. Pilgrim's Mechanical Explanations, Tips,and Tricks
Pilgrim's Mechanical Explanations, Tips, and Tricks
OK - before we go any farther with this, let me say that I am not a mechanic, PHD, MMI, or otherwise. I'm a guy who works on his own scooter and has learned from experience. What I offer here is nothing but stuff that I've either found to work for me or I have personal knowledge of it being done (or not done, as the case may be) by people I know and trust. If you decide to try something you see here have at it, but if it doesn't work out don't tell anyone that I said you should, 'cause that's not what I'm doing here.
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An inexpensive, easy set of vents for the lowers on your FL-whatever.

About heat and oil and gauges and coolers

Cam change for 96" Twinkie motor.

What is "Timing"

Setting Timing by Reading Plugs

Dual Fire, Single Fire,
and Waste Sparks

That Harley Sound - Why Is It?

Indexing Plugs

Why Not Drag Pipes?

Wrapping Your Exhaust Headers

Welding ABS Plastic

Finger Clutches & Quarters

Warming up Your Evo or Twinkie

Checking Your Charging System

Torquing Bolts, and Torque Wrenches

Detonation - it's a BAD thing!

VOES? What the heck is that?

Building a big gas tank.

A mod to let you time your engine
alone from the right side.

Changing the back tire on an FXRT or FLT that has an enclosed chain drive.

Setting Your Timing by Reading the Plugs

I'm going to tell you how I set my timing, and you can adopt it or not, as you see fit. I first heard it from an old-time wrench down in Puerto Rico. I thought it was bogus until I saw in William Denish's book on HD High Performance a reference to the factor the old guy mentioned. I started using it, and it works for me.

First of all, this does not work for the Twin Cam engine, and I don't know it if works or not for fuel injected Evos. It does work for carbureted Evos, shovels, and on back.

Your spark plug tells you a lot about what's going on in your engine. Today's fuels make it harder to read the details of combustion on your plugs, but basic "too lean" vs "too rich" are still pretty clear, and a couple other things.

The burn line Among them is advance position. Starting with a fairly clean plug, you can spot what I'll call a "burn line" on the ground electrode of the plug, the one that arches out over the center electrode. The burn line is a clearly visible spot where the color of the electrode changes. Usually it will be darker toward the tip of the plug and lighter toward the base of the electrode. That burn line ought to be somewhere close to the 90 degree curve of the electrode. If the line is closer to the base of the electrode the ignition is relatively advanced, and vice versa.

So what I do is get the motor started with a static timing job. Then I go ride it for a while to get it thoroughly warmed up. Running along at 60 or so in top gear I pick a safe spot. I pull the clutch and chop the ignition off using the kill switch, both at once. Then I coast to a stop, holding the throttle open. The purpose of that is so that the plug does not load up with carbon and blur the burn line, as it would if I came to a normal stop.

Now let the engine cool down. (If you try to pull the plug too soon, you may strip the threads in the head. Then you won't be thinking about timing for a while.) A handy way to do this is to pick your stopping place so that you roll into the parking lot of a tavern. You can go inside and tell your bros what you are about to do. Half will call a penalty for bullshit, and the other half will think "Gee, he really knows some good stuff."

Have a look at the plug. If the burn line is too close the base, RETARD the timing, since being close to the base means it is already too advanced, right?

First, mark the timing plate with a scratch. That becomes your reference mark. Then use a fine marker or pencil to mark the inside of the cone beside that reference mark.

Now move the advance plate couterclockwise to retard the timing. I'm not gonna tell you how much, I don't know. But think of "bracketing" the right spot; get enough movement that you can read the plug change easily.

Ride, check, and adjust again. If the first change was too much, and now you are retarded, split the difference, and check again. And again, until it's just where you want. Then mark the cone alongside the plate reference mark with something permanent so you can always come back to that setting.

If you are running points you should be aware that adjusting the point gap changes the timing, so get that right first.

Indexing Plugs

You'll also note the brown stain on the side of the white insulator in the picture above. It indicates which way your plug is "indexed," that is, which way is the plug gap pointing inside the cylinder. There is some efficiency to be gained by having the gap point at the intake valve, so that the incoming fuel charge blows by the spark as it circulates in the cylinder. The brown stain is caused by fuel flowing against the plug from the intake valve, so that stain tells you where the intake valve is in relation to the gap. In the plug shown, it is just right. You can change which way it points by getting some indexing washers of differing thicknesses and putting them under the plug when you install it.

Good luck. Let me know how you make out.

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Why Not Drag Pipes?

