Tech Questions & Answers | Shop Talk

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Things that go bump in the road
I put new tires on my 2007 V-Star 650 Custom and have felt a bumpity-bump sensation most noticeable as I slow down under 50 mph. It's like going over a washboard—very rhythmic and possibly about 2 bumps per second. I returned the bike to the shop, and they balanced the front tire but that didn't help. I took it back again and they removed the front tire, found no flaws. They had a "pro" ride it and he said he didn't notice. I double-checked the tires to make sure they were the right ones. I opted for the same Bridgestone Exedras that were on the bike when I bought it. I put 10,000 smooth miles on those tires. The shop has offered suggestions like, there might be a flat spot. The pro thought the shocks were soft. No one seems to agree if it's the front tire or the rear tire. I do not notice anything at faster speeds and the mirrors don't seem to be vibrating more than usual. At slower speeds, I can actually see my windscreen go up and down. I have never experienced these bumps before, with new or old tires. Meanwhile how's that affect the wear of the tire? I think I'm going to have to get a new front tire, then maybe a new back tire. Any ideas?
Yvonne
Via email

_The sensation you’re describing has nothing to do with suspension settings, spring rates or the ambient temperature. Rhythmic imbalances are always caused by some sort of mechanical problem within the tire or rim assembly. Something is causing the tire to act as if it’s elliptical rather than perfectly round and only a few things can do that. The tire may be grossly out of balance, the tire may have a manufacturing fault and be out of round, the rim itself may be out of true or the tire could have suffered from some sort of mechanical damage: a broken belt, or bent bead wire. _

_First, check the rim and tire for axial (up and down) run out. Look for a pronounced hop or a high spot when the tire is rotated. If the rim is at fault, it’ll have to be trued. If the rim checks out, look for a high spot in the tire- if one is found, you can try rotating the tire 180-degrees on the rim, but the real solution is to replace it. _

If no high spots are found, have the wheel dynamically balanced. If that fails to cure the problem, and you feel the problem is serious enough to warrant further attention, contact the dealer and Bridgestone. I can assure you that Bridgestone takes the DOT TREAD act very seriously, even if the dealer doesn’t.

Gears are good
I bought my Kawasaki 800 Drifter about a year ago, after you said it would be a good buy. You were right, it's fantastic. My mechanic says the chain and sprockets are now worn out, the bike has 22 k miles on it and I was thinking about a Scoot Works belt conversion. But I'm low on bucks, so I'll probably go with a new chain and sprockets—what would you recommend to get rid of the looking for 6-gear syndrome and lowering the noise?
Joe Lewis
Via-email

_Glad you like the bike. The easiest (and cheapest) way to raise the overall gearing is by adding one tooth to the countershaft sprocket. That should give slightly better mileage, more relaxed cruising, and for what it’s worth, a little more speed in each gear. It’ll hurt acceleration slightly, but that should barely be noticeable, and it will reduce the overall noise level slightly. _

The advantage to doing it this way, rather than by reducing the number of teeth on the rear sprocket, is that if you decide you don’t like the new ratios, it’s a lot easier to swap the countershaft sprocket than it is to replace the rear sprocket, and far cheaper—an important consideration these days.

**Upon reflection **
I have a '09 Star Raider that my wife bought me for my birthday. (She is the best!). The bike has reflectors on both sides; amber up front and red on back. I was looking at custom bikes and they do not have those reflectors. I was considering taking those off. What is the real purpose of those? DOT requirement? Are they there so that car can recognize a parked bike in the dark? Even when riding at night, the chances of those reflectors being seen are very slim. Headlights don't point at the side of the bike often. So would it make much difference if they were missing?
Jose Garcia
Windsor, CT

The reflectors are a DOT requirement, and are only installed on bikes headed to the U.S. They are intended to make the bike more visible from the side, though their usefulness is debatable. It’d be irresponsible, and against the law, for me to tell you to remove them, but you’ll notice they’re held on in very flimsy manner, and might easily fall off if you aren’t careful.

Tech Questions & Answers | Shop Talk - Motorcycle Cruiser Magazine