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Old 02-23-2013, 08:10 AM   #74026
jessepitt
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Quote:
Originally Posted by Harry94025 View Post
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   #74027
sandwash
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Long shot here,auto comp messed up?
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Old 02-23-2013, 08:22 AM   #74028
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Quote:
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.
Quote:
Originally Posted by Harry94025 View Post
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   #74029
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Quote:
Originally Posted by procycle View Post
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   #74030
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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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Old 02-23-2013, 10:18 AM   #74031
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Could I just get new rings and fix this?
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Old 02-23-2013, 10:19 AM   #74032
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Yes ... I remember from your build thread that you had trouble getting the piston into the bore and trouble compressing the rings. I remember you mentioned it was a "TIGHT FIT". To me that is a Red Flag. Either you were given incorrect rings or out of spec cylinder or incorrect piston. (???)

Did you measure each piece before assembly?

Perhaps the ring gaps were not positioned correctly? And of course measuring ring end gap is part of the process.

When you do this again ... try to organize your work area a little better.
Take your time, go step by step, check everything along the way.

New sleeve (or barrel), piston & rings?

Good luck, let us know what you find after measurements ... maybe you've got a refund due you?

Quote:
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Could I just get new rings and fix this?
No way. The Piston an cylinder are badly scuffed ... They look finished to me. Bummer.
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Old 02-23-2013, 10:37 AM   #74033
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Quote:
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.
Obviously the scoring you found is a problem....

I'm suffering through a safety seminar today and unable to listen to your video at the moment; just wanted to share that my high compression piston upgrade also introduced nasty noises that progressively got worse. I replaced the spring loaded cam chain tensioner with the manual one I bought from Procycle and she's smooth as silk again.

I would recommend getting one on order to install once you've corrected the scoring problem.
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Old 02-23-2013, 10:42 AM   #74034
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Quote:
Originally Posted by planemanx15 View Post
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.
Quote:
Originally Posted by Adv Grifter View Post
of course measuring ring end gap is part of the process.
Quote:
Originally Posted by planemanx15 View Post
Could I just get new rings and fix this?
The first step would be to hone the damage out of the cylinder. This must be done with a rigid hone not a spring loaded or ball hone. Then measure to see if the bore will still be within spec. If you're lucky it may still be usable. It just depends on how deep the scores are in the cylinder wall.

You'll need at minimum a piston and rings. And of course check the ring gaps and file them as necessary to avoid a repeat.

The ring instructions call for .0045" of gap per inch of bore for the top ring. This works out to .020" Because DR650s do such good job of cooling the piston and have an air cooled cylinder I fudge this spec down to .018". The second ring should have a .004"-.008" larger gap. The oil control rings should have a minimum of .015" gap.
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Old 02-23-2013, 10:50 AM   #74035
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Originally Posted by procycle View Post
The first step would be to hone the damage out of the cylinder. This must be done with a rigid hone not a spring loaded or ball hone. Then measure to see if the bore will still be within spec. If you're lucky it may still be usable. It just depends on how deep the scores are in the cylinder wall.

You'll need at minimum a piston and rings. And of course check the ring gaps and file them as necessary to avoid a repeat.

The ring instructions call for .0045" of gap per inch of bore for the top ring. This works out to .020" Because DR650s do such good job of cooling the piston and have an air cooled cylinder I fudge this spec down to .018". The second ring should have a .004"-.008" larger gap. The oil control rings should have a minimum of .015" gap.
Alright, sounds good, thank you for the weekend help .

Please PM\email me when you get a chance about the cost of a new piston and rings and a possible cylinder exchange.

I just went to look at it again, and the cylinder seems fine, it suffered very minimum damage compared to the piston. How can I tell for sure if its okay?

Top ring: .020"
2nd ring: .024-.028"
Oil ring: .015"
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Old 02-23-2013, 01:12 PM   #74036
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So sorry for the results, PM. The school of hard knocks has taught me to read instructions twice, go slow & follow the step by step. I still get caught occasionally being a guy....and then going back to do it right.

I'm sure with some measurements, PC will be able to tell you if it's recoverable with a hone, new piston & rings.

Best of luck with the fix.
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Old 02-23-2013, 02:04 PM   #74037
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Quote:
Originally Posted by planemanx15 View Post

I just went to look at it again, and the cylinder seems fine, it suffered very minimum damage compared to the piston. How can I tell for sure if its okay?

By honing out all the visible scrape marks and then checking to see if the cylinder is still in spec. The shade tree way to do that is to push a piston ring into the bore squarely with an upside down piston and check it's gap at the top, the middle and the bottom of the cylinder with a feeler gauge. the gaps should be the same and consistent with the correct specified ring gap. A set of bore mic's are better but this method has worked well for more than a century.
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Old 02-23-2013, 05:30 PM   #74038
Harry94025
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Quote:
Originally Posted by planemanx15 View Post
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.
That kind of scoring happens when the oil film fails. Not sure how much engine experience you have, but are the rings positioned correctly? The compression rings are usually directional; they have a top indicated with a dot or other mark. If they were upside down, the blow-by would cause the oil film to fail.

Regards,
Harry
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Old 02-23-2013, 05:45 PM   #74039
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Yep
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Old 02-23-2013, 05:58 PM   #74040
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Quote:
Originally Posted by planemanx15 View Post
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.

Dang, I guess I was being optimistic thinking it was a valve. Sorry for your misfortune.
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