Author Topic: What are the symptoms of bent valves?  (Read 2289 times)

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Offline CarbonK

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What are the symptoms of bent valves?
« on: July 30, 2017, 03:37:54 PM »
I got a CB550 that ran alright before I took apart the top end to replace some leaking gaskets. While I was in there I also put in new piston rings and lapped the valves. Put it all back together by the book, rubber bands on the tappets and all that. After adjusting valves, cam chain, timing, and doing a carb sync I have an issue. I'm stuck with a rough idle and when I open the throttle it doesn't go back down to idle as quick as it should. There is also a periodic clicking coming from the top end after shutting off the engine. It almost sounds like what it would when one wiggles a loose valve tappet.

My question is could this be something pertaining to the valves? Is it possible to check for bent valves without removing the head?

Offline eigenvector

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Re: What are the symptoms of bent valves?
« Reply #1 on: July 30, 2017, 04:10:30 PM »
Low compression. 

Understand that low compression will produce it's own symptoms.

I would eliminate everything else before assuming you bent a valve - if you have a borescope, then by all means jam it into the hole and take a gander.
Rob
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2018 HD Softail Heritage
1979 CB750K Limited Edition
1977 CB550K
1984 CB700SC Nighthawk
1983 VF750S Sabre

Offline Keith

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Re: What are the symptoms of bent valves?
« Reply #2 on: July 30, 2017, 04:29:00 PM »
Clicking after running is usually the engine cooling off...did it get too hot? I would double check valve adjustment. BTW, Did you thoroughly clean all valve grinding compound? Is cam timing correct? Vacuum leaks? Throttle cables out of adjustment or hanging up?

Offline BomberMann650

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Re: What are the symptoms of bent valves?
« Reply #3 on: July 30, 2017, 05:07:53 PM »
Yeah, the motors make a little noise as they cool.  Not nearly as much noise as other bikes with cooling fins.

The symptoms are typical of messed up dirty carbs. But since you just did a top end job.
Try these;
Check ignition and cam timing.
Verify tappet clearances to spec.

If those are okay, then you'll prolly need to work on the carbs.

Offline CarbonK

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Re: What are the symptoms of bent valves?
« Reply #4 on: July 30, 2017, 06:08:56 PM »
Clicking after running is usually the engine cooling off...did it get too hot? I would double check valve adjustment. BTW, Did you thoroughly clean all valve grinding compound? Is cam timing correct? Vacuum leaks? Throttle cables out of adjustment or hanging up?

I first noticed the clicking after I did a quick charging system check to see if I hooked everything back up right. Turned on, a little rev to make sure the battery was charging and then turn off. The bike wasn't even on for a minute. I found it strange because I never had this noise before getting into the engine. Was also diligent with the cleaning.
Followed the info I read on here about cam timing, set to TDC, lined up the notch on the cam at 3 o' clock. Sprayed the boots and intakes with WD40 and noticed no change in idle. Really at my wits end.

Yeah, the motors make a little noise as they cool.  Not nearly as much noise as other bikes with cooling fins.

The symptoms are typical of messed up dirty carbs. But since you just did a top end job.
Try these;
Check ignition and cam timing.
Verify tappet clearances to spec.

If those are okay, then you'll prolly need to work on the carbs.

I'm gonna recheck everything tomorrow. The last thing I did was pull the carbs off, check all the jets, and made sure all holes were cleared using an air compressor so I can rule that out.

One thing I forgot to add, when hooking up my Carbtune Pro to sync the carbs I wasn't getting any readings until I reved up to around 2k. Not sure if it was a fault with the tool, which is only a couple of years old, or whatever I did to the engine.

Offline CarbonK

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Re: What are the symptoms of bent valves?
« Reply #5 on: July 31, 2017, 11:57:36 AM »
Kicking myself, I think I'm off by a tooth. This is where it's at with TDC.

Offline strynboen

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Re: What are the symptoms of bent valves?
« Reply #6 on: July 31, 2017, 12:07:06 PM »
think never i got mine total lined up. even i got a new thain put inn...but the bike ran fine..one tooth vrong can not kill the valvets i think.
..that look less than 1 tooth vrong. it dont look that badd

.shure you not are thasing ignision firing point instead of top dead senter..
« Last Edit: July 31, 2017, 12:13:20 PM by strynboen »
i kan not speak english/but trying!!
http://forums.sohc4.net/index.php?topic=60973.0
http://forums.sohc4.net/index.php?topic=144758.0
i hate all this v-w.... vords

Offline CarbonK

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Re: What are the symptoms of bent valves?
« Reply #7 on: July 31, 2017, 12:31:45 PM »
.shure you not are thasing ignision firing point instead of top dead senter..

Yeah its on top dead center, I got it lined up correctly now. I guess I'll find out if this was the issue when I get it all buttoned up again.

Online Don R

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Re: What are the symptoms of bent valves?
« Reply #8 on: July 31, 2017, 12:44:25 PM »
  Hope it runs fine when you're done. Take your time.
No matter how many times you paint over a shadow, it's still there.
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 You don't need a weatherman to know which way the wind blows.

Offline CarbonK

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Re: What are the symptoms of bent valves?
« Reply #9 on: July 31, 2017, 07:51:41 PM »
  Hope it runs fine when you're done. Take your time.

I got it sorted out, thankfully. Turns out the cam being off by a tooth was the problem.

On a different note, I found a bit of oil coming from this cap? under the points cover. Can anyone tell me what it is?

Offline BomberMann650

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Re: What are the symptoms of bent valves?
« Reply #10 on: July 31, 2017, 09:03:36 PM »
Its a cap plug with an o-ring on it.  They get old and loose and often leak.

Offline CarbonK

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Re: What are the symptoms of bent valves?
« Reply #11 on: August 01, 2017, 02:45:32 PM »
Its a cap plug with an o-ring on it.  They get old and loose and often leak.

Alright cool, thanks for the info. It ain't too bad, I'll change it out during my next oil change.