No valves get tighter when wore from dirt or burning. Every 4st motor I ever worked on they got tight not loose. Honda 450 was notorious for it and was exact symptoms we all have.Only makes sense if the valve seats wore excessively. Usually valves get looser in my experience with working on friends high RPM 4 stroke toys. Maybe the valve seats are a bit soft on the 1049? Easy enough to check for with a compression/leak down test though. If I found tight valves I'd want to pull the head and look at the seats, AND port an polish while I'm in there.
A vacuum tester will show a leaky valve. Needle will go crazy bouncing. Its something always in back of my head wondering if valve clearance variances were actually the reason for running variances and not so much the flashes themselves. Always trusted Yamaha but now that they are using Chinese crap in there engines that trust is suspect. Hoping I dont find anything since I dont see a better alternative in snowmobiles.
DVW
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Exhaust valve clearance fell below spec (tight) long before Arctic Cats recommended 25,000 mile inspection interval. On my 7000 the symptom of the problem was poor idle while the engine is warming up. Arctic Cat recommends valve clearance inspection at 25,000 miles. Twice before I got to 25,000 miles the valves got tight. The first time at the 15,000 mile mark the cause was assumed to be a defect with a valve part or the assembly process. Without determining root cause a completely new cylinder head was installed with Arctic Cat sharing the cost. The valves got tight a second time at the 24,000 mile mark. This time a valve clearance adjustment and a bleed down test fixed the problem. It should be noted that a valve clearance adjustment is rigorous procedure requiring engine removal. Just because this happened to me does not guarantee it will happen to others. I hear Yamaha riders put the miles on and would be interested to hear what others have experienced.Wow I have almost 13,000mi on mine. So very interested in the valves. Isnt check at 20000mi? Or is yours the Suzuki motor?
blueironranger
TY 4 Stroke God
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I would think the Pre-16's would still be top notch but who knows how long they have been installing "lowest bidder" components . I know some of the Single Cylinder ATV engine are completely farmed out now (Grizzly 708)A vacuum tester will show a leaky valve. Needle will go crazy bouncing. Its something always in back of my head wondering if valve clearance variances were actually the reason for running variances and not so much the flashes themselves. Always trusted Yamaha but now that they are using Chinese crap in there engines that trust is suspect. Hoping I dont find anything since I dont see a better alternative in snowmobiles.
Havent heard it from anyone else but we ALL have had crappy Idle and starting issues from day one.Exhaust valve clearance fell below spec (tight) long before Arctic Cats recommended 25,000 mile inspection interval. On my 7000 the symptom of the problem was poor idle while the engine is warming up. Arctic Cat recommends valve clearance inspection at 25,000 miles. Twice before I got to 25,000 miles the valves got tight. The first time at the 15,000 mile mark the cause was assumed to be a defect with a valve part or the assembly process. Without determining root cause a completely new cylinder head was installed with Arctic Cat sharing the cost. The valves got tight a second time at the 24,000 mile mark. This time a valve clearance adjustment and a bleed down test fixed the problem. It should be noted that a valve clearance adjustment is rigorous procedure requiring engine removal. Just because this happened to me does not guarantee it will happen to others. I hear Yamaha riders put the miles on and would be interested to hear what others have experienced.
DVW
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To calm potential fears I will describe the unique symptoms of tight valves on the Yamaha engine in the Arctic Cat 7000. When I had tight valves the machine started when super cold and ran well when it warmed up. It would struggle to idle while it was warming up. As things progressed it would not run by itself and it would die. While it was cranking to restart I could hear the faint sound of air escaping past the exhaust valve(s). The sound came thru the muffler. When it did start and run by itself it sounded a little like a two cylinder motor. Also the motor would die when you would abruptly chopped the throttle.
I believe I can check the valves without removing engine. Only reason I can think of for removing engine if adjustment were needed is to get at tensioner?Exhaust valve clearance fell below spec (tight) long before Arctic Cats recommended 25,000 mile inspection interval. On my 7000 the symptom of the problem was poor idle while the engine is warming up. Arctic Cat recommends valve clearance inspection at 25,000 miles. Twice before I got to 25,000 miles the valves got tight. The first time at the 15,000 mile mark the cause was assumed to be a defect with a valve part or the assembly process. Without determining root cause a completely new cylinder head was installed with Arctic Cat sharing the cost. The valves got tight a second time at the 24,000 mile mark. This time a valve clearance adjustment and a bleed down test fixed the problem. It should be noted that a valve clearance adjustment is rigorous procedure requiring engine removal. Just because this happened to me does not guarantee it will happen to others. I hear Yamaha riders put the miles on and would be interested to hear what others have experienced.
This describes almost all our sleds other than not running by itself! Always blamed the tune.To calm potential fears I will describe the unique symptoms of tight valves on the Yamaha engine in the Arctic Cat 7000. When I had tight valves the machine started when super cold and ran well when it warmed up. It would struggle to idle while it was warming up. As things progressed it would not run by itself and it would die. While it was cranking to restart I could hear the faint sound of air escaping past the exhaust valve(s). The sound came thru the muffler. When it did start and run by itself it sounded a little like a two cylinder motor. Also the motor would die when you would abruptly chopped the throttle.
blueironranger
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This describes almost all our sleds other than not running by itself! Always blamed the tune.
Since I'm more than likely to pretty much disassemble the whole sled this summer out of boredom, I'll check the valves on mine to see what one with 2,000 on it has for clearance.
Me too. Has always been on my mind.Since I'm more than likely to pretty much disassemble the whole sled this summer out of boredom, I'll check the valves on mine to see what one with 2,000 on it has for clearance.
I know alot of the engine manufacturers ran into trouble when the use of Berrilium valve seats was discontinued because the fumes and dust created when machining Berrilium is very hazardous to health. Not sure what we have for seats. I do know we have steel intake and Stainless exhaust valves.
Harvest1121
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Mine never had an issue with warm starting till about 10.000 miles it was getting worse when it was warm out and I was riding.
Allan
TY 4 Stroke Junkie
Makes me wounder if this is the reason why mine drops the idle rpm down to 1300 from 1700 when staring cold and then goes back to normal when warm. 17500 km. this only started in the last few weeks.
Mine does same thing Allan. Hopefully all these weird run quality issues are just the programming/flash and not a internal engine issue like tight leaking valves. Will soon find out. I have one more ride planned for next weekend then will dig in.Makes me wounder if this is the reason why mine drops the idle rpm down to 1300 from 1700 when staring cold and then goes back to normal when warm. 17500 km. this only started in the last few weeks.
Allan
TY 4 Stroke Junkie
Mine is still under warranty tell Dec 2018 , Its the 16.5 motor with 11000 miles. Might take it to dealer and get it checked.Mine does same thing Allan. Hopefully all these weird run quality issues are just the programming/flash and not a internal engine issue like tight leaking valves. Will soon find out. I have one more ride planned for next weekend then will dig in.
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