How to Start an XT500
Or any old magneto ignition 4 stroke single.
Starting a kick-start motorcycle with magneto ignition is becoming a lost art. Read this if you've discovered a great old bike from the distant past.
If you're not familiar with kick-starting a big single cylinder motorcycle here's a tip:
New owners of old XT500s sometimes assume that to start the bike you simply have to turn on the gas and key and kick the start lever. This works on a two-stroke engine or a small 4 stroke but kicking a 500cc single cylinder engine through the compression stroke can cause an injury or damage to the bike...especially if the ignition is on.
Kicking an XT500 with good compression over TDC of the compression stroke is almost impossible and the forces are so high something important might break. The de-compression lever has to be used to set the engine to a certain state to start easily. There never should be a time when you kick and feel like the lever is going to break.
There is a time when the engine can be spun through the compression stroke easily and and that is at the very end of a properly set-up starting kick when the engine is spinning rapidly and the crankshaft has enough inertia to rotate through TDC.
Always use the de-compression lever to set the bike up for a kick......
There's a simple trick:
The postion of the engine in relation to the kick-lever is critical to getting a full kick-stroke and starting the engine. The kick lever shaft must latch into the starter ratchet at the very top of the kick stroke (so the kick lever is almost vertical) to give a full rotation through all 4 cycles.
With the kick lever you should feel the starter latch and the engine start to rotate close to the vertical position of the kick lever. If you use the flag in the kick "window" to position the engine, adjust the position of the flag so the kick lever starts to turn the engine as soon as the kick lever is moved. If the kick-lever won't engage the starter gear with the flag in the middle of the kick-start "window", advance the cam flag indicator a little more until it does. Then remember that postion for future referance....
The spark that ignites the engine doesn't happen until the very last part of the rotation so if the kick lever is allowed to latch on a later ratchet position the stroke is reduced and the engine will not rotate enough to start.
First...carburetors depend on air-speed through the venturi to make enough vacuum to suck gas into the air-flow through the carb. When the piston is moving very slow, such as when cranking, opening the throttle will slow the air-flow and even further reduce the vacuum and no gas will be mixed with the air. However at slow cranking speed, the air-speed is high in the pilot-circuit because it is a much smaller opening, but only if the air-flow isn't bypassed with an open throttle.
Second....Keep your hand off the throttle for another reason. The choke circuit on an XT500 makes a rich mixture for the pilot-circuit so if the pilot circuit isn't working because the throttle is opened, the mixture enrichening won't be available either.
Third....The kickstart lever only spins the enigne less than 2 revolutions so there will only be ONE SPARK for every kick, and it will be near the END of the kick-stroke. It's vitally important that the engine position is correct at the start of the kick and that the kick is complete so the engine is moving fast enough to rotate through TDC when the spark plug fires at the end of the stroke. If you kick the bike too early in the exhuast stroke there might not be a spark at all during the kick.
Hot starting versus Cold starting:
When a engine is cold, gas that is drawn into the carburetor venturi doesn't evaporate or atomize into the airflow easily. Instead it tends to stay in larger droplets so even though enough gas is actually present, it is in larger particles which makes the mixture act lean. The mixture enrichener valve (choke) increases the richness and promotes starting.
When an engine is hot, all the gas is vapourized in the air-flow immediately so the mixture tends to be richer. In this case a small amount of open throttle can lean out the mixture and aid starting. But, any wide throttle opening will slow the air-flow too much preventing the bike from starting. In this case the "hot-start" button on the carburetor idle-adjustment can be pushed up to open the throttle just a little to aid-starting. The button will automatically retract once the engine is started and the throttle is actuated.
MIKE'S SURE FIRE XT500 STARTING DRILL:
DO NOT TOUCH THE THROTTLE!!!
1. Put the sidestand UP.
2. If the bike is cold, push down on the choke lever. If the bike is real hot there's a small hot start button on the idle adjustment. Push it up only if the bike won't start without it.
3. Holding the compression release lever in, crank the bike slowly until the shiny flag shows in the window on the camshaft cover. This position is the start of the POWER STROKE. This is important because there will be little resistance to your kick at the start, and you can get the engine spinning through the compression stroke.
If you try to kick the bike at the top of the compression stroke, IT WILL KICK YOU BACK HARD!
4. Make sure the RUN/STOP switch is switched to RUN, and turn on the ignition.
5. Kick with a quick motion from the top right to the bottom. Resist the urge to give it gas!
A proper kick sequence will be smooth and easy.
If you made the mistake of cracking the throttle before you crank the bike, open the throttle wide, push in the compression release and crank the bike with the ignition off 5 or 6 times then try again. This will clear the flooded condition and it will start normally. This method is much better than removing the plug to dry it.
If you drop the bike, or stall in traffic you may have to use the method above to get it going. Thankfully the XT500 never stalls if it's running right unless you are really silly.
If your bike isn't an XT500 and it doesn't have a "window" on the camshaft cover, just slowly crank the start lever until you feel the stiff resistance of the compression stroke, then using the compression release ease the piston past the top-dead-center point and then kick. Virtually all 4-stroke (kick-start) single cylinder motorcycles will respond to this method.
XT500s have a reputation for kicking-back. With the spark timing set properly, the mixture is set to ignite 8 degrees BEFORE top dead center so if the engine hasn't been rotated past TDC when it is kicked it's possible for the bike to fire immediately before the stroke has progressed.
Also kick-back can happen even if the engine has been set to the kick-start position if the kick-stroke is too short or too slow to spin the engine past the firing point before the mixture burns.
A 4 stroke single cylinder engine will usually stop (when the key is shut off) on the compression stroke because that's when the stiff resistance to rotation will begin...so usually if the engine is just cranked when starting without positioning it will be on the compression stoke and the mixture will ignite as soon as the crank lever is actuated. This early in the stroke the piston is moving at low speed and the combustion will happen before TDC and it will drive the piston BACKWARDS and the lever will kick-back.
A proper kicking sequence would be when the kick lever starts with the engine in the POWER stroke (just after TDC) when the cam-flag is in the kick-indicator window. In this case the engine will rotate almost 2 revolutions before the bike fires, so when you kick, the engine's rotating speed has to be fast enough and your kick long enough to make the piston travel past the start of combustion before powering the piston down.
That means that if you are timid and try to move your foot off the lever early, or your kick slows at the end of the stroke, a kick-back is likely.
This tag was often supplied with new XT500s to help in the start procedure:
The starter shaft is equipped with a ratchet mechanism that disconnects the lever mechanism from the shaft once the bike is started but it will not protect you from a kickback. It's purpose is to dissengage the starter shaft when the bike starts and runs...If you look at number 4 in the instruction list you will see the note to
"kick the engine thru until the K.S. lever HITS THE RIGHT FOOTPEG."
The kickstart lever turns the engine 2 revolutions so if the kick begins correctly just AFTER TDC (the firing point) the engine WON'T FIRE UNTIL THE VERY END of the kick-stroke.
If the lever stroke is slowed or stopped BEFORE the piston goes past TDC at the very end of the stroke, the engine will fire before TDC and the piston will drive the engine BACKWARDS and cause a kickback.
At the end of the stroke, the engine should be running and the ratchet will disconnect the starter shaft from the engine, and the starter lever can be allowed to return to it's resting position.