Knocking noise from the bottom of the motor on my GPX250

[LLmoose]

I have a 1992 GPX 250 and when I start the bike up from cold there is a knocking sound coming from the bottom of the motor. When the clutch is pressed in the noise stops and when the bike warms up it stops aswell. It has been like this since I got the bike and I changed the oil and filter on the weekend and its still making the noise.

Any ideas?

[Neka79]

expensive??

possibly sumthin bad..like a big end bearing... ??

[Daisy]

It may not be that bad, in fact it seems to be quite common. Does it go away at all when the motor has warmed up?
Mine did that for about 12000 kilometres without getting better or worse.

[LLmoose]

Yeh it doesn't seem to be anything major affecting the bike, just sounds a bit rough and goes away once the bike is warmed up.

[mike-s]

call it a characteristic of the engine (same in zzr & gpx 250's).
my old EL250 had it (used the same motor) and used to knock if the revs got too low when it was cold. Once the engine warmed up the sound of a golfball in a milo tin would vanish.

Ask anyone else as well as look on any other forum, many many newbies asked the same question (including myself at one stage).

[AltonaGreeny]

I new to motorbikes and this forum aswell but being a mechanic I know that on some engines when the engine is cold on start up the pressure from oil being pumped up thru the lube holes on the big end bearings can sometimes cause the crank to bounce slightly. This is due to the crank not being warm and therefore slightly smaller. It is very common and all manufacturers have compensated for this in their desighn. Nothing to worry about really but as it is suggested with any engine allowing to warm up before use is highly advised.

[Slow and wobbly]

parallel twins. Is it more of a thump or a clack than a knock? "They all do that"
Its a Kawasaki. Its a Kawasaki 250. 15 years of novice abuse hasn't killed it yet, don't think your gonna either

[Strika]

All Gpx 2fiddies and even the KLE500/GPZ500/ER5 motors share a similiar knocking noise. It's a concern till you line up next to 20 others and hear the same noise! You mention yours dissapears when the clutch is pulled in. This could be a little Clutch basket knock. It happens commonly also. They are a pretty good engine and providing the cam chain is not rattly, and you change the oil regularly they will go almost forever. Watch cam chains, I have seen a couple eat there way out of the engine cases!!!! It's not funny, but hard not to laugh when a rider comes in and says there is oil leaking from the front of my motor!!! London to a brick it's cam chains hanging in the breeze!

FWIW, I sold a GPX250 with 88,000klms (one owner with a full workshop history by Kawasaki) to a guy who did another 80,000 klms on it before it needed any rejuvination internally. It went throu a few cam chains in that time, but bugger all else!

[Steve_TLS]

I remember when my ex bought a brand spanking GPX250 many years ago and I told the salesman we didn't want that one the bottom end is going to fall out of it. He said they all do it. So I got him to start the new one up next to it, same noise. Then he started the XXXXXkm old one up, same noise. It did it from the day she bought it until the day she sold it