Tuesday, October 02, 2012
Simple Guide to Valve Adjustment
Written By: GearHead.com
So you just got a killer deal on a bike on CycleTrader and you want to make sure everything is in tip top shape before your big upcoming ride. Whether you know if your valves need adjusting or not, it’s a good idea to at least check them periodically, especially in bigger or high compression engines where valves need to be adjusted more frequently. This simple guide will get you started with the basics on how to check and adjust your valves. This guide is for most 4 stroke motorcycle engines, but does not cover every make and model, so consult a repair manual for specifics for your bike. Valve adjustment can seem intimidating but it’s fairly simple on most bikes and can save you lots of money in the long run instead of having to take it to a mechanic.
· Valve clearance specifications (Exhaust and Intake in mm)
· Basic knowledge of your bike (how to get to TDC)
· Feeler gauges – Feeler gauges that match the specs you need to measure. (Some automotive feeler gauges are too big) Any local auto or motorsports store should carry some.
· Basic Tools – Basic tools like screwdriver, sockets, pliers, and wrenches to remove the valve cover, sparkplug, and turn over crankshaft nut.
· Valve cover gasket – Just in case the old one is bad or gets damaged. (Always buy factory OEM gaskets)
How to check and adjust the valves:
1. Remove spark plug(s).
2. Take off valve cover and set aside. They may need a love tap from a rubber mallet to break loose. You should be able to see the rocker arms and valve stem/springs at this point.
3. Crank the engine over so that the timing marks point to top dead center (TDC) and it’s at the top of the compression stroke. Rocker arms on intake and exhaust will usually have slight amount play in them since all the valves on the cylinder will be closed. There is usually a timing mark you can view through
4. Check valve clearance by measuring the gap between the rocker arm and the valve stem with the feeler gauge. (see photo at right)
a. If valve clearance is correct, there will be a slight drag felt on the correct feeler gauge. If the gap is incorrect, you’ll need to adjust the valves. If you have a shim type valve, you’ll most likely need to remove the rocker arm to replace the current shim with one of the correct size. This may mean more work to make sure that timing isn’t affected and trial and error to get the right shim size. Consult your bikes repair manual for specifics on your bike. If you have a screw and locknut style valve adjuster, then you can simply loosen the locknut and adjust the screw to the correct specs.
5. Set valve clearance with adjusting screw and then tighten locknut. Check the clearances after the locknut is tightened then replace the valve cover (with new gasket if needed) and tighten in crisscross pattern. (Do not over tighten!)
6. Do the same for all valves on that cylinder and then move on to other cylinder(s) using steps 2-5.
7. Install spark plugs. (Do not over tighten!)
8. That’s it! Now go out and ride that freshly tuned beast like you stole it.
If you run into or cause any broken parts along the way, (bolts, gaskets, etc) be sure to replace them with genuine factory OEM motorcycle parts. Gearhead.com offers free online parts diagrams and sells millions of OEM and aftermarket parts, gear and accessories for all major makes and models of motorcycles.
Note: For a more in depth guide on valve adjustment, please see our other article, “How to Adjust Valves on a Motorcycle or ATV.”