Tuesday, May 29, 2012

More Noise

One of the few complaints I've had, concerning my VTR250R, is the lack of exhaust "note". It is exceptionally quiet and I have a hard time hearing it even when I'm sitting at a stop light (disclaimer; in an effort to avoid further damage to my hearing, I used to race loud cars, I wear Hearos foam ear plugs). So, in an effort to increase the exhaust note without being obnoxious, I removed a portion of the end cap. A big thanks goes to the guys on forum boards. A few of them have already done this and it does not require any carburetor work (re-jetting, etc.). It's a 'simple' muffler modification.

Thanks to forum-mate John, here's a great image of what we're going to accomplish:

image courtesy of John Hilmer
The upper muffler is a stock unit. The lower muffler, which is actually attached to the exhaust system on John's bike, has been modified. If you look closely at the upper muffler, you'll see a distinct ridge (most noticeable at about 7 o'clock). That's a weld line and makes a perfect locator for the larger (2") hole saw.


  • A lot of torque is generated by the drill (I used a 1/2" drill but I think a 3/8" would work OK, too). It is not uncommon to have the bit catch and wrench the drill from your hand. Hold the drill securely.
  • The muffler is round which makes it hard to clamp in a vice or other securing device. So, leave the muffler on the bike, for now.
  • Most hole saws work best at lower RPM (200). You don't need to be at maximum RPM of the drill to get good results.
  • Be sure to use some cutting lubricant (drain oil, WD-40, Marvel Mystery Oil, etc.).

1/2" drill with stabilizing handle and 2" hole saw
The above image shows the set-up I used for the hole saws. I happen to have a auxiliary handle for my drill. In my previous experience with holes saws, I find it useful to have the extra handle. If you don't have one, be sure to maintain a firm grip on the drill and use a lower RPM. That way, if the bit does catch in the work, it won't wrench the drill from your hand. Do Not use the trigger lock (for obvious reasons).

Above, I've started cutting using that previously described welding ridge as a guide. I'm not using a pilot bit because there's nothing for the bit to drill into. Use some newspaper or cardboard to catch the metal chips (there will be a lot) and the cutting oil drips (the oil may run down the underside of the muffler and drip, to the ground, near the swing arm pivot. Make sure you have enough coverage). Note: wear hearing protection. The saw, cutting through the steel, makes a lot of noise.

Here, I've completed the cut. Notice the amount of metal chips on the muffler. There's at least twice as much on the ground and maybe three times as much inside the muffler.

Now, make the second cut. You have a choice here; 1 - you can use a 1.125" ( 1 1/8") hole saw which as an inner diameter of 1". The inner diameter, of the hole saw, is the same size as the outer diameter of the tube that protrudes from the end cap. However, the tube that's hidden behind the end cap has a diameter of 1.125" (1 1/8") which is the same size as the hole saw.

If you look closely, you can see the outer diameter, of the protruding tube, is shiny and has had some material removed. However, as you cut through the end cap, you cut right into the tube on the opposite side  of the end cap, resulting in this:

If you would prefer not to cut into that inner tube, you could go with choice 2 and select the next larger size hole saw; 1.250" (1 1/4"). This will allow you to cut through the end cap and not cut into the hidden tube. However, you will not have anything to help you center the hole saw. If you're of steady hand, you should be able get the cut started, albeit slowly, and get the results as shown in the first image (provided by John). Note the amount of metal chips generated by the cut. There's more hiding inside the muffler can.

Here's the (small) piece that we removed. To complete the job, you're going to need to remove the muffler (unless you don't mind shooting metal chips out the back of your bike - actually, given the small amount of air coming from the motor, there may not be enough pressure to do that). Unbolt the muffler from the hanger and loosen the clamp.

view from ground level
If your VTR is anything like mine, it's going to take some wiggling of the muffler to loosen it from the sealing gasket. The bike is going to want to roll backwards. Resist the urge to use your left foot as a chock. If the muffler suddenly comes loose, it's going to hit the inside of your left knee. And, that's going to hurt, bad (I did it twice so I know).

Here I have the muffler removed. The red arrow indicates the sealing gasket. Hopefully yours is in as good a condition. I used a little Scotch-Brite to remove the surface rust. If yours is shot, you may want to consider replacing it. I wouldn't be surprised if there's some asbestos in that gasket. Use caution when dealing with it.

Removing the metal debris, from within the muffler should be pretty simple. I just kept shaking the muffler until chips stopped falling out. However, due to the shape of the end cap, chips can get trapped. I have one of those small magnets on a (telescoping) handle. A few passes collected a lot of additional chips. I was surprised at how much more came out. I purchased a drum shaped grinding stone to help smooth the ragged edges from the hole saws. In retrospect, I should have purchased a cone shaped stone instead. I have a Roto-Zip tool and elected to buy the drum shaped stone from Dremel. However Vermont-American makes grinding stones that will work in a drill (they have a larger diameter arbor). V-A sells both drum and cone shaped stones. Again, choose the cone shape.

