Friday, April 15, 2011

Researching Carburetors, NX Style

OK, so I have this neat little commuter bike with a cancerous carburetor. There's got to be a reasonably priced used carb out there somewhere. Putting a little more thought into my search made me realize that the NX125 cannot be the only model, that Honda produced, that uses the Keihen PD carburetor. So, I started searching through on-line parts fiches. I didn't have much luck but I did see several things that looked pretty close. Additionally, the Honda motorcycle part coding system wasn't revealing much (more on that in a moment). While searching through the flea market postings on Adventure Rider, I came across a highly modified CR85R with an XR100 motor (modified to be 115cc). It happened to sport a carburetor from a 1986-87 ATC200X. It looked very familiar with the only difference being the float bowl and the choke lever stay. So, back to the on-line parts fiches for verification. Yep, the body of the carburetors appear to be very, very similar, if not identical. They also happen to use the same (or very similar) intake manifold. So, off to the largest on-line auction site to see if we couldn't find some used carburetors for an ATC200X. At this point, I decided to become more knowledgeable regarding Honda Motorcycle Part Numbers. The internet is awesome and I quickly found this: Group W Racing's Honda Part Numbers page. A big thanks to Michael Bateman for his hard work. If you're not interested in clicking through, I'll re-post here (I hope Michael doesn't mind - Michael, if you do mind, please let me know through the Comments, thanks):

Honda Motorcycle Part Numbers

All parts on a Honda motorcycle have a unique part number. Honda divides parts into two broad categories, General Parts and Standard Parts. General parts are those unique to Honda, such as valves, pistons, gas tank etc. Standard parts are parts that follow universal standards, such as nuts, bolts and such.

General Parts

General parts have a part number divided into 3 sections, such as 22201-217-600 (clutch friction plate for the CL160).

  • The first string of digits (22201-XXX-XXX) indicates the Honda function and component number for this part. For example, there are several different part numbers for the CB160 clutch friction plate, all sharing function/component number 22201. Clutch steel plates have f/c code 22311, indicating same function but different component.
  • The second string of digits (XXXXX-217-XXX) is the product code, also known as Parts Classification Number in hondaspeak. This is the number that indicates the product (motorcycle) where this particular part was first used. Click here: Product Codes for a complete listing of older Honda product codes (big pdf file). 217 indicates that the CB/CL clutch friction plates where first used in the CB160. You will find these same plates with this number in later Honda Motorcycles. Some of the CB160 parts bear the 028 part code, indicating it was first used in the S90. Honda often lists several different part numbers for the same part, indicating slight differences in the part, such as different supplier etc.

          All General parts having a different product code are "recycled" from other Honda models. Only parts with code 217 were originally designed for the CB160, but may have been used in later Honda models. The product code is probably the most interesting portion of the part number when trying to determine interchangeability of Honda parts between various models.
  • The third string of digits (XXXXX-XXX-000) is the Classification Number. It is mostly used to indicate various suppliers or improvements for the same part. Also any potential color code is tacked at the end of the classification number as digits (letters) 4 & 5.

Note that some pretty universal parts are still listed under General Parts number. For example most oil seals carry a general parts number. Luckily Honda parts fiche lists the actual dimensions for parts like this.

Standard Parts

Standard Parts have a part number divided into 2 sections, such as 93500-06032 (6mm x 32mm pan screw, for example right side engine cover).

  • The first string of digits indicates the function/type of the standard part, all pan screws are 93500-XXXXX.
  • The second digit indicates dimensions for the part.
  • Standard parts occasionally have a third string of digits indicating the ISO standard designation and chemical surface treatment.

Given all of that information, I need to see how the part numbers, for both carburetors and associated parts, 'match up' (NX versus ATC). After a lot of data manipulation, they're not a similar as I would like them to be. I have found an ATC carburetor, on the large on-line auction site, and have asked the seller to provide some images from inside the float bowl. We'll see if they look similar to the NX's carburetor body and are lacking the corrosion from which my carburetor is suffering. Stay tuned.

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