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Hydraulic valves v.s. solid lifters


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If you could put some kind of hydraulic bucket type deal on top of the over head cam engines we have now, that could be interesting. You would lose a little bit of snap and you wouldn't be able to keep track of valve/seat wear without pulling the head, but you also wouldn't have to do any adjusting.

I still would like to see someone try this............http://www.coatesengine.com/technology.html

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If you could put some kind of hydraulic bucket type deal on top of the over head cam engines we have now, that could be interesting. You would lose a little bit of snap and you wouldn't be able to keep track of valve/seat wear without pulling the head, but you also wouldn't have to do any adjusting.

I still would like to see someone try this............http://www.coatesengine.com/technology.html

I looked at that article ontime, but couldn't figure out how they seal the "ball valve" during the compression stroke. Maybe it has some type of ring in the ball bore, idk.

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I looked at that article ontime, but couldn't figure out how they seal the "ball valve" during the compression stroke. Maybe it has some type of ring in the ball bore, idk.

Yeah, I dunno.......here's their text on it..........

"They rotate on ceramic carbon bearing with no oil lubrication, the spheres do not make contact with any part of the housing. The seals are a floating type and are also made of a ceramic material. They have two piston rings and are floating in a small cylinder-type chamber, they are activated by the compression and the combustion strokes of the engine which allows 100 percent sealing effectiveness, when compressed.

Because the valves rotate away from the combustion chamber and are vented and charged on the opposite side of each sphere, this creates a lower combustion chamber temperature, allowing for higher compression ratios to be used thus creating an extremely efficient engine. Some of the Coates Spherical Rotary Combustion Engines are at 12 to 1, 13 to 1, 14 to 1 and 15 to 1 compression ratios depending on the application."

...............they don't have very good illustrations or images to show you the details though, trying to keep their secrets I guess.

This claim on a test engine......."The maximum RPMs on the poppet valve engine were 5700 RPMs; the Spherical Rotary Valve Engine in comparison reached 14,850 RPM's."........speaks well for our application.

I would just love see to if it could make a big difference from what we have now. A lower CG, only three moving parts including the chain, no more dropped valves and the claimed performance gains with lowered emmissions, all excellent things we could benefit from! Only thing I can't figure out how to accommodate would be the auto decompression.

If only..............:banana:

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Hydraulic valve adjusters use engine oil. The engine oil pressure forces the lifters wider to take up all the valve lash,the lifters often have a check valve in them to prevent them from bleeding down when the engine is off (and from squeezing too much of the oil out during operation). Think of them as little hydraulic pistons that are only supposed to go one way. If they were just a sealed unit, there would be no way for them to expand to take up slack as the valvetrain wears.

I just did some research on them, and Wikipedia says at high RPMs hydraulic valve lifters have a tendency to over expand meaning the valves never fully close.

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That is the entire point of hydraulic lifters. Reduce noise and reduce maintenance. They aren't supposed to do anything else.

Adjusting valves on some 4 strokes is easy, the ones that use an adjusting screw and jamb nut are. The ones like mine where you have to pull the camshaft out is not so easy.

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That is the entire point of hydraulic lifters. Reduce noise and reduce maintenance. They aren't supposed to do anything else.

Adjusting valves on some 4 strokes is easy, the ones that use an adjusting screw and jamb nut are. The ones like mine where you have to pull the camshaft out is not so easy.

you mean you meant to answer him "no there's no other benefit"

I own a couple that have to have the cam pulled, I found it pretty easy, if a rider cant handle that, I think a XR type motor is probably the right bike for them, unless they have $ to give a dealer

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Since typical hydraulic lifters are generally limited to 6,000 rpm, your 250 4 stroke mx bike would be a 98 lb weakling when the motor is designed for peak hp at 12,000 rpm. You could (and would) re-design the 250 4 stroke motor to have peak hp at near 6000 rpm to work with hydraulic lifters, but then you'd have a 15 hp girl friends bike.

The performance impact of hydraulic lifters would be less on a 450 (because these peak at lower revs such as 9000 rpm), but there still would be a performance impact. Keep in mind that these are general numbers I'm throwing around here.

A 650 with hydraulic lifters? Maybe it work OK, or maybe you'd need an even bigger motor to keep the revs down.

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Just did some more research on them. Hydraulic lifters in push rod applications typically max out at around 7000 RPM. However hydraulic lash adjusters in over head cam applications look like they can handle about 8500 RPM before they start to collapse.

8500 would be more then enough for a 650, but would hurt a 450 race bike a bit. Might be good for something like a trail 450 though.

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