Monday, April 25, 2011

The Replacement

First, let me rant a little bit regarding the US Postal Service; the seller is located approximately 230 miles from me (in a suburb of Indianapolis, IN). My parents happen to also live in a suburb of Indy. How can it take a letter (from me to them, or them to me) a maximum of three days to arrive and yet it took the carburetor ONE WEEK (shipped on 4/16, arrived 4/23)? How!? It's no wonder the USPS continues to lose market share. The government should privatize the US Mail. Others have shown it can be done more efficiently and cost less. Grrrr. OK, rant over.

Since my long weekend was pretty much over by the time the carburetor arrived (Easter Sunday was a day with family), I did manage to get it disassembled and cleaned. It looks like it had been bead blasted yet there was still quite a bit of foreign matter in the jets and emulsion tube (it almost looked like dirt). Fortunately, a healthy dose of GumOut carburetor cleaner did the trick and it now looks pretty good.

It's hard to tell from the image but the exposed surfaces have a slightly 'grainy' texture indicative of bead/sand blasting (not my chosen method for cleaning carburetors). There is some evidence of corrosion but much less than the OE unit currently on the NX. I have taken measurements to compare and contrast against the OE unit. I also plan to use Gasolia E-Seal, instead of the Teflon tape, to help seal the emulsion tube to the carburetor body.
Most of the remaining internal pieces will go unused (perhaps with the exception of the float and the float valve). The emulsion tube, air/fuel mixture screw, pilot jet, return spring and main jet are different parts (understandably so, since this carburetor fed a 200cc motor). The OE float is hollow plastic and, at some point, may begin to fill with gas (failure). The phenolic float from the replacement carburetor is solid and cannot fail in this manner. Additionally, it has an adjustable tab so the float height can be adjusted. However, I'm not sure if the phenolic float will fit in the OE float bowl. I can also make use of the slide, provided they're the same. The replacement carburetor came with a 105 main jet. That's one (perhaps two) steps richer than OE (which is 100). It also has a 35 pilot jet, one step leaner than OE (which is 38) and is partially clogged. The replacement came with no needle (I knew this) which undoubtedly had a different profile anyway. I plan to replace the carburetor-to-manifold o-ring as well as the manifold-to-engine o-ring. These are basic hardware store items (it helps to have an 'industrial' hardware store, that caters to the trades, close by).

The weather this week is forecast to be damp but variable. I may get to ride a couple, three days - fingers crossed.

Wednesday, April 20, 2011

Old Man Winter - Still Not Done

This week has been miserable with respect to riding conditions. I awoke to 1/2" of slushy snow on Monday, with appropriate temperatures. Tuesday's weather can aptly be described as "soaked" (I'm pretty sure it rained 90% of the day) and Wednesday (today) started with soggy conditions and drizzle. Throw in some severe weather during the overnight hours and you've got one water-logged week as of this writing. Needless to say, the NX remains ensconced in the garage.

I decided to purchase a used ATC200X carburetor to see if the body can be used in place of the original equipment unit. The price was right so if it turns out to be fruitless, I'm out less than $30. I have also decided to contact Sudco to inquire about the the Keihin PE series of carburetors they sell. From the looks of things, the PE is very similar to the PD series (which is what the NX came with from the factory). Perhaps a new carburetor is what's needed to make this bike as reliable as dirt.

The Seattle Sports waterproof backpack arrived and looks like it will work as planned. I will need to experiment with loading the pack and attaching it to the NX but I think this will be a better option than using the heavy top case.

Good Friday is a holiday for my company so I'll have a three day weekend to see if I can't get everything sorted. Hopefully the (used) carburetor will arrive before Saturday.

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.

Monday, April 11, 2011

Pixies Ate My Carb

Apparently the Supreme Being decided that Chicago had suffered enough of a miserably cold and wet Spring and decided that last weekend should resemble July instead of April. I took advantage of being able to work in the garage, with the door open. I decided that I was going to tear down the carburetor one more time to determine, once and for all, what was 'not right' in there. With the bright sunlight, it was pretty easy to see into passages and small spaces. As usual, I didn't find anything that struck me being wrong or out-of-place.
However, upon closer inspection of the threaded opening for the needle jet, I see that the threads have corroded somehow. I can only assume that there was water in the float bowl, for quite some time, at some point. I don't think that gas turning to varnish would cause aluminum to 'decompose' like that. I'm still not sure how that would cause a lean condition. I would think that if fuel were leaking by the needle jet, it would cause a rich condition. Perhaps air was getting sucked into the needle jet through the corroded threads? It would seem that the air pocket, in the float chamber, would be above the baffle (that tan colored funnel shaped thing). Therefore air couldn't make it past the needle jet. I'd love to chat with a carburetor expert and find out for sure. The (temporary?) resolution seemed to be to wrap the needle jet threads with Teflon tape. I was careful not to cover any holes in the needle jet or leave extra Teflon past the threads. I reassembled the carb, re-installed it and warmed the engine. Clearly, the fuel/air screw was out of adjustment because the motor would barely idle. So, I took it for a short spin because it would run better at higher rpm. After warming the engine and adjusting the fuel/air mixture (+ 1/4 turn - the fuel/air mixture screw is at the bottom of the picture), I went for a ride. It runs better, noticeably better. It pulls in all gears and the hesitation is gone. Additionally, I can run without any choke and it still runs well. On the ride to work this morning, it felt the same. I even noticed myself 'short shifting' into a higher gear instead of having to spin the motor like mad to keep up with traffic. It was actually fun not having to worry about someone behind you running you over (because you're too slow). What concerns me now is if the Teflon will 'hold', that is will it be a solution or just a temporary fix? I've already started searching for used NX carburetors, just in case.

