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With so many threads about non-starting bikes, a basic checklist would clear up recurring issues and get better, faster help from GSR.
Oh Gawd! Bike won’t start!!
First, check the idiot things.
If so, then elaborate (to yourself, quietly) what “not starting” means.
Does the engine turnover but not catch?
If the engine won’t turn over at all (silence, or click click), then you have fundamental power problems on the battery end. Check your battery charge, connections to the starter motor, etc. If everything checks out and still nothing, check out the Electrical/Ignition forum. Do a search for threads on non-starting bikes. If that doesn’t help, launch a post there.
If the engine turns but won’t start, you have different possible culprits. Let’s review some basics
OK - every bike needs 3 things to start/run.
If you have all 3, your bike will start. Even if you have a weak piece of this Trinity, your bike will start, but may struggle and/or idle badly.
How do I know what’s missing?
First, check the plugs.
Are they wet with fuel? If so, no spark.
Are they dry? If so, no fuel.
Compression is a different creature. We’ll get back to that.
Spark/Wet Plugs - If you aren’t getting spark, that means (a) no spark; (b) weak spark; or (c) missed spark. Mr. Matchless (c/o BassCliff) poops out how to root out your spark problems.
If you have spark but no fire, check timing. Matchless again:
You can only test the Forward timing (can't get 2,350 RPM). But a bike with poor advance timing will start, even if it won't run well.
Air/Fuel
This part of the Trinity is two-fold, because you need fuel and air. Unless the bike is in a lake, there is air for it. But listen closely:
IS YOUR AIR FILTER (BOX or PODS) ON THE BIKE?? PUT IT ON TO START IT.
or at least cover the intakes with a shop rag. You can't start a bike on raw air. If it does start, it will run way too hot.
Otherwise, check your fuel supply.
If not, root out the petcock or float level/float valve problem to get fuel flowing. Check out the Carb/Fuel/Exhaust forum. Do a search for threads on non-starting bikes. If that doesn’t help, launch a post there.
Compression
If fuel and spark check out, then you have a compression problem. I left this for last because a bike with bad compression usually will start
If it starts but is rough,
CHECK AND ADJUST YOUR VALVE CLEARANCES.
Actually, if the bike starts and runs great, but you are new to the bike
CHECK AND ADJUST YOUR VALVE CLEARANCES.
Seriously, the other compression problems are a lot of work. Having bad valve clearances leads to those problems. Adjusting to proper clearance gives swift and certain improvement to operation. Also, every time a GS runs on out-of-spec valves, God crushes a puppy. Think of the puppies.
Otherwise, test your compression. It should be even across the cylinders and close to specs in your service manual. As the bike will be cold, your compression numbers will be lower than stated in the manual, so don’t sweat that. So for my bike, the compression should be in the 125-150 psi range, but a cold test might only get 90 psi. That should still be enough to start the bike. If they are ridiculously low (like 30 psi) or zero, there is a bigger problem in the head. Either a bad valve is not closing, or the cam timing is off so the spark and fuel are going into the chamber at the wrong time. Either way, your bike needs serious help, expensive gaskets and an expedition into the top end. If you think you need to explore that, check out the Engine/Drive/Train forum for 4-cylinders or 2-cylinders Do a search for threads on non-starting bikes. If that doesn’t help, launch a post there.
I hope that this thread can sort out some of the recurring questions on these forums. If other folks that know more than I do (i.e., everyone else here
) have other pieces to the puzzle, jump in.
Oh Gawd! Bike won’t start!!
First, check the idiot things.
- Kill switch off?
- Ignition key on?
- Battery not dead?
- Any safety kills (kickstand, clutch, etc.) still on?
If so, then elaborate (to yourself, quietly) what “not starting” means.
Does the engine turnover but not catch?
If the engine won’t turn over at all (silence, or click click), then you have fundamental power problems on the battery end. Check your battery charge, connections to the starter motor, etc. If everything checks out and still nothing, check out the Electrical/Ignition forum. Do a search for threads on non-starting bikes. If that doesn’t help, launch a post there.
If the engine turns but won’t start, you have different possible culprits. Let’s review some basics
OK - every bike needs 3 things to start/run.
- Air/Fuel Mixture;
- Compression;
- Spark.
If you have all 3, your bike will start. Even if you have a weak piece of this Trinity, your bike will start, but may struggle and/or idle badly.
How do I know what’s missing?
