How to Set the Timing on Honda Bikesby Contributing Writer
Periodic maintenance of your Honda bike dirt bike includes setting the timing for maximum engine performance. The correct setting ensures that the spark plug generates spark in conjunction with the combustion stroke of the piston. The timing unit is located behind the timing cover on the right side of the engine crankcase. You set the timing by aligning a mark on a flywheel with an indicator-pointer at the top of the timing plate. Setting the timing on a Honda bike requires a few hand tools and a timing light.
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Set the crankshaft to top dead center. Remove the timing plug from the engine case using the large flat head screwdriver, and set the "T" mark so it aligns exactly with the line in the center of the window on the case. When turning the engine with the bolt on the alternator, you must use a ratchet and a deep socket. Do not turn it counterclockwise, even if the manual tells you to. This can result in internal parts being loosened, and serious damage can occur. If you pass the mark, keep turning the engine clockwise until the mark comes up again.
Mark the timing mark on both the left and right hand side camshaft pulleys with metal marker or white out. Do the same with the timing marks on the case. This makes it easier to visually line up the marks while installing the new timing belts.
Install the right side timing belt first. Run the belt around the crankshaft pulley, using care not to turn it at all. Route the belt inside the tensioner, leaving the tensioner as loose as possible. Route it around the camshaft pulley, ensuring that the timing marks are exactly lined up. Once the belt is in place, tighten the tensioner bolt slightly. Check the "T" mark in the timing window, and ensure that it is still lined up exactly. If it is not, remove the belt and redo the process until the "T" mark is exactly in the center at the same time that the timing marks are lined up.
Repeat the process for the left timing belt. Ensure that the "T" mark and the timing marks for the right timing belt are still aligned when the left timing mark is aligned. Do not turn the engine over at all until all of these marks are aligned exactly, because a difference of as little as three teeth on any of the gears or the timing belt will result in serious engine damage.
Tighten the tensioner bolts. Carefully turn the motor over using the ratchet and deep socket one time, until the timing mark comes back around to the center of the window. Check all timing marks again. When all marks are aligned, and the tensioner and all pulley bolts have been tightened, install the timing belt covers.
Items you will need
Standard metric hand tools
Large flat head screwdriver
Metal marker or white out
Park the motorcycle on its kickstand. Loosen and remove the timing cover bolts with a metric socket and ratchet. Save the bolts and pull the cover off by hand. Carefully remove the rubber gasket from the face of the timing housing by hand. Save the gasket.
Clip the red wire lead from a timing light onto the spark plug wire. Clip the black wire lead onto the black ignition coil wire. Start the motorcycle and allow the engine to idle at normal speed.
Aim the timing light at the indicator-pointer at the top of the timing plate. You will notice that each strobe of the light illuminates the timing mark on the flywheel. The timing is set when the mark is directly in line with the indicator each time the light strobes.
Loosen the small screws on the face of the timing plate one-half turn with a flat-tip screwdriver. Insert the tip of the screwdriver into the adjustment notch at the base of the timing plate.
Aim the timing light at the indicator. Twist the handle of the screwdriver to the right or left, as necessary, until the timing mark is directly in line with the indicator. Tighten the screws securely on the face of the timing plate.
Turn off the engine. Disconnect the timing light leads from the spark plug wire and the coil wire. Press the saved rubber gasket into the recess on the face of the timing housing by hand. Reattach the timing cover and tighten the bolts with the socket and ratchet.
Items you will need
Metric socket and ratchet
Take the spark plug out and put the bike in neutral.
Remove the alternator cover. This is the mostly round cover, on the left side, just above the shifter. The cover has "Honda" on it. Be careful not to tear the gasket.
Turn the alternator rotor counterclockwise, using the nut in the middle, until the contact breaker points are opened the maximum. A cutout in the rotor will allow you to see them.
Check the gap with a feeler gauge. It should be 0.012 to 0.016 in. (0.3 to 0.4 mm). If the gap is okay, skip to Step 8.
Notice a pry area, by the points. Also, notice a screw that holds the points down, preventing them from being adjusted. Slightly unscrew it, just enough you can adjust the gap. You do not need to remove the rotor.
