'nothing but an air-pump': "More air in = More Power". Yeah... more or less true, but you really, really need to know what you are doing.

Best advice would be to become an expert at what "Powerband", and "Torque Curve" mean, before you do, or touch anything. "Bigger is better" is very rarely true in this case. Think "Air/Fuel mix Velocity" and "Volumetric Efficiency" for a Streetbike Vs. just "More". Consider compromises and balance.

Rideability and street-ride enjoyment suffers when we narrow the powerband, and move all the power way too far up the RPM range for bragging rights. Think "Flat Torque Curve, and Wiiiide Powerband. No one really cares what your "peak" HP is if you can't keep up with the group. Big Carbs, oversized valves and high lift, long duration cams are best left for the dragstrip or salt flats types, not for the street or road race style bike.

5.) Replacing the rear tire with a big fat one, 'cause it looks cooler. Very bad idea. Design engineers spend months.. years, developing and carefully calculating the correct suspension geometry. Replacing the rear tire w' a fat 'un will totally foul up the handling, create more rolling resistance, and you'll be scalloping through turns like a pie crust maker. For straight line riders only, or for bikes not meant to be ridden, but only looked at. The best handling and cornering bikes have very well performing, carefully designed tire widths, material compositions and profiles for a reason.

6.) Becoming addicted to the Dynamometer. Easy to do, especially for newbies. Dyno's are great for comparing "before" baselines to whatever changes one has made, but far too many folks become totally enthralled in the "Top", or "peak" HP numbers, at the detriment of everything else (See: Rev Limiter "extenders"!!). Beware. Control it, and realise that the chart is only one of about 4 or 5 other equally important performance indicators.

It's just a piece of paper, so don't become a "Paper Racer". The bike with the best "Average" HP and Torque across the Powerband rpm range and the widest, flattest Powerband win the "race" for an excellent Streetbike, not the one with the most peak paper "Power". Choose wisely between Maximum Horsepower and Maximum Performance. They are very, very different.

Also be aware that 1 or 2 HP on some Dyno is the + or - error range. Learn how to professionally read the charts, and for a street use bike, the torque / HP powerband, it's peaks, it's percentage of the whole range, and when it rises and falls are what you should be studying. The "peak" hp # is something you'll use maybe 1% of your street riding time. Bragging about this number is for newbies, amatuers and the very uninformed. Who cares?

Another point to be aware of, especially when viewing amatuer "Back to Back" tests, is that as the engine heats up, Thermal Efficiencies rise naturally, so by the third or fourth comparison, the engine is significantly warmer, and the results badly skewed. Better to run the same test after everything cools down, in the reverse order to confirm the original results.
By the way, I've yet to see a truly, 100% unbiased, well balanced, and well planned comparison test by an amatuer on the internet. The approach is rarely intended to seek "improvement", but rather to prove out or validate a personal theory, or money spent on some ill-advised "mod". Tests results usually then are biased laughingly towards the testers preconcieved notions. Caveat Emptor!

Bottom Line: Use the Dyno as a performance development and monitoring tool, not a bragging "proof of peak HP" sheet of paper. You'll bore everyone to death, and Pro's in the know will look at you funny.

7.) Seriously listening to self ordained "Internet Expert Mechanics" (yes, I guess that might very well include me as well, but I'm really not a "Mechanic"... nor an "Expert" by any means! I try to learn something new every day.) and blindly taking their 'advice'. Newbie's are the most vulnerable to this, and quickly develop embarrassing Hero Worship tendencies, if not "Man Crushes" (eeek!) on these types, so beware, beware, beware.
Note that if these so-called "experts" were really that knowledgable, they would be far too busy building fantastic winning racebikes, or consulting to the various global manufacturers, as opposed to tapping away at a keyboard at 2:00 am doling out questionable advice to newbies and squids. Also look behind the scenes to see if these are thinly disquised Vendors, pushing thier products on the unwary and naive (Not all Vendors are bad, but unfortunately some...).
They're obviously not employed by nor connected with any actual or successful raceteams or manufacturers, so ask yourself why. Better to research carefully, study thoroughly and find out such things on your own. It's a fantastic learning experience, and it will increase your riding skill, enjoyment and appreciation.