First, check the plugs.
Are they wet with fuel? If so, no spark.
Are they dry? If so, no fuel.
Compression is a different creature. We’ll get back to that.
Spark/Wet Plugs - If you aren’t getting spark, that means (a) no spark; (b) weak spark; or (c) missed spark. Mr. Matchless (c/o BassCliff) poops out how to root out your spark problems.
Basic test, remove spark plugs. Fit them to the plug HT leads and ground them to the engine. Turn engine with starter and see if plugs spark. If any one spark plug does not spark swap it out. If the spark seems good on all 4 plugs, the ignition system is very likely in order. If spark is not present or very weak proceed with the following tests.
If the spark is weak but present, inspect the HT leads and plug caps. Suspect coil wires and spark plug caps, or voltage at the coils and thus the battery condition. It could also be due to coils with partially shorted windings, but do not jump on this cause immediately, and they may get hot.
If there is a spark, but the engine will not fire, it could be due to ignition timing, valve timing or fuel problems. Ignition timing and valve timing problems are more likely on a bike that has not run yet after being disassembled and more unlikely to be the cause if the bike was not taken apart and was running before.
A quick test with a few drops of fuel directly into the cylinders before replacing the spark plugs and then trying to start will prove it to either the fuel system or ignition system.
If the engine then starts and runs for a few RPM's the ignition is correct and you need to look at the fuel and carburettor side.
A quick test with a few drops of fuel directly into the cylinders before replacing the spark plugs and then trying to start will prove it to either the fuel system or ignition system.
If the engine then starts and runs for a few RPM's the ignition is correct and you need to look at the fuel and carburettor side.
Then finally the ignition timing must be set properly. At less than 1500 RPM connect a timing light to #2 or # 3 spark plug and check that the timing marks line up for 2-3 on F, then move to #1 or #4 spark plug and check that marks line up for 1-4 on F. Check the advance by pushing revs up to 2350 RPM and the timing marks should both line up on the 45 mark behind the signal generator mounting plate through the sight hole at the top. The three mounting screws can be loosened and the mounting plate can be moved slightly in the elongated holes to meet this.
Air/Fuel
This part of the Trinity is two-fold, because you need fuel and air. Unless the bike is in a lake, there is air for it. But listen closely:
IS YOUR AIR FILTER (BOX or PODS) ON THE BIKE?? PUT IT ON TO START IT.
or at least cover the intakes with a shop rag. You can't start a bike on raw air. If it does start, it will run way too hot.
Otherwise, check your fuel supply.
- Gas in the tank?
- Does it flow on PRI?
- Does it flow in ON/RES when you suck on the vacuum tube (don’t drink gas)?
- Fuel in the float bowls?
If not, root out the petcock or float level/float valve problem to get fuel flowing. Check out the Carb/Fuel/Exhaust forum. Do a search for threads on non-starting bikes. If that doesn’t help, launch a post there.
Compression
If fuel and spark check out, then you have a compression problem. I left this for last because a bike with bad compression usually will start
If it starts but is rough,
CHECK AND ADJUST YOUR VALVE CLEARANCES.
Actually, if the bike starts and runs great, but you are new to the bike
CHECK AND ADJUST YOUR VALVE CLEARANCES.
Seriously, the other compression problems are a lot of work. Having bad valve clearances leads to those problems. Adjusting to proper clearance gives swift and certain improvement to operation. Also, every time a GS runs on out-of-spec valves, God crushes a puppy. Think of the puppies.
Otherwise, test your compression. It should be even across the cylinders and close to specs in your service manual. As the bike will be cold, your compression numbers will be lower than stated in the manual, so don’t sweat that. So for my bike, the compression should be in the 125-150 psi range, but a cold test might only get 90 psi. That should still be enough to start the bike. If they are ridiculously low (like 30 psi) or zero, there is a bigger problem in the head. Either a bad valve is not closing, or the cam timing is off so the spark and fuel are going into the chamber at the wrong time. Either way, your bike needs serious help, expensive gaskets and an expedition into the top end. If you think you need to explore that, check out the Engine/Drive/Train forum for 4-cylinders or 2-cylinders Do a search for threads on non-starting bikes. If that doesn’t help, launch a post there.
I hope that this thread can sort out some of the recurring questions on these forums. If other folks that know more than I do (i.e., everyone else here
) have other pieces to the puzzle, jump in.
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