Service
SERVICE
PAUL DEAN
Electronic fuel infection
Q Just returned from a few weeks riding Wyoming and Colorado with my wife on my Harley Fat Boy, which is my first bike with that new-fangled electronic ignition and fuel injection. I also added a programmable Vance & Hines Fuelpak to go with a 2-into-1 exhaust and an open airbox. In past decades, all my bikes would not idle at the top of Pikes Peak and ran at a reduced power level at higher elevations. But this Harley idled perfectly at high altitude, ran normally and got fuel mileage over 50 mpg, sometimes up to 60 mpg. At sea level here near Tampa, this same bike only gets 40 mpg, idles unpredictably high and sometimes even stalls returning to idle. Why can't my bike's electronic "brain" work as well around here or does it just have to get high? Larry Malinoski Ruskin, Florida
A No drugs or alcohol needed for your Fat Boy, Larry; my best guess is that your Harley’s “brain”—the technical term for which is Engine
Control Module (ECM)—is being confused by the tuning modifications you described. Installation of a V&H Fuelpak requires downloading the correct fuel map for each specific engine and its state of tune (which is affected by any changes to the exhaust and intake systems), as well as an adjustment of the throttle position sensor (TPS). Missteps in those procedures can easily result in symptoms such as erratic idle, too-rich or too-lean fuel mixtures (which would account for the wild variations in fuel mileage) and failure of the system to do one of the things that fuel-injected engines normally do so well: automatically adjust for changes in altitude and air density.
Since I don’t know who installed the Fuelpak on your Fat Boy or how it was done—and I’m also unsure about what you mean by an “open airbox” on an engine that doesn’t really have what is normally called an airbox—I suggest you take the bike either to a reputable H-D dealer or a highly regarded Harley repair shop and have them diagnose the problem. If the Fuelpak’s installation and adjust-
ment procedures are followed, your bike should idle and run properly in Tampa, Pikes Peak and everywhere in between.
Clutchless in The Keys
QI Adventurer currently ride 900 a and 1999 its Triumph evil twin brother, a 2000 Sprint RS. I sometimes shift into the upper gears without using the clutch, never power-on, though always firmly but gently. Back in the day, when I rode enduros on a KTM (née Penton), I recall hardly ever using the clutch, and no damage resulted. Am I harming anything on my Triumphs? How about downshifting with appropriate blips of the throttle? Bob Baimc Longboat Key, Florida
A Yes, you can perform clutchless upshifts and downshifts without incurring damage to the transmission or anything else in the driveline. But the operative word here is “can,” because there is no guarantee that you won’t damage anything.
In most motorcycle transmissions,
including those in your Triumphs, every gear ratio involves the coupling of two gears—one connected to the rear wheel via the final drive and one connected to the crankshaft via the clutch and primary drive. (The exceptions are certain transmissions in which one speed— usually, but not always, top gear—is a direct drive between clutch and output sprocket.) Every time you change gears—up or down, with or without the clutch—the shift mechanism uncouples the engagement dogs of two gears which, obviously, have been spinning at the same rpm, then it engages the dogs of two other gears that have not been turning at the same speed. If the shift is done perfectly, the very brief moment that the throttle is either closed (when upshifting) or blipped (when downshifting) changes the rpm just enough that the speed of the gear connected to the engine closely matches that of the gear driven by the rear wheel, allowing the dogs to mesh smoothly and quietly.
If you use the clutch when shifting, perfectly matching the speeds of engaging gears is not as important. The gear connected to the rear wheel is being driven by the inertia of the entire motorcycle, so it’s not able to change speed if it suddenly is thrust into engagement with a gear that’s spinning at higher or lower rpm; instead, that faster/slower gear instantly must change its speed to match that of the other. And it does so rather easily because the clutch is disengaged, which disconnects the gear and its shaft from everything but the inner clutch hub and its plates. That assembly’s inertia is so small that it usually can react to sudden changes in its speed without causing any damage.