8.) Changing the air filter to... "a less restrictive one". Obviously this sounds like a "good" thing, and may be - just make absolutely sure that you are still filtering out either as much as, or more than the original OEM, clean stock paper filter. Many aftermarket (DNA for one) filters do nothing more than delete some of the filtering media layers, for more "airflow". Read up and study thoroughly first, or you could be significantly shortening your engine life in exchange for 1 or 2 measley peak HP points (see #6). Not worth it for the street. Look for the SAE (Society of American Engineers) ratings, comparisons and test results. If a person needs to resort to an air intake filter as a "performance" mod... they're really grasping at straws don't you think? 2 HP gain? Where (at what RPM) in the powerband does this occur should be the questions. How often will you be at that RPM? Now decide.

9.) Open to your suggestion.

10.) Open to your suggestion.

Note once again that the above are well intentioned suggestions, and opinions, and not ever dictatorial. Do what you will of course, just a friendly reminder to tread extremely carefully. Think! Calculate the gain Vs. $$$ spent. Is it a good, practical investment? How does it widen, or equally increase the Powerband? Can I actually FEEL, and experience the improvement on the street? Has it increased my fuel efficiency? Lap times reduced? 1/4 Mile ET (if that matters) decreased? How often will I use this "improvement"?

Personally, I've always adhered to the 4/5 philosophy. That is, if four out of five verifiable, and "proven track record" sources agree upon something, chances are it is a good way to go.

I look to experienced folks like Kevin Cameron, Dave Vizard, John Dalton, Peter Williams, Gordon Jennings, and Phil Irving to name a few. Google those names, then "motorcycle" and you are on your way to some great advice and technical detail from bonafide racers and tuners. You will find that their approach is usually 180 from the typical Internet Wrench Benders ways. One wins actual races and works hand in hand with the Manufacturers and design Engineers, the other... well, you be the judge.

If you can't get significant agreement out of 5 resources, something is probably wrong, research further, or change the approach.

Hang around the local track pit lane to see what the winners are doing (if you can!). Talk is cheap, lap times are real. That said, also realise that race bikes are built to run maybe 1000 (500?) Hrs at best, then they are torn down and rebuilt. Longevity and reliability long-term are not as important as on a street bike. Think about it.

Lastly, ponder the fact that there are an almost infinite variety of Bikes, riders, and what they ultimately intend to do with their rides. Vary rarely are two exactly alike. Street Bikes, drag racers, road racers, endurance folks, Salt Flats speed demons. All are totally different, and all require different approaches. Compromises are always a challenge, but also always a reality.

To para-phrase an old, very often misrepresented quote:

"Speed costs money, how much do you have?" (what total B.S.!)

Should be:

"Speed, better stated as 'Performance', takes excellent planning, technical intelligence, thorough research, and a well balanced, focused approach. How much do you have?"

Ride Safe! (and Smart!)

Bob

__________________

• A good traveler has no fixed plans, and is not intent on arriving. ~Lao Tzu
• Motorcyles are not my whole life, but they make my life whole. ` me

The Prophet

Here's a possible #11.

"Messing around with air filters, pods and carburetor jetting, and getting hopelessly caught up in the "mines bigger than your's" jet size contests you see on a lot of the technically lesser bike sites.

Ponder deeply that roughly 13.2 A/F ratio is the optimum for the "Greatest Possible Power" but not necessarily the best for total burn, fuel efficiency, and keeping raw fuel out of the crankcase. The difference between 13.2 and say 13.7 is almost undetectable, and you can actually go a little leaner and still have a great running bike. Note as well that most Dyno A/F read outs are at WOT, and don't tell the whole story of what is going on at say 1/4, 1/2, and 3/4 throttle openings. This is where an actual, well trained and knowledgable Pro steps in and puts it right.

