Timing issue, center intake valve keeps breaking off - Yamaha Rhino Forums - Yamaha UTV Forum
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post #1 of 3 (permalink) Old 11-13-2012, 11:39 AM Thread Starter
1/4 Throttle
Join Date: May 2010
Location: Mesa, Az
Posts: 7
Angry Timing issue, center intake valve keeps breaking off

Any ideas anyone ? I have a 2005 Rhino 660, After a complete top end engine rebuild I have had problems with the center intake valve. I have replaced it three times now. Engine runs fine after initial replacement then when i take out to riding area the valve breaks within 10-15 minutes ride time. The issue is the piston is making contact with the valve. First two times it broke I was at full throttle, this time I was at about 50% throttle when it broke. All alignment marks are correct for the cam gear, cam and decompresion springs. I just replaced the timing chain and installed NEW 700 chain tensioner on most recent rebuild. I'm at a loss for what going on. The cam is a Hot cam installed by a previous owner. I have had Weller Racing look at the cam, head and valves and they have supplied the parts and done the machine work. Is it possible that the pin inside the cam that contact the center valve isnt working properly ? Somehow this thing is going out of timing. When I disable the motor the timing alignment marks are still correct. There is no damage to the pistion just a little mark where the valve made contact. Any ideas anyone ?
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post #2 of 3 (permalink) Old 11-18-2012, 03:38 AM
1/4 Throttle
Join Date: Jun 2012
Posts: 15
I think it is best to see a really good mechanic and get a proper diagnosis of the problem. Timing problems are intricate and would require precise solutions. Trial and error won't solve it. Just my $0.02
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post #3 of 3 (permalink) Old 02-25-2020, 10:24 AM
1/4 Throttle
Join Date: Jan 2020
Posts: 6
is the decompressor working correct , pin in at rpm weights out ? everything moves freely ?

Last edited by Red Good; 02-25-2020 at 10:31 AM.
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