The Service Dept
THE SERVICE DEPT
JODY NICHOLAS
HONDA 350 VIBRATION
I presently own a 1971 Honda CB 350 with just over 3000 on it. Overall it is an excellent machine, with one exception—vibration. Up to 50 mph or 5000 rpm the motorcycle is perfectly smooth. Above 5000 the vibration starts and is mostly apparent in the foot pegs, the only place it is severe enough to bother me. Most of my riding is done at speeds between 55 and 60 mph, so the vibration just starts to distract me during my normal cruising. Evidently this foot peg “tingle” is normal because all engine, foot peg and seat bolts have been tightened and my dealer also has
checked the machine, saying the vibration level is normal.
While I’m sure there is no real cure for this problem, I have an idea that might help. I plan to replace the stock 3.50-18 rear tire with a 3.75 or 4.00-18 unit. I have been told this will cut down my rpm by about 1000 in top (5th) gear. Therefore, at 55 my rpm will be 4500, thus cutting out (or down) the machines shaking. Since the 350 will need a new rear tire soon this seems more logical than changing the gearing.
Will this cut down my performance significantly? Currently the 350 runs quite well, but just how much would the larger tire affect it? The thing will run just under 100 mph (indicated) now, so how much will this tire reduce my top end? Overall, do you think this is a wise thing to do? Do you have any better suggestions?
Steve Hurd Columbus, Ohio
The 350 Honda is notorious for vibration in the speed ranges you mentioned, which makes it a little uncomfortable for long trips. For short trips around town the bike is really very nice and quiet.
The substitution of a 4.00-18 rear tire for the standard 3.50-18 one will reduce your rpm somewhat, but it will
also reduce your acceleration a little, too, and will probably reduce the top speed, as well.
If reducing the vibration levél at cruising speeds is your main concern, by all means fit a 4.00-18 rear tire. However, if you want all the performance your machine was designed to give, replace the worn-out tire with a standard 3.50-18. /—\ R51
