What does a bike actually sound like without the quieting gears?

The reason I ask is that I've got a CBR250 MC17[1] which blew up an engine and the replacement engine rattles quite a bit at low revs, it seems to run perfectly however and I can find nothing wrong with it and seeing as I have 3 NC35's I have no enthusiasm to fix it. I was wondering if maybe it might have been the previous engine owner removed the quieting gears but I have no idea what it sounds like.

Does anyone have any sound clips of a bike without the gears in?

Druid

[1] It's now sat for 3.5 years I've finally come to the conclusion that I'm never going to get it sorted and I'm going to put it on ebay later today.

how much do you want for it and whats wrong with it?

The easiest way I can explain is that it sounds like a bag of spanners.

Sort of an unbalanced carbs sound but more mechanical, the sound should go away when its not idling though?

Neosophist wrote:how much do you want for it and whats wrong with it?

Dunno, I was just going to put it on ebay.

Main problem is it rattles! Lost initial enthusiasm we got the NC35 (after it blew up), got a new engine but it rattled when fitted and lost enthusiasm again. I've just got zero enthusiasm for it anymore and it's just sitting there, I've got the original engine which I've rebuilt the bottom end on and swapped cranks and rods on (it blew a big end bearing).

The easiest way I can explain is that it sounds like a bag of spanners.

Sort of an unbalanced carbs sound but more mechanical, the sound should go away when its not idling though?

It sounds like a metallic tapping sound, seems to go on any kind of throttle and above about 5k.








Druid

Likely then to be somthing a little more serious.

Top end bearings??

No free play in any of the pistons[1] so while not impossible its unlikely.

I can't locate where it's coming from either, does sound as if it might be from the gear drive.

Druid

[1] Drop each piston to just after TDC and see if it can be pushed down, if it can then either top or bottom end is shagged.

Do you have a stethescope? Pretty usefull in pinpointing. You would need an attatchment probe rather than the conventional pad

Psychosomatic88 wrote:Do you have a stethescope? Pretty usefull in pinpointing. You would need an attatchment probe rather than the conventional pad

I tried the old using a screwdriver against my ear and every point I tried sounded fine and couldn't hear the rattle!

Don't care anymore, I have NC35's to fettle! Ebay item 120335172475 anyway.

Druid

Losing the quietening gears gives them a very 'tappety' noise (ok, if not done properly!), most noticeable at idle, probably because my bikes are too loud to hear them at anymore revs. It's not very loud or offensive, I like it.

You could take off the tappet cover and check quite easily.