Thursday, April 7, 2011

Magical Repairs

I continue to deal with the pixies that inhabit my carburetor. I must have appeased them, on the way home last night, as suddenly the NX started running as I think it should. There have been a few moments, over the past few weeks, when something happens that causes the motor to run great. I liken it to experiencing the end of a cold, when your inflamed nasal passages finally clear and you can breathe freely, through your nose, once more. On more than one occasion I've had someone say; "run the piss out of it, it'll eventually clear out". Those statements are, no doubt, relayed along because 1) it worked for the person saying it and 2) there is some truth in it as it applies to older motors (motors that aren't encumbered by all sorts of electronic sensors). I take statements like this with a grain of salt because A) they usually don't work (for me) and B) I try to be easy on my equipment (I usually work on everything I own and hate paying to fix something that wouldn't have broken had I not treated it harshly).

A lot of my mechanical expertise comes from working on mid-60s muscles cars; more specifically Mustangs (including Shelby GT-350s). I've also raced a 1967 Austin-Healey Sprite Mk IV in SCCA's F Production class. There were times when "running the piss" out of one of these cars actually did some good. However, cleaning out the carburetor was usually a manual process that involved disassembly, cleaning, reassembly and re-installation. Carburetors have a tendency to not "clean themselves". There are too many passages and small orifices that will clog and not become unclogged by simply running more and more fuel (with or without cleansing additives) through the carburetor.

Getting back to the NX, I would consider the carburetor to be "old school" in that it requires some cleaning/maintenance on a regular schedule but the bike also has electronic ignition (which the previously mentioned cars did not - I eventually installed a crank-trigger ignition on the Sprint but that's another story). So, the NX's CDI and regulator/rectifier should either work or not work. They seem to be working. The only item left that has some type of 'variable' condition is the carburetor. And, since it seems to be running great now, I'm hesitant to mess with it. One of the ways that I've determined if the motor is running properly is how it performs while in fifth (top) gear. Recently, a shift into fifth (usually around 45-50 mph) results in sluggish performance and a slow loss of rpm/mph until it's necessary to down-shift into fourth. Both yesterday and today I was able to accelerate in fifth (today while encountering a head wind, no less!). So, unless (until?) it reverts to its (evil/nasty) previous condition, I'm leaving it alone.


I was able to determine way the fender flap was being sucked up under the front fender; it's due to deflection caused by a front suspension compression. In English, that means that when the front forks (violently) compress, say rinding over a curb/gutter, the flap is soft enough to not react to the compression (quickly enough). This causes the bottom of the flap to encounter the front tire tread (which has some deep sipes) and subsequently be sucked up between the tire and the fender. I happened to be riding helmet-less (yes, bad) because I was listening to the way the motor was running while in motion. I rode hard over the gutter, at the end of the driveway, and then heard one of the plastic flap-supports get sucked up. A few more "tests" confirmed my suspicions. I now watch for things that could cause similar circumstances; curbs, potholes, rough railroad crossings, etc. In these cases, I'll have to slow down some. For the gutter at the end of the driveway I can ride across it at more of an angle which lessens the jolt enough to keep the flap away from the tire.

Tuesday, April 5, 2011

Frustration, Repairs and Cargo

I continue to be thwarted in my attempts to resolve a lean condition with respect to carburetion (fuel). I've discovered that if I run the NX, after the engine comes up to temperature, with the choke partially on, it runs without hesitation. However, if I run at speed (say 45 mph) for a considerable distance, the engine begins hesitating (not quite missing), like it's running low on fuel (in the float bowl). There are times when the bike will accelerate normally and other times when it just doesn't seem to "have it." I've removed, disassembled, checked (and re-checked), assembled and re-installed the carburetor several times now and haven't discovered any (potential) issues. The bike is totally stock yet it doesn't seem to run as it should. Eventually, I'll probably take it to the local Honda shop to see what they think. However, I'm not quite ready to 'surrender' to the dealer just yet. Frustratingly, there's no information on the stock carburetor (a Keihin PD 52 E). I'm guessing Honda made it for a short time and then decided it was worthless (??). I wonder what type of carb a NX125 Transcity (the non-US model) comes with. I had hoped that a carb rebuild kit might be helpful and even managed to locate one on eBay. However, after chatting with the eBay seller, it appears to be for a California model with the #98 main jet instead of the #100 - that's all I need, a leaner main jet). I managed to look for and located my compression tester. I'll see what the compression is but I'm guessing it's OK. If it wasn't, it certainly wouldn't run very good regardless of the rpm (I would think). I added a small zip-tie to the choke cable below the adjuster knob. That prevents me from pushing the cable all the way in thus keeping the choke partially on.

I did fix the rain/debris flap on the front fender. I used a small piece of plastic from a very large ketchup bottle to provide some support (and prevent the rubber flap from getting sucked up under the fender again). However, that plastic piece isn't as strong as I would like and I may end up replacing it with a similarly sized (and shaped) piece from a liquid laundry detergent container. Again, stay tuned.

After my weekend tear down (see above), I was a little disturbed to find that the Givi top case, fully loaded, is quite heavy (10-15 lbs., I'm guessing). While that doesn't seem very heavy, having that weight supported by the turn signals gives me reason to re-think my original idea regarding cargo carrying. I would prefer not to wear a backpack for the simple reason that it usually prevents a jacket from venting (by covering up the exit vents on the back of the jacket). Also, I need something that's waterproof. I came across a waterproof backpack from Seattle Sports. True, it's a backpack but it's pretty much one of their dry sacks that happens to have D rings for a harness. So, I could simply strap the backpack to my rear rack (thus leaving my jacket to vent properly) and use the shoulder straps when I get to work. I will miss being able to lock my helmet (and gloves) in the top case but that's not a terribly big deal. I'd prefer to get some weight off the bike.