Rotate a flat-blade screwdriver one way or the other to open or close the points gap as needed until it's correct.
Tighten the set screw. Don't be surprised if tightening the set screw changes the gap; it happens often. If so, you will have to loosen it, readjust the points and retighten the set screw until you get the set screw tightened with the points gap correct.
Note the electrical connection coming from the alternator, out of the casing and up the frame. About eight inches above the casing, notice a connector. Here, disconnect the rotor's electrical connection.
Connect one of the leads from a test light to the engine, to ground it. Connect the other lead to the black and white wire you just disconnected.
Turn the alternator rotor counterclockwise, using the nut in the middle, until the "F" on the rotor aligns with the mark on the engine casing. This mark looks like a "V." It's on the casing just above the rotor, and just below where the cylinder mates with the engine casing.
Observe the points gap and the test light. The rotor has a cut out area that allows you to see the points. The points should be slightly opened and the light should be dimmed, but not out. If this is the case, skip to Step 13.
Adjust the points gap until they are slightly opened and the light dims. See Steps 5 to 7 for how to do this.
Check the points for excessive wear. See Steps 3 and 4 for how to check the maximum gap. If it is now too much, the points are too worn, and you should replace them.
Replace the alternator cover with gasket and the spark plug, and reconnect the alternator's electrical connector.
Items you will need
Simple test light for static timing
Remove the points cover. On single-cylinder Honda motorcycles, the cover is usually on the right side of the camshaft. On a multi-cylinder motor, it is usually on the crankshaft on the right side.
Turn the motor over until the largest part of the points cam is against the points. This is when the points are open at their widest. Measure the gap with a feeler gauge. Check your service manual for the correct points gap. Honda gaps are usually .012 inch to .016 inch. If you set the gap at .014 inch, you will be pretty close.
Connect the ground of a test light to an engine ground, and the positive side to the points wire. Turn the motor over using the crankshaft nut. As the "F" timing mark comes around to the mark on the crankcase, the light should come on just as they line up. This mark is before the top dead center (TDC) mark. It the light comes on at any other time, loosen the screws on the points plate and turn it so the marks align as the light illuminates.
Attach a timing light to the number one spark plug wire. Run the engine at about 4000 rpm and shine the light in the timing hole. The timing mark on one side of the "F" mark should line up with the stationary mark when the light flashes. This is the full advance mark. If this does not line up, adjust the points plate to the right or the left to align the marks.
Check the points gap again to make sure it has not moved significantly during these adjustments. Ensure that the adjustment screws on both the points and the points plate are tightened properly. Replace the points cover.
Purchase a camshaft and cam gear suited for your motorcycle. These are available from Hot Cams and several other manufacturers. Ensure that you follow the instructions for the installation of the cam, and the valve clearance adjustments afterward carefully. Engine damage can occur if you do not. The installation can be very simple with a single-cylinder Honda, or more complicated with in-line four-cylinder models. Follow manual instructions carefully.
The cam gear will have slots instead of holes to bolt the gear to the cam. This allows the cam to be turned from the stock position. Set the valve timing first to the stock position by lining up the TDC mark and the timing marks on the cam. This way the engine is at stock TDC.
Advance or retard the valve timing depending on the desired performance, following the instructions provided with the camshaft. Advanced timing to a point will increase performance and horsepower. Beyond that point, performance will get worse. Retarding the timing produces a more fuel efficient motor, again to a point. Both adjustments can move the power band of the motorcycle from low rpm to high as well. After each adjustment, test ride your motorcycle and judge the results.
Test your results on a dynometer. The best way to check your results exactly is with dynometer time at a local race shop. This can be very expensive, so be sure your bike is tuned and in good shape before you arrive, including a clean air filter and a fuel filter if your bike is equipped with one. After each cam adjustment, run your bike on the dynometer to determine horsepower and torque gains, as well as where the adjustment has moved the power band.
Assemble the motorcycle completely and take it for a ride under a variety of conditions to ensure that your valve timing adjustments have achieved the desired results.
Items you will need
Basic hand tools
Aftermarket cam gear/camshaft