Pulse Generator Transplant

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After troubleshooting every other electrical component on my 1984 Honda Shadow VT700C, I determined I’m not getting spark because I have a bad pulse generator. Later model bikes use a single pulse, but the ’84 VT700C has two pulse generators, one for each cylinder. This equates to double the possibility of failure and headache cubed when one or the other it actually does fail, since they have to be replaced together as an assembly.

Testing the pulse generators is a pretty simple process of disconnecting the pulse generator assembly from the rest of the electrical system and taking an OHM reading on the leads for each pulse generator. The connector is easily assessable, tucked away on the right side of the crankcase by the fuel filter.

One of the pulse generators tested at 440 OHMs, well within tolerances. The other pegged out my multimeter, indicating a bad pulse generator.

Finding a “new” OEM replacement proved to be impossible. At least three websites claimed to have the part, but when I spoke to a live salesperson, in each case I was told the part was discontinued and no one manufactures a replacement.

I tracked down a used pulse generator assembly on eBay. It’s amazing that idiots like me desperate enough to spend $100 for a $10 part. Since the one I picked up was the lowest priced on eBay, and since the VT700 is scrap metal without one, I considered myself lucky.

While testing the pulse generators is easy, replacing them is a pain. I had to remove the right foot controls, the right-side exhaust, part of the frame, the right crank case cover, and both the clutch inner and outer.

Before installing the “new” pulse generator assembly and putting the bike back together, I decided to test it. Just like the original, it had one good pulse generator and one failed pulse generator.

In the spirit of Dr. Frankenstein, I began hacking at the two assemblies, tossing the bad generators in the junk bin and cobbling the two good generators into a single pulse generator assembly.

When I began routing the pulse generator wiring back through the crankcase, I discovered I had shorted one cable by half an inch. Clearances are tight in the crank case, with the wiring routed around several moving parts, so that half inch may as well have been a mile.

I set my Frankenstein’s monster of a pulse generator assembly to the side, and decided to take a break to check my email and check the status of some other parts on order from eBay. On a whim, I checked to see if anyone had posted another pulse generator assembly.

And there it was: a pulse generator off of a 1983 Honda Shadow VT750, for $15, plus $5 shipping. What did I have to lose?

This assembly arrived two days later. Both pulse generators tested within specifications, and it routed perfectly into the crankcase.

Now it’s time to button this thing up and see if we have spark.

Bad Ticker

I can’t say I’m surprised that my aging VT700 project bike has a bad ticker. Specifically, one if the two pulse generators it’s testing bad. The pulse generators are basically the pace maker of the bike. As the pistons move up and down, they turn a sprocket with an arrow-shaped piece of metal on. As the sprocket rotates, the tip of the arrow passes two magnets, each positioned I about 70 degrees apart.

As the arrow passes the magnet, the magnet zaps an electrical signal up to the ignition computer, which then zaps a signal to the ignition coils, which causes the spark plugs to spark, which if nights the air and fuel mixture, which moves the cylinder, which pushes the pistons, which turns the sprocket, which moves the arrow. The circle of life is complete.

Each pulse generator signals one cylinder to fire, and they are positioned so that each signal fires in the optimum sequence for power (and Federal emissions standards). When on pulse generator fails, only one cylinder works, and the other is just dead weight.

So, the the Honda shop manual says that the pulse generators should have a continuity between leads of 480 OHMs, plus or minus ten percent.

One of my pulse generators tests at 430, which is close enough. The other doesn’t read at all.

The connectors and wiring are good on the failed pulse generator, so the problem is likely a break in the mile or so of thin copper wire wrapped up around a magnetic post inside the pulse generator.

Like everything else in this bike the pulse generator assembly is discontinued at Honda, and there us no aftermarket option. After a week of hunting online, I purchased a used replacement assembly off of eBay, but it’s fails exactly the sameway. My theory is that the lower pulse generator, because it is immersed in oil all the time, is exposed to greater heating and cooling variations compared to the top pulse generator, which does not always sit in an oil bath.

So now my plan is to scavenge the good pulse generators from the two bad ones and try to makes a working assembly.

I have had to remove the clutch assembly to get to where I can work on the pulse generator, so it looks like I’m rebuilding the clutch, too.

The excitement never stops!

 

SOLD: 1985 Honda VT700C Project Bike

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SOLD

Oden Motor Shop has 1985 Honda Shadow VT700C for Sale! This is a great project bike with 32,000 miles on engine. It’s running and has good compression, but needs new head gaskets, carbs cleaned, fluids changed, and some TLC.