Results: Upon initial start up I was a little disappointed as the sound wasn't that much greater than the unmodified muffler. However, after the ride to work this morning, I'm pretty happy. The exhaust note can clearly be heard (over traffic and through my ear plugs). I seem to notice a "drone" right around 4500 RPM but it quickly dissipates above 5000 RPM. I also think I will try some muffler paint or BBQ grille paint before the exposed metal starts to rust.

Tools used:
  • 3/8" drive ratchet
  • 12mm socket
  • 12mm open/box end wrench
  • ball peen hammer
  • drift
  • 2" hole saw with arbor (Milwaukee brand)
  • 1 1/8" (alt. 1 1/4") hole saw with arbor (Milwaukee brand)
  • 1/2" drill with aux. handle
  • Grinding stone (cone shaped - Vermont-American)
  • Magnet on a telescoping handle

Monday, May 14, 2012

Heat Sinking the Regulator/Rectifier

One of the weak points of the 1988-90 Honda VTR250 is the regulator/rectifier.  The rectifier converts the AC current, created by the motorcycle’s alternator, into DC current to charge the battery. Additionally, the regulator ensures that the battery is not over charged by “dumping” extraneous voltage to ground. In the process of regulating and rectifying, the unit can get very hot. Having it mounted just aft of the rear cylinder, within the VTR’s bodywork, is not helpful either. When a regulator/rectifier fails, due to overheating, it usually causes the CDI (Capacitor Discharge Ignition) unit to fail as well. Usually, there’s a distinct smell when these components fail (or “fry”) and there might even be some melted wiring.

As you can imagine, this is not an inexpensive issue to fix. It’s even more concerning on a VTR due to the fact that the regulator/rectifier is a rare object and commands a high price (whether new or used). So, in an effort to help the regulator/rectifier shed some of the heat it generates, attaching a heat sink would be beneficial. There are various ways in which this can be accomplished. The following details the steps I chose.

The image below illustrates the first dilemma. The image is oriented such that the valve cover, of the rear cylinder, is at the bottom of the picture. The red arrow indicates the location of the coils. The yellow arrow indicates the location of the regulator/rectifier. I estimated the distance between the two to be about ½” (0.5”). That’s not a lot of room in which to squeeze a heat sink (and have it be effective).

The second dilemma isn’t so obvious. If you look closely at the image above, you will notice that the side of the regulator/rectifier that faces the coils is the one where the circuitry is installed and sealed. This side of the unit will not be good at transferring heat. What’s the solution? “Flip the unit over and mount it the other way”, you say. Not so fast my friend. If you choose to do that, you’ll end up with the issue you see illustrated below. The yellow arrow indicates the gap, created by flipping the unit, between the mounting ears of the regulator/rectifier and the support bracket. Additionally, the mounting studs are now too short and there’s no room on which to thread the nut.

So, we need to figure out how to 1) secure the “flipped” regulator/rectifier to the support bracket, 2) secure a heat sink to the regulator/rectifier and 3) space the support bracket such that there’s room to accommodate the heat sink between the coils and the regulator/rectifier.

Reconfiguring the support bracket to accept the “flipped” regulator/rectifier

The first thing that needs to occur is to remove the existing studs that hold the regulator/rectifier to the support bracket. The studs are spot welded to the bracket. I used a hack saw to cut between the bracket and the base of the studs. The yellow arrows in the image below indicate the stud bases.

Once the studs have been removed, you can replace them with M6-1.0 x 25 button head screws (I initially used Allen head cap screws but that causes clearance issues with electrical connectors – so, use something with a low profile). Secure the screws to the support bracket with an M6-1.0 nut and M6 flat washer. The nut/washer combination acts as a spacer for the mounting ears on the regulator/rectifier (as indicated by the red arrow in the image below).

Securing the heat sink to the regulator/rectifier

I was able to find a heat sink out of an old personal computer. If you have an old PC lying around, it might have what you’re looking for. You could always check with a work station services tech at your place of business or ask the neighborhood ‘geek’ if he/she has an old computer you could pillage. Computers are very recyclable and most municipalities have recycling centers. I highly doubt they would mind if you pilfered a couple of machines for parts. The last resource is the internet. Lots of companies sell heat sinks. Depending on the material, they’re pretty cheap. You’re looking for one that’s about 1.75” (W) x 2.5” (L) x 1” (H). The key dimensions are the height and width. There’s not enough room for a heat sink with more than one inch of height. Additionally, the width must be less than two inches or it may interfere with the mounting screws. I had to cut mine down so it was 1.75” wide and less than one inch high.

