metallic tapping noise

[Dave_17954]

I was suspecting a fuel issue at first to. I've played with the air/fuel mixture screws with no results. they are set at 2 1/4 turns out all the way across. I regularly use shell gasoline its the best brand around here (no plug intended). I figured if it were fuel related I'd hear in the other cylinders as well. going down the road it has power to spare. very smooth and stable idle. starts right up everytime. how far out can i turn the air/fuel screws without hurting it? I was thinking lean to but the plug color shows normal burning.

 

[bwisted]

Maybe a little more info on the noise. A bearing knock typically sounds like knuckles rapping on something and comes from the bottom end. wrist pins are slightly higher pitched and come from the cylinder area. Detonation is a metallic sound, like you explain, that almost sounds like rattling, when the engine is under load. Idling and cruising are usually not enough load to make it audible. The mixture must be good if changing the mixture screws has no effect on the noise. You right on with saying a fuel problem should result in all cylinders having the noise. Have you looked in the cylinder with a boroscope?

 

[Dave_17954]

the noise sounds like if you would take say a screw driver and tap it against the side of the case. although it is slightly metallic in sound. it comes from higher up in the motor specifically the valve/ shim/exhaust area of the #4 cylinder. no i havent looked into the bore except with a small flashlight. i can only see the usual carbon build-up on top of the piston. i have tried different octanes of gasoline but it runs the best on 87 unleaded gas and standard d8ea plugs. you can hear it very plain as you bring it up through the gears or even if you ride in a lower gear at a higher rpm say around 3500-4000 rpm. leaving the bike in nuetral and revving it you can hear it briefly not under a load coming from the same area. the noise is definately higher up. no doubt about that for sure. its not a ticking noise but also not a knocking noise either. somewhere in between those two. also i have noticed when riding down the road at say 55mph i can pull the choke on and it has no affect on the bike. i would think it would choke itself and bog the motor down but it doesnt. might try pulling the exhaust off and looking behind where the pipe sits in the cylinder. i do have new exhaust gaskets in also. it averages right around 50 mpg when cruising. i know aluminum can transfer sound rather easily but this noise i've never noticed come from any other area.

 

[catbed]

i have a metallic tapping noise from the #4 cylinder of my bike too. i can only hear it at idle. i dont worry about it.

 

[Dave_17954]

well since its raining today i decided to pull my clutch and exhaust off to give everything a good look. I put in a newer (approx 1000 miles) clutch on this bike when i first got it and done everything according to the manual but again i'm just revisiting areas that maybe will give me a clue. the same with the exhaust area. darkness has settled in so tomorrows another day. any suggestions on what areas to look at while i have the clutch out? :-k

 

[49er]

Could it be just an excessive cam endfloat knock?

 

[Dave_17954]

found everything to be in good shape in the clutch area. everything is assembled correctly and torqued to spec according to the service manual. also checked the exhausts for anything touching the frame clamps especially and there is good clearance all the way around. also after reassembling everything the noise is still there. the noise will start around 3,000 rpm and is intermittent at cruising speeds. also noted when I disconnect the #4 spark plug and ride it at highway speeds there is no noise. reconnect the wire and the noise comes back. also noted that the #4 plug looks to be running hotter than the other 3. adjusting the air/fuel screw on #4 carb doesnt change anything as far as noise goes. I also took out the plugs and rolled the #4 piston just past tdc and push down on the piston with a dowell rod and found it to be tight with no play. also went from a 20w50 castrol oil back to a 10w40 pennzoil with no change. probably just continue to ride it as there not much left of the riding season and i have no major rides planned. maybe do a top end tear down this winter and maybe carb kits to. give me something to do to while away those cold winter nights lol. i'm gonna figure this thing out if kills me. LOL

 

[Flaggo60]

....You are dealing with roller bearings, not plain.....

A GS650L is a shaft drive machine, isn't it? If so, it has, for some strange Suzuki reason, plain bearings, not rollers. Could never figure out why we 650G and GL owners were so blessed with that feature ...:-k

 

[flyingace]

A GS650L is a shaft drive machine, isn't it? If so, it has, for some strange Suzuki reason, plain bearings, not rollers. Could never figure out why we 650G and GL owners were so blessed with that feature ...:-k

Looks like a case where we're both wrong. I was wrong in assuming the GS650 engine has roller-type engine bearings, which it does not. In looking at the parts fische, I see that only the larger GS engines (850 and above) have roller bearings regardless of model.