It has a minor dent in the tank, which is repairable, and the tank is free of rust. The are other minor cosmetic issues, but it is a complete, working bike. Used parts are readily available via eBay, and Oden Motor Shop has a small inventory of parts for this model as well.

The tires still have at least 10,000 miles left in them, and the bike is still a smooth ride. It comes with a clean title and Honda Service Manual. The price is $899.00, or Best Offer.

All sales are final, but as with all Project Bikes supplied by Oden Moto Shop, it comes with 90 days of email shop support.

For more information, please email curtis@OdenMotorShop.com.

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New Photo Gallery: 2012 Rolling Thunder – Ride of the Patriots

Ride of the Patriots is a lead-up to Rolling Thunder put together every year by Patriot Harley-Davidson in Fairfax, VA. About 6,500 riders gather together in Fairfax to ride a police-escorted parade rout to join up with about half a million more Rolling Thunder participants at the Pentagon parking lot.

I Brake for Working Brake Lights

100_0114I was first alerted to a problem with the brakes on my bike when I started slowing down to make the left turn into my neighborhood and was suddenly assaulted by a blaring horn an obscenities from behind me. The guy driving the express delivery truck must have been pretty mad, because I could hear him clearly over the rumpling of my Screamin’ Eagle, and inside my half-face helmet. I made a quick check of my turn signals (I new I hadn’t forgotten to press the left turn button), and everything checked out.

A few minutes later, when I was back at home, I ran through a quick check:

  • Did something fall off my bike and hit the other car? — No. Everything was where it should be.
  • Did I have anything offensive written on my clothing?— Nothing that would elicit more than a disapproving glare from my grandmother (then again, she was very open minded and tolerant).
  • Were my tail lights out? No. When I pressed the footbrake, it all lit up.

But…

I check the brake again, using only the handbrake, and tail brake light stayed dark.

When I took off the break lever, the pressure-pin on the brake switch (which the brake releases when depressed) was stuck in its housing. No amount of coaxing could get it out.

So I headed down to Patriot Harley-Davidson in Fairfax, VA, and picked up a replacement switch for about $30.00 USD.

I was a bit nervous about replacing the switch myself: I can turn a wrench and change oil, but electrical troubleshooting is a bit beyond me. But the replacement switch came with good instructions with lots of drawings, so I decided to go for it.

Removing the brake lever was a simple task, since I’d already done it to check out the problem. Removing the electical switch housing and getting in to the bad switch proved challenging because my wiring is run inside the handlebars, and there really was no slack.

The brake switch was completely burnt out and had melted itself in a locked position. I had to gently muscle it out of the housing.

When I go the new switch in, I found that the release button (the part the brake pushes in and lets out to trigger the brake signal) was jamming. I loosed the screw holding the switch in to give it a little play, and jamming ceased to be an issue. I suspect this is what cause the earlier brake switch to burn out.

After some close wiring work (at least it was close to me), I got the new switch in and screwed and bolted everything back together.

When I tested the brakes using the hand lever, the brake light lit up instantly.

Hopefully the express delivery guy appreciates my effort and won’t drop my packages in the mud.

Fat Boy on a Softail

This 1993 Heritage Softail Classic isn’t a small bike, but when Curt gets on it, it looks down-right tiny! Fortunately, an aftermarket Screamin’ Eagle motor helps him keep up.

Z-Rod: Undead V-Rod

While it may be hard to believe, one of Big Daddy’s little buddies trashed his V-Rod, most likely as a result of doing something he shouldn’t have been doing, somewhere he shouldn’t have been, and probably with someone he knew better than to be doing anything with.

It’s funny how many Oden Motor Shop projects start out this way.

We’re not sure how Big Daddy ended up with the wreckage, although repayment for bailing the previously mentioned Little Buddy out of jail is a strong possibility.

For a while now, Big Daddy’s been wanting to get Son Number One off of his tiny 1980 Honda CX500 Custom, and onto something more suited to a man of great … stature.

Granted, the CX500 is a great motorcycle, but the circus clowns want their bike back.

So, for Son Number One, a junked out V-Rod is zombified by the mad geniuses of Oden Motor Shop. We give you: Z-Rod!

Big Daddy’s New Ride

Do you ever get that not so fresh feeling? Well, at some point in the life of every one of Big Daddy’s motorcycles, the seat stops smelling so much like leather, and starts smelling like old, hairy, STANKY, Big Daddy ass. When that inevitability happens, Big Daddy goes shopping.