I have a 2003 EX500 (Ninja 500R) with 4,000 miles that makes a pinging/rattling/vibration type of sound when accelerating. Here is some additional information:

It seems to run fairly well at idle and while cruising, though I am new to biking and I may be accepting too much roughness out of a 2 cylinder.
If I put the bike up on its center stand, the engine runs fine at any speed. I also tried putting the bike into gear and occasionally using the rear brake to put a little load on the engine, but could not reproduce the sound.
The left spark plug has black deposits on it, the right plug looks great.
I recently cleaned the carbs because the bike was running very rough when I got it a month ago. The carbs were very clean.
I also adjusted the valves. They were a little tight, but not far off.
I have also replaced the plugs and the air filter.

Any ideas? I want to check the carb syncronization, but I am not sure from the Clymer book where I am supposed to connect the vacuum gauges.

Thanks for any suggestions.

-Jim

 

doing a carb sync would be very important in your case. The mercury gauges are usually more accurate. you need to hook the lines up to the top of the carbs where the other vacuum lines are normally hooked up. Don't hook the gauge lines into the drain nipples on the bottom of the carbs.

 

Thanks for the quick response. The Clymer manual states that there is a lock nut that must be loosened prior to turning the adjusting screw. I can't find any lock nuts and the screw seems to turn easily. Am I missing something or looking at the wrong screw? The screw I am looking at is on the round bar between the two carbs to which the accelerator/decelerater cables are attached. It looks like it is going to be a pain to adjust with the tank on.

-Jim

 

It sounds like you're looking at the right adjustment screw. There should be a nut that locks it in place. I think it's an 8mm nut. You need to take the tank off. I don't think you will find any way around it. Generally, you use a small portable gas tank with a line extension on it to sync your carbs. that's how most people do it

 

Thanks again. Where is the locknut supposed to be? There is a spring between the screw head and the bracket that the screw is attached, but I can't find the nut. Attached is an image of the screw I am talking about.

[IMG]local://upfiles/3208/22F8C37C233049538E4BE30D4B7E9066.jpg[/IMG]

 

It's hard to say, but that looks to be it. I have never done a carb sync on a 500 before, but I can't think of anything else that would be.

 

Does the sound appear to come from the front of the bike? does it usually occur at about the 4k-4,500rpm range? My 2006 has this odd sound when accelerating through the 4k range at a moderate pace (i.e. quarter throttle vs WOT). Turns it to be one of two things, there is a cable guide on the front of the bike that tends to vibrate and creates a harmonic resonance. The other, as seems to be the case with my bike, is that the radiator cover vibrates at a resonant frequency. the sound usually goes away once I get out of first and into second or get up above 5k. I've read elsewere that a bit of electrical tape around the cable guide usally dampens the vibration and kills the noise.

 

I do have the same vibration you are referring to in addition to the problem I have described earlier. At a point in the 4,500-4,600rpm range, regardless of which gear, there is a vibration that sounds like it is coming from something metallic. I figured that there was some component with a natural frequency in this range, but never got around to finding it. I'll try the electrical tape idea on the cable guide and see how that goes. Were you able to get rid of the radiator cover vibration? Thanks for the information.

-Jim

 

No, I never really did anything about the radiator cover vibe. I only really notice it when I hover just a hair under 4k and I usually accelerate right through that point. The noise mostly manifests when i'm sort of putting through parking lots etc...

Any luck chasing down that other noise?

 

I taped the cable guide closed with electrical tape and the vibration at ~4500rpm is now gone. Thanks for that suggestion. I think the noise during acceleration was due to the chain. I tightened it a bit more and the noise is almost completely gone. I am now running into one of the cylinders missing, so I need to track that down. Thanks again.

-Jim