| NOTE: Inspect and adjust the valve clearances while the engine is cold (below 35°C or 95°F). |
| Inspecting and adjusting the valve clearances is probably the most difficult task that a regular ACE owner might attempt on their own. Any owner that has a basic aptitude for maintenance and doesn't mind spending a day tearing their bike down can do this task and the biggest benefit is that it will save a hefty fee from the dealer. Most bike shops, if they do the job properly, will charge at least 2 hours shop labour, if not more. If you are going to do this yourself, then expect to take around 4 to 5 hours. Also, you will need a good work area with lots of room to lay out the parts you need to disassemble. As for tools, you will need the basic kit that is included with the bike, as well as a couple of special tools just for this job. They are a feeler gauge and a 4mm open end wrench for the tappets, or a special tool built for the job. |
Required Tools:
- Wrenchs - 4mm, 8mm, 10mm, 12mm
- Sockets - 8mm, 10mm, 12mm
- Allan Keys - 22mm Hex (5/32" Hex), 5mm Hex
- Feeler Gauge Set
- Needle Nose Pliers
- Philps Screwdriver
- Slotted Screwdriver
|
| Step 1: Prepare the bike: |
Park your bike on a flat surface on it's sidestand where you can work uninterrupted for 4-6 hours. Also, it would be good to lay out a piece of cardboard or a workbench so you can lay the various parts down and keep track of the hardware etc.
Start by removing the seat(s) and the side covers. |
| Step 2: Remove the gastank: |
| NOTE: Before disconnecting the fuel line, turn the fuel valve "OFF". |
|
Remove the speedometer by removing the four hex-head bolts. Lift the assembly up and disconnect the 9-pin connector. Now is a good time to clean under there! |
|
Place a rag under the fuel valve to catch any fuel that comes out then remove the fuel tube from the valve by squeezing the clip ends and sliding the clip back down the tube. Pull the tube from the valve. On the other side of the tank there is a slim air vent tube that you can just pull off the tank easily. Remove the fuel tank mounting bolt and then slide the tank back a bit and lift it clear of the bike. make sure the speedo harness is out of the clip holder on top. |
| Step 3: Remove the Steering Cover: |
|
Remove the trim clips, then remove the two halves as an assembly. Remove the joint clip if you wish to seperate the halves. |
| Step 4: Remove the Air Cleaner & Air Chamber: |
|
| Remove the two (2) air cleaner housing bolts (not the 6 hex head bolts for the cover!). Then loosen the air cleaner housing to chamber band clamp with the screw. Pull the air cleaner housing away. |
|
For the air chamber, you need to loosen the band clamps at the intakes for the carburetors. Then pull the chamber a little aways from the frame and disconnect the crankcase breather tube from the chamber. Remove the air chamber. |
| Step 5: Remove the Carburetors: |
|
Loosen the carburetor drain screws and drain the carbs.
Disconnect the fuel tube from the fuel joint. |
|
Remove the screws and throttle cable holder.
Disconnect the sub-air cleaner tube.
Loosen the intake insulator band clamp screw for the rear cylinder. |
|
Remove the throttle cables from the throttle link. |
|
Remove all the spark plug caps.
Remove the bolts and then remove the rear cylinder left side fins and choke (SE Valve) knob and bracket. |
|
I also removed the forward cylinder ignition coil from the frame and moved it and the two plug wires back and out of the way... to give a bit more access room above the cylinders. |
|
Disconnect the sub-air cleaner tube from the front side carburetor.
Loosen the intake insulator band clamp screw on the forward cylinder and remove the carburetors together through the LEFT HAND side of the bike. (Note: the Honda service manual incorrectly says to remove through the right hand side. They will only fit through the left hand side!!!) |
| NOTE: As you remove the carburetors, take note of the routing for the choke cables. Maybe draw a picture or take a picture with your digital camera. Because the carbs can be re-installed with these cables routed wrong and then the choke may be difficult to open or may have too much spring-back on it, like I found out on my bike. |
| Step 6: Remove the sub-air cleaner housings: |
|
Remove the sub-air cleaner housings from both cylinders. The rear cylinder is only held on with one bolt and the front cylinder's is held on with 3 bolts.
Also remove the remaining fin covers from both sides of the front cylinder. |
| Step 7: Remove the Thermostat Housing Mounting Bolt: |
|
Remove the mounting bolt holding the thermostat housing and move the housing upward to give you room to remove the cylinder head covers. |
| Step 8: Remove the Cylinder Head Covers and Gaskets: |
|
| Remove the cylinder head covers and gaskets. Take care not to damage the gaskets or to scratch the clear coat finish on the covers. You might also have to remove the coolant lines to get the covers out. If you do, watch that you don't spill coolant onto the heads and in the oil. Take it slow and careful here! |
| Step 9: Remove the caps from the Crankcase and Timing Holes: |
|
Remove the caps from the crankcase hole and the timing hole on the left-side cranckcase cover. |
| Step 10: Inspect / Adjust the Valve Clearances: |
|
Notes:
Adjust the Front Cylinder Valves first.
Valve Clearance Limits:
In: 0.13-0.17 mm (0.005-0.007 in)
Ex: 0.18-0.22 mm (0.007-0.009 in) |
Front Cylinder:
You need to find Top Dead Centre (TDC) on the compression stroke of this cylinder. The easiest way to do this is to use a socket on the crankshaft nut (via the crankcase hole) and rotate the crankshaft counterclockwise. Make sure the bike is in neutral. Now watch the rocker arms as you rotate the crankshaft slowly. They will move up and down. When you see all the rocker arms in the up position, look in the timing hole and keep rotating the crank slowly until you see the "FT" Mark line up with the line on the edge of the timing hole. That means the front cylinder is now at TDC and all the valves are closed (compression stroke).
Now measure the clearances with the feeler gauge. There are two intake valves (side by side) and one exhaust valve per cylinder. Start with the largest gap you can allow. For example, on the exhaust valve, try to insert an 0.009" gauge between the rocker and the tappet. If you can insert this gauge easily, then the gap is excessive. Once you have determined that there is adjustments to be made, adjust each valve to it's minimum limit. To adjust the valve, loosen the lock nut (using a 10mm box-end wrench) then turn the tappet adjusting screw using a 4mm box-end wrench until the gauge just fits but still has some drag. Now tighten the lock nut back up. Recheck the gap after you tighten the lock nut, because when you do the tightening, it tends to pull everything together and loosen the gap up a bit. It might take a little trial and error to hit the gap you are shooting for after everything is tight. Once you are happy about the gaps, recheck that ALL the lock nuts are tight!
Rear Cylinder:
Repeat this process with the rear cylinder now., but this time you are rotating the crank until the rear cylinder rockers are all up and the mark you are lining up in the timing hole says "RT". Again, once you are happy with the clearances, double-check that the lock-nuts are tight! By tight, I mean they should be torqued to 17 foot-pounds, so don't go Arnold on them and try to torque them to 100 ft-pounds! |
| Step 11: Put it all back together!: |
Now that the valve clearances have been checked and adjusted, you can start putting everything back together. Just go in reverse of the instructions above and take note of the following...
- Clean the gasket surfaces on the cylinder heads before re-installing the covers
- Put a little grease on the threads of the crankcase hole and timing hole caps
- Make sure you route the choke cables properly as you insert the carbs
- Make sure you tighten the carb drain screws before opening the fuel valve
- You lose a little oil from the heads, check the level after you run it
- If you had to disconnect the coolant lines to get the head covers off, make sure you check the coolant level after running the bike.
|