More often than not, the fuel economy (MPG) suffers badly, and you'll end up spending a lot o' cash on gasoline, merely for bragging rights on some lame website. I actually just read a post on one of these sites recently where a guy was loudly bragging about getting only 110 miles per tank, the stock bike getting nearer to 150 miles. Someone explain to me how this is a "performance improvement". Sounds more like he really screwed it up. Most expertly prepared performance bikes see an INCREASE in fuel efficiency, due to the obvious improved perfromance of the motor, not a decrease.

The first question to ask yourself always is: How often do I ride at WOT, and require "Full Power"?

Most would answer about 5%, maybe 10%, so 90% of the time you're just wasting fuel, and thinning out the oil in the crankcase, thus shortening the life of the bike. But... you can brag with the same misinformed souls about how big yer jetz R.

Your choice of course, maybe some guys go WOT all the time, and rev their bikes to max rpm at every shift. Do you?

Reason #567 of why not to buy a second hand bike from a total stranger.

Ride Safe (and smart)!

Bob

Forchetto

In all my time on another Triumph forum I was unable to convince anyone of the importance of the idle jet and related transition ports on CV carbs. Lots of them quoted those old charts that show it only affects throttle up to 1/8 to 1/4. This mistake is even repeated in Jenk's Bolts oft-quoted tuning advice document. Those charts are only valid for normal slide-type carbs of course.

The idle circuit, jet + idle screw, affects running up to as much as 3/4 throttle and is often the only tweak required to sort a lot of problems. Of course they all ride at WOT all the time there. Strange, I often find myself cruising on the flat at something like 100 kmh and find the throttle is only just cracked open.

I tried showing them the evidence of the huge difference in idle jet sizes between slide and CV carbs for the same cylinder capacity to no avail. I gave up.

The tuning guide can be downloaded here. Lots of info including the "fact" that a simple change to a Unifilter element gives you +7 bhp, a change to Triumph's off-road pipes +6 bhp, that's nearly a total of 25% power increase with just those two mods, amazing, eh?...

Even purchasing a Triumph-approved exhaust system like my Arrows doesn't guarantee anything. My dealer was unable to provide any sort of proof of a power increase and this is a $1000 item made by a large and reputable firm that presumably know what they're doing and not some back-street shed outfit.

The Prophet

Reference: CV style Carburetors / Street Riding.

I think non-technical folks envision that the throttle cable is directly attached to the slide, and as you twist the throttle, the slide goes up accordingly. To them it would understandably also be easier to envision that the faster you go... the higher the slide goes! This is an easier perspective to accept than trying to fully understand constant velocity, vacuum, depression, atmospheric differentials, metered flow through an orifice, etc., so many buy into it.

Hamfisted, wrench bending interet mechanical experts then blurt out such things loudly as gen-u - ine fact, and the newbies have all the confirmation they need. Main-jet manufacturers must love this stuff, as they certainly must sell a ton of jets to those naive newbies. Note as well that many instantly equate "Performance" to larger and larger Main Jet sizes. "Hey, I'm running 165's!"

Nor do these same folks know anything about Venturi effects, or Bernoulli's Principles. How many times have you seen some hack blarting out about bigger and bigger carbs, and hogging out the valve seat diameters for "more power"? More WOT power on the Dyno Chart perhaps, but watch all that usable low end torque and pleasurable rideabilty go bye-bye.

You are dead-on correct that at constant highway speed, the slide/needle jet is barely above the emulsion tube, and the vacuum level on the inlet side of the slide is raised, drawing fuel from the pilot system.

At this same moment, he fixed diameter of the non-tapered portion of the needle has not risen enough to expose the tapered portion, therefore any fuel being metered through this fixed size orifice (the ring-like area between the needle, and the needle tube) is smaller (at less than 7/8 throttle to WOT) than so many would comprehend. The needle needs to rise ABOVE the needle tube, exposing more and more of the tapered portion, in order for the Main Jet fuel system to begin adding significantly more fuel to the A/F charge.