In short, because they don't work well for the engine when ridden on the street. They are called "drag pipes" for a reason: they work best when the engine is operated at wide open throttle, and only then. All their power is developed at high rpm, not down low where you want it from traffic light to light. If you like a ride that's hard to tune the carburetor on, difficult to get a cam to work in, and is doggy on the street no matter what you do except when you have it wound up tight, then drag pipes are for you. Oh, and noise too. If you just want noise instead of performance, they are just the ticket (which a word that will probably come up again after you have run them for a while, enjoying the noise).

If you absolutely, positively must have them for looks and sound there is a way you can make them work better. Notice I did not say "well", but better. You'll give up a little, just a little, sound, but you'll gain a lot of torque in the lower range, and that's performance you can feel in the seat of your pants all the time.

For under $30 most places you can buy a set of baffles to go in the pipes. All you need to install them is a drill motor and a quarter inch bit. Drill a hole about 2" from the end of the pipe, on the side against the swingarm, so the head of the bolt you will use won't be seen. Slip the baffle in (it's about 6" long) and bolt it in place.

Now you'll probably have to rejet the carb by going down one size, and maybe half a turn in on the idle air screw, but the motor will be a whole lot happier. It will idle much more smoothly, and your departure from stop signs, while still noticeable from a couple blocks away, will be much quicker and smoother.

All in all, a good deal.

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Wrapping Your Exhaust Headers

Internal combustion engines are said to be air pumps, but that's actually a second order description. In fact, they are heat-actuated devices, depending on air and fuel to generate the heat to make pressure to push down on the piston.

As long as you don't exceed the ability of the component metals of the engine and oil to handle the heat, and don't get so much heat that it causes detonation of the fuel/air mix, the more heat you keep in the motor the better.

Not only do you want to keep heat in the engine, you want the exiting exhaust gases to stay at a high temperature - that's because the higher the temp, the higher the exhaust gas velocity stays going down the tube. And that matters because those gases moving down the pipe create a vacuum at the exhaust port (think of pulling the plunger up on a syringe) which scavenges the cylinder of burnt gases. It can even make a lower pressure in the cylinder, which helps draw in the next intake charge when the intake valve opens.

And for those of you who think about such things, you'll realize that having an exhaust pipe that's too big for the engine is not a good thing. It reduces that scavenging effect because as the exhaust gases expand into the large volume of a bigger pipe they lose their velocity. A big pipe is not always better; it depends on the size of the cylinder it's draining. Depending on the cam to some degree, engines up to about 103ci do best with an inch and three-quarter header.

A wrapped exhaust will help keep heat in the combustion chamber and exhaust pipes making power, instead of radiating it to air where it makes no power and, gawd help us if AlGore is to be believed, it contributes to global warming.

You can get a lot of the same effect for your pipes by having the inside of them ceramic coated when new. There are also coatings of various types that you can coat your piston tops and combustion chambers with the reject heat, forcing it to stay in the combustion chamber. For the piston, they also add some degree of protection from meltdown.

That's why you see a lot of race bikes with wrapped exhausts; it's not to keep the rider from burning his leg.

If you want to get in touch with one place I know personally does a good job with internal and external coatings, drop by this website.

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Welding ABS Plastic

If your scooter has tupperware parts on it, like fairings, bags, lowers, etc. this tip may be handy for you. It does not work for fiberglass though.

Your parts are black ABS under that paint. You can buy it in sheets of varying thicknesses from plastic supply places; there are several in Seattle, and certainly others can be found on the net. You can also buy ABS rod in from some body shop supply houses. Mostly it'll be white, but that doesn't matter. You'll want 1/8th inch rod.

Like metal, you use heat to weld ABS, only much less, of course. You can use one of two sources. There are heat guns available that have a special tip that focusses the hot draft on a small area.

Or you can make a "welder" out of a 80 watt soldering iron. First get a piece of 1/8th" ID stainless steel (but copper will work) tubing. Freeze it so it will shrink, then measure the outside diameter to a thousandth or so, then get drill bit just that size. Drill a slightly angled hole through the tip of the soldering iron, aimed so that it comes out about 3/8ths to 1/2 inch away from the end. Now, with the tubing cold, slide it through the new hole. On the bottom, the end closest to the tip of the iron, trim it off flush. Trim off the top, but leave about 1/8th" to 3/16ths of it sticking up. A cutoff wheel in a Dremel tool will cut it nicely, and you probably won't even have to deburr the tubing. If you want to get fancy now, flare the top of the tube a little bit. You have just made an ABS welder.

Get some scrap ABS, maybe a busted saddlebag lid or something, and practice on it. First thing to practice fixing cracks, 'cause it is probably what you will need to do before anything else, is repair cracks. You can learn to join fresh pieces later.

