No matter if you have EFI or Carbs, a Harley or a Honda, here is a list of 5 common problems and triage steps you can take to diagnose the nature of a mechanical issue. Even if you can’t fix it, you don’t have to blindly trust your hard earned cash to the honesty of the nearest “reputable” mechanic. Get your tool box out it’s time to lift the tank!
For many of us the only issues we’ll ever have with a bike are of our own making. Most bikes have at least two cables that can go bad and cause headaches, the throttle and clutch cables.
The throttle cable normally lets you know it’s going bad by refusing to snap back the throttle grip when it is turned and released. Never ride such a bike, because they call that a “suicide throttle” for a reason. It’s also a wise idea to get in the habit of checking now and again to see that your choke or throttle isn’t affected when you turn the handlebars completely from side to side.
The clutch cable is far sneakier, and creeps into your perception as perceived clutch slippage. What really happens is that it moves less and less inside the sheath and eventually the cable and sheath as a whole start to fuse into one nasty mass that overpowers the return spring. This doesn’t allow the clutch to release all the way and causes it to slip.
The three main causes of cable woes are wrong routing, it's too short after changing handle bars or crashing and, most often, not properly maintained. The best thing to do is use a purpose made cable lube attachment available at the local power sports store; still in a real pinch, a cable that has recently stuck can most times be salvaged by:
1. Remove the cable from the bike
2. Twisting it around your arm or a wide pole to separate the wire from its sheath
3. Apply a readily available spray lubricant from a gas station like WD40 and work the inner cable up and down in the sheath
I’ve even seen people create makeshift funnels out of silly putty and soak the cable overnight in liquid wrench on the way to Sturgis with OK results. Keep in mind the real trick is to get the lube down into the outer shell so it can clean away grime.
If all else fails you can ride without the clutch
Running on Empty
It’s a sinking feeling when you give more gas but the bike sputters out and dies anyways. Naturally the first thing you want to do is get safely out of the way. Then check that you didn’t hit the kill switch and the battery can still turn the engine. If it can’t, you most likely have a charging or battery issue and need to call AAA. If the engine spins over, then these are the steps to take.
First, make sure that there is gas in the tank and the petcock is set to On, Reserve, or Prime. I helped a very embarrassed young man out the other day and the issue was pretty obvious and covered by our basic motorcycle safety courses in California. It helps if it’s set to “ON.”
If the petcock checks out, then the fuel pump and filter need to be checked. Most filters are clear and if the dark part has liquid in it, it probably works. Pumps can be tested by putting a finger on them and clicking the ignition from off to on. You should feel the pump “click” as it primes. If there is no click check the fuses. If it clicks more than 4 times, it’s likely being starved by a jammed filter, kinked line or it's going bad. You can find the pump by tracing the lines and it most often is easily accessible for a quick check.
If you’ve checked the petcock and don’t have a fuel pump, heck even if you do, give the tank a shake so any gas stuck in the sides of the tank is pushed towards the rear and the fuel petcock. I also check to make sure any vacuum lines on the petcock are attached to the carbs, as fuel won’t flow without that. You have to actually look because sometimes you have a vacuum control but still say ON and OFF like the older petcocks that didn’t.
On California and newer emissions controlled motorcycles, I see a lot of cases where the bike runs out of power and stalls. Once pulled over, they restart ok, and then stall again 3 miles later. In these cases, try running with the gas cap open! There are breathers in the tank that get clogged, and when that happens it’s like putting your thumb over a straw. The gas can’t flow out. Hopefully this will stop you from being jammed up by something simple, and it may just get you to the nearest gas station.
If your bike isn’t idling right, warm it up and take note of if adding choke (making the mix richer) or cracking the throttle ever so slightly (making leaner) makes the bike change behavior. Even Electronicly Fuel Injected motorcycles reveal a lot by “blipping” the throttle. Rich bikes are getting too much gas, so they idle high but lose power when given initial throttle because they can’t burn all the gas. For carburetors that suddenly show signs of being in a rich condition, gently whacking the bottom of the carbs to make sure the floats (tiny little pieces that control gas flow like the rubber piece in the back of your toilet) are free. Also check that the choke cable works. After that, solving a rich condition gets more involve such as checking the spark plug gap or fuel bowl levels.
Lean running engines tend to “hang up” at high rpms when the throttle is let go, and they also rev down slowly after the throttle is closed. A key clue is that the issue gets better as the bike warms up or that you are running hot. Extremely lean motors can also stall out completely when given some light throttle. Another signs of lean running is the “hunting idle” where the motorcycle revs up randomly, changes RPMs or takes forever to come down to idle.
First, start simple and look for a loose or open vacuum hose. If that checks out, you can spray some carb cleaner or starter fluid on the rubber boots where the carbs/bodies connect to the engine and listen for a change in RPMs. Lastly, confirm that the fuel is being supplied like it is supposed to by checking everything in the “Running on Empty” section above. If it is, lean running is the number one sign you need carb work but it can also indicate you’ve really gone a long ways between tune-ups.
For EFI specifically, much of the old-fashioned carburetor malaise is done away with. Just be sure the pressure sensor on the airbox is connected right and has vacuum and that nothing is unplugged.