That’s not the case if you shift gears without the clutch and fail to match the speeds of engaging gears very closely.
As stated before, the gear connected to the rear wheel has the massive inertia of the moving motorcycle and its cargo behind it, so it’s not going to change speeds; and the other gear is still solidly hooked to the fully engaged clutch, the primary drive and all of the powerplant’s spinning and reciprocating components, so it also is reluctant to instantaneously speed up or slow down. But in that contest between the irresistible force and the immovable object, the irresistible force (the engine-connected gear) loses; it has to change speeds, and the shock wave of
that clash is much more likely to result in a minor amount of damage, such as a slight rounding of the gear dogs or a tiny tweak of the shift fork. Over time, the accumulation of transmission damage brought about by less-than-perfect clutchless gearchanges will lead to problems—missed shifts, stiff shifting, jumping out of gear, etc.—much sooner than if all the shifts in that same period had been made with the clutch.
By the way, the KTM/Penton you rode in enduros back in the day did not have a traditional gear-dog transmission. It instead used a ball-selector design in which gears were engaged by small steel balls that were pushed up into recesses in the inner diameter of each gear by a long rod that ran through one of the transmission shafts. But that’s another story altogether.
The smoking gun
Q I have a 22BMW Ri 15OGS with only 22,000 miles on it. The bike is fully shop serviced and ridden gently, but sometimes, when I start the engine, the exhaust gives off a big puff of smoke that lasts for a few seconds. It
only started doing this a few thousand miles ago. It happens mostly on long journeys, especially if loaded up, but often on short rides, too, and only if started after being left on the sidestand. I’ve asked a few non-BMW techs about it, and they think it’s a known issue with Boxer engines, having something to do with oil draining into the left cylinder.
But if that is the case, why doesn’t it do this all the time? Have you ever heard of this or do you think I am looking at a developing problem that could end up being a big issue? Brian Woolston Submitted via www.cycleworld.com
A Not to worry, Brian; what you describe is indeed common for BMW Boxer Twins. When the bike is parked on its sidestand, the left cylinder is aimed downward. As a result, any oil
that might have splashed onto that cylin der's walls beneath the piston just before the engine was turned off can now run downhill, seep past the piston rings and enter the combustion chamber, where it is
burned the next time the engine is started. This doesn't happen every time for a number of reasons. It's most likely to occur when the engine is shut off after running at full operating temperature,
such as at the end of a long ride. That's when the oil is its thinnest and the cylin der walls their hottest, factors that help the oil run downhill more easily and gradually bleed past the piston rings.
What'si~1ike1i~Jsmoking upon startup can be dependent upon where the left cylinder's piston stops when the engine is shut off. If it ends up at or close to Top Dead Center, a lot of that cylinder's wall is exposed below the piston, providing more area where oil can pooi. But if the piston stops at or near Bottom Dead Center, very little or none of the cylinder-wall area is exposed, so not much, if any, oil can collect there.
Less oil beneath the piston means less chance of smoking upon startup. As far as why the smoking only sur faced fairly recently, that could be the result of change in the orientation of some, or perhaps all, of the piston rings. It's not uncommon for rings to gradu ally move around a piston during normal running so that the end gaps are not always in the same location. If all of the ring gaps on a Boxer engine's horizontal
left-hand cylinder happen to be near the `~upper side of the piston, there is less chance of residual oil slipping past the rings than if some of the gaps are on the lower side. So, perhaps the rings in your engine have shifted enough in the past :few thousand miles to permit more oil seepage than they previously allowed. : In any event, you have nothing to lose j sleep over. Your Boxer engine is simply being. . .a Boxer engine.
