Motorcycle Repair: 250 suzuki intruder pinging, suzuki intruder 250, exhaust manifold stud

Question
Hi Mike,

Thanks in advance for any info.

I have a 98 Suzuki intruder 250 with 60k.  My situation is this, when I ride the bike alone it runs pretty strong.  Once you get it up to 6000 rpms you can hear a ticking (pinging)coming from the left piston or valve train...and the noise then stops at 6800 and above.  The noise is reminescent of my old 66 mustang (when the header screws were loosening on their own and I was getting an exhaust leak).  

When I have a passenger on the back the noise is their any time I hit a decent hill or accelerate quickly between 3500 and 5000-6500 rpm although the bikes still runs ok at that time

I just got it tuned and the valves adjusted, (I have no idea about the tensioner adjustment) but the mechanic only tested it alone and without a passenger, so he didnt hear any of the noises in talking about. He just said it was would need a new (secondary?)diaphram in the carb very soon.

Also the exhaust manifold stud and bolt are fused (rusted together) on the side thats giving me the noise, each time I tighten it seems to back out over time, and passes a bit of oil onto the fins of the motor each day, on that side and im not sure if the exhaust gasket (o-ring) is blown or cracked on that side.

Let me know if you have any ideas, the mechanics here arent really diagnostic guys for this sorta thing, they just sorta keep em running...

Best to you  William  

Answer
The oil leaking out the exhaust port is not a good sign and is something that should be investigated further. Remove the left spark plug and check to see if it is oil fouled, if so you are probably looking at a top end rebuild.

The loose exhaust bolt is a likely cause of the noise you're hearing, as it allows exhaust gas and noise to escape. If not repaired, this can actually damage the engine by making the left cylinder run leaner than the right (less exhaust back pressure means a leaner fuel mixture and hotter combustion, which can melt valves and pistons). The harder the motor is working the louder the noise will be. And I gotta say it here, but it sounds like you are thrashing your poor 250 really hard - 6800rpm while hauling a passenger is going to HURT that motor over time.