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Old 02-23-2013, 06:55 AM   #74041
jessepitt
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Originally Posted by planemanx15 View Post
It does sound very poor, but has no problem revving. I'm 90% sure it's the top end. What should be done if the valve is touching the piston?

Does the exhaust sound bad? Like if you ignore the engine noise and just listen right at the muffler does it sound like it should or is it missing/sounding wierd? I dont know why a valve would have hit the piston other than being miss adjusted (unlikely as it weas riding just fine before) or the valve adjustment lock nut came loose and allowing the valve to move.
Either way if the valve has contacted the piston chances are you will be replaceing the valves (and valve springs as that could be another culprit). A weak valve spring combined with your new monstor motor could have caused this problem... How many miles on the bike again?
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Old 02-23-2013, 06:57 AM   #74042
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Originally Posted by jessepitt View Post
Does the exhaust sound bad? Like if you ignore the engine noise and just listen right at the muffler does it sound like it should or is it missing/sounding wierd? I dont know why a valve would have hit the piston other than being miss adjusted (unlikely as it weas riding just fine before) or the valve adjustment lock nut came loose and allowing the valve to move.
Either way if the valve has contacted the piston chances are you will be replaceing the valves (and valve springs as that could be another culprit). A weak valve spring combined with your new monstor motor could have caused this problem... How many miles on the bike again?
The exhaust sounds fine, its just the valves, as if I adjusted then on the wrong TDC. But like you said the bike was fine right before and only started this under a highway load. Im 100% sure I did the valves on the correct TDC.
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Old 02-23-2013, 07:03 AM   #74043
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Originally Posted by planemanx15 View Post
The exhaust sounds fine, its just the valves, as if I adjusted then on the wrong TDC. But like you said the bike was fine right before and only started this under a highway load. Im 100% sure I did the valves on the correct TDC.
It would not have run if you had adjusted them on the wrong cycle. Maybe start by just pulling the valve covers and checking your settings before removeing the head, that way you will know if anything has moved and have a better idea what the cause may be.
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Old 02-23-2013, 07:05 AM   #74044
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Kinda suprised Jeff hasnt chimed in on this but he may have missed your post on fri. and I think they are closed weekends. You may want to give them a call on monday if you havent found the problem.
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Old 02-23-2013, 07:06 AM   #74045
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Originally Posted by jessepitt View Post
It would not have run if you had adjusted them on the wrong cycle. Maybe start by just pulling the valve covers and checking your settings before removeing the head, that way you will know if anything has moved and have a better idea what the cause may be.
Strange part is I've done that, and there is no noise at all. Its only when running that I hear it. I would think that I would hear some sort of "Clink" when turning the motor by hand
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Old 02-23-2013, 07:06 AM   #74046
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Originally Posted by planemanx15 View Post
The exhaust sounds fine, its just the valves, as if I adjusted then on the wrong TDC. But like you said the bike was fine right before and only started this under a highway load. Im 100% sure I did the valves on the correct TDC.
I, on the other hand, did NOT do the valves on the correct TDC. Mine sounded close to that (CLACK CLACK CLACK CLACK CLACK ...), but I had only done the intakes (completely wrong), and shut it off pretty fast. I certainly didn't try to rev it, but... yeah - they're only little covers... take them off and see if you don't have gobs of space between the valves and the rockers now (like I did).

I mean, that would be the easiest thing to check first before even taking off the clutch cover... but then you're the one who is there, and if you're sure the sound is coming from the clutch, then so be it.
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Old 02-23-2013, 07:11 AM   #74047
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Originally Posted by planemanx15 View Post
Strange part is I've done that, and there is no noise at all. Its only when running that I hear it. I would think that I would hear some sort of "Clink" when turning the motor by hand
I dont think you would necesarilly hear it turning the engine over by hand.It could be that they dont touch unless they are running due to the high speeds and tight tolerances we are talking about with the valve train.
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Old 02-23-2013, 07:12 AM   #74048
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I, on the other hand, did NOT do the valves on the correct TDC. Mine sounded close to that (CLACK CLACK CLACK CLACK CLACK ...), but I had only done the intakes (completely wrong), and shut it off pretty fast. I certainly didn't try to rev it, but... yeah - they're only little covers... take them off and see if you don't have gobs of space between the valves and the rockers now (like I did).

I mean, that would be the easiest thing to check first before even taking off the clutch cover... but then you're the one who is there, and if you're sure the sound is coming from the clutch, then so be it.
Thats what I sounds like, But Im sure I did the valves fine. The bike ran good for 50 miles before any of this noise started. When i checked it last night, the space between the rockers and the valves were minimal. I have a strong feeling I have a bent valve.
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Old 02-23-2013, 07:14 AM   #74049
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Yeah, me too. Could you get a feeler gauge in there or are they tight tight?
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Old 02-23-2013, 08:06 AM   #74050
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It does sound very poor, but has no problem revving. I'm 90% sure it's the top end. What should be done if the valve is touching the piston?
If the valve is bent, I am curious how it would still have enough compression to start...
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Old 02-23-2013, 08:10 AM   #74051
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If the valve is bent, I am curious how it would still have enough compression to start...

It may not be very far off and has hammered itself to shape so that it runs. Planemanx said it died when he first pulled over but it would idle by the time he got home. He may have riden it far enough to make it semi-reseat. IDK just thinking out loud, the tear down will tell the tail.
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Old 02-23-2013, 08:19 AM   #74052
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Long shot here,auto comp messed up?
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Old 02-23-2013, 08:22 AM   #74053
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Originally Posted by planemanx15 View Post
Thats what I sounds like, But Im sure I did the valves fine. The bike ran good for 50 miles before any of this noise started. When i checked it last night, the space between the rockers and the valves were minimal. I have a strong feeling I have a bent valve.
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If the valve is bent, I am curious how it would still have enough compression to start...
Correct, it would not run (or even start) with a bent valve. Besides that there is a ton of clearance designed into the 790 piston. It would take some unusual circumstance for a valve to contact the piston.

I would not start it again. It will have to be disassembled to find the source of the noise. I read back through the install thread and did not see any mention of checking/adjusting the ring end gaps. Did you check the gaps?

Any guesswork done from listening to the noise is just that - guesswork.
It's a bummer to have to tear it apart but like Rob said it is easier and goes faster the second time.
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Old 02-23-2013, 08:39 AM   #74054
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I read back through the install thread and did not see any mention of checking/adjusting the ring end gaps. Did you check the gaps?
This was also a question I posed to Planemanx in his build-up thread. This was my guess as well. Ran the bike long enough to get it completely up to temp on a cold day, rings expanded without enough gap, possibly broke due to expansion?
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Old 02-23-2013, 10:08 AM   #74055
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Thanks for all the suggestions everybody, I opened everything thing up and found the issue:









The valves were completely fine.

As you can imagine I'm pretty disturbed. Everything ran fine, even on the highway going out to the twistys. On the ride back i assume the rings expanded too much and this happened. As I said in my build thread, I did not measure the end gap. I assume had I done this, I could be riding today.
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