Service

SERVICE

Paul Dean

Strip search

During my usual winterizing ritual, I stripped the threads in the oil drainplug hole on my wife’s 1986 Honda Rebel 450. I tried all the local shops between Seattle and Everett for a solution, but no one was willing to do any kind of repair, short of installing a whole new set of engine cases. She would like to keep the bike, since she has restored it to near-mint condition and it only has 18,000 miles on it. I think it would be unwise to run the bike without oil or with just a winebottle cork in the drain hole.

Epoxy thread-repair kits or helicoils seemed like the best bet. But even after thoroughly draining the oil and washing the area with brake cleaner, some oil always remained on the cases and I couldn’t get a really good repair with an epoxy kit. Before I spend $50 on a helicoil kit, please tell me if it will get the job done. Fifty bucks is a cheap fix, if it works. David Dailey Edmonds, Washington

Without a doubt, installing a helicoil (essentially a piece of square-section wire wound in a tight coil) or a solid threaded insert (a thin-wall sleeve with threads on the inside and outside) is the most effective and permanent

way of repairing a stripped hole. But because the installation of these inserts requires the damaged hole to be drilled and tapped, preventing metal chips from getting into the crankcase can be a challenge.

In a perfect world, you would perform this operation only after tearing the engine all the way down to its bare lower crankcase. But if the world were perfect, you probably wouldn’t have stripped the hole in the first place; and we both know that you ’re hoping to avoid the time and/or expense of disassembling the entire engine. But not to worry; if you ’re careful, you can install one of these inserts in an hour or less without contaminating the crankcase with metal chips.

First, do not tilt the motorcycle way over or lay it on its side to perform this repair; put a makeshift platform of some sort under each wheel to raise the bike off the floor far enough to work comfortably beneath, and securely prop or strap the bike in a perfectly level, upright position. All your drilling and tapping, therefore, will be done directly upward from under the bike, allowing any metal chips to fall harmlessly to the floor instead of into the crankcase. And to further reduce the likelihood of aluminum getting into the engine, run the drill at the slowest speed possible without it stalling, and remove and thoroughly clean the tap after every full turn.

After the drilling and tapping are complete, but before installing the insert, put a light coating of thin grease on your little finger, angle it up through the hole, and sweep it around the area adjacent to the hole to collect any residual aluminum chips that might have collected there-although if you have performed the previous steps carefully, you should find none.

Sportbikes get shafted

I’m an avid sportbike rider, but enjoy a laid-back ride occasionally. While cruising recently on a friend’s Virago 535, it came to me: Why are there no shaft-drive sportbikes? I enjoy the definite “connection” of shaft drive, and in stop-and-go traffic, a shaft seems so much smoother.

Clifton Ogden Auburn, Alabama

There are, in fact, a few shaft-drive sportbikes on the market, including the Moto Guzzi Sport 1100, which earned fairly high marks in our December, 1995, test. But with rare exception, manufacturers do not use shaft drive on sportbikes, especially those expected to be used in roadracing, for a number of good reasons. Shaft drive 1) adds considerable unsprung weight that makes it more difficult for the rear wheel to follow any undulations on the road surface; 2) is less efficient than chain drive and thus consumes more horsepower; 3) tends to induce undesirable chassis reactions under acceleration and deceleration (although Guzzi and BMW have all but eliminated that problem); and 4) does not allow easy gearing changes, which can be a significant drawback in racing.

Who’s there?

My 1994 Honda Magna has some sort of knocking problem. Different dealers have told me that the noise originates from the transmission, the cam, that it’s a spark knock, etc. The sound is not evident at speed, and it comes and goes at idle. At one stoplight it might sound like a diesel, and at the next light it might run as quietly as a digital watch.

Performance has never suffered in the least; the bike runs great. It only has 5000 miles, but the unwanted sound effects started shortly after break-in was completed. Do I just live with this or should I expect an internal catastrophe somewhere dowrw the road? Mike Rigsby

Dallas, Texas

You haven’t given me much diagnostic information to work with, Mike, but I suspect that the noise may be the result of improper carburetor adjust ment, if the idle speed is set too low, or if the carbs are not properly synchronized-or both—the idle can be just erratic enough to result in a rapid, cyclic fluctuation in engine speed. This, in turn, can cause some driveline components-usually those in the clutch or transmission-to rattle bacl& and-forth noisily.

There ’s a tiny amount of freeplay between the primary-drive gear on the crankshaft and the driven gear on the clutch hub; between the tabs on the clutch plates and their mating grooves in the clutch hubs; and between tm mainshaft transmission gears and those on the countershaft. There’s not enough freeplay in any one of these areas to cause noise; but the combined play of all these pieces can be enough to cause a knocking sound if the idle speed is fluctuating.

Have a reputable mechanic adjust and synchronize your Magna s carbs and the rattling should disappear.