Service
SERVICE
Gee Vee Double Ewe Arr
PAUL DEAN
Q I ride an ’09 BMW R1200GS and have a question about tire pressure. I get so many conflicting answers that I want an answer from someone I can trust, and that’s you. I weigh 310 pounds and ride with the BMW Vario bags and topcase, and I often have my 120-pound son on the back. I run Metzeler Tourance tires at both ends. For tire-pressure recommendations, I’ve been told everything from 32/38 (front/rear) to 37/44 psi. What do you recommend, and should I be changing pressure when my son is riding with me? Andrew Freeman
San Francisco, California
A Thank you for the compliment, Andrew; I’ll try to live up to your expectations and provide the most complete answer I can manage.
Let’s start with a few specifications. Your R1200GS has a GVWR (Gross Vehicle Weight Rating) of 970 pounds, which means BMW recommends that the total weight of the bike with a full tank of fuel, the rider(s) and any accessories not exceed that amount.
The company also claims that the GS itself weighs 504 lb. with a full tank, meaning you can load it up with 466 lb. before going over the GVWR. So, if you combine your weight (310 pounds, but don’t forget to add in the weight of your riding gear), that of your son (120, plus gear) and the trio of Vario bags and their mounting hardware (I can’t find a weight for them anywhere, but let’s just assume a total of about 40 lb. empty), you have a 470-plus lb. load, slightly over the limit. And that’s with all three bags completely empty.
You’re still within the window of safety at that point; but once you put a substantial load in the bags (the maximum recommendation for the side cases is 22 lb. and 11 lb. for the topcase), you start wandering into more-dangerous territory, since all of that 55 lb. of possible weight will be on the rear wheel. The tires can cope with it (Metzeler says the GVWR of the rear tire is 716 lb.; 536 for the front), but the handling will be adversely affected. This doesn’t mean the frame will snap or the suspension will collapse or anything that catastrophic. It does, however, mean the suspension, particularly the rear, will probably bottom too easily or the chassis might wallow in some corners or the steering may not offer the same comfortable feedback—or all of the above. I can’t say how badly these performance factors would be affected, but if you’ve been riding the bike in an overloaded state, you probably already have some idea.
I haven’t forgotten that your question was about tire pressures, but I felt the need to explain these other factors first. According to Metzeler, the front tire should be inflated to anywhere between 32 and 42 psi, depending upon the bike’s payload, and the rear tire to between 36 and 42. Given what was just discussed here, I would recommend that you keep both tires inflated to 42 psi at all times. Even without your son on board and with empty bags, your GS is carrying a considerable (at least 350 lb.) payload, which is easily the equivalent of two 175-lb. occupants. That’s enough to warrant the higher pressures. But pressures aside, when you travel with loaded bags and your son on board, I strongly suggest that you ride with exceptional care.
Lean and not so mean
QMy 2006 Kawasaki EX500 had 8000 miles on it when I bought it from someone who had very little riding experience. (I’ve been riding and home-wrenching for 53 years.) It has been great except that it sporadically “stumbles” when maintaining a constant 60 to 65 mph. Trying to determine if it is an air or fuel problem, I added choke and the engine smoothed out considerably. On two occasions, I have torn down the carbs and soaked them overnight in cleaner, and I have added fuelinjection cleaner at least three times.
The stumbling has all but disappeared but it still happens once in a while. I have run out of ideas and hope you can help me figure this out. Jim Laney Lacey’s Spring, Alabama
A Just about all motorcycles built over the past few decades have a natural lean condition that usually is at its worst at smaller throttle openings— such as when cruising at steady highway speeds. This has been a necessary concession made by the manufacturers to help their bikes meet federal emissions regulations. The lower the displacement, the more pronounced that leanness tends to be, particularly with carbureted bikes such as your EX500. Normally, this condition isn’t so noticeable, especially when the engine is fully warmed; but when you combine that leanness with the ethanol content in today’s gasolines, the kinds of erratic running like you describe are more prevalent.
What this means is that you could continue cleaning and rebuilding your Kawasaki’s carbs until the end of time and still have the engine occasionally stumble. The only reasonable solution is to remedy the lean condition by installing an aftermarket jet kit, such as part no. 2128 ($85.65) from Dynojet (www.dynojet.com). You’ve already had the carbs apart twice, so you should be able to install the jet kit without any problems. Afterward, not only will your EX500 no longer stumble, its overall performance and throttle response will be much better.
