Which oil should I use in my SOHC4?10-40w MINERAL oil is what Honda recommends. When these bikes were first sold, the API oil rating and formulation level was SD or SE. 20W-50 MINERAL oil can be used on older, worn motors.
Don’t use synthetics. Synthetics have a reputation for a high detergent action. That is, if you have an old engine that has some sludge or deposits internally, the synthetic will sometimes remove it in chunks. There is some risk of plugging or restricting the oil pickup
screen, which would starve the engine of oil. It also affects some old seals adversely causing them to leak (from shrinkage if I remember correctly) and often leads to clutch slippage (see Clutch FAQ for clutch slippage comments).
Article on Oil:
www.yft.org/tex_vfr/tech/oil.htm (Mick750F)
Motorcycle Oil Filters Exposed!:
www.tobycreek.org/oil_filters/index.shtml (Mick750F)
Which fuel should I use in my SOHC4?Many SOHC4s have a relatively low compression of 9:1 and the manual typically recommends low octane fuels: 91 octane is roughly equal to 87 pump octane in the US. Most unleaded gasoline today is rated at 87 octane, which is sufficient for engines with compression ratios of up to about 9 to 1. Higher-octane gasoline requires more heat and pressure to ignite, meaning it's actually harder to ignite. The primary characteristic of higher-octane fuels is longer hydrocarbon molecules. These are stable and more difficult to ignite, but when they do ignite they burn slower, producing higher cylinder pressures. To capitalize on higher-octane fuel, the engine must be set up with more compression and in many cases, more ignition timing. The higher octane gasoline you use, the slower the fuel will burn, and the cooler your car will run......with the potential for this fuel to leave carbon deposits in the engine. The residue of unburned hydrocarbon becomes a deposit, and potentially a "hot spot.” So the same high octane fuel which should prevent "pinging" and at the same time give a cleaner motor (at least according to the Shell ads I have seen) could actually give a dirtier motor and the possibility of pinging due to predetonation induced by hot carbon deposits.
High and low octane fuels have for all practical purposes the same potential energy per volume. Use the lowest-octane fuel on which the engine will run cleanly and efficiently. By burning the fuel more efficiently more of the potential energy will be used, and the engine should run hotter. If you have good high compression (perhaps because your firing chamber is full of soot ;-)), you need to run higher octane or you'll get pre-ignition and eventually detonation, which will rob your bike of its rideability and you of your money to fix it. If you are using low octane (or old) fuel you may experience pinking: change to a higher octane. Otherwise, if you continue to experience pinking, you may need to change your ignition timing. If my memory serves me correctly, you may need to delay timing, as pinking is caused by early combustion, which is before the piston has actually reached TDC.
There is an oil leak coming from my shifter seal – how do I change it?1. Undo the bolt on the back of gearchange (foot) lever. 2. Make a mental note of the usual position of the gearchange lever, and then pull it straight off of its splined gearchange shaft. 3. Undo the bolts on the left-side engine case that covers the front sprocket for the chain, and pull the cover straight off. There is no gasket or oil behind this cover. Just the chain sprocket. 4. Using needlenose pliers or a similar tool, try to grab the old O-ring shaped Oil Seal and pull it out from it's insert on the side of crankcase body. Do not scrape or damage the seal insert area. Slide the Oil Seal outwards along the gearchange shaft to remove it. Even if this Oil Seal looks good, discard it. This Oil Seal MUST fit snugly, otherwise oil will continue to leak out from behind the gearchange shaft. Oil is intended to squirt through a small channel from inside the crankcase into a hollow ridge on the backside of the Oil Seal in order to keep the gearchange shaft constantly lubricated. Remember, the old Oil Seal may have hardened or changed shape slightly over time. 5. Install a new Honda O-ring Oil Seal (approx $5.00). It might help to find a hollow rod (like the handle of a hydraulic jack) slightly longer than the gearchange shaft in order to lightly tap the new Oil Seal into its insert. The Oil Seal should fit almost flush inside crankcase insert. 6. Re-install the engine case (cover). 7. Prior to re-installing the gearchange lever, slide a rubber spacer (similar to a garden hose washer) onto the gearchange shaft right up against the engine case. THEN install the gearchange lever. This will limit lateral (sideways) movement of the gearchange shaft, thus reducing the chance of the new oil seal from getting caught up on the shaft and gradually pulled out of its insert. Make sure that the gearchange lever can still move freely up and down - just not sideways.