 

[Bribird]

With out hearing the noise it is very hard to rule things out. Wrist pin is what comes to mind for me. Bad wrist pin sounds almost like detonation but more hollow sounding.
The other, and I only mention it because I had this happen on my 650, is a broken valve guide. Now I did not hear any noises, but did have smoke at start-up and a little when it was wide open.

Bri

 

[Dave_17954]

I'm leaning towards the wrist pin myself now. How do you check for detonation? and would that cause my plug to burn hot? :-k I'm thinking bout getting one of those colortune plugs.

 

[Bribird]

The color tune plug is great as long as you take it somewhere very dark. I have one and it really does work great. Detonation is caused when the air/fuel is ignited at the wrong time. Typically it is caused by having your timing out of adjustment. The other thing that can do it is carbon knock. Carbon builds up in the combustion chamber to a point where it then has changed the compression ratio.
Yes, detonation will destroy a spark plug, tyipcally it looks scorched white and some times I have even seem then partially melted.
Do you have access to a bore scope? If so, take out the plug and have a peek in there. If you suspect carbon knock, you can run some cleaner thru that cylinder.

good luck

 

[bwisted]

Bribird does have a good point with the wrist pin though. Hadn't thought of that. I would stay away from the valve train also. You don't change anything in the valve train by just unplugging a spark plug wire. It still spins around exactly the same. Cylinder pressure doesn't act upon that part of the engine, so no cylinder pressure won't change a thing up their.

As for checking detonation, it is a difficult thing to trace sometimes. I would start with making sure the timing is on par. Then mixture ratio. You stated earlier in the posts that changing the idle mixture didn't change anything. Was that on all carbs or just the number 4 carb? You should be able to notice a change in RPM when adjusting each one individually. Adjusting the mixture screws to achieve highest idle for each carb is a common way of setting idle mixture. If you get no change in RPM when adjusting the mixture, you may need to inspect the carbs. Easy way to check this is to lightly seat the mixture screw. This should cause either the engine revving up, or a stutter/misfire on that cylinder. If it continues to run the same way, I would expect to find the idle circuit plugged up.

A colourtune will also help in diagnosing mixture problems.

 

[Nessism]

Detonation only occurs at high load, not all the time, and wrist pins are almost foolproof so I doubt that is the problem unless the engine has over 100,000 miles on it.

Color tune is for setting the idle mixture. It won't solve the issue at hand. Nice tool, but the problem is not related to idle mixture.

Sorry to shoot down these ideas, but they are off track.

Dave, there are a good many GSR folk within riding distance for you so why not take the bike for a ride and let a more experienced person listen to the engine. Bwinger is in Indy and there are various people through out Ohio. Just a suggestion.

 

[Dave_17954]

would running some sea-foam in the gas help clean out the carbs/cylinders or is there something better out there that would help de-carbon the combustion chambers a bit better? 3 good suggestions there tho...... 1) giving the carbs a good cleaning and 2) checking the timing and 3) looking for carbon in the cylinder.

 

[Nessism]

would running some sea-foam in the gas help clean out the carbs/cylinders or is there something better out there that would help de-carbon the combustion chambers a bit better? 3 good suggestions there tho...... 1) giving the carbs a good cleaning and 2) checking the timing and 3) looking for carbon in the cylinder.

Seafoam can't hurt, but carbon in the cylinders is not likely the issue or you will have detonation in all cylinders, not just one. And cleaning the carbs is always a good idea but not likely to solve an engine noise either unless you have one cylinder that is not firing.

 

[Dave_17954]

I have nessism....its got them stumped also.

 

[srsupertrap]

Could it be just an excessive cam endfloat knock?

Well, you blew by 49er's suggestion which may explain a knock emanating from the valve train. Normally the cam endfloat knock is pronounced @ idle, like Catbed mentioned. My GS started making this noise around 43K but your GS650 is in the mileage ballpark and next time you have the valve cover you should rule it out by measuring the slop and visually inspecting the thrust ring contact surfaces. The Pdf is located @ Basscliff's website

 

[Dave_17954]

this noise dont start happening until at least 3,000 rpm. anything less and its quiet.

 

[Nessism]

Did you check out the cam chain tensioner yet? Some times the adjustment rod gets worn and won't spring back as it should.

Not sure what to suggest other than like I said before, have someone else more experienced listen to the noise - another GSR member. The GS engines are not quiet per say but there shouldn't be any hard knocking either. An experienced GS rider can judge the noise and tell you if it's normal or not.

Good luck.