The way in which we ride, and the way the CV carburetor reacts and operates on the street is vastly different than what is commonly illustrated on a typical Dynamometer chart. Unfortunately, as spelled out in a seperate thread, it seems that only a handful of folks on any of these Interent Forums realise what a Dyno Chart is, other than a sheet of paper to prove Peak HP bragging rights.

In the end, it's fruitless to fight it, as you can tell by the odd reactions to any Scientific, or Fluid Flow Dynamics explanations that these are "Flat World" devotee's that are impossible to convince.

Plus, from a positive perspective, they do keep a lot of folks gainfully employed in manufacturing brass main jets, and operating Dynamometers.

Ride Sfae!

Bob

Speedtrip

Had to share this with you Prophet. This is an airbox mod some fool from the ZX10R net (they had the good sense to ban him) made. I especially like the holes he cut in the frame for better air flow. Also like the GP "pipe" he made.


Flickr: ShervinRRR's Photostream

The Prophet

To Forchetto’s great comments, and Speed’s insightful link attachment – This is a fantastic, and perfect example of “misinformation” highway, and the negative aspects of anyone and everyone becoming “experts” if they have an inordinate amount of spare time, an inexpensive digital camera, and access to a computer. Thanks for sharing such revolutionary ideas Mr. Shervin RRR… oops, it appears thast perhaps you forgot all that pesky Fluid Dynamics, Strength of Materials, Structural Integrity, and basic Internal Combustion Engine Breathing principle stuff.

This guy obviously is one of those fella’s that still lives at home with the folks, or grandma, has a TON of time on his hands, has figured out a digital camera and how to post numerous (too many some might say…) pics, but sadly neglected to bother with any Engineering or Science studies. There are well crafted Airbox improvements, then there are a gazillion Airbox elimination kit “discoveries”, then there are airbox atrocities, then there is … this.

If he had stuck firm to the neon lights mod’s as so lustily illustrated and detailed on pgs. 7 – 10, we may have latched onto something totally exotic. Mr. Roboto anyone? The Electric Cowboy? A new, and exciting realm for Safety Fanatics?

Regarding exhausts, and the never-ending, wonderous claims of “More Horsepower!”

I suggest that many get totally confused and disoriented (CO inhalation?) around exhaust systems, most instantly equating LOUD to “better”. There is a site with a running thread on this, and it is now up to 531 (and counting) posts.

Back when it was in the mid-400’s I wasted some valuable time and performed a detailed summary:

Roughly 25% of the posts contain zero data, information, or content, as in “Wow, that’s cool!”, or “Whoa, that is a Bad-ass sound!”.

Of the other 75%, 99% only commented on the sound, none displayed any acceptable proof of any measurable performance gain. “All I know is…”, is NOT an acceptable scientific study.

Only 4 of the 450 even remotely discussed the need for any other adjustments or changes to the bike. All four discussed the “possibility” of a carb adjustment, but none ever followed through.

Oddly, someone(s) gave this "Exhaust" thread a "5 Star" rating. Wierd.

100% though, provided "testimonials", all extremely similar to "Man, this exhaust has TRANSFORMED my bike, the horsepower gains are MASSIVE!", and so on. Interesting reading.

Side Note: Safety Tip o' the Week - Keep that Garage or Shed door open when trying out the new exhaust system. CO gases are extremely dangerous, and you may become disoriented, sleepy, lethargic, etc. serious illness, and eventual Death are possible. Better to start the bike up outdoors, in a well ventilated area.

Folks also become confused and disoriented when hearing things like “At the Isle of Man TT Races, they use open pipes!!” (They are going 160 to 200 MPH all through the course, we need to ride in city traffic, and much slower. Huge Difference.

