Figure 1. Read and follow the book. The Honda Service Manual, that is. (Though Robert Pirsig also has something to say about tappet adjustment.)
David Pitfield, November 2005
This page describes checking and adjusting the valve clearance on a 2005 CRF230.
Disclaimer: Your outcome is your responsibility. The information on this page is not a substitute for instructions in the Honda Service Manual. Read and follow those instructions. Although I believe the information on this page is correct, I disclaim all responsibility for any consequences of your use of this information. So there.
Feedback welcome! Please send me any corrections or
comments. I can be reached at crf230 <at> codewins <dot>
com.
Figure 1. Read and follow the book. The Honda Service Manual,
that is. (Though Robert Pirsig also has something to say about tappet
adjustment.)
Two specialized tools are required. First, you need a feeler gauge. I first tried a feeler gauge from Sears with about 20 blades in a single tool (top of Figure 2). Don't get this style. It's too awkward for working in the cramped space of the valve adjusting hole. (You can see how I hand-bent some of the blades to try to get them properly positioned.)
Instead, get something like the bottom of Figure 2. It's pre-bent and the blades at each end are attached to a rigid handle. For a few dollars, I got an assortment of different size gauges. You need 0.002", 0.003", 0.004", and 0.005".
Figure 2. Sears and Motion Pro feeler gauges.
If your valve clearances are out of tolerance, you also need a valve adjusting wrench. Honda makes one which you can order from a dealer (see the Service Manual for the part number). Or you can get an aftermarket one. I got a Motion Pro universal tappet tool set from Cycle Gear for about $45 (Figure 3).
Figure 3. The parts of the Motion Pro tappet tool set needed for
the CRF230.
Valve clearance must be checked with the engine cold (below 95 F).
Make sure your bike is clean before starting. You don't want crud falling into the open engine.
Remove the left side cover by removing two 10 mm bolts and one #3 Phillips screw (Figure 4). Don't lose the metal spacer behind the top bolt.
Figure 4. Left side cover.
Remove the right side cover by removing one #3 Phillips screw (Figure 5).
Figure 5. Right side cover.
Loosen the two 12 mm seat bolts (Figure 6) and remove the bolts, nuts, and collars. Remove the seat by sliding it backwards.
Figure 6. Seat bolts.
Turn the fuel valve off and disconnect the fuel hose from the valve (Figure 7).
Figure 7. Fuel valve and hose.
Pull the fuel tank breather hose out of the steering stem nut. Remove the fuel tank mounting strap (Figure 8).
Figure 8. Fuel tank strap.
Remove the two 8 mm fuel tank bolts (Figure 9). Lift off the fuel tank.
Figure 9. Right-hand fuel tank bolt.
On the right-hand side of the bike, remove the rubber cap on the engine hanger plate. The plate is held by three 12 mm nuts (two of which are behind this rubber cap). Remove all three, and remove the right-hand engine hanger plate, then the left-hand engine hanger plate. (Figure 10.)
Figure 10. Engine hanger plate.
On the left-hand side, remove the timing hole cap with a 6 mm hex key (Figure 11). Also remove the crankshaft hole cap. (I didn't have a metric key large enough, and carefully used a 3/8" hex key since this cap is fastened with low torque. You, of course, will do it correctly with a 10 mm metric key.)
Figure 11. Timing hole cap and crankshaft hole cap.
To check the valve clearance, the piston must be top dead center (TDC) on the compression stroke. Use a 14 mm socket to rotate the crankshaft counterclockwise (Figure 12) until you see the "T" through the timing hole and the line to the left of the "T" is aligned with the index notch in the timing hole (Figure 13). (Unlike me, don't forget to remove the timing hole cap washer that you see in Figure 13 so it doesn't get lost.)
Figure 12. Rotating the crankshaft.
Figure 13. The "T" mark is aligned with the timing hole
index mark.
At this point, the piston is at TDC of either the compression stroke or the exhaust stroke. However, you need to make sure it's the compression stroke. One clue is that, as you approach the "T" mark on the compression stroke, you'll feel greater resistance in rotating the crankshaft (due to the compression). In a couple of steps, I'll describe another way to verify you are at TDC of the compression stroke.
