it's been a while since I posted here at ZXForums but here I am hoping again for the Gods to smile upon me...
Lets begin my new story...
So just last week I picked up a 2006 ZX-14 with 18,500 miles on the clock. The guy was selling it because couldn't pay his rent and he said the bike had a rattle and stopped running on him. He took it to the dealer and they told him he needed the valves adjusted.
This apparently was a repair he could neither perform nor afford.
So he posted the bike for sale.
Here I come all googly-eyed and drooling... I'm decent with the wrenches so I figured, I'll fix this thing lickety-split. I beat the guy down on the price and got it for $1500. I get the bike home, throw the battery on a trickle charger and wake the next morning to fire it up. Yeah, it stopped running because the battery was dead. A
nyway, I fire it up and am immediately greeted with the most awful metal-on-metal knocking. I immediately turn off the bike because honestly, the noise had me shook. I pick up my balls and I fire it up again. I blip the throttle and the noise goes away. Slowly increase the RPMs and the noise returns.
I frantically begin searching the interwebz and find that Gen 1's have a well-documented history of spun bearings. My heart sank immediately.
I go out to my garage and I start tearing the motor down to see if I can diagnose the problem. From my ears and my screwdriver stethoscope, it sounds like the top end. So I get the valve cover off and check the valve clearances. All the exhaust valves are tight, and two of the intake valves are tight. They're tight, but not tight enough to have this kind of knock. It sounds like a ball-peen hammer beating at the inside of the engine case.
So I pull off the exhaust because I'm gonna drop the oil pan and have a look at the crankshaft. I notice that all of the inner exhaust header bolts (around cylinders 2 & 3) are finger-tight at best. I get everything off and I'm feeling around on the crankshaft where the connecting rods bolt up... everything feels tight, no up down or lateral movement. Then upon closer inspection I see that the con rod cap on cylinder 4 is a bit discolored.
At the edges, where the cap meets the crank dampener and the counterweight, you can see some darkening of the metal. See below.
Here's a shot of the #3 cylinder cap for comparison:
The caps are clearly not the same color and the darkened edges are not visible on cylinder 3 either.
I rotated the motor so 1 & 4 are at TDC and on the downstroke, I insert a screwdriver into the spark plug hole of cylinder 4 and push down. No movement. Tight as a Tiger. Everything tells me, aside from my visual inspection and what appears to be possible heat discoloration, that this cylinder is fine.
But then I get to thinking... the noise is intermittent when at idle unless you blip the throttle. When you blip the throttle, the noise speeds up with the RPMs, but it goes away sometimes. In my mind, I wanna say when it goes away it's not spinning loose on the crank journal. But when I hear the knock, the bearing is maladjusted and banging around in there.
I don't want to remove the con rod cap because you're not supposed to reuse the bolts. And if I take it off and the bearing is fine, then I just pretty much f-cked myself because the bolts have to be replaced and you can't (shouldn't) re-torque the nuts on the old bolts. Plus the big end of the con rod may be out-of-round, causing all sorts of new havoc.
So I'm looking for opinions, does this con rod cap look like it's suffering a spun bearing underneath? Do you guys suggest I just bite the bullet and pull the f-cking cap? Is it possible that the knocking was a result of those loose exhaust header bolts? There appears to be no loss of power and the engine is still running strong on all 4 cylinders. Like i said, the rattle goes away sometimes.
I'm stumped... or frozen... HALP.