Service
Service
RAY NIERLICH
REHAB LOUD PIPES DO WHAT? BEST USED BIKE TIRE PRESSURE GAUGES
What most people think of when they think ZX-14. Reader Roger Tremblay would like to make his into a sport-tourer.
ROLL YOUR OWN SPORT-TOURER
Q I am looking for a little suspension adjustment advice. I picked up a very nice 2007 Kawasaki ZX-14 with a bit less than 10,000 miles. The suspension feels taut and in good condition. It just seems a little harsh and hard-edged for general sport-touring. With gear and ready to ride, I am at about 210 pounds. What would be good baseline settings to start from and not be too far off to make small changes and test? I primarily sport-tour with a little blast through the twisties now and then, but in general I ride at about a sixor seven-tenths pace.
ROGER TREMBLAY GRAND PRAIRIE, ALBERTA, CANADA
A I’ve been tempted myself to
make a fast solo sport-tourer out of a ZX-14. Since Honda decided to quit producing the CBR1100 XX Blackbird and the Suzuki Hayabusa has a more sporting edge, the ZX-14 is the obvious choice. It would be so easy to buy a Concours 14 instead, but what is the challenge in that?
Assuming that your ZX suspension is in good general condition, the harshness is most likely caused by a combination of springing and damping. Fresh fork oil certainly won’t hurt but is unlikely to make an appreciable difference. It is also possible that with your stated weight, plus the age of the bike, the fork and shock springs have settled enough so the suspension isn’t working at the intended ride height, which can also cause harshness.
Race Tech suspension (racetech.com) has a large catalog of testing experience and recommends upping fork spring rate from the standard çyokg/mm to io.okg/mm (Race Tech part #FRSP S3825100, $129.99) and increasing the rear shock spring from the OE 9.7kg/ mm to íoykg/mm (#SRSP 5818107, $114.99). To improve damping, Gold Valve kits are recommended front (#FMGV S2040, $169.99) and rear (#SMGV S4005, $169.99). These valve kits are designed to reduce harshness over small irregularities such as
expansion joints yet improve damping response overall, and in our experience they are effective.
LESS BLAMMO, MORE WHAMMO
Q A Davidson buddy of Softail mine has Slim. a HarleyHe changed the exhaust to a D&D system and had a cam (longer duration, I’m guessing) put in it. The bike runs well. The thing is, that exhaust makes it way too loud. Is there a way to significantly increase a Harley’s performance without pissing off the neighbors? I like the idea of a cam that moves the power curve to a higher engine speed, but I suspect the exhaust flow resulting from higher rpm would be too much for the stock exhaust. What do you think?
BOB SHEEHAN NEDERLAND, CO
A blowing, It’s all about Bob. sucking Engines and are air pumps: The more you can suck in, the more you can blow out.
It is designed as a system, and only changing one or two components often doesn’t change performance much.
But, typically, the exhaust is where most of us start, which on the Softail Slim is the wrong place to begin if you’re after performance gains. There is only a maximum 5-hp improvement to be had by changing the exhaust on an otherwise stock Twin Cam 103.
The best first step to boosting performance on the TC 103 is to improve intake breathing. As much as 10 hp can be freed up with the Screamin’ Eagle airflow kit alone. Perhaps he had this done with the cam change? If your buddy did intake and cam work, he won’t want to refit the fairly restrictive original mufflers, which have catalysts.
If only the pipes were changed, his bike is most likely not much, if any, faster, but it might feel faster to him because of the racket. You don’t state what D&D system he’s using, but the company’s louvered baffle is the quietest it sells. If his bike is really obnoxiously loud, the crowd chasing him with pitchforks might improve his response times, though.
GOT A MECHANICAL OR TECHNICAL PROBLEM with your beloved ride? Perhaps we can help. Contact us at cwservice@cycleworld.com with your questions. We cannot guarantee a reply to every inquiry.