Drilling for performance
Q I recently purchased an `08 Triumph Daytona 675, and CW rand sundry other moto-rags nailed it I when describing the most harmonious exhaust tone of this mo/to do/ce Triple. The punk-ass kid I purchased it from, however, also "got it," and to amplify the mellifluous tone, he drilled two 5/16inch holes through the exhaust pipe just before the underseat muffler. Sounds frick'n great! But a couple weeks ago, I heard the "Car Guys" on National Public Radio telling some caller about how a muffling system is designed for something called back-pressure, and if it is altered, it might be detrimental to the valves (read: burn `em up!). These holes
have approximately 5 feet of tailpipe from the manifold, and I could easily cover them with a stainless hose clamp if needed. Am I damaging this sweet ride by operating the engine with this intentional "flaw"? John Willmann Tucson, Arizona
A I've never performed any Black & Decker exhaust modifications on a 675 Daytona, so I can't say for sure what the outcome might be. But as small as those holes are and as far as they are from the exhaust valves, I doubt they will cause the engine any harm. I'm also fair ly certain that they aren't doing a thing for engine performance, either. The 675 might sound faster, but if actually making a bike go faster involved merely drilling a couple of holes in the tailpipe, twist-drill sales would go through the
roof and companies like Akrapovic and LeoVince would be selling toaster ovens and leaf blowers rather than full exhaust systems and slip-ons.
If an engine had no exhaust system whatsoever, it would tend at certain rpm to expel some of the fresh, incoming fuel mixture out through the exhaust port along with the burned exhaust gases; in certain other rpm ranges, some of the spent gases would be pushed back into the cylinder when the exhaust valve opened, contaminating the fresh mixture. A well-designed exhaust system, however, uses sound waves that are moving away from the exhaust port to help extract all of the burned exhaust gases from the cylinder, just as it uses sound waves that are moving back toward the cylinder to prevent unburned fuel mixture from being expelled along withthe exhaust. The latter
effect is commonly referred to as “back pressure,” since it involves sound waves that are moving back toward the engine.
Once again, those two small holes in your 675’s tailpipe probably have not negatively affected the back pressure enough to alter the performance in a
meaningful way. All they have done is made you smile—and maybe put a frown on your neighbors’ faces when you start the engine in the morning.
Want fries with that?
QI 400 acquired on which a ’93 the Suzuki CDI box Bandit was burned out, so I replaced the box. Upon starting, the engine fired through once and the replacement box burned up. I now have another new CDI box, but I don’t want to install it only to have it burn out. The boxes are hard to find and pretty expensive. What should I be looking for and how can I test for the problem? Tim Shumaker
Georgetown, Tennessee
A Problems like this one can be
solved through a short process of logical deduction. The only thing that can fry a CDI box so quickly is excess electrical voltage; the only source of excess voltage on the entire motorcycle is. the AC alternator; and the only way that excess alternator voltage can reach the CDI box is if the charging system’s regulator/rectifier is failing to either convert the AC to DC and/or limit the current delivered to the rest of the elec-
trical system to under 14.5 DC volts.
Conclusion: Your Bandit’s voltage regulator/rectifier has gone south, allowing the full high-voltage AC output of the alternator to reach the CDI box, which is designed to run on controlledvoltage DC current. Result: The box is fried almost immediately. Solution: Replace the regulator/rectifier (cost new: approximately $200) and the problem should be a thing of the past. U
Got a mechanical or technical problem with your beloved ride? Can’t seem to find workable solutions in your area? Or are you eager to learn about a certain aspect of motorcycle design and technology? Maybe we can help.
If you think we can, either: 1) Mail a written inquiry, along with your full name, address and phone number, to Cycle World Service, 1499 Monrovia Ave., Newport Beach, CA 92663; 2) fax it to Paul Dean at 949/631 -0651; 3) e-mail it to CW1Dean@aol.com: or 4) log onto www.cycleworld.com, click on the “Contact Us” button, select “CW Service” and enter your question. Don’t write a 10page essay, but if you’re looking for help in solving a problem, do include enough information to permit a reasonable diagnosis. And please understand that due to the enormous volume of inquiries we receive, we cannot guarantee a reply to every question.