“MotoGP bikes use … blah, blah, and blah” Next time you run a MotoGP Race, you should probably consider doing the same. For the street, and average everyday riding, it’s a totally different set of challenges.

In the end, it is most likely that the ‘sprung’ weight reduction (others on our great Forum have alertly concluded this as well) of a smaller, more lightly made - compared to Stock, which is made to comply with the many EPA legislationary specs, and thus heavier – and less bulky sheet metal, less packing material and baffling, etc. muffler system. Most newbie’s also do not fully understand the function of a cross-over pipe, which cancels out a ton of “backpressure” discussions.

If you study carefully any of the Manufacturers, or over-zealous Consumer “Dyno” charts proclaiming “The HP gains will transform your bike”, you may see a 2-4 HP gain, but more likely Way up in the RPM range that you may realistically use perhaps 2-3% of the time, probably less.

Compromise (as always!) is what it’s all about. Want super low end torque? Install small diameter, long pipes to generate super high intake and exhaust A/F charge velocity. Unfortunately, this set-up will choke itself out at higher RPM’s. Want big, high RPM “Horsepower” readings? Install large diameter, open, shorty pipes. Unfortunately, this set-up will destroy any low RPM charge velocity, hence Volumetric Efficiency, hence low – mid range Torque. Great for Dyno Racing, very bad for street riding. See: “Loud Harley Squid”.

Try blowing as hard as you can through a drinking straw, then try the same on the big diameter extension tube for your garage Shop Vac. One moves air at super high velocity, and you can see how this would easily fully atomize any A/F mix. But you soon would become “out of breath”. The other moves a LOT of air, but unfortunately at a much lower velocity. This doesn’t help with atomizing fuel, but when the RPM’s rise near the top of the range, at least it’s available (hey… hand me dat bigger Main Jet!). Somewhere in between these two extremes lies the answer…

So, as we can see, we need to make extremely careful, well calculated compromises to end up with an even and flat power output widely felt across the RPM band. “Seat of the Pants”, personal observations are arguably the best in this case, as no one knows our bike’s better than we do, but I suggest that one might keep those SOTP results to themselves, so we do not gravitate as well into the common “All I know is…” category of “Misinformation Highway” technology.


In closing, this in no way is to say that no one should change the exhaust on their bike, so by no means should anyone read it that way. it is to say:


1.) All of our bikes, and the way, as individuals, we ride them are very, very different, therefore there is no "One Way" to improve our very different exhaust system requirements.

2.) Be extremely selective of which - if any - aftermarket exhaust kit you may choose. Not all weigh up to the loftly claims, and we all need to fully understand what (and more importantly where in the RPM Band) the proposed performance gains might be experienced, and at what cost. It may be that the capital investment might realistically be better focused elsewhere.

More importantly - Always maintain an open-minded approach to these performance discussions, as well as the often "interesting" articles such as this particular one from Mr. Shervin, "teaching" us all about... stuff.

Ride Safe!

Bob

Forchetto

I was a bit bored the other night so I Googled "ShervinRRR". It seems that he's an Internet Legend. Everyone is talking about him...good laugh though.

The Prophet

Ya know... I have a soft spot for guys like the illustrious and legendary Mr. ShervinRRR.

Imagine what the world might be like WITHOUT folks like this? Where would the "bar" then be re-leveled at?

For example, how many out there in cyberland have the tenacity to post these:

Unsuccesful projects - a set on Flickr

Fantastic stuff. Hours of educational reading and psuedo-erotic viewing pleasure say I.

I now take a semi-firm stand, and disagree with everyone on this, now leaning towards the thought / concept of ol' Sherv' being a totally misunderstood genius of sorts. A madman, perhaps, but who else would think of "Speed Holes" for the license plates.


Not me! I don't see ideas like this spewing out from the rest of you guys! Shameful!

Should we recruit this guy? Or just peek in from time to time at the ever forward moving progress? Perhaps the latter idea is more pragmatic for now...

Ride ... safe!

Bob