How did intake valve get so chewed up? - Honda Rebel Forum
 
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post #1 of 10 Old 05-08-2019, 01:32 PM Thread Starter
 
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How did intake valve get so chewed up?

1987 Honda rebel 250. Got the bike for free. Owner couldn't figure out why it wouldn't run. Obviously it was due to, among other things, this bent and chopped up intake valve.

My question is how did it get so chewed up? Bike only has 6000 miles on it. You cant really see it in the pictures but there is also a pretty significant bend.

Makes worried that the original owner was maybe... putting metal or some **** in the spark plug holes??


Thanks in advance.
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post #2 of 10 Old 05-08-2019, 04:46 PM
 
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Mystery to me. I'll keep an eye on this thread to see what others with more experience say about it.

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post #3 of 10 Old 05-08-2019, 06:13 PM
 
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How does the top of the piston and the cylinder head look ?

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post #4 of 10 Old 05-08-2019, 07:19 PM
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Quote:
Originally Posted by UltraBlue09 View Post
How does the top of the piston and the cylinder head look ?
yes, we need more pics

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post #5 of 10 Old 05-09-2019, 06:48 AM
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That looks like valve has seized when open and piston has been hitting it causing bend and damage to valve on edges . Most likley damaging piston and conrod . Would be cheeper and easier to look for another motor



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post #6 of 10 Old 05-15-2019, 04:45 AM
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I agree with wjmrty about the cause of the damage. I just went through this same thing with my 1985 Rebel 250 though the damage was much less severe. My valves were slightly bent causing loss of compression but with only a nick on the top of the piston. I've replaced all four valves and it runs fine now, except that since I didn't replace the valve seals, oil leakage is causing a lot of smoke from the exhaust. So, unfortunately there's another teardown in my future. Good luck with yours.
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post #7 of 10 Old 05-16-2019, 09:02 AM
 
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are the nicks curled up or chipped out?
curled could mean repeated hits from the piston head, chipped could mean burned/eroded from the ignition

you could be lucky it might have been stuck down from years of storage (87 with only 6k) and the valve got bent when the starter was used, freeing the stuck valve and it only burned and didn't do much to the piston head.
since you are showing us pics of the valve, you must have gotten the head off, can you share pics of the piston's faces?

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post #8 of 10 Old 05-16-2019, 02:49 PM Thread Starter
 
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The valve is chipped out. As in not jagged edges folded around. It looks more like a mouse had been taking bites out of it.. if that makes sense.

Pistons are actually in good shape. No nicks, major indents, scrapes, or stuff like that on both the piston face and side. Right piston has significantly less carbon build up on it. Probably from all the unburned gas running through that piston from the Original Owner trying to turn it over with the bent valve.

Picture is from a little while ago. New valve is installed and the bike is running pretty good.
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post #9 of 10 Old 05-16-2019, 02:57 PM Thread Starter
 
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Also here is the cylinder head before the busted valve came out.
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post #10 of 10 Old 05-20-2019, 08:38 AM
 
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Watch an episode of "forged in fire" where they use coal forges, at least one competitor will overheat their steel and you see the end crumble like coffee cake when they try to hammer it.

Glad to hear its running great with the new valve!

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"The bravest thing for me to do is admit when I am wrong" - unknown
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