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DT125R Forum -> POWERVALVES -> Noob question
Post Info TOPIC: Noob question
MDK


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Noob question
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if there is no cables then its pinned with out the cables and servo there is no real way for it to open or close

like so has your bike got these on ?

http://www.ebay.co.uk/itm/dt-125-r-power-valve-servo-motor-pulley-cables-end-cap-seal-5-wire-casing-/251249130411?pt=UK_Motorcycle_Parts&hash=item3a7f9d7bab



-- Edited by MDK on Friday 22nd of March 2013 12:06:15 AM

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Dt Danny


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ive seen loads of diffrent stlyes of powervalves and i was curious how do they work ?
ive seen some on here with cables coming out of them ? but mine doesnt o.o lol



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i blew my dt up ... but i fixed it.... Then i crashed it.... but i didnt fix it right and 2 scouser's come in the middle of the night and left me with a working bike 
tunertom


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your dt has no cables? its pinned then.

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Dt Danny


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i dont think it is because i can feel when it opens because there is a surge of power

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i blew my dt up ... but i fixed it.... Then i crashed it.... but i didnt fix it right and 2 scouser's come in the middle of the night and left me with a working bike 
Dt Danny


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Nope lol so it is pinned haha

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i blew my dt up ... but i fixed it.... Then i crashed it.... but i didnt fix it right and 2 scouser's come in the middle of the night and left me with a working bike 
tunertom


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fit the servo and set it up and your bike will be alot faster

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AndyYam


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The surge of power is the powerband kicking in. The powerband is not a physical thing. It just visibile on a graph of the power ( dyno chart) and is the point where the power is most prominant. On 2 strokes this is around 6-9krpm. Below 6 there isnt much power and is becuase the exhaust port is timed by the piston and speed the piston is travelling.At lower rpm some of the mixture is able to escape un exploded out oif the exhaust port before the piston comes up to close the port. The powervalve blocks of the exhaust port at lower rpms to stop the lost mixture. It gradually opens as the revs rise to allow the power to build faster. The servo unit controls its movements via a pulley and cables. It takes it information from the cdi/control unit which tells it what revs the engine is doing and so where the powervalve should be. Google YPVS and you'll find better explanations of Yamahas version. There are many versions and most these days use sliding gates as opposed to the cylindrical twisting valve that is on the DT125R

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Calum122


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Also it is worth adding that just because the bike doesn't have cables this isn't an indication of not having an operating power valve. As Andy you'll know the yz has a power valve and that is mechanical.

Also the powerband is determined by multiple factors. Yes on modern two strokes it's pretty safe to say between 6-9 rpm. But race two strokes don't have theirs kick in till 9k +. But I digress. Andy is pretty clued up so I agree.

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Dt Danny


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Wow how old is this topic lol

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i blew my dt up ... but i fixed it.... Then i crashed it.... but i didnt fix it right and 2 scouser's come in the middle of the night and left me with a working bike 
AndyYam


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Lol hadnt even looked at the date. Havnt been using the forum for ages so just saw it as one of my un read topics.

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