Service
SERVICE
Mix-and-match two-strokes
I have heard that if you mix two-cycle oils (synthetic, castor and petroleum) in your bike, you could destroy your engine. Is this true? I have a 250 that I started off with synthetic oil and then switched to another oil which wasn't synthetic. After the change. the bike's rod bearing failed. Was this an oil problem or otherwise? Glenn Kantook Santa Rosa, California
Switching oils sliouldn t cause am problems. but we'd recoiziniend against mixing substantialli' different types of oils. We've heard ofafl~'w (rare,) cases of oils being incompatible when mixed in the oil tank ojan oilinjection system. or as pre-/nix in a gas tank. If iou i'an/ íü c/lange oil types, do it when the gas tank or oil reservoir are enipti'. A sfor your rod-hearing Jà ilure. it most likely was not oil-related. but there's no way we can be certain of 1/la!.
More on turbo plugs
Concerning Honda 650 Turbo sparkplugs. as discussed in the ser vice column, December, 1 985, Cycle World: The AC-Delco equivalent of the suggested NGK sparkplug is the AC R 121 CXLS. The Champion counterpart is RA6YC. These cost about $ 1 .70 each. I have used the AC plugs. and find them to last about 1 900 miles. as opposed to 2300 miles for the NGK or ND plugs. Order the AC plugs in a quan tity of at least six from your local auto parts store: my order took over a month to come. If you must use the expensive NGK or ND plugs. try National Catalog Stores (1-800-8543 110). They carry these plugs at a better price. Nick Da Leo Bryan. Texas
Weaving Wing
I own a 1979 GLI000 on which I have fitted two Aspencade saddle bags. but it doesn't have a fairing. When the bike reaches 100 mph. the handlebar begins to oscillate, and the bike rocks side-to-side, increas ing in amplitude until the bike be comes uncontrollable. Please advise me how to avoid this situation. Maybe you have heard about it before. Stephane Nadeau Neuville. Quebec. Canada
What iou and i'our Gold Wing are experiencing is known as straight-line teave, and is not uncoinnion at all. The ,,iosi frustrating tiling /5 that this weave can often be difficult to eli,,iinate. Generally, adding weight to the rear oJ,noiorci'cles i;iakes thiei;i iiiore susceptible to weave, and so the addi tion of saddlebags niav have increased your hikei~ tendency to weave. But doii `1 hurry to remove them; there are oilier things to tri'f~i. First, check tile tires. Did the weave fii~i appear a//er changing tire brands? I/so. iou nught want to c/lange back. Is your inflation pressure correct? Try running the tires at the upper range of~ recommended pressures. Is the rear tire substantially worn? A worn rear tire makes a motorcycle more weave prone, and perhaps should be replaced earlier than simple tread-depth read ings indicate. Other things to check include wheel alignment, wheel and tire runout, swingarin-bearing tightness, steeringhead-bearing adjustment. Also, check the condition of the rear shocks and the fork to determine is they provide adequate damping. If after everything is brought to spec, the bike still weaves, the final measure we would recom mend would be changing tire brands, though we're not sure which brand might offer improvements.
Braking: Suzuki vs. Harley
In your February, 1986, issue, why does the Suzuki GSX-R 1100 you tested with a "front brake powerful enough to lift the rear tire right off the ground" take 124 feet to stop its 471 pounds from 60 mph, while the Harley FXRD you tested with "room for improvement in the brakes" takes 121 feet to stop its 697 pounds. It would seem that the Har ley, carrying the extra weight of 226 pounds while stopping in a shorter distance, is getting the job done in spite of the "mighty effort" re quired, and it does it without any wheel lifting. To me, this seems the more controllable situation. Richard Swarez Okanagan Mission, B.C., Canada
In our full-on panic-stop testing, the FXRD stopped in a slightly shorter distance than the GSX-R1 100 for a number of logical reasons. To begin with, the leverage afforded by the Har ley `S sit-up, wide-handlebar riding po sition allows more absolute control over a squirming, hard-stopping inotorepcle than the GSX-R `s hunchedover, clip-on-barred roadracing po sition. In addition, the H-D `s long wheelbase and low center of gravity preclude the kind offront-wheel unicycling that occurs with the GSX R, which-as a necessary side-effect of being a quick-handling roadrace-style bike wit/i miles of cornering clear ance-has a considerably shorter wheelbase than the Harley, and a higher center of gravity. Also contributing to the H-D'S short panic stops was the Herculean effort required to lock its front wheel. Simply by> grabbing a big handful offront brake, an FXRD rider can attain near-inaxi inuni braking power while feeling reasonably sure that the front tire isn `t going to skid. On the Suzuki, however, the rider must do a bit of brake-lever modulation during a panic stop to avoid either locking the front wheel or having the rear wheel come too far off the ground.
