broken_rod
January 13th, 2008, 10:47 AM
so, i just checked the valve clearance on my 07 crf450, and was fully expecting to have to make a shim change. it has 68.1 hours on it, but to my surprise, the clearances were the same as they were when i last checked at 28.4 hours. i was surprised because my 05 started eating its intake valves at about the same number of hours. they had lost all clearance at 65 hours, and by about 72 hours i had to replace them completely with ferea stainless valves (no trouble after that.)
so, i've come to a conclusion, and that is that tom morgan was right. he told me that the reason some people never have valve trouble with hondas, and some, like me, couldn't keep stock valves in them was because of manufacturing inconsistency that caused the centerline of the valve stem to be out of line with the centerline of the seat bore. that causes the valves to squirm a bit when they close, and that of course eats the hard coat off the titanium. as some of you know, you're done at that point.
i maintained my 05 crf450 and now my 07 exactly the same way as my yamahas. they have a different valve design that's inherently less prone to wear, but nevertheless, yamaha valves seem to be bulletproof. so....unless honda has used some new coating or changed the seat shape or made some other minute change - including fixing the centerline problem - i'd have to conclude that tom was right. i think it also goes a long way to disproving the idea (that i never bought in to) that air filter maintenance and oil change intervals are the culprit. i run full synthetic 15w-50 and change it every 4-6 hours. most people would be horrified at how long i leave an air filter in before i change them.
maybe this info will help some other honda owners.
wp.
so, i've come to a conclusion, and that is that tom morgan was right. he told me that the reason some people never have valve trouble with hondas, and some, like me, couldn't keep stock valves in them was because of manufacturing inconsistency that caused the centerline of the valve stem to be out of line with the centerline of the seat bore. that causes the valves to squirm a bit when they close, and that of course eats the hard coat off the titanium. as some of you know, you're done at that point.
i maintained my 05 crf450 and now my 07 exactly the same way as my yamahas. they have a different valve design that's inherently less prone to wear, but nevertheless, yamaha valves seem to be bulletproof. so....unless honda has used some new coating or changed the seat shape or made some other minute change - including fixing the centerline problem - i'd have to conclude that tom was right. i think it also goes a long way to disproving the idea (that i never bought in to) that air filter maintenance and oil change intervals are the culprit. i run full synthetic 15w-50 and change it every 4-6 hours. most people would be horrified at how long i leave an air filter in before i change them.
maybe this info will help some other honda owners.
wp.