Tuesday, October 25, 2011

Winter's Coming - Help Choose a Project

As much as I hate to admit it, my riding season is drawing to a close. While it's beautiful here today; mostly sunny, breezy and about 70º F, the weather will change drastically tonight and I'll be lucky if tomorrow's high temperature is in the lower 50s. I still hope to squeeze in another month on the NX but I'm not certain it that will be possible.

So, help me select an NX-related winter project. I have a spare set of front forks and was thinking of rebuilding them and, of course, documenting the process. Or, I have a spare motor and could do a tear-down or do a tear-down/rebuild (it's missing a camshaft which is no longer available from Honda. It also needs an intake valve but those are available). A motor rebuild is going to be a little more expensive, than a fork rebuild, especially if the cylinder needs to be bored or if the bottom end is trashed. I also have a spare set of wheels but they don't need much attention unless I attempt to remove the steel lining in the hubs (if that's even possible). Lastly, I was thinking about removing, cleaning and lubricating the swing arm.

I'm guessing there may be something that you'd like to see as well. Feel free to vote through the Comments. If nobody has any preferences, I'll go with the forks and proceed from there based on budget. Thanks for your input.

Wednesday, October 19, 2011

Back to Adventure

Back in July (2011), I wondered if the NX would work as an adventure bike (link). In that post, there's a picture of yours truly, on the NX, navigating County Divide Road in Jo Daviess County, Illinois. One of the group, that I was riding with that day, finally posted the video:

So smooth.......

Wednesday, October 12, 2011

Carburetor Adjustments - Smooth Runnin', Finally

Ever since I started riding the NX, I've sensed that all was not right with respect to fuel delivery. I've wondered about corrosion in the carburetor (found and dealt with), air leaks (rectified with a carburetor rebuild kit) and timing (checks out OK). There are only two adjustments that can be made to the Keihin PD52E (PD52F in California) carburetor; idle speed and fuel/air mixture (also known as the pilot screw). Since I recently adjusted the valves, I figured it would be good to revisit the carburetor adjustments.

One of the issues with the adjustment is the limiter cap that's installed at the factory. The bikes are adjusted to be lean so that they pass emissions tests. The limiter cap ensures that the bike leaves the dealer in the same state of tune as when it left the factory. There's a stop cast into the float bowl and the tang on the limiter cap prohibits the screw from being adjusted to enrich the mixture. I've read that heat will defeat the adhesive that holds the limiter cap. I chose to simply grind the tang off when I had the carburetor apart for rebuild. You could also grind the stop off the float bowl, if you so choose. Regardless of what you do, don't allow aluminum shavings to enter the carburetor.

If you refer to the Chapter 4 - Fuel System PDF on the Resources page, you'll want to review the Pilot Screw Adjustment procedure on page 4-10. Basically, you want the engine at operating temperature and idling around 1300 (+/- 100) rpm. I use an off-set ratchet to make the adjustment.

The hard part is not burning your hand while trying to adjust the pilot screw. In the image below, the float bowl of the carburetor is identified by the yellow arrow (behind the rear brake light wiring and switch). If you use an off-set ratchet with a straight blade insert, you need to insert your right hand between the engine and exhaust pipe (pink arrow) and use your left hand to manipulate the off-set (lime green arrow). It's not easy and you can get hurt (burned).

I've found that using a welder's glove allows me to put my right hand on top of the engine case, palm up,  without being injured. Yes, your hand does get warm-to-hot inside the glove but you're protected. At this point, I use the middle finger of my right hand to hold the off-set in place while I adjust the pilot screw with my left hand. You are instructed to "turn the pilot screw in or out to obtain the highest engine speed". If you're using an offset ratchet, obviously, you can only turn in one direction at a time. Chances are, you'll want to turn counter-clockwise (from the initial setting of 1-7/8 turns out from bottomed) to enrich the mixture since the initial setting is lean. I've considered a screwdriver with a flexible shaft but have yet to see one with an attachment that keeps the blade in the screw head slot. Once you've obtained the highest engine speed (rpm), re-adjust the idle screw to 1300 (+/- 100) rpm.

This "tweak" has the NX running as I think it should. It warms up quickly, uses less choke and it accelerates smartly. There are times when it still struggles for pace but much less than it used to.

