Monday, August 8, 2011

Basic Maintenance - Oil Change

Yes, this is pretty simple stuff but the NX is a little particular compared to some of the other bikes I own (or have owned).

Tools: 1/4" drive ratchet, 12mm & 10mm sockets, 1/2" drive ratchet, 15/16" (or 24mm) socket, oil drain pan, funnel and paper towel or rags.

As you can see, it's very helpful to remove the engine pan (or skid plate or engine guard) and the shift lever to gain access to the oil drain plug (and oil strainer). The drain plug is located just behind the tip of the shift lever.

Use the 1/4" ratchet with 12mm and 10mm sockets to remove the engine pan. The 12mm bolt is at the leading edge of the pan, where it meets the frame. The 10mm bolts (2) are at the trailing edge of the pan. At some point you may consider replacing the hex bolts with Allen bolts. Allen bolts have a tendency to maintain their internal hex shape even if they come in contact with a rock or a curb. If a hex bolt's head is rounded off, it may take a vice-grip to remove it.

Use the 1/4" ratchet and 10mm socket to remove the pinch bolt from the shift lever. The bolt has to be completely removed from the lever before the lever can slide off the splined shaft. Make note of the location of the tip of the shift lever in relation to a fixed point on the engine. You'll need to put the lever back in the proper location so that you can easily shift gears. The splined shaft allows the lever to be replaced in different orientations.

Here, the pan has been removed and the shift lever as well. There's now plenty of access to the drain plug. Remove the drain plug after placing the drain pan under the engine. Be careful when unscrewing the plug. There's a spring loaded strainer (screen) behind the plug. Chances are that the oil will push the screen out and into the drain pan. You really don't want that to happen because you'll have to go "fishing" for the screen in the old oil. If you're careful, you can use the spring to remove the screen (which is about the size and shape of a thimble). Place the plug, spring and screen on a rag or piece of paper towel. Allow the oil to drain completely (this may take several minutes before it stops dripping). I even raised the kickstand to see if tilting the bike further to the left would speed the process. It did, kind of.

Here's the completed job before re-assembly. Old socks make nice rags. I use Honda GN4 10w-40 oil because I got about 12 quarts of it with the bike. I may switch to synthetic once I've exhausted the supply. Right now, I change the oil every one thousand (1000) miles. That may be excessive but the sump is only one quart and the motor revs pretty high (50 mph = ~6K rpm). The transmission also seems to shift better with fresh oil. Always use an oil that's rated for a wet clutch. Automotive oils contain additives which can cause the clutch to work improperly (that is, slip).

Inspect the screen for debris. If there are metal chips you may have more serious issues to address. Be sure the screen is clear. Replace the screen, spring and plug as an assembly. It can be a little difficult to try to push (against the spring) and get the threads started. Be patient and use an extension (3") with the socket, if necessary. Tighten the plug so that it's good and snug but not overly tight. You don't want to strip those threads. I have to use an offset funnel to fill the sump because the fill hole is very close to the frame. Replace the shift lever and engine pan. Inventory your tools to ensure you didn't forget something. Properly dispose of your drain oil (most auto parts stores recycle used oil - my local Auto Zone still does). Start the engine to be sure everything is OK. Other maintenance things to consider while changing the oil: clean the air filter, clean & lubricate the chain, check tire pressures and/or lubricate frame pivots.


  1. Hey! I just picked up a 1988 Honda NX 125 two weeks ago. There isn't a whole lot of information about them online, so I have found your website to be extremely helpful! Thank you for posting all of this stuff! Your instructions are extremely thorough, and the pictures are very nice. My bike didn't come with an owners manual but I found your service manual posted. Unfortunately none of the links work :- ( Any chance you will be re-posting the links?

  2. Nope, after considering what it costs to defend myself from copyright infringement,. I decided to remove all of the copyrighted material I had posted on-line. However, if you want to provide your email address (i.e. Bonneville AT email [dot] com), I might still be able to "help" you, if you get my drift.....

  3. Could really use some "help" with my 1990 nx 125 without any manual or electrical diagrams. I've read thru all posts and can't find much on the ol intrnets. Thanks

  4. Jason, I haven't owned an NX125 for more than three years. I would suggest you register on Adventure Rider and post for help on this thread: That's a thread I started and you'll find more info and help from others that own the same bike. Be aware that Adventure Rider just underwent some major changes. So, it might be a little clunky for a week or two. Good luck.

  5. I am truly thankful to the holder of this site
    who has shared this enormous paragraph at
    at this place.

  6. thanks for this I was trying to figure out where the Oil filter was and could not find it. now I know

  7. Glad I could help Martin. I no longer own this bike but I'm going to leave the blog posts up. It may help someone else, in the future. Happy Riding, be safe.

  8. I just need to know how much oil it takes, seems to be the hardest thing to find in the world