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raspy sounding exhaust above 1/2 throttle

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I have an 06 XC450. I was on a 100 mile trail ride yesterday and around 70 miles the exhaust tone changed (it got louder and raspy sounding) above 1/2 throttle. It seems a litttle down on power above 1/2 as well. It runs fine below 1/2 throttle. I suspect the TPS is bad, not advancing the spark as it should for higher revs. I asume that the retarded spark timing at high rpm is leaving incomplete combustion causing after-burn during exhaust stroke and that is what I am hearing. Has anybody experianced this problem? What are the correct resistances when measuring the TPS output leads at closed and full positions?

Happy Trails,

Jeff

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My xc did the same thing when my PMB endcap S/A got loose. Silicone sealer at the joint from the core to the S/A, and new packing fixed it.

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I found and fixed the problem, The intake valve clerance got tight. I adjusted them and now my 450 runs like new again. BTW,the TPS tested ok on the bench and was not the problem.

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