metallic tapping noise

[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? 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.

[srsupertrap]

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

Can you reproduce the 3000+ rpm tapping noise when the bike is neutral? If so get a friend to maintain the throttle in "noise zone" while you find the noise using the long screwdriver method. Place the screwdriver tip next to the #4 sparkplug to identify a wrist pin knock. Then move to the top of the valve cover. You will hear a lot of background cam chain racket but if its tapping in neutral you will isolate it. Place a fan in front too.

I am sure you have checked already but have you thrown a timing light on it to see if your GS timing is advancing correctly? Next is the #4 cr the same as the rest?

[Dave_17954]

yes i also have checked the cam tensioner has good action to and moves freely. i'll be digging into the carbs this winter. like you say it never hurts to clean them and put in some kits. i've been riding since 1976 and i've never had a cycle make this kind of noise and i have ridden suzukis before to cant remember if they were gs's or not tho. i do recall haveing a suzuki 550 and it being black cant recall the model tho. i do know it never had engine noise tho. ive been a small engine mechanic for a number of years have been around engines most of my life so when i hear a noise coming from a motor i know somethings amiss. eventually i'll find it. i dont throw in the towell so easily thanks for all the imput

[Dave_17954]

yes you can hear the noise in nuetral when you rev the motor. i took my cycle down to the cafekidd who lives nearby and he could hear the noise also we did the revving and listened with the screw driver. noise just seems to come from the upper end of number 4. You can hear it much easier when you ride it which the kidd did. ive rechecked shim clearances (twice) and everything else mentioned in my posts and posted some pix to. I have more pix of this area if anyone wants to see. going to check the timing when i get the chance. for now my vaca's over and its back to work. so i can only work on it on the weekends now. and as ive mentioned the #4 plug is running hot compared to the other 3. i can pull them and take a pic of the ends if that would help show how they are burning. let me know.......

[Bribird]

I still think carbon knock is a possibilty here. For instance... lets say the #4 valve seal (or even bad rings) leaks oil into the combustion chamber, yes a good amount gets burned off but it leaves a residue. In time the residue builds, raises the compression ratio and carbon knock shows it self.
The facts are, has a noise in just one cylinder above 3000, that same cylinder has a plug that shows signs of overheat. Maybe a super lean condition on the #4 carb but that typically shows itself in the exhaust popping when you let off the throttle.
I totally agree that it is hard to diagnose a noise that we cant hear, but there are only so many things it can be on the #4 cylinder.
If it were me, I would run some top engine clean(or B&G) thru the intake vacumm port on the #4 carb. Just be carful not to hydrolock the motor.

Just an thought.

Good luck with it Dave

[Dave_17954]

I couldnt find any b&g around town so I went with the seafoam. followed instructions on can. I put around 5oz down in the #4 cylinder actually through the intake of carb. and about 1 1/2 oz into the tank left it sit the appropriate amount of time started it up and there was lots of smoke for sure. after letting it clear itself i took it for a ride (20 miles) and yes the noise is still there same as always. maybe check the timing this weekend.........