Heat sinks are manufactured to be attached to computer chips so they’re already lapped (very smooth/flat) on the mounting surface. If you have to cut one down to size, be sure to keep the mounting surface free from gouges and burrs. I used some electrical contact cleaner and a piece of Scotch-Brite to clean the mounting surface of the regulator/rectifier. There’s more dirt there than you think. I chose to use Arctic Silver Alumina Thermal Adhesive (part # AATA-5G from, ~$8). It’s a two-part ceramic epoxy specifically formulated to bond heat sinks. Even though it comes in small quantities, you don’t need much. After scrubbing the regulator/rectifier, I cleaned the mounting surface with rubbing alcohol (per the Arctic Silver directions).

I wiped down the mounting surface of the heat sink with rubbing alcohol as well. I then mixed the epoxy per the manufacturer’s instructions.

The amount I used, total, had to be about the size of a penny (diameter and thickness). Arctic Silver recommends that the adhesive be the thickness of two sheets of paper (that’s not much) between the components. Since the heat sink is lapped, I applied the adhesive to that surface. The “pot” time (amount of time you have to apply the adhesive once it’s mixed) is only 3-4 minutes (very short), so work quickly. I put the heat sink and the regulator/rectifier together and, with a very slight twisting motion of the heat sink, made sure that the two parts had made good contact. I used one of those Vice-Grip Quik-Clamps to hold the parts together while the adhesive cured (initial cure is sixty minutes, total cure is about four hours). Now is a good time to go grab some lunch, do some laundry, check the scores, whatever.

After the initial cure, the adhesive has set enough so that you may put the regulator/rectifier back on the support bracket and install the bracket on the bike. You can reuse the Honda flare nuts to secure the regulator/rectifier to the support bracket.

To provide additional space, between the coils and the heat sink, I used longer hex head cap screws (M6 – 1.0 x 35) and a 1/4” x 3/8” x 1/2” steel spacer.

Here you can see the lower fastener with the spacer between the support bracket and the mounting tab on the frame. Note: the upper fastener captures a grounding lug from the wiring harness. Be sure that the lug is between the spacer and the mounting tab on the frame.

 Here’s everything in-place before the electrical connections were re-attached.

Now that the upper mount, of the support bracket, is spaced away from the frame mounting tab, make sure the wiring harness is not pinched between the support bracket and the frame. I simply pulled the harness out, away from the frame, so that it rests outward of the bracket. Here, everything has been re-attached.

The heat sink is indicated by the yellow arrow.

I estimate there is about .25” clearance between the heat sink and  the coil support bracket.  There appears to be about .5” clearance, after re-installing the side cover (bodywork), between it and the support bracket. Even if I push inward on the bodywork, it does not contact the support bracket. Problem solved (hopefully)!

Parts List:
2 - M6-1.0 x 25 button head cap screws
2 - M6-1.0 x 35 hex head cap screws
2 - M6-1.0 nuts 
4 - M6 flat washers
2 - 1/4" x 3/8" x 1/2" steel spacers
1 - Arctic Silver Alumina Ceramic Epoxy
1 - Heat Sink (approx. 1.75" x 2.5" x 1.0")

Wednesday, May 2, 2012

Some thoughts on changing oil

So, I took the opportunity to do an oil change on the VTR. Now that I know the drill, I'll be able to better document it the next time I do one (I'm guessing some time in the mid-Summer). If you need immediate data, refer to the Lubrication (Chapter 2) section of the Shop Manual on the Resources page. The directions are straight-forward and accurate. Thought #1: use a shallow drain pan with plenty of under engine clearance. I used one of those "self-contained" pans that have a big screw-off lid. Under that lid was a drain grate. It was too close to the bottom of the motor to easily get the oil filter out. Thought #2: have three quarts of motor oil. Even though the manual says "2.11 US quarts at oil filter change", it's more like 2.5 US quarts. Thought #3: ensure that the washer, between the spring and the filter, is retained. It appears that the previous owner did not notice that the washer was stuck to the old filter (and it was discarded with that filter). They're only a couple of bucks from Honda but now I have to remember to order one before the next oil change (while I'm at it, I'll get a filter support o-ring, too). Thought #4: ensure the the crush washer, on the drain plug, is good. Even though my VTR has only 5600 miles, it's seen at least three or four oil changes (hopefully more). The crush washer on the drain plug wasn't in very good condition. I replaced it with a copper spark plug indexing washer. Thought #5: be sure that the bike is vertical (to level ground) when checking the oil level in the site glass. Even when the sump is full, the site glass is empty when the bike is on it's side stand.