Monday, October 10, 2011


I have added a "Pages" section in the header. In an effort to better present information, this section will allow me to organize data. Sub-sections include Home, About Me (which used to be in the right rail) as well as  Resources. The Resources page will allow me to link to PDF files of the Shop Manual. I'm in the process of scanning each chapter. Please be patient while I go through the process. If you need something specific, just ask (in the Comments). I may also add a Photo Gallery in the future. If you'd like your NX added to the gallery, let me know. Thanks.

Monday, October 3, 2011

Adjusting Valves - A necessity for small displacement engines

I believe I mentioned that the motor in my NX was rebuilt. If I didn't, I apologize. It seems that owner #1 (I'm owner #3, owner #2 had the motor fixed) managed to run the engine low on oil and wipe out the camshaft and intake valve (the donor motor came with the bike). For those of you familiar with this series of Honda motors, you already know that keeping the oil level up is a major concern (especially if you have leaks or consumption issues). I've heard a few knowledgeable people say that it's OK to overfill, slightly. The extra oil will be pulled up to the head by the cam chain where it's best used (for this motor). An oil change refill is .95 US quarts (0.9 liters) according to the shop manual. That extra .05 quarts (0.1 liters) is what I mean by "slightly".

I've put about 2800 miles on the NX since I purchased it in January 2011. I checked the valve clearances when I bought the bike but figured the motor needed some break-in time. This past week I could hear a slight ticking while the motor idled. 2800 miles is plenty of time for the valve train to become broken-in. So, I adjusted the valve clearances over the weekend. Here's the page from the shop manual:

I know that's a little small to read so let me enumerate the steps;

  • Note: the engine must be cold to adjust the valves (below 35º C / 95º F).
  • Remove the fuel tank (to do that, remove the side panels, remove the seat, remove the tank fairings, disconnect the fuel line and then remove the tank).
  • The manual does not say this but I also remove the spark plug. First, it allows you to check the condition of the plug tip and, second, it means you don't have to fight against the engine's compression when trying to find Top Dead Center on the compression stroke.
  • Remove the valve hole adjusting caps (15/16" or 24mm)
  • Remove the crankshaft hole cap and timing hole cap. In the image, these caps have a slot (for a large screwdriver). My NX uses caps with Allen (hexagonal) sockets.
  • Rotate the crankshaft counter-clockwise and align the "T" mark on the flywheel with the index mark on the left crankcase cover. The "index mark" is a slot cut through the threads in the timing hole. Rotate the crank slowly because it's easy to miss the ("T") timing mark.
  • Make sure the piston is at TDC (Top Dead Center) on the compression stroke. I've found the easiest way to do this is to find the ("T") timing mark and then make sure the valve rockers are "rocking". That is, they will be loose (a relative term), you can move them slightly up and down and hear the 'tick' as the rocker hits the valve stem. Also, my motor turns past TDC very easily. So, don't be surprised if you find yourself repeating this step a few times. I use a 1/2" breaker bar and 14mm deep socket. If you use a ratchet, the motor may spin past TDC.
  • Check the valve clearance by inserting a feeler gauge between the adjuster screw and the valve stem.
  • Valve Clearance (Intake and Exhaust): 0.10 mm +/- 0.02 mm (0.004 inch +/- 0.001 inch)
  • In the pictures, the feeler gauge is shown attached to the pack. I find it much easier to remove the one gauge you're using from the pack. Now, bend the gauge into an "L" shape and insert it into the hole on either side of the rocker. This will allow you to find the gap between the rocker and the valve stem much more easily. It's also provides better feel when you're actually adjusting the clearance.
  • Adjust the clearance by loosening the lock nut and turning the adjusting screw until there is a slight drag on the feeler gauge. Hold the adjusting screw and tighten the lock nut.
  • Tools: 10mm x 12mm combination box end wrench (see image below) and adjusting wrench (Honda Part #: 07908-KE90000). I have an adjuster tool from Suzuki. They're the same. I understand that a wood deck screw with the square hole (available from home improvement stores) works as well.
  • Torque: 16 N-m (1.6 Kg-m, 12 ft-lb) Lock nuts may come loose if the proper torque is not applied. Don't over tighten, replacing a rocker is not fun.
  • Replace the valve hole caps
  • Reassemble in reverse order.

The engine is much more quiet and starts more easily now. The inspect/adjustment interval is every 2500 miles. I'm trying to figure out if there's a way I can scan my shop manual to PDF and post it here. I may have to create some sort of "archive" or "resources" page or something. I'll keep you posted.