FeedbackLoop
Q like to read your Service section each month because I usually learn ing new about motorcycles, but when it comes to the tools you feature, I can’t help but wonder what universe you live in. I mean, a $100 leak-down gauge? How often would someone use that? A $50 red plastic thing for holding drill bits? Pretty, but not worth half a Benjamin. A little torque wrench that costs $110? How many tiny nuts and bolts does anyone have to torque to justify that expense? And $54 for a couple of little rollers that you put the rear wheel on for lubing a chain? I just roll my bike along as I do that job, and it’s free!
In these terrible economic times we’re all trying to survive, I don’t understand why you would even consider pitching expensive tools that people could easily do without. Or is your life out there in La-La Land so good that you aren’t even aware of what the rest of the world is going through? Wake up and smell the unemployment, Mr. Dean. Edgar Holmes
Enterprise, Alabama
Al’m sorry you feel that way, Edgar, but I think you may have overlooked an important point: No one is obligated to buy anything I include in Tool Time. If any of our readers feel that a tool is too frivolous, too expensive or entirely unnecessary, they are free to ignore what I have written and move on to the next subject that interests them; no harm, no foul.
My only objective with that section is to find tools that I think might be of interest to readers who love to work on motorcycles and present those items for their consideration. But what I do is not a sales pitch; it’s simply an offering of potentially useful, hands-on information. What anyone chooses to do with that information is purely a personal decision.
Flood insurance
QI have noticed that most fuel-injected motorcycles do not have petcocks or shut-off valves on their gas tanks, but all carbureted bikes do. Why
is this? Is there not concern about fuel seeping into the engine when the bike is sitting unused, whether overnight or for longer periods? Todd Newsome
Submitted via America Online
A Injected bikes don’t need petcocks simply because the fuel in the tank has no way of entering the engine when the ignition is off. On a carbureted bike, gravity constantly pushes the fuel in the tank down to each carb when the petcock is open; and if the needle and seat in any carb are not sealing properly—which can happen quite easily if the needle and seat are worn or a tiny piece of contamination gets between them—fuel can continue to enter the float bowl and overflow into that cylinder and flood the combustion chamber. This is why it’s always best to turn a manual petcock to Off when the bike is not in use, and why some bikes use vacuum-controlled petcocks that automatically shut off when the engine is not running.
A few carbureted bikes are fitted with external electric fuel pumps because their fuel tanks are either below or not sufficiently higher than the carburetors to provide adequate fuel flow. Due to the presence of a pump between the tank and the carburetors, engine flooding is far less likely to occur with these systems, but it still is a possibility. Things are much different with fuel injection. For one, the fuel line that exits the tank is fed by an electric pump inside the tank rather than by the force of gravity acting on the fuel itself; some leakage past the pump and into the line is therefore still possible but not as prone to occur as with a carbureted system. Besides, such leakage would be inconsequential, because the fuel line leads to injectors that always remain closed until receiving an electrical signal from the ECU; when the engine is not running and the ignition is off, all the injectors are closed, preventing any fuel from entering the engine. Thus, a fuel-tank petcock is unnecessary.
CandidCameron
QBack the butterfly in the “old” valves days, in carburetors streamlining supposedly was important to help maximize the intake efficiency of high-performance engines. All the modern fuel-injected motorcycle engines I’ve seen, however, use butterfly valves made of thick brass, with large shafts and protruding screwheads. What gives? And why brass? Frank Jenkins
Menlo Park, California
A There are a couple of things going on here. One is that most fancier (i.e., higher-priced, racing-intended) fuel-injection systems do use tapered, lens-shaped throttle plates whose surfaces are not interrupted by big brass screws. Another is that when injection was adopted, there was no longer a need for a venturi anywhere in the system; instead, metering information is stored in software and no longer “measured” as a venturi pressure. Consequently, the intakeport diameter upstream of the cylinder head is made very large to minimize flow loss; and in such a large port, the butterfly offers much less of a flow disturbance than it would in a smaller port with faster-moving airflow passing over it. That being the case, production fuel-injection systems can use inexpensive, less-aerodynamic components of the kind that you describe.
