Join Date: Sep 2014
Location: Ontario, Canada
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Horrible Top End Noise
Good afternoon. I'm brand new to this forum, but not a newbie when it comes to the RC51, having owned mine since 2005. Up until now I've never ever needed this forum because my bike has been so damn reliable. It's a 2001 SP1 with 40000km (24850 miles), which is actually less because it had a smaller front sprocket on it when I got it, which I changed back to stock.
I took it out for my first ride of the year in June, on a warm but not hot day. About 30mins away from home I had to slow down to go through a town, wait at a red light, and then was able to continue on. Of course, the bike got a little warm, showing a high temperature of 93 Celsius (about 200 Fahrenheit), which is normal for my bike having to slow down. When I was able to increase my speed, I did so gradually, and started hearing a loud ticking sound coming from the motor. It didn't last too long because the bike stopped running right after the sound started and, once stopped, wouldn't even crank over. I had it towed home, let it cool down and dropped the oil out of it, but didn't find any metal in it. Once I replaced the oil and filter, I started it to see if the noise was still present, and it was.
It sounded like a very expensive noise, so I parked it until last week when I started taking it apart to check the valve clearances thinking that could be the problem. I started it once again and isolated the noise to the top end of the rear cylinder. When I pulled the valve cover off, I noticed some small metal shavings above where the left (looking from behind) intake valve is. I checked the valve clearances as per my Honda service manual and came up with the following:
Left Intake - .025in (.635mm)
Right Intake - .014in (.356mm)
Left Exhaust - .010in (.254mm)
Right Exhaust - .011in (.279mm)
I was shocked at the amount the intake clearances were off from the factory specs, especially when the exhaust clearances were so tight. Upon further investigation I discovered some metal in the wells next to the valve lifters, and then discovered what appears to be damage to the intake cam journals. I've attached some pics to show what I'm referring to. Sorry for the long post, just wanted to give as much info as possible. Thanks.