GS300L Engine Knocking

[Chopper Dave]

Hello all. I am new to the forums and new to owning a suzuki. I bought a gs300l at a swap meat extremely cheap. Looks good, runs pretty well for having sat for 4 years. I do have one problem though that I need help with. When the engine is warm, I hear a loud knocking noise coming from the lower right front side of the engine which is RPM dependant. It is most prominent at lower RPM's and goes away at higher (at least I think it does, it might just be drown out with the other noises). It is a mechanical knocking sound that honestly sounds like something is loose or bearings may be failing. I dont think it is main bearings as it is coming from the oil pump area of the engine. If it is the oil pump, do I need to pull the engine and break it apart to replace it? I dont have a manual on this bike, nor can I find one. Any help would be greatly appreciated.

[tkent02]

It's rare on the smaller bikes, but on the big ones the clutches get rattles, sounds about like you describe.
Pull in the clutch, does the sound change or go away?

[friedshrooms]

loose rods
bad crank bearing
loose clutch housing
transmission bearings
as previously stated see if it makes the noise with the clutch pulled in, if it doesn't it's likely the transmission. Otherwise you've got a heck of a project.

[Chopper Dave]

It does not go away when I pull the clutch in.

[chuck hahn]

even if the clutch hub nut is tight the sound still may not go away when ya pull in the clutch lever.. remove the clutch basket and see if the dampner springs in the back are loose. They should be really snug and have no easy play what so ever. Re install everything and be sure the clutch hub nut is tighten properly. If the springs are loose the likely culprit is that the flywheel on the clutch basket rattles around. Since it messes directly with the crankcase gear it may be mimmicking a rod or crank bearing noise. Oh and by the way.. my 78 750 has the exact same symptoms..the tip off is when its warmed up and that the sound goes away at higher RPMs. You can still ride it with the loose basket springs. There are a few guys here in the forum that can point you to a rebuild shop. let us know what ya find, but i am 99.9 % sure youre gonna find some loose springs there.

[Chopper Dave]

Would this remedy also apply if the noise became quieter as you lean it to the right (or left, I dont remember)? Once its sitting up straight for a few minutes, the noise returns.

[chuck hahn]

dont know about the leaning..just relaying what my experiences have been and hope it helps...still it doesnt take that long to pull the clutch basket and be double sure all is in order there. Have you drained the oil and stuck a magnet in the old oil to see if its full of metal shavings? If its full of ground up metal from the crank or any other steel parts the magnet will collect the stuff. Stick it in and swish it around for a while and see if anything sticks to it.

[Chopper Dave]

Uh Oh... Bad news. I stuck the magnet in. Not much came out. A few small chunks which may have just been build up sludge. The part i'm worried about; while I was "swishing" around, a milky substance came to the surface. I'm guessing bearings are going. Also, I just changed the oil about 30mi. ago, and the oil is much darker than I expected. Might just be built up junk from sitting so long. The clutch basket is not obviously loose. I took it apart and it seems pretty snug. I'm thinking an engine rebuild or find a used engine. Any other input?

[tkent02]

Abuse the heck out of it while you are finding a better engine, after you swap them out, take it apart and let us know what you find... The milky substance is probably water, was it left out in the rain with some cover off or a spark plug out?

[Chopper Dave]

What are the chances the bearings in the crankshaft balancer are on their way out? That is where I hear the noise the loudest. Are there any other parts of that balancer that could be loose? I still dont have a book yet, so I'm guessing from exploded views on bike bandit. I did find a book to cover the 250, 400 and 450. I'm hoping it will cover this as well considering the engine configuration is very close.

[Chopper Dave]

So new discovery this morning. I grabbed a hold of the bolt on the end of the crankshaft balancer (very close to the clutch) and was able to move it in and out about .050". Is this normal?