My motor seized recently and I've dismantled it. I'm conducting a "post mortem" on the motor trying to decide on the cause. I think that actually there are several causes. Here's the first thing that caused me some alarm when I got the motor apart:
It appeared to me that the left cylinder was the one that seized, and I have included a photo of the head. The exhaust valve appears reddish white and a lot lighter than the it's counterpart on the other side. It also looks "whiter" than any other honda valve I've seen (not that I've seen very many).
To those of you who have a bunch of experience in this area, does this whitening indicate that the valve got superheated and probably damaged, or does it look to be within the range of normal valve coloration?
Thanks,
nander
Reading valve color
Reading valve color
Re: Reading valve colorA bit Lean or mistimed.
Install a plug and fill with lacquer thinner or similar fluid and look into the intake and exhaust ports to see it the liquid gets by the valve seats. If it does ya may want to consider a valve job. ........lm
Thanks Loud Mouse. I will test the cylinder head and see what happens.
I had checked the timing with an automotive strobe light not long before the seizure and everything looked ok. The bike seemed to be running normally. But, upon disassembly, when I looked at the cam sprocket, I found the reverse threaded nut wasn't very tight. So, it could be timing, or perhaps there was an air leak at the carb. The other unknown variable here is that the bike fell over the night before I took it out on the short trip that seized the motor. It fell on the left side, and like I said, the left cylinder appears to have failed. I've got scored piston skirts, a blued crank with a bad bearing. I'll post pics of these. I just wonder if there's a connection. Perhaps when the bike tipped it messed up the seating of the cam assembly or the crank, possibly causing, or at least contributing to the problems I am seeing.
Hi,
Did it fall on the clutch cover side ? I assume the clutch cover was bolted on. Which crank bearing was blue ? The small end of the con rod ? Did you check both cylinders on (dynamic) timing ? How did the spark plug look like ? Jensen assembly of Japanese motorcycles requires great peace of mind (Pirsig)
Jensen,
It fell on the clutch side. Cover was bolted on. Squished the shifter pedal into the case a little bit. I had checked both cylinders dynamically and all was well. The spark plugs looked fine. Light brown color. One area of the interior crank weight on the right side shows some bluing. I've attached a photo. The pic is oriented funny but I'm talking about the the side of the crank at the bottom of the photo. I pulled the roller bearing off the shaft on that side and it has some play and a rough spot in it's rotation. What's odd is that this is NOT on the cylinder that I believe failed. I don't know if the bluing occurred at the time of failure either. I can imagine a situation where the bike tipped over (I wasn't riding it at the time), still running (although only for a few seconds), and all the oil moved to the left side -- leaving the right side unlubricated.
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