Engine Knocking on start-up

[ggeiger]

I've got a problem that I hope someone can diagnose. When I start my GS, the engine runs really rough. It sounds like a knocking sound. Once warmed up, it's fine. Is this a symptom that I need a valve adjustment? My 2002 GS has about 5500 miles on it, only 2,000 of which I put on.  I noticed the symptoms after having it on the highway for several hours, which was the first time I took a trip of more than an hour. Any thoughts?

[gsmetal]

This sounds really stupid but....do you have enough oil in it?

[scratch]

Yep, I agree with gsmetal, check your oil level first. Second, valve adjustments need to be performed every 4000 miles, and the oil should be changed at that time, too. Get into the habit of checking your oil level weekly.

[ggeiger]

I thought of that one too. The oil level is right where it should be. I check before every ride.  I've got it on the side stand though when I check it. Would that make a difference?

This sounds really stupid but....do you have enough oil in it?

[scratch]

Yes, very much!! Check it after a 5 minute or longer ride, let it cool for at least 5 minutes, and put it on the centerstand. Do not screw the dipstick all the way in; it is supposed to just rest on the threads.

http://www.gstwins.com/gsboard/index.php?p=96564

[ballyhoo]

Rough running and knocking might be pre-ignition of the spark plugs, or other ignition probs. Since it runs fine when warm, it's probably not a timing problem. Check the plugs, do they look normal? Make sure all the electrical connections associated with the ignition are sound, and also make sure the choke is working properly.

[ggeiger]

Thanks guys for the advice.  I'll check into all of your suggestions and hopefully I'll solve the problem.

[Jace009gs]

I agree sounds like sludgy oil....what Wt. is in it? what's the air temp at start up>? ....some of that heavier Wt oil might take a few minutes to circulate up to the cyl. head when the temp dips down near freezing....If it's knocking at 60ish mph it might be something clogging the oil pick-up [higher the rpms the higher the oil presure=more oil being sucked up and distributed] Or the valves are out of wack as someone suggested.


I don't think it's ignition since it only happens at high speed or start up...ignition it would be knocking all the time constantly.

[makenzie71]

yeah that sounds like a combination of little problems...not a big one.  Serious oil problems don't just go away once warmed up and oil-damage makes it's self apparent at about 2500rpm and on in most cases.

It's winter.  First thing to take into consideration is that you should be running a slightly thinner oil.  I doubt this is your problem, though.  Heavy, cold oil typically results in valve noise on start-up, not knocking.

What you're probably hearing is pre-ignition.  Pre-ignition is when the fuel detonates prior to the piston reaching TDC, thus acting as a braking force.  This is typically brought on by poor tune.  As others have said, check your valves.  It wouldn't hurt for you step up in your fuel quality, either.