DOUBLE, DOUBLE, COIL AND TROUBLE
I own a 1993 Kawasaki ZRiioo. This bike came from the factory * with four coils and eight spark plugs. When each coil fires a cylinder, it also fires in a different cylinder on the exhaust stroke. I suppose this is to reduce emissions. Is this necessary?
I was thinking of taking the exhaust ignition wire and hooking it up to the second plug of each cylinder. This would give the cylinder better flame propagation and burn more of the gases. What are your thoughts on this?
TERRY ROBINSON ORLANDO, FL
A Well...yeah! You’ve got twin
spark plugs from the factory in B that beast; let’s take advantage of them and get a bigger, faster flame front and more power without detonation worries. Woo-hoo! Only problem is, firing both plugs at the same time is exactly what the tricky engineers at Kawasaki have done.
You’ve posed an excellent question here, and my gray cells are still smarting from thinking this one through. The Zephyr fires each pair of its four coils every crankshaft revolution, 180 degrees apart. So it is firing pairs of coils twice per four-stroke cycle. These are twinlead coils firing pairs of cylinders with one slightly before TDC on compression and the other cylinder 360 degrees out, slightly before TDC on valve overlap.
The second spark is thus wasted with no effect on emissions or power.
The clever bit is that the second of the two coils in the firing pair is both wasting a spark in the same cylinder as the first coil and firing a plug under compression in the same cylinder as the first coil in the pair. Why is this so good? Spark plugs typically require an average of 15,000 volts or so to fire under compression pressure and way less than that if under no pressure, as on overlap.
Thus, with two coils firing one plug each in any cylinder at the same time, the peak voltage required per coil is greatly reduced. If you were to switch your spark plug leads around so that one coil has both leads going to the same cylinder, your Zephyr may still run but the voltage requirement per coil as it fires would almost double.
Don’t change anything!
ASK KEVIN
Q I have my first shaft-driven motorcycle, a Yamaha FiR. I can certainly say that I don't miss the chain, what with adjusting, cleaning, lubing, replacing, and cleaning filth off of the back of the bike. However, a belt drive seems to be even simpler still, less expensive, with more efficient power transfer, and less maintenance. Why haven’t more manufacturers embraced belt drive? What are the drawbacks? OREO SEEOER SANTA ROSA, CA
A . As you note, toothed belts have their attractions. But unlike a chain, they can rise up out of engagement and slip if given enough slack (note that cam belts on engines have fixed adjusters that remove all slack). The obvious solution for achieving zero slack in a motorcycle final toothed belt drive-making the front sprocket concentric with the swingarm pivot axis-interferes with using driveline tension to oppose the rear-end squat that otherwise occurs during hard acceleration. For these reasons, toothed belts tend to be used either on machines with very limited rear-wheel suspension travel or with tensioner systems of some complexity. Chains continue to be generally used because they are not subject to these requirements and because they provide great strength in a compact form. -Kevin Cameron
FUEL FOR THOUGHT
Q • My 1998 Honda XR400 runs fine. But under power at about 3,000 rpm in third gear, it flattens out, sputters, and loses power. It keeps stuttering after an upshift, but downshifting to first fixes it until midway through third again. Any ideas? MIKE ALUMBAUGH VIA CYCLEWORLD.COM
A . This is classic fuel starvation. If the amount of fuel entering the bowl doesn't keep up with demand, fuel level drops until the main jet gulps air. The pause in fuel demand
from a downshift allows the bowl to fill, and power returns only briefly before the engine starves again.
Assuming you checked the float level and saw that the jets and needle were clean and unworn, here are a few basic tips: Open the gas cap for the next test ride. If the problem disappears, your fuel tank vent is clogged. No air in means no gas out. If there's no change, pull the fuel line off at the carb and see if gas runs out with the petcock on. It should be a good stream. If not, pull the petcock apart to clean it. Clogs are way more common these days with the advent of ethanol in our modern fuels.
