82' GS 650 Engine Knock Noise?

[cafecustoms]

Hey Everyone!

My name is Paul and I purchased my 82' GS 650 last summer, she rode great and since its winter, I wanted to go through and tune my bike to prepare for this years riding season. Anyways, when I bought the bike it had a faint knocking noise coming from (what i think) is the engine... It knocks when it sits idle every 2-3 seconds but when i ride I dont notice it much. It also doesnt do it everytime I ride. Since I hadnt addressed the issue, bc it hadnt affected the way i rode last year, I cant place a certain situation where it would vs wouldnt knowck. Ive heard that old bikes do this sometimes, but I wanted to find out if anyone has experienced this and what to do about it?

Thanks,
Paul

[spyug]

Welcome aboard. As you may suspect, engine noises are damned hard to diagnose through a forum since describing it is most difficult. It would be best if you can capture some vieo with sound so we can analyse it.

It might also be helpful if you can determine where the noise is coming from. Top of the engine? bottom of the engine? transmission area (behind the cylinders)? With the bike on the centerstand, start it up, let it warm up then walk around and listen for the noise. Get down close to the engine. Rev it a bit and see if you notice any changes. To help listen for a noise you can get an automotive stethescope (good automotive stores or Harbour Freight) which you can touch to various points on the engine to listen. Alternatively, you can use a long handled screw driver or piece of scrap rod in the same way. Touch one end to the engine block and bring your ear to the other end.

If you can pinpoint a bit more for us we maybe able to nail it down. It should be noted that every engine does have different noises at different revs but "banging" is not usually one of them and could be cause for concern. I would want to fully check it out before using the bike much.

Good luck and please give us some more detail.

cheers,
Spyug

[tom203]

The shaft 650's have plain bearing crankshafts- these are kept happy by higher pressure oil pumps (maybe 50 psi above 2k rpm). At idle, this pressure is weaker; more so with thin old oil and/or worn bearings. I try some new oil and filter and see what happens. what's your mileage?
Hopefully, you have studied Basscliff's site and are catching up on overdue maintenance.

[cafecustoms]

Thanks for the replies!

Hey spyug, thanks for reaching out to me. The bike is in its reassembly stage so once i get her running again, I'll try to locate the orgin of the noise and see whats going on.

Tom, this model is actually a chain driven bike, but I do plan on changing the oil/filter/ and plugs and will see how she runs when i get it back together. And i just discovered Basscliffs and have been going through it for sure.

Ill keep ya updated.

Paul

[spyug]

As Tom alludes, banging sounds often can be bearing related and usually piston rod bearings. A lose or worn bearing causes the rod to move side to side and "slap" the wall of the crankcase or lower end of the cylinder liner on its way up or down the bore.

Its usually most notable at startup and low revs and can disappear as the revs go up.Definitely not a good situation, as ultimately, something will break.

Let us know what you find out.

cheers,
spyug

[2BRacing]

It could also be the "cam walk" noise that occurs irregularly every couple of seconds at idle. He does not hear it every time, and not at higher revs. Use search function to look for old posts on "cam walk" noise.

[Toasty]

Out of sync carbs can cause funky knock sounds as well.

[BassCliff]

Greetings and Salutations!!

Hi Mr. cafecustoms,

These engines, especially the 8 valve engines, have to be very badly abused in order to hurt them. I would suspect "cam walk" too. If you install new "half moons" backwards it will help. There is a more permanent fix but it involves some precision machine work.

For most of the general maintenance, have a look at all of the information in your "mega-welcome". It's dandy!

If you are here you probably have a 30 year old motorcycle that needs about 20 years worth of maintenance. You'll find all kinds of helpful tips, procedures, manuals, diagrams, "how-to" guides, etc, in the links below. Let's get started.

Let me dump a TON of information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. Now let me roll out the welcome mat for you...



Please Click Here For Your Mega-Welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[Steve]

It could also be the "cam walk" noise that occurs irregularly every couple of seconds at idle. He does not hear it every time, and not at higher revs. Use search function to look for old posts on "cam walk" noise.

If it is a knocking sound that happens for a second or two, then goes away for a few seconds and repeats, try one thing:
slowly increase the engine speed to see if the sound goes away completely about 12-1500 RPM.
If it does, my vote would be for "cam walk". There is a fix, but it's rather involved.

My wife's bike had that sound when we got it almost 8 years ago. It now has over 20,000 more miles on it.
The sound is still there, and has not gotten any worse. It's really not worth worrying about.

.