Question1999 Honda Rebel 250, bought this bike for my son in July with 2500 miles, no mods. Easy to start hot or cold, runs and idles smooth, no hesitation, able to go 65mph on freeway without problems. To our surprise the bike did not have an air filter but purchased filter and clip, installed a week later. Trying to locate a low tone "whistling" or whirring noise that was present before and after installing filter. Will try to be as detailed as possible:
Hot or cold; choke or no choke, start bike and you hear the sound all around the bike. Strongest sound to me is the right side of bike near airbox and carb (single carb) and front of engine around exhaust pipes and starter. Rev engine and tone of sound will raise a bit but nearly the same. The sound is not constant at idle, slightly varies between higher and lower tone but the difference is not that great making it sound almost constant.
Covered both stock exhaust outlets and weep holes under muffler at idle and the sound remains. Checked all exhaust bolts and crossover clamp. Followed all drain hoses and plugged them off one by one, no change. Sprayed carb and intake with carb cleaner to see if any leaks, engine did not change RPM (was thinking the butterfly shaft). All vacuum hoses are pliable with no cracks and clamps are good also. Removed crankcase hose from bottom of air box and held closed with finger, sounds the same. Took oil dipstick out while at idle, sounds the same. Thinking now it may be cam chain? Any ideas would be greatly appreciated. Thank-you Pete
AnswerPete, get a hold of a 3 foot piece of 5/8-3/4 inch diameter rubber hose. Hold one end to your ear and sweep the other end over the bike until you locate the source. The hose will help you focus on the sound by eliminating other noises. If you have an single foam ear plug for the other ear it will help too.
Once you have located the source, I can give you some ideas about what's causing it.
Regards
Rich