You can check EFI for vacuum leaks the same way you do carbs, so ignore “educated” bikers who scoff at you for not knowing “they don’t make those anymore” when you pull out the carb cleaner. EFI bikes also all have a handy “self-diagnostic mode” which will flash out a numeric code through the gauges. A simple web search reveals both how to activate this feature and translate most codes and even resolve the issues.
Dude! Where’s my ignition!?
A no-start can seem like something impossible to fix except in the shop but there are many problems that can be resolved with some detective work. First, ensure the battery is good and that the engine turns over. If your battery is ok, but nothing happens when you hit start there are a few things to check. Make sure the batteries black ground cable is solidly connected to both the battery and grounding point on the engine (that is where the big black battery cable connects to the engine) and that the fuses on the main switch (connected to the big red battery cable in most cases) are good. Clutch switches, kickstand switches and the neutral light can all break to cause this type of problem. Try starting with the kickstand up, clutch in, and bike in neutral and see if the motor spins. If not, these switches can normally be bypassed with a paperclip pressed into both ends of the connector one at a time. Some of the connectors are easy to find, like the electrical thing pluged into you kickstand is the kickstand switch, but others may be really elusive without a schematic on a newer motorcycle.
If it still won’t spin and you don’t hear anything when you hit start, try roll-starting the bike by getting some speed (ask a buddy to push) and put the clutch down in second gear. If it starts, somethings wrong with the starter system, check the connections.
Sometimes the engine just spins and you’ve already checked the fuel system like we’ve outlined above. In this case you need to ensure you have spark. Rotate the wire ¼ a turn in both directions before you pull it to help prevent the connection from breaking. Whatever you do, do not yank at it! In a pinch or if you don’t want a special tool you’ll hardly use, set the wire against the engine with a metal screwdriver in it and look for a blue flash. Because there are fire risk and real big electrocution risk, I suggest that it is better to buy tester for 10 bucks. If there is a spark, check the plug gaps. If there is no spark, and the connections are tight you’ll have to do some in-depth troubleshoot on the coils, crankshaft pickup and wiring harness. Not a light job.
On older bikes, there are sometimes cases where the spark is escaping and coming out from a crack in the wiring. This is only really visible in the dark; luckily, it is normally also audible as a regular crackling while turning the engine.
The Big Ones
Sometimes the motorcycle breaks in a big way. While you can’t fix these you can diagnose them. They don’t tell you about these major failures when you buy the thing, and motorcycle safety courses I guess figures you won’t ride a bike like that… but I guess they’ve never heard of YouTube and I've had a person ride to meet me on a motorcycle with a spun rod bearing thinking it was a bad gear or something.
Diagnosing the difference between valves and bearings is a bit of an art on a motorcycle because the whole thing vibrates throughout the frame. In general the rules are as follows:
Valves lifters when they tap are a very “plinky” tap at idol and tend to get better if the bike is turned off and on, you correct the oil level, or the bike heats up. If your noise is like that, you probably just need an oil change. On a bike without hydraulic lifters, you need a tune up.
Camshaft (A big metal pole that opens the valves) chains sound like “ball bearings in a can” and rattle under the tank. Cam chain rattles need to go to the mechanic but are normally not horrible in cost to fix. If the plink doesn’t get better with topping of fluids or heat, it’s something that will need to get fixed.
Valve issues on the other hand tend to “suck.” No literally! Sticking valves cause suction on the tailpipe and Valves are also often the cause of black smoke.
Major engine troubles on motorcycles sound like a metal scrape. Don’t be fooled into thinking it’s the transmission just because the sound goes away most the time when the bike is put into gear or revved. Engine heat doesn’t make much difference with these noises, and a low oil pressure light is a dead giveaway.
A rod, piston or serious knock is not subtle and you can change the noise by manipulating the throttle. The real thing to look for in all engines are a marked “rattle up” or “rattle down” noises that follow the throttle. You should not run bikes making noises like this at all.
Transmissions are easier to decide if it’s a little or big problem. If it spits you out of gear, jams in gear or just won’t go into gear, than there's very little hope that anything but a total rebuild will fix the issue (for most motorcycles). But if the transmission “sputters,” rattles or pulses as you put it in or out of gear it’s normally just the clutch. The best thing you can do for your transmission is to always make the full shift, the gears are mostly damaged by half shifts. A clunky gear box, which sometimes makes a metal punch noise doesn’t usually mean much except that it's designed to shift fast and take abuse. It seems transmissions can shifted quietly or fast, but physics gets in the way of making it do both.
I designed this guide to help people clear up the “simple fixes." You need gas and spark to run any engine and good controls to use it. This story evolved from being about choosing the right mechanic to bike fixes, because identifying what's wrong with your bike before you get the mechanic will help you pick the right one.
Ultimately, when it comes time to take it to the shop, give plenty of details and make sure that you'll receive detailed information in return. Ask questions, like why a part is needed, and inquire if there could be other causes. If there are repairs to be done, ask the expert what these repairs will work. If a technician isn't willing to give you five minutes of their time to do that, then why give hours of labor to their business? Don’t feel bad walking away from a bad shop, because it's much worse to walk away from a basket case bike or to not walk away at all because of an overlooked mechanical falt.
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