Spaugh 1 Posted November 8, 2007 did my valves again this week. the intakes were tight about .0015" after putting 120 hard miles on em in superstition last weekend. Why do they tighten up instead of getting loose? are the stems getting elongated everytime they close back up? Seems couter intuitive. Share this post Link to post Share on other sites
Joliet 0 Posted November 8, 2007 did my valves again this week. the intakes were tight about .0015" after putting 120 hard miles on em in superstition last weekend. Why do they tighten up instead of getting loose? are the stems getting elongated everytime they close back up? Seems couter intuitive. The stems can stretch but usually it is that the valves (or seats) are wearing, which causes the valve to sit into the seat further, which closes the gap between the valve and cam (on most bikes). The seats are usually harder than the valves so the valves will wear instead of the seats. If the aircleaner is not totally sealed (which is why we put grease around the rim), or the boot isn't on quite right or you can even suck small particles through the carb vent lines, small pieces of sand, dust ect. run through the engine and it is usually the intakes that wear from this. Or so they tell me. Ken Share this post Link to post Share on other sites
dirt dame 561 Posted November 8, 2007 did my valves again this week. the intakes were tight about .0015" after putting 120 hard miles on em in superstition last weekend. Why do they tighten up instead of getting loose? are the stems getting elongated everytime they close back up? Seems couter intuitive. The stems can stretch but usually it is that the valves (or seats) are wearing, which causes the valve to sit into the seat further, which closes the gap between the valve and cam (on most bikes). The seats are usually harder than the valves so the valves will wear instead of the seats. If the aircleaner is not totally sealed (which is why we put grease around the rim), or the boot isn't on quite right or you can even suck small particles through the carb vent lines, small pieces of sand, dust ect. run through the engine and it is usually the intakes that wear from this. Or so they tell me. Ken That's right, the old Honda XLs and XRs in the mid eighties had stellite coated exhaust valves, but when the coating wore off, the valves would beat themselves silly, crack and pull up creating all kinds of nightmares for their unsuspecting owners such as loss of compression, dropped valves or pieces of valves breaking off where they contacted the seats. Later, better materials were used (thankfully) and the coating was abandoned. Share this post Link to post Share on other sites
Joliet 0 Posted November 8, 2007 did my valves again this week. the intakes were tight about .0015" after putting 120 hard miles on em in superstition last weekend. Why do they tighten up instead of getting loose? are the stems getting elongated everytime they close back up? Seems couter intuitive. The stems can stretch but usually it is that the valves (or seats) are wearing, which causes the valve to sit into the seat further, which closes the gap between the valve and cam (on most bikes). The seats are usually harder than the valves so the valves will wear instead of the seats. If the aircleaner is not totally sealed (which is why we put grease around the rim), or the boot isn't on quite right or you can even suck small particles through the carb vent lines, small pieces of sand, dust ect. run through the engine and it is usually the intakes that wear from this. Or so they tell me. Ken Also if you check the gap when the bike is warm the gap will be tighter. It needs to be totally cold (not run for many hours) or you will get a tight reading. It is best to let it set overnight and check them cold. Why it is tighter cold I don't know. It would seem to me that the valve would get longer when warm and the gap would tighten, but it doesn't work that way. Ken Share this post Link to post Share on other sites
Spaugh 1 Posted November 8, 2007 thanks for the replies. Now how much wear is too much? I know you are supposed to replace after they have to be loosened X amount. What is that X? 5 thou, 10 thou? Maybe too specific for each bike, but I've got 40 hours and only the last 4 hour ride caused them to move. But I was flogging it really hard this weekend. Share this post Link to post Share on other sites
Joliet 0 Posted November 8, 2007 thanks for the replies. Now how much wear is too much? I know you are supposed to replace after they have to be loosened X amount. What is that X? 5 thou, 10 thou? Maybe too specific for each bike, but I've got 40 hours and only the last 4 hour ride caused them to move. But I was flogging it really hard this weekend. If it were me I would check them at the next oil change to verify that they have not moved. If they have not moved go back to checking them according to the manual. If they are moving I would not wory about it until they have moved at least .005 -.010 then start looking for some one to do the top-end. And like I said earlier, always check them after the bike has sat overnight so you get consistent readings. Good luck. Ken Share this post Link to post Share on other sites
tntmo 911 Posted November 9, 2007 Is this a new or fairly new bike? If so, there will definitely be some wear early on in the life of the engine. Perfectly normal. You don't need to get worried about it until you start having to adjust your valves often which is a sign of something serious wearing out. Share this post Link to post Share on other sites