Brass, meanwhile, has been used in carburetors for years for the same reason it was so common in the navies of the world:
It is naturally corrosion-resistant. Water is a product of combustion, so at the particular rpm at which the exhaust system blows back through the intake somewhat on valve overlap, parts in the intake stream will get wet. Anyone who has serviced carbureted bikes after a period of storage will have seen such effects first-hand. —Kevin Cameron
St-st-stuff ering 600
Q About 18 months ago, my 1996 Honda CBR600F3 developed a stutter at 6000 rpm. The bike is well-traveled with 100,000 kilometers (60,000 miles, for my American friends) on the odometer. The stutter is like a misfire, but once it gets past that rpm, normal power resumes. The stutter is most pronounced under load and has occasionally caused the engine to shut off completely. I’ve tried new high-tension leads and sparkplugs, but to no avail. Any clues? Steve Dickinson
Auckland, New Zealand
A Given that your Honda is a
15-year-old high-miler, along with the fact that I know virtually nothing else about its condition or state of tune (has the engine ever been rebuilt, have you made any performance modifications, such as exhaust system, jet kit, aftermarket air filter, etc.?), this is a tough one. My first thought is of a similar set of symptoms I once experienced on a high-mileage Honda ST 1100 when the diaphragms in that bike’s Keihin CV carbs began developing tiny cracks. Because the diaphragms regulate the height of the carb slides according to throttle position and intake-manifold vacuum, such a leak can have an adverse effect on the engine’s performance. The leaks on the ST 1100 were fairly small but still enough to let the carb slides fluctuate at steady engine speed, resulting in erratic running and a mild stutter.
You might also check all of the related electrical junctions and ground wires (including both ends of the battery ground cable and the bolts that attach the ignition coils to the frame) to see if there’s a bad connection somewhere along the line. Often, a loose connection doesn’t make itself known until a certain engine vibration frequency causes it to make intermittent contact.
Travel by air or water?
QI am ready to step up and buy a touring bike. I hope to take some long trips on it and am trying to decide between bikes with liquid-cooled and air-cooled engines. I rode a 750 Honda 30 years ago and it was flawless. Won’t I just be adding potential trouble and maintenance to go to liquid-cooled?
Will I notice a difference during a long trip or am I just asking for a breakdown? Jim Schlesinger
Submitted via www.cycleworld.com
A At one time, maybe 25 or 30 years ago when you were riding your air-cooled Honda, this might have been a concern, but it’s not one today and hasn’t been for a long time.
Correction
I agree completely with your évaluait ation of the 1999 Harley-Davidson FXDX Super Glide Sport (Best Used Bikes) in the February issue but with the following exception: The Twin Cams of that era were
Snot 80-cubic-inch engines but instead were 88 inches. I had a 2001 FXDX and presently own a 2004 FXDX, and they are super-handling bikes, the best of the Dyna family. Great article, though! Steve Knight
Submitted via www.cycleworld.com
5e ” '¿is*
That was an unfortunate typing mistake on my part, and I failed to catch it afterward. I did, however, correctly refer to the engine’s 1450cc displacement in its metric form, and I am fully aware of the Twin Cam genesis and history. I’ve had many of those engines apart, and I wrote dozens of articles involving Twin Cammers in the Power & Performance: Harley-Davidson magazine our company used to publish. So, my apologies for the error; I’ve duly reprimanded my right index finger for pushing the wrong key.
I honestly can’t remember the last time we’ve had to deal with any cooling issues on a liquid-cooled street testbike; even the cooling-system repairs we’ve had to perform on dirtbikes usually were caused by a crash or contact with a big boulder, not by a system failure. I once did split a radiator crossover hose on my personal Husqvarna four-stroke dual-purpose bike when grinding up a long, rocky, difficult hill at about 1 mph on a 95-degree day, but an air-cooled bike might very well have seized under those same conditions. I was able to replace that short hose on the spot in a few minutes; repairing a seized piston would not have been so simple.
When riding in stop-and-go traffic on a really hot day aboard a few liquidcooled bikes, I’ve seen the temperature gauge climb toward the upper end of the scale before the electric cooling fan kicked in. I’ve also gotten letters and emails from readers who were concerned after having the same thing happen with their bikes, but none of them has ever reported any engine damage as a result. And as I have explained to some of those readers, if they had instead been on an air-cooled motorcycle equipped with a temperature gauge (which those bikes normally do not have), they would have been surprised at the extreme cylinder-head temps it reached.
Your choice of touring bikes, then, should be based on the one you like the most, the one you can best afford or the one that will provide you with the features you desire, not because of its system of engine cooling. □
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 CW1 Dean@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.
