Service
SERVICE
Paul Dean
No black-box magic
Wow! Gas at over $2 per gallon and not likely to go back down ever again? Okay, but we’ve now got EFI-equipped motorcycles with computer-controlled ignition timing, and Power Commanders and other black-box modification kits designed to “increase power and driveability.” So, can the computer on a modem motorcycle be modified to enhance fuel economy at the expense of absolute power? I’d gladly give up 11-second quarter-miles and 36 mpg for 15-second quarter-miles and 60 mpg. Peter Susi
Lodi, New Jersey
Interesting idea, but not entirely feasible. You 're talking about increasing gas mileage by almost 70 percent; realistically, that is too ambitious to be achievable simply through the reprogramming of the black box. Engines that operate efficiently-whether in terms of outright performance or optimum fuel economy-have to be coordinated systems designed to attain specific objectives. For an engine to get 60 mpg on a regular basis, all or most of its tuning cíeme nts-cam timing, valve sizes, exhaust-system dimensions, compression ratio, combustion-chamber shape, throttle-body diameter, bore-and-stroke ratio, port design, etc.-have to be geared toward that particular outcome. Consequently, merely dialing back the fuel and spark can 't turn a high-performance engine-which is what most contemporary motorcycle powerplants are-in to a fuel miser. A sharp tuner or engineer no doubt could significantly increase the fuel-mileage potential of a typical modern bike engine by programming very conservative values into its fuel-injection and ignition systems, but the results would likely fall far short of your 60-mpg target.
Drill-bit tuning tips
I own a 2003 Suzuki Volusia 800. I recently drilled my pipes as so many on the Volusia Owner’s League website have done. Many of them go so far as to pull the rear baffles out altogether. I drilled six 3/4-inch holes in each pipe through the metal surrounding the center outlet. It sounds great, but I’m afraid I may be causing my engine to run too lean. I worry about long-term damage, because this bike is said to be very lean from the factory. I have not changed the air filter and wonder if I should rejet. 1 could just turn the mixture screw, but for some reason, Suzuki solders it over, probably so I don’t mess with it. Shawn Suppa
Posted on America Online I suspect that your Intruder could very> well be running too lean. It came from the factory with lean jetting, which it needed to pass EPA emissions standards, and the holes you drilled in the muffler may have made it leaner yet. When people make unproven, home-grown modifications to an exhaust system, it becomes virtually impossible for anyone to provide specific tuning advice. The exception, of course, would be if the advisor had performed those very same modifications on the very same model of motorcycle and developed the requisite tuning adjustments. I have not, and I don 't know anyone who has. My advice is for you to take your Intruder to a shop that does dyno tuning and have them dial-in the carburetion. They can run the engine under load and, either by using an exhaust-gas analyzer or taking sparkplug readings, determine the extent of the leanness throughout the carburetor’s entire range of metering systems. You are correct in assuming that the mixture screw has been covered to deter tampering by the owner or anyone else. The cover can be easily removed, but that screw only adjusts the mixture at idle and very small throttle openings. If your Intruder’s mixture does prove to be too lean, necessary adjustments will more likely involve changes to the needle, needle jet and main jet.
Things that go clunk
I have a 1978 CB750F that makes a noticeable clunking noise at idle. When I apply the clutch lever it goes away, and when I release the lever the noise comes back. What is going on in there? Break it to me gently if it is something major... Relax, it probably isn’t major. In all probability, the noise is being caused by two factors: The clutch drive plates have gotten loose in the clutch hub, and the engine is not idling smoothly.
Bob Davison Kingston, Pennsylvania>
The clutch drive plates are the ones with the large tabs around their circumf erence that fit into wide slots in the outer clutch hub (commonly called the clutch basket). Though the tabs fit fairly snugly in those slots when the clutch is new, they shift back-and-forth slightly every time the throttle is opened or closed when the bike is in gear. Over time (your bike is, after all, 26 years old), the tabs gradually get beat up enough to become slightly narrower and fit more loosely in the slots. The slots also get hammered enough to become a little wider.
When the engine is idling in neutral with the clutch engaged, the clutch drive and driven plates are locked togeth er and rotate as a unit, along with the en tire mainshqfl of the transmission. But when normal wear has increased the freeplay between the drive-plate tabs and clutch-basket slots, the entire clutch pack is allowed much more movement in the slots. If the engine idles smoothly, this movement usually goes unnoticed. But f the engine idles unevenly, it undergoes small but constant fluctuations in rpm that cause the clutch pack to jiggle back and-forth in the slots, creating the noise you hear.
When you squeeze the clutch lever, the drive plates and driven plates are separated. The drive plates continue to rotate with the engine, but the driven plates, which are connected to the transmission mainshaft via the inner clutch hub, slow down and stop. Because of the presence of oil on the clutch plates, a slight bit of drag exists beleen the drive and driven plates. That tends to keep the drive-plate tabs pushed up against one side of their slots, thereby eliminating or greatly reducing the noise.
The solution, then, is to remove the clutch cover and inspect the condition of your Honda clutch plates and clutch basket, and replace either or both if necessary Then have the engine tuned, including a good carburetor synchronization, so it idles smoothly. In fact, f the clutch still is in half decent condition, getting the engine to idle smoothly may stop the noise altogether
A sticky problem
I put some some carb cleaner in the gas tank of my Suzuki 1400 Intruder, and now the vacuum slide in the carb is sticking, causing the sparkplugs to blacken. What can I do to fix this problem?