While there's much to be said about a braking system that resists lock-up, the FXRD `s braking characteristics are advantageous only when aflill-on panic stop, or something approaching one, is called for. The rest of the time, when the bike need be stopped only at a normal, more-gradual rate, or just slowed down rather than brought to a complete stop, its brakes are not as beneficial. So much lever pressure is required, and so little feedback is transmitted back to the rider, that for many riders it tends to discourage use of the front brake for anything but panic stops. The GSX-R, however, handles those normal braking situa tions easily and predictably, with just a two-finger application.
It's important, then, to understand that the difference in panic-stopping distances between these two bikes has little to do with the quality of their brakes and much to do with the dynamics of their chassis. If you put the GSX-R `s brakes and tires on the FXRD, or gave tile Suzuki the wheel base, the center of gravity and the riding position of the Harley, either would perform a panic stop in a shorter distance than they could in their current configurations.
Getting off down under
I am the owner of an XR25ORE trail bike and would class myself as only an average rider who generally doesn't fall off of bikes very often. What has bugged me several times since I bought this bike new has been that I have fallen off more often than I like, and it seems to be the same each time-that is, the front wheel seems to skid out from under me very suddenly and usually without any warning. This happens most often on dirt around a sweep ing bend or corner.
`iIave you any experience with the same bike doing similar things? Would increasing the wheelbase by fitting a longer swingarm reduce the tendency for the bike to be so twitchy? George Krooglik Albury, New South Wales
We didn `t have that problem with our U.S.-spec XR25OR, but we could suggest two changes that might help your problem. The first change is one of ha rd ware; switch to a different front tire-a motocross knobby, either a Metzeler, a Pirelli, a Dunlop or what ever seems to work best on the local tracks. The second would be one of riding style; when you `re going around the type of corners that give you trou ble, slide forward and put as much body weight as possible on the front tire. That should help keep the front end planted. Also, a longer swingarm should make the bike less twitchy.
Shaking and rolling
I am the owner of a 1984 Harley Davidson Sportster motorcycle. Have you or any of your readers> suffered any problems with this make as a result of excessive vibra tion? In particular, I would be in terested to know whether you have experienced headlamp bulb failure as a result of vibrational problems.
My Harley-Davidson is the sec ond that I have owned, and both have, in my opinion, vibrated exces sively. whilst my present bike has suffered three broken headlamp sealed beam units in close succession. Stephen Ward Stockport. England
Yes, Sporisters vibrate. Thei' vibrate so much that i'ou would think that as tiler proceed down tile /iighwai', a trail of parts would be sha ken free,~ but, in truth, we've encountered no ill effects as a result of vibration wit/i the last three or four Sportsters we `ye tested. Nor ha ye we experienced failed ii eadla nips.
Howevei~ the headlamp used in Sporisters is designed specifically to cope with tile vibration, and a non Harlei `-Davidson replacement unit might not be so tolerant. If your prob lemii doesn `t arise from i/ic use of a non-stock light. rou miiight also check I/ic motorcycle's electrical system, specifically, its voltage regulation. Tile headlamp could as easily be failing fromi i overvoltage as from vibration. Also, a/il' changes in headlamp ml iou ii iingfromn i/ic original arrangemiletit could be intensifi'ing vibration.
