No matter if you have EFI or carbs, a Harley-Davidson or a Honda, here is a list of five 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 toolbox out: it’s time to lift the tank!

Stuck Cables

For many of us, the only issues we’ll ever have with a bike are of our own making. Up until very recently, most bikes have had at least two cables that can go bad and cause headaches: the throttle, and clutch cables.

fci 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—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 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 handlebars or crashing and, most often, not properly maintained.  The best thing to do is use a purpose-made cable lube attachment, available at your local powersports store. Still, in a real pinch, a cable that has recently stuck can, most times, be salvaged by:

  • Removing the cable from the bike.
  • Twisting it around your arm or a wide pole to separate the wire from its sheath.
  • Applying a readily available spray lubricant like WD-40 and working 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 try riding without the clutch.

Running on Empty

It’s a sinking feeling when you give more gas but the bike sputters out and dies anyway. Naturally, the first thing you want to do is get safely out of the roadway. Then check you didn’t accidentally hit the kill switch. Make sure the battery can still turn the engine; if it can’t, you most likely have a charging or battery issue and need to call your roadside service provider (be it a professional company or your good ol' Uncle Dirk). If the battery is OK, these are the steps to take:

fci clear tank

First, make sure there is gas in the tank and the petcock is set to On, Reserve, or Prime. Riders with more modern motorcycles will have no idea what a petcock is, but it's worth making sure your bike isn't equipped with such a thing. I helped out a very embarrassed young man 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 four times, it’s likely being starved by a jammed filter, a kinked line, or it's going bad. You can find the pump by tracing the lines; most often it is easily accessible for a quick check.

If you’ve checked the petcock and don’t have a fuel pump issue – 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.

On 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, 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.

False Idles

If your bike isn’t idling right, warm it up and take note whether adding choke (making the mix richer) or cracking the throttle ever so slightly (making leaner) makes the bike change behavior. Again, if you ride a modern bike you'll have no idea what a choke is, but even Electronically 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 involved – such as checking the spark plug gap or fuel bowl levels.

FCI Tach

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. Extremely lean motors can also stall out completely when given some light throttle. Another sign 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 No. 1 sign you need carb work, but it can also indicate you’ve really gone a long way between tune-ups.

For EFI, much of the old-fashioned carburetor malarky 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-seal 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, as well as how to 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 battery's 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 to 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, MacGyver-style. Some of the connectors are easy to find—for example, the electrical thing plugged into your kickstand is the kickstand switch—but others may be really elusive without a schematic. Especially on a newer motorcycle.

FCI Wiring Diagram

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, something is 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 a quarter turn in both directions before you pull it to help prevent the connection from breaking. Whatever you do, do not yank 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 and look for a blue flash. Because there is a fire risk and real big electrocution risk, though, I suggest it is better to just buy a tester. 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 troubleshooting 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 – 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, figure you won’t ride a bike like that...

fci big one

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 horribly costly 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. 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 is marked “rattle up” or “rattle down” noises that follow the throttle. You should not run bikes making noises like this.

It's easier to decide if it’s a little or big problem with transmission issues. If it spits you out of gear, jams in gear, or just won’t go into gear, then 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 – gears are mostly damaged by half shifts. A clunky gearbox, 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 be shifted quietly or quickly, but physics gets in the way of making it do both.

Parting Thoughts

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 tackle 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 you 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 cost. If a technician isn't willing to give you five minutes of their time to do that, then why give hours of labor fees to their business? Don’t feel bad walking away from a bad shop. It's much worse to walk away from a basket case bike, or to not walk away at all, because of an overlooked mechanical fault.

Original article published January 01, 2018

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