Just like steel welding, use a Dremel tool or something similar to carve out a shallow groove along the length of the crack. Then using the soldering iron tip to soften the mother material, feed rod through the tube as you go. It is a slow process; there's no way to hurry it up. Hold the iron at an angle and push it along the crack slowly, sweeping the tip slightly side to side, so you soften an area on each side of the crack, and feed rod into the "puddle", althought it's not really quite liquid. Let the tip of the iron skate on top of the plastic; don't let it dig in and gouge. You'll wind up doing some stirring with the iron as you go.

You MUST practice before you try if for real though. There are things you must see and note about how the plastic reacts to heat. For instance, support the back side if you can, because if it is a horizontal surface it will sag away from the iron if a broad area gets hot. And you gotta figure there will probably be some damage to paint where you weld.

Once you get the crack all welded up (weld both sides if you have to) you can go to work with sandpaper and paint. The process will almost always leave a few small voids, so be prepared to put on a little skiff of Bondo to fill them as you sand.

It's a nuisance to have to do it, but if you have a busted up part it's way cheaper than buying a new fairing, for example.

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Bending ABS

ABS is pretty neat stuff to work with. That's one of the reasons the factory uses it, I guess. There are some good adhesives for it, and it bends nicely with heat.

To apply that heat, purchase a heat gun at the hardware store. Get the adjustable kind with about ten settings. You can get a pretty good one for $60 to $80, and even cheaper at the hock shop. If you want to spend a few additional bucks, get one that will give you a focussed beam and you can weld ABS with it.

In addition to bending or welding ABS you can also use it on heat-shrink tubing, and once you do you'll wonder why you spent so many years trying to do it with matches or, if you're a hi-tech kinda guy, a Bic lighter. There are lots of other good uses too, like taking decals off helmets or other gear. You'll find 'em.

Anyway, ABS is friendly stuff. It cuts easily, and forms with heat easily, even to pretty complex shapes. The problem in really complex shapes comes in recognizing how to cut it out so that it will do what you want. I can't cover that here (mostly because I'm not very good at it!) . But if you take your heat gun and learn how to evenly heat the surface you want to mold, you'll be amazed at the shapes you can make.

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Using a Quarter to Measure Clutch Clearance
If you have to adjust the old-style three or five-finger style clutch (shovelhead and early Evo) you will know that the book calls for clearance to exist between the pressure plate and the outer plate. The range of clearance is 7/8ths of an inch to one and one-thirtysecond of an inch. In one of those cosmic instances of good fortune that show up once in a while, it just so happens that the the diameter of a U.S. quarter falls nicely within that range. So all you have to do it turn the nuts down on the studs until a quarter will just stand up between the plates alongside each spring, and there you are. No ruler required.

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Warming Up Your Evo

One of the commonest engine abuses performed by guys who generally think of themselves as careful of their engines is improper warmup. Too many of them them think it's enough to just let oil pressure stabilize, then ride away, taking it easy on the throttle for the first few miles.

Not so. That practice is probably responsible for more base gasket leaks than any other: here's why.

Unlike shovels, pan, knucks, etc. which bolted their cylinders to the cases, and the heads to the cylinders, the Evo takes another approach. On an Evo there are four long STEEL studs that stick up from the crankcase. First you slip a base gasket onto them, followed by the cylinder, then a head gasket, then the head. Once the head is on, the head bolts, which attach to those studs, are torqued down.

Now, you don't actually put a lot of torque onto the head bolts on an Evo, espcially not compared to what older models use. It's about half the amount, or a little less. Why is that?

It's because the studs are steel, which does not expand much, and the cylinders and heads are aluminum, which does.

As the engine heats up, the result is this. The cylinders and heads expand vertically (actually, in all directions, but vertically is what we are concerned with here) , and so do the studs. But aluminum expands from heat at a rate about twice what steel does, so while the cylinder/head stack tries to get tall, the studs can't keep up. See the effect? The expansion of the cylinder and head exerts a strong clamping pressure on the gaskets, making up for the relatively low torque on the studs that also clamp them.

But if you try to ride off before the cylinders have reached a pretty warm temperature, you are stressing the gaskets, both head and base. The internal pressures are pushing out on gaskets that are not yet fully clamped from expansion of the aluminum. While base gasket leaks are the common result, it is possible to blow a head gasket if you have bumped the compression up and really get into the throttle too soon.

So the best, absolute best, thing to do is to not ride off until the cylinders have warmed up enough that you feel a distinct warmth in them. That usually takes a couple minutes, time enough to do a walk-around of the bike, and put on your jacket and one glove. Reach down with your bare hand and feel the top of the cylinder or the bottom of the head. If it is warm enough that you don't want to leave your hand on it very long you are good to go. Your scooter will love you for it.

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