Locate the valve adjusting hole caps (Figure 14). Make sure the area around them is clean. Then remove them using a 24 mm socket. I couldn't find a six-point 24 mm socket, and instead used a 15/16" six-point socket (23.8 mm) which works just fine.
Figure 14. Valve adjustment hole caps.
Figure 15 shows the engine with the valve adjustment hole caps removed. We're looking at the right-hand side of the bike. The left hole exposes the intake valve. The right hole exposes the exhaust valve.
Figure 15. Valve adjustment holes.
Figure 16 is a close-up of the intake valve adjustment hole. The end of the rocker arm has an adjusting screw, the bottom of which presses against the valve stem to open and close the valve as the rocker arm pivots up and down in response to the cam lobe (which operates against the other end of the rocker arm, not visible in this picture).
Figure 16. Inside the intake valve adjustment hole.
If the engine is at TDC in the compression stroke, there will be some play in both the intake and exhaust rocker arms. (The adjusting screw can be moved up and down slightly.) Figure 17 shows me testing this on the exhaust side. On the other hand, if the engine is at TDC in the exhaust stroke, there will not be any play in the rocker arms.
You must position the engine at TDC in the compression stroke. Check that there is play in the rocker arms. If you're not sure, rotate the crankshaft one full revolution (until the "T" mark is again aligned with the timing hole index mark) and check for play in the rocker arms again.
Figure 17. Checking for play in the rocker arms.
We're finally ready to check the valve clearance!
Starting with either valve, insert a 0.002" feeler gauge between the bottom of the adjusting screw and the valve stem. The easiest way to do this is to "walk" the feeler down the adjusting screw until you feel the gap, then insert the feeler. Starting with a thin feeler will help you get the hang of this.
Let's assume the 0.002" feeler can be easily inserted. Then repeat the process with the 0.003" feeler, then the 0.004" feeler.
The correct clearance is 0.004" (both intake and exhaust). This means the 0.004" gauge should just fit (you will feel some resistance inserting it) and the 0.005" gauge will not fit. If you can't insert the 0.004" feeler, the valve clearance is too tight. If you can insert the 0.005" feeler, the valve clearance is too loose.
You need to check both the intake and exhaust valves. Figure 18 shows the feeler inserted in the exhaust valve.
Figure 18. Checking valve clearance.
In my case, the exhaust valve clearance was fine but the intake valve clearance was too tight. So I needed to adjust it.
To adjust the valve clearance, use the 10 mm valve clearance adjusting wrench to slightly loosen the locknut. Then fit the valve clearance adjusting tool over the square peg at the top of the adjusting screw. If the clearance is too tight, turn it slightly counterclockwise. If too loose, turn it slightly clockwise. The amount of adjustment required is very slight! I needed less than 1/32 of a turn (about 10 degrees). Adjust a little, then recheck with the 0.004" feeler gauge. The clearance is correct if the 0.004" feeler can be inserted and moved with slight drag or resistance.
Once you get close, put both the 10 mm valve adjusting wrench and the adjusting tool on together. Check the clearance with the 0.004" feeler and make any final adjustment (Figure 19). Remove the feeler gauge. Then, while holding the adjusting tool to prevent the adjusting screw from moving, tighten the locknut with the 10 mm wrench. Remove the adjusting tool and wrench and recheck the clearance. Assuming it's still ok, use a 10 mm socket to torque the locknut to 14 N-m. Recheck the clearance one more time.
Figure 19. Adjusting valve clearance.
Reassembly proceeds in opposite order of disassembly.
Clean the O-rings on the valve adjustment hole caps and lightly coat them with clean engine oil. Install the valve adjustment hole caps and torque them to 15 N-m.
Similarly clean and apply oil to the O-rings on the crankshaft hole cap and the timing hole cap. Install them. Torque the crankshaft hole cap to 8 N-m. Torque the timing hole cap to 6 N-m. (Not very tight at all.)
Reinstall the engine hanger plates and the three nuts and bolts holding them. Torque the three nuts to 34 N-m. Reinstall the rubber cap over the two upper nuts on the right-hand side.
Remount the fuel tank and secure with the two bolts, and reattach the fuel tank strap. Reattach the fuel line to the fuel valve.
Remount the seat and secure with the two bolts and nuts. As shown in Figure 6, the collar and nut go on the inside.
Remount the left and right side covers.
Congratulations, you're done!