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valve float

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what is it i hear alot about it??

Also when on the topic can anyone explain what the weight of the springs does or means??

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Valve float is when the rpms are too high, and the valve spring cannot return the valve to it's seat quick enough. When this happens, the combustion process can blow into the the intake and exhaust manifolds, and cause banging and misfiring, or valve to piston contact. If your valve springs are good, valve float should'nt be a problem, the rev limiter will kick in first before valve float.

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When the engine (piston) speed is so fast that the valves can't close fast enough. Depending on the engine design the valve can make contact with the piston causing some "problems" :)

re: springs. Are you refering to suspension springs or valve springs?

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The weight of the valve spring refers to how much pressure the spring exerts on the retainer attempting to close the valve.

Most references will be seat pressure, how much pressure the spring is exerting when the valve is closed on the seat. The other is "over the nose", or open pressure. This is how much the spring exerts at maximum cam lift.

Too little pressure, the valves will float, causing loss of power or engine damage. Too much pressure, wears stuff out prematurely and also robs power.

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ah i see so the valve spring pressure is precise for a certain part or area of the rev range(mid, top or bottom) ?

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ah i see so the valve spring pressure is precise for a certain part or area of the rev range(mid, top or bottom) ?

No, the spring pressure is usually measured at the installed height this is called seat pressure. Then it is measured for coil bind, this is max lift that the springs can handle with the correct install height. When the seat pressure is not high enough for the specific valve the valve can float. The springs only function is to keep the valve tight to the cam.

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Too add to what has already been said here. The camshaft profile can also cause valve float. If you install an aftermarket camshaft with a higher lift than the stock cam this will cause valve float as well if the proper valve springs are not installed with the cam. Hot Cams for instance claim you can run stock valve springs with their cams and not have to worry about valve float because they are not as radical as say Crower cams which require using heavier duty valve springs. This is one of the reasons when someone starts moding their bike that the reliability goes away. By the way I have noticed quite a few of your threads and you have had a lot of great questions. :)

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thanks man. Im just trying to please the masses, does that get me good gas, jks jks

on a serious note though if one changes the cam profile to more aggressive(crower/webcams) and the valves/springs to suit, will it stay reliable as stock or is the reliability staying in the top of the rev range

or is there something im not getting here??

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thanks man. Im just trying to please the masses, does that get me good gas, jks jks

on a serious note though if one changes the cam profile to more aggressive(crower/webcams) and the valves/springs to suit, will it stay reliable as stock or is the reliability staying in the top of the rev range

or is there something im not getting here??

No it wont. As mentioned before in this thread the stiffer the valve springs you have to run the more wear on your valve train. The best set up I've seen so far when it comes to performance and reliability at a reasonable price is Williamsmotowerx. Talk to EVSRacer or anyone else here on the forum that has had his work done. Bottom line is the more performance/power you try to squeeze out of your bike the less reliability you will have. More power means more strain on the components of the bike ie transmission gears, clutch, crank, valve train etc. :)

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