Newer motorcycles do not have an adjustment for ignition timing, as the timing is controlled electronically. Honda motorcycles made prior to 1980 have point ignition systems or early electronic modules that can be adjusted. Camshaft timing can still be adjusted on some newer motorcycles, although often this requires the purchase of an aftermarket camshaft and camshaft gear. Valve timing affects duration and valve overlap, which greatly affects engine power output and emissions.
Things You'll Need
- Feeler gauge
- Test light
- Timing light
- Basic hand tools
- Owner's manual
- Aftermarket cam gear/camshaft
- Dynometer time
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.
- Dan's Motorcycle: Battery Point Ignition
- "Camshaft Timing"; Honda Motorcycle Certification Course Materials; Joe Ritrivato; Motorcycle Mechanics Institute
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