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Old 08-31-2011, 11:05 PM   #1
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Question im thinkin a bent or stickin valve

I bought a 650 v2 this past winter, the damn thing has never run right. I of course had no idea what the previous owner has done. After much tweaking,(Vforce clutch work, Dyna tech ignition, etc..), out of desperation I took it to a dealer, they rejetted etc, still runs like poop or worse. Twice in the last few months, I had a similar thing happen, I had the quad idling n warming up and it seemed to load up, I took it out and tried to blow the crud out it was running horribly and it was smoking badly and running worse. When I returned I realized my right pant leg was covered with oil, I traced it to the duck bill drain out of the bottom of the aircleaner box.

On tear down to the airbox it seems the rear cylinders carburetor's rubber boot had more oil in it which might make you think it is the rear cylinder with the valve issue. BUT...if I think this through, and I am thinking a stuck intake valve is the problem, the rear carb rubber boot may have collected more oil residue due to the fact that its valves are operating properly, creating a negative pressure and inhaling the oil and fuel residue expelled out of the Front cylinder with the stuck intake valve into the airbox!!!
My head hurts!
Could this be a stuck valve, what the heck else could create enough positive pressure in the airbox to make it spew oil and fuel onto my pant leg?

am I barking up the wrong tree? W
What do you think?
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Old 09-01-2011, 11:08 AM   #2
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You might also consider worn rings. Compression getting past the rings pressurizes the crankcase pushing oil into the airbox through the vent. Put air pressure to the cylinder and roll it through about 8 cycles. If you get air out the intake or exhaust when that valve should be closed there you have it. If it comes through the crankcase vent you may be looking at reringing it.
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Old 09-01-2011, 03:25 PM   #3
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V2's are notorious for timing chain issues as well and here is the good news the motor has 4 different timing chains...If I were a betting man Id say that could be the issue!!!
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Old 09-01-2011, 06:54 PM   #4
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I also would lean towards the rings. Blow by around the rings is pressurizing the crankcase forcing oil vapor into the air box.

First, compression test, if good conduct a leakdown test. The leak down should tell you what the problem is.

How many miles on motor?

If the compression is good, you could pull the crank case vent off the air box, clean the air box, put a new set of plugs in a see how it runs.
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Old 09-01-2011, 10:45 PM   #5
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 Quote: Originally Posted by texasrapier View Post
I also would lean towards the rings. Blow by around the rings is pressurizing the crankcase forcing oil vapor into the air box.

First, compression test, if good conduct a leakdown test. The leak down should tell you what the problem is.

How many miles on motor?

If the compression is good, you could pull the crank case vent off the air box, clean the air box, put a new set of plugs in a see how it runs.
I should have made it clearer that I would expect that if I put it all back together it would probably run almost normal, but would usually miss at idle on one cylinder, and it might run for weeks before it belhes oil again. I will try and get a compression check on it and get back to all of you guys good enough to respond.

Thank you,

Doug
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Old 09-08-2011, 07:34 PM   #6
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disconnect the chokes and run it and see what it does. also a dynatek cdi will let it rev high enough to blow some oil out of the case vent into the air box. you may need a catch can on the vent line
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Old 02-16-2013, 10:10 AM   #7
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what should be leak down results compession 60 rear and 50 front with 60 psi leak the rear had about 5% loss front 89% heard air past rings and some out exhaust engine was cold and out about 50 degrees no way to warm up
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Old 09-17-2013, 11:30 PM   #8
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Worn out intake valves

The OP discribed the problem I was having and this is what I found.
ALL the intake valves worn and were being pulled into the intake port, causing frequent valve adjustment, and hard starting.
Also will be replacing the piston rings while inside. The chains and the guides are fine, no wear on the guides or chains. The valve seats are undamaged and will be able to have new valves lapped in.

2700 miles to date.
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Old 09-18-2013, 08:28 PM   #9
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 Quote: Originally Posted by Made in the USA View Post
The OP discribed the problem I was having and this is what I found.
ALL the intake valves worn and were being pulled into the intake port, causing frequent valve adjustment, and hard starting.
Also will be replacing the piston rings while inside. The chains and the guides are fine, no wear on the guides or chains. The valve seats are undamaged and will be able to have new valves lapped in.

2700 miles to date.

Unless you verify that the timing is perfect, or measure the chains it is very dificult to see if a chain has stretched.
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