A Weak Link

Because I yet do not know enough about Charter Schools to write an editorial, I am going to shed some light on what seems to be a rather prevalent motorcycling ailment.  There are a number of internet forums that have the thread, "Motorcycle Chain Clacking." It ranges from dirt bikes to street bikes.  The common consensus seems to be it is unavoidable.  The chain makes noise traveling over the front sprocket and also in other places along its travels.  Recently I encountered this problem on my 2001 Honda XR-200R. Since I have owned it never has this particular phenomena been a problem until now.  This summer as I have attempted to trail ride behind my house, I began to encounter this same annoying clattering sound coming from the drive train.  It was difficult to pinpoint.  There are many places the chain makes contact with other parts of the suspension.  There is a thing called a "Chain Slider" of which I was not aware.  The first thing I did was disassemble this piece of what appeared to be white plastic.  The chain rides across it as it runs onto the rear sprocket.  It is a guide that feeds the chain directly onto the teeth of the rear sprocket.  It was filled with dirt and also had grooves worn in it where the sides of the chain had created friction.  I put it back on.  Same noise.  I scrutinized the plastic shielding parallel to the swing arm.  It was somewhat loose and could have been making contact with the chain.  That was all that I could see.  This sound religiously was disrupting my riding experience.  As some non-riders may not know, the motorcyclist uses both his "ears" and sense of touch to control the bike.  One's ears hear the revving of the engine, and this tells you many things.  Most prominently it is when to shift gears.  Certainly I do not look at the speedometer and shift at a documented spot, while many speedos do indeed have indications for the appropriate gear range.  You use your ears.  When the engine gets revved up too high, you shift into a lower gear.  With a bit of artistry one can make the sound of a motorcycle engine sound noble by its shift points and velocity.  You can shift slowly or quickly depending upon the type of ride you desire.  I would assume upon reflection the majority of engine sound is coming from the exhaust pipe.  With the increasing popularity of the Harley Davidson as a machine of choice, it has become common in the United States to remove any baffling from the exhaust system.  Literally that means the sound of the explosion of gas and air in the cylinders is transmitted directly out of the pipes.  It is loud, almost unfathomably loud.  I am not sure exactly what is the appeal of this horrendous roar.  It could be a combination of intimidation, defense, or simply awareness.  I have heard riders of Harleys like the idea that other motorists clearly can hear them coming.  What I wonder is how that sensation feels underneath one's crotch?  To each his own I guess.  What I know from experience is the combination of engine vibration and sound of a Honda are quite pleasing to the human psyche.  That may not be as true for "stock" motorcycles or bikes that have been left the way they have been "tuned" at the factory.  It seems to be common knowledge that for E.P.A. standards Hondas purposely are tuned "lean."  That means the fuel/air mixture in the carburetor does not quite have enough fuel thus exhibiting erratic behavior when the engine is cold.  Simply this means the bike is "cold blooded" and takes a long time with the choke on to warm up properly.  I had this problem with my own 2008 Honda CB-250 Nighthawk.  It had a very problematic stutter upon acceleration.  After reading a few forum posts on the internet it was easy to discern that the carb. was jetted lean.  With documentation provided by a few conscientious Nighthawk owners, I was able to figure out how to solve the problem.  It was not dissimilar to how I had "uncorked" my Honda XR-200R.  If you removed the baffles from the stock exhaust then the tuning of the engine is disrupted.  The calculated air flow through the cylinders from the carb. to the exhaust is changed.  There is MORE airflow at the exhaust side with no increase on the carb. side.  I experienced the results of this first hand on my 200.  Before realizing I needed to re-jet the carb., I proceeded to uncork the exhaust by replacing the stock baffle with a Thumper racing insert.  It opened up the airflow somewhat and gave the XR a bawdy pig sound.  Without the increased fuel and air flow from the carburetor  the engine bogged during acceleration.  I rode it anyway unknowing.  After reading up I learned that if you opened the exhaust in this manner, you needed to increase the jet sizes in the carb.  I did going up one size.  It solved my problem without ever having to consider changing the needle clip position (if there was one.)  This increased the performance of the 200 engine considerably.  I knew that the Nighthawk would benefit from a similar program.  First like the XR, the CB-250 needed an increased airflow air filter in its air box.  Stock air boxes from Honda I believe are required by law to possess metal grills to thwart a possible air box fire.  That is the only reason I can assume for this rigid and difficult to bend screen.  On the XR I ripped out this metal obstacle and installed a K&N filter made of foam.  This coupled with the larger jets and opened exhaust constituted the "uncorking" of the XR.  Voila!  A great result.  The CB-250 had a spring-loaded, metal-contained, paper filter.  I really did not want to abolish this well engineered device and did not see an easy way to attach a "pod" filter with a simple clamp.  Some structural modification would have been needed.  Instead I took the filter to a friend and auto mechanic's shop where we tackled the dilemma.  After a bit of hacking and sawing we were able to modify this metal unit eliminating its own paper filter.  With a few concise cuts to allow more room within the housing, a "pod-type" filter clamped directly onto the preexisting tube inlet.  Success!  The unit would clamp in and out of the air box with the preexisting spring-loaded lever.  No modification of the inlet or air box was necessary, only the filter housing itself.  With this done I experimented with the jetting of the carburetor.  I tried one size larger jets and two washer shims on the jet needle.  This produced a favorable result, but intuitively I felt the little CB could gain even more performance with two sizes of larger jets.  I installed these and one more washer on the jet needle.  Bingo.  I feel with these modifications I have one of the best sounding engines in our town.  It will accelerate with a Harley from zero, and at 50+ m.p.h. with a full opening of the throttle the engine will sing with the full throatiness of a baritone opera singer.  It is spectacular.  Even without altering the stock baffles in its pipes, the performance of the engine is stellar for me.  It is purrs like a kitten with moderate throttle at speed, it roars with acceleration when pushed, and otherwise is inaudible except for its pleasant vibrations under your thighs.  While its engine tuning was crucial to eliminate that dangerous hesitation upon acceleration, two other modification also were necessary.  One was the installation of a set of aftermarket "Daytona" handlebars.  These were more akin to the geometry of dirt bike bars and controlled the slightly heavy front end better.  The second task completely solved this seeming heaviness in the front end.  There is a large gas tank on this machine, and when it it full obviously the front end seems heavier.  One simple task alleviated this sensation.  I replaced the stock six-year-old front fork oil with a slightly stronger fluid, fifteen grade instead of ten.  Even without installing a not-available "Progressive" spring, this change of oil remarkably changed the handling of the Honda CB-250.  Now it responded like a "sport" bike.  It was an amazing change.  Now I have both the XR-200R and the Nighthawk in tip top riding condition and just in time.  The 100 degree plus "dog days of summer" almost are at an end.  Let the good times roll.  By the way put a new heavy-duty "O" ring chain on your machine.  It will cost more, but it will eliminate the chain's lateral movement keeping it from clattering on the engine's other metal parts.  Simple.  Done.  Honda.  Great.