"Pinging" sound on a fresh engine build - ideas?

[Big Rich]

So here's the story: last season there were some issues with the bottom end on my GR650. Nothing major, just a couple oil leaks around the oil pan and a stripped thread for the sprocket cover. Since I have a couple engines around I figured I'd swap the top end from that engine to another bottom end I had. Now that riding season is pretty much here in PA, I've noticed a high pitched ping sound from about 2k to 5k rpm. I dumped the low octane gas from the tank and put in some 93 octane in, but the problem persists. Any ideas what to look for? Here is some info about the engine / intake / exhaust:

Aftermarket VM34's with a K&N filter (jetted similar to what's found on an XS650).
New gaskets throughout the engine.
Valve seals replaced, valves lapped.
Valve clearances within the high side of the spec.
Pistons / rings / cylinders in good condition.
2-1 exhaust with Supertrapp muffler.

Thanks in advance for any and all help.

 

[tom203]

If this pinging doesn't get more noticeable under load (like going up steep hill), it's not a octane problem.
so you got the original top end on another bottom end? Have you tried fiddling with the camchain tensioner?

 

[Big Rich]

Yep - the pinging noise is constant from 2k-5k rpm (and maybe higher up but I can't hear it), and matches engine speed.

And correct about the original top end on a different bottom end. The top end has been run for a couple years with no issues, and the bottom end came from a low mileage bike that was wrecked.

And I have not messed with the CCT since the engine was reassembled. I can check it out though soon.

Thanks!

 

[Buffalo Bill]

Looks like you jetted the carbs based on experience, but have not done any follow up to check it.
Like: Colortune or plug tip observations.
Those mods would lean the mix, you may have to richen it up in some of the usual ways.

 

[Big Rich]

Hmmm.... I'm not 100% sure about that Bill. The last entire riding season I had on the bike (with the original top & bottom end) I had the same intake settings, and a modified MAC 2-1 exhaust with the Supertrapp muffler. So aside from the bottom end swap mentioned above, the other difference is the new 2-1 exhaust.

While I did some carb tuning for the original setup, I can definitely look back into it this week. I'll also be double checking valve clearances and cam timing while I'm there.

Thanks gentlemen.

 

[Big Rich]

So this morning when I got off work I did a compression test after the motor was warm: 170 on the left, 165 on the right. Started checking the carb sync, but ran out of time.

I was talking to a coworker and he asked about the oil and filter. He said there is another guy here that had a clicking noise from his GSXR and the problem turned out to be the wrong filter was installed from a shop (too restrictive I guess?) which caused the ticking from minor oil starvation. Anybody else heard of that?

Hopefully I get some good news this week since I'm off for a couple days.

Edit: I thought the oil filter comment was interesting because I changed the oil & filter recently, and had to use a K&N oil filter.

 

[Big Rich]

Problem solved!

I finally pulled the fairing off to better diagnose the source of the sound - and as soon as I did I could see the exhaust collar rattling. The stock header bolts are 8x38mm, and for years I have been using 8x35mm. But when I was ordering parts for the engine rebuild, I also ordered the stock size bolts. Years of debris must have accumulated in the bottoms of the female holes in the engine, because the 8x38mm bolts were tight..... but not tight against the exhaust collar. Some cleaning solution, a dental pick, and some compressed air = problem solved!

Thanks again to everybody for the ideas though. It's nice when it is a simple fix.

 

[Buffalo Bill]

Yeah ok and good for you.
Be careful about the words you use describing engine sounds. Engine “ping” has a specific meaning: premature ignition.

 

[Grimly]

Hah; once again, the escaping exhaust gas sounds like a terminal engine problem.
How many GS owners have had their imaginations and fears play with them because of that?

 

[tkent02]

Yeah ok and good for you
Be careful about the words you use describing engine sounds. Engine “ping” has a specific meaning: premature ignition.

Actually the ping you hear is detonation. Normal ignition you won't hear now matter how early it is. If it's early enough it can cause detonation, just like a lean mix or a poorly shaped combustion chamber.

 

[JamesWhut?]

Problem solved!
...
Thanks again to everybody for the ideas though. It's nice when it is a simple fix.

Hehe, this reminds me of a time on a trip my wife's GS500E developed a just off idle knock that I swore was big end bearing failure. Turned out to be a broken case guard mount that was letting the guard rattle against the frame.

 

[Big Rich]

Hah; once again, the escaping exhaust gas sounds like a terminal engine problem.
How many GS owners have had their imaginations and fears play with them because of that?

That's just it (especially in my case). A strange sound coming from the engine turns into a game of "what is going to blow up next?".

I've never heard detonation and / or pre-ignition in an engine, so I assumed that's what it was.