Lamar Schenk
Downey, California I don't know which curb cleaner you used, but it apparently has gummed up the slide enough to make it hang up rather than allowing it to move up and down according to throttle position and intake vacuum. Some of the automotive carburetor cleaners don ’/ work well in motorcycle carbs, and in fact don 't even do such a good job in automobile carbs. In any case, you 'll have to remove the slide and clean it by hand with contact cleaner or other solvent that doesn 't leave a residue. Actually, you should remove the curb altogether and thoroughly clean it piece by piece. The same residue that gummed up the slide may also have partially clogged a jet or left deposits on other internal curb parts.
gottasickmodifiedrd
i own 1975rd350 ported pollished fiberreeds expansionchambers stockpoints and timing k+n filters dont remember the jetting misses at 80mph wont go faster love bike can you help and or recomend book
Ken Hill Swanton, Ohio
id liketo helpyu but yu havent given me muchinfo to work with probably the jetting is the problem yu should start by doing plugchops at fullthrottle if plugs are black go leaner on jetting if they re light gray or white go richer also check ignition timing with a strobelight at higherrpm
Seriously, Ken, if you want to read a good book on the basics of two-stroke engines, try to unearth a copy of Gordon Jennings' “Two-Stroke Tuner’s Handbook.” It’s been out of print for a while, but if you browse sites like eBay or amazon.com, you ’ll find used copies available. A few other choices are, “Two-Stroke Performance Tuning,” by A. Graham Bell; “Motorcycle Tuning: Two-Stroke,” by John Robinson; and “Two-Stroke Cycle Engine: Its Development, Operation and Design,” by John B. Heywood.
The cable guy
I’ve installed adjustable handlebar risers on my 1994 Honda VFR750 and have found that the height to which I can raise the bars is inhibited by the choke cable and the two throttle cables. If 1 raise the bars up to where they provide the level of comfort I desire, the cables are not long enough to maintain the slack necessary for safe riding. If I were to have some custom cables made, how much longer could they be extended and still be able to function safely?
James Eng Trenton, New Jersey
Within reason, the length of a control cable has no effect on its ability to perform its in tended function. As evidenced by the ridiculously high ape-hanger handlebars on some radical choppers, overall cable length is not a problem. What is important is the difference in length between the cable’s inner wire and its outer sheath. As long as that differential is maintained with any degree of accuracy, and some sort of inline adjuster is incorporated, extended cables should not present your VFR with any safety; or operational problems. Just make sure you have the cables made by someone who is experienced in that craft, and that the throttle cables in particular are long enough to allow full left/right steering movement without binding or affecting the throttle opening. □
Recall Roster
NHTSA Recall No. 04V137 Big Dog Boxer, Bulldog, Daytec Chopper, Mastiff, Pitbull, Ridgeback Model year: 2004 Number of units involved: 1906 Dates of manufacture: Sept. ’03-Mar. ’04 Defect: On certain motorcycles, the piston in the rear master cylinder may have been improperly sized, which could cause the rear brakes to drag or lock up. This could result in a crash.
Remedy: Dealers will remove the piston from the rear master cylinder and replace it with a new piston. Owners who do not receive the free remedy within a reasonable time should contact Big Dog at 316/267-9121.
NHTSA Recall No. 04V187 Victory Vegas, ANSS Vegas, Kingpin Model year: 2004 Number of units involved: 3230 Dates of manufacture: May ’03-April ’04 Defect: On certain motorcycles, the hose that connects the rear-brake fluid reservoir to the rear-brake master cylinder may have been damaged during shipment, which could cause it to leak brake fluid. This could possibly cause a loss of rear braking capability, increasing the risk of a crash.
Remedy: Dealers will inspect the rearbrake reservoir hose and, if the hose is damaged, replace it. Owners who do not receive the free remedy within a reasonable time should contact Polaris/Victory at 763/417-8650.
TECHTIPS
A clamp is not a clamp is not a clamp. Not when it comes to the alloy U-clamps that secure some tubular handlebars to their top fork crown. On many bikes, those U-clamps are perfectly symmetrical-that is, both of their “legs” are exactly the same length. But on some bikes, one leg of each clamp is slightly longer than the other, and that inequality calls for a different procedure when tightening their bolts. With a conventional clamp, you tighten both bolts evenly to achieve an equal gap between the bottom of both legs and the mating surface of the handlebar mount on the fork crown. Because the legs are of equal length, it makes no difference which way the clamp is mounted. Not so with asymmetrical clamps, which have some sort of marking that indicates either the “top” or “front,” denoting the longer of the two legs. On some clamps, the mark is a cast-in arrow that points forward; on others, it’s a small dot or punch mark next to one of the holes. Whatever the marking, the clamp should be installed with its long leg toward the front, and the bolt that passes through that leg should be tightened before the other bolt is even snugged. The idea is to fully tighten the front bolt until the long leg of the Uclamp is pinched tightly against the mating surface of its handlebar mount. Only then is the other bolt tightened, the end result being a large gap at the rear of the clamp and no gap whatsoever at the front. The front-axle clamps on some bikes, particularly certain older models, also are made with unequallength legs. They, too, should be installed in the same fashion, with the long leg facing forward and the front attaching bolt fully tightened first. -Paul Dean
