My son and I are working on a late 80's GSXR 250 project and have some engine noises that we need to track down. After a general tidy up, new oil & plugs, fiddly carb balance, she is running sweet and seems to rev freely without any unusual behaviors. We haven't been able to road test it yet as it is not registered but all is ready for the roadworthy inspection. When idling, there is a rattle that is almost like a loose cam chain, which disappears once the revs climb above 2000. With the old screwdriver to the ear stethoscope, the rattle appears to be coming from the alternator side of the motor but is hard to tell exactly. If anyone has experience on these engines, I would appreciate any advice / guesses as to what might be the cause of such a noise. Graham
If you could get a video with good audio of the noise it would help. Cam chain / tensioner noises generally lessen the higher the RPM.
Have you had the cover off that side yet ? It would appear that in old age some of these are developing a history of loose magnets in the rotor. Also things are very tight around the front of the motor on that side. Is the hose clip on the barrel fitting touching an exhaust pipe ?
Haven't had the alternator cover off yet. Will check the area for things like clamps + clips rubbing as you suggested. Hadn't thought of that. Cheers
Picture with the cover off, no magnets are broken or loose but the this plastic coating around them has come off in spots, thoughts?
Hmmm thats a weird one.....could be cam chain...does the sound change if you pull the clutch in..could be a worn clutch basket.....also if the carbs are out of sync at idle most 4 cylinders bikes will make a racket...... PS(edit) did you check if any play in the mains when the alt cover was off?
We nailed it. Thanks Wozza for the direction, it was carburetor tune & balance. We figured that the noise changes with carb adjustments so we chased the balance/idle jet adjustments until a satisfactory result. The carbs are old and worn so it has been a challenge, but all good now.
