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Building a Ride Glide

I would like information on how to make my 1988 Harley Sportster 1200 ride smoother. I need to have the smoothest ride possible because I have a kidney condition. I love the Sportster very much except for the rough ride.

I read your article, “Project Sportster 1200," in the February issue, and I would like to know if those shocks and springs from Progressive Suspension would give me the softest ride, or is there something better yet? I'm willing to sacrifice handling for a smooth ride.

Ernest Grimm Brenham, Texas

Don 7 worry a boni the handling; if you 're willing to live with a taller seat height, you can get your 1200 Sportster to deliver an acceptably smooth

ride. First, phone Corbin Seats (Box 1562, Watsonville, CA 950771562; [408] 728-0169) and order the G unfighter And Lady saddle we described in that February article, but with some additional padding in the

rider's area to make the seat even more plush. The seat height will be elevated an inch or so as a result, though. Then, do install the Progressive Suspension fork springs for a better ride up front, but don 7 use the

Progressive shocks; there is nothing wrong with them, hut they are the same length as the Stockers, and you need something with longer travel to further soften the ride.

Instead, get in touch with Gil Vallaincourt at Works Performance (8730 Shirley Ave., Sort bridge, CA 91324; [818] 701-1014) and tell him you'd like a set of custom-tailored rear shocks for your 1200. He'll ask you a lot of questions, such as how much you weigh and the length of your inseam, then build you a set of shocks that will increase your Sporty's rear-wheel travel and offer far better springing and damping values. You might have to space the rear muffler out a fraction of an inch to clear the axle nut, but the shocks are otherwise a bolt-on proposition. They'll set you back $200, including springs, but the improvement will be significant. The longer shocks will slightly quicken the steering geometry, as well, but not enough to have any detrimental effects on the Sportster's handling and stability.

Notes from the flame front

Settle an argument for me, please. A few weeks ago, I had no choice but to put some unleaded regular gas in my ’84 Suzuki GS 1 1 50’s tank, and it made the engine ping like crazy until I could get to a station that had something with a higher octane. When discussing this with one of my friends, I called the pinging “pre-ignition,” but he said it was called “detonation.” We then asked the mechanic at my Suzuki dealer and he said we both were right, and that those were two different names for the exact same thing. Who’s right? I need to know, because my friend and I have a $ 10 bet riding on it.

Dave Herschel

Beaumont, Texas

Pre-ignition is the term used to describe what occurs when something in the combustion chamber (it could be a glowing piece of carbon, or a red-hot edge of a valve or a piston, or even the heat generated by compression when a fuel of insufficient octane is used) ignites the mixture before the sparkplug does so.

Detonation, on the other hand, is a different phenomenon that happens af-

ter the sparkplug ignites the mixture. Normal combustion involves a smooth, controlled burn as the flame front (the leading edge of the burning mixture) spreads outward from the sparkplug to the edges of the combustion chamber. Detonation occurs when the combustion is not smooth and controlled, when something in the combustion chamber (usually, too-high of a compression ratio, too-low of a fuel octane or excessively high engine-operating temperatures) causes the mixture ahead of the flame front literally to explode rather than burn. That explosion creates a shock wave in the combustion chamber that is so powerful it can be clearly heard outside the engine as a “ping. ”

But while detonation and pre-ignition are two different problems, detonation can lead to pre-ignition. Detonation raises combustion-chamber temperatures above normal levels, and that is one of the biggest causes of pre-ignition.

Although both these phenomena can wreak considerable havoc in an engine, pre-ignition can be the most troublesome, since it emits no audible clue the way detonation does. Preignition does its damage through the excessive heat generated when the two flame fronts (the normal one ignited by the sparkplug and the abnormal one ignited by something else) collide. The result is an extreme hot spot in the combustion chamber that simply melts things, usually the piston crown, if the condition is allowed to continue. Unchecked detonation usually is more destructive, however, for the force of its shock wave acts like a jackhammer that can cause all sorts of mechanical failures, lovely problems such as broken piston crowns, fractured ring lands, cracked combustion-chamber domes, even connecting-rod and bearing failures.

Neither of these two ailments is very friendly, but you have good reason to despise detonation more than pre-ignition: It just cost you $10. E3