Posted October 16, 200915 yr Hi All, Just bought a 1988 TZR 125 today! being dropped off tomorrow. It's my first bike, so I thought i'd get something cheap to learn on for a year or so. Ive got a question! apparently it's got a manual power valve. The valve is closed at the moment as the bike has had a rebuild and is being run in - what does this mean exactly? I'm new to 2 strokes as i've always had cars. When i've run the bike in, what can i expect perfomrance wise if i open the power valve? The bike also has a stainless exhaust. Cheers, Paul.
October 16, 200915 yr Moderator Hi All, Just bought a 1998 TZR 125 today! being dropped off tomorrow. It's my first bike, so I thought i'd get something cheap to learn on for a year or so. Ive got a question! apparently it's got a manual power valve. The valve is closed at the moment as the bike has had a rebuild and is being run in - what does this mean exactly? I'm new to 2 strokes as i've always had cars. When i've run the bike in, what can i expect perfomrance wise if i open the power valve? The bike also has a stainless exhaust. Cheers, Paul. Firstly welcome, by manual power valve it means it is one of the earlier modles where the servo system was only supplied to full licence holders as it improved the output of the motor to around 22 hp. What people generally do is move it to a position they prefer, all low power, all top end depends if you like wheelies or speed. As a realistic option leaving it open some will liven the bike up and keep the drivability or retro fit the powervalve controlls. There are folks on here know how. J
October 16, 200915 yr Author Firstly welcome, by manual power valve it means it is one of the earlier modles where the servo system was only supplied to full licence holders as it improved the output of the motor to around 22 hp. What people generally do is move it to a position they prefer, all low power, all top end depends if you like wheelies or speed. As a realistic option leaving it open some will liven the bike up and keep the drivability or retro fit the powervalve controlls. There are folks on here know how. J Thanks for the reply! So with the valve closed, will all the power be at the top end? Also, ae you saying the the further open the valve is, the lower down in the rev range the power band is? Cheers, Paul.
October 17, 200915 yr Moderator And sorry, mistyped the year, it's a 1988 model! Paul. No with the valve closed all the power will be low down, you engine will go mad from tick over to around 6tho and thats it. Have it wide open (you need the exhaust off i believe to be certain) and it will go mad FROM 6000 but you will have very little below that. As a cautionary note when me and my mates were dicking around with these wonderfull powervalve motors when they were new (now i feel old) you had to change the mixture by upping the main jet to around 190 200, and get rid of the restrictors, one in the exhaust, i think the carb slide needed moding, tweak the reed block and do something with the airbox but i can't remember what. It was all in a kit you could by if you produced a full licence. As i said back in the day we used the PV stuff from old 350's and used a couple of choke cables, remember them to control the valve. There were also quite a few of em wrecked by bad bodging so be careful.
October 18, 200915 yr Author No with the valve closed all the power will be low down, you engine will go mad from tick over to around 6tho and thats it. Have it wide open (you need the exhaust off i believe to be certain) and it will go mad FROM 6000 but you will have very little below that. As a cautionary note when me and my mates were dicking around with these wonderfull powervalve motors when they were new (now i feel old) you had to change the mixture by upping the main jet to around 190 200, and get rid of the restrictors, one in the exhaust, i think the carb slide needed moding, tweak the reed block and do something with the airbox but i can't remember what. It was all in a kit you could by if you produced a full licence. As i said back in the day we used the PV stuff from old 350's and used a couple of choke cables, remember them to control the valve. There were also quite a few of em wrecked by bad bodging so be careful. thanks for the info - been told by the bloke that sold me the bike that all I need to do is open the valve half way to get power at the top end? The bike does have a stainless exhaust already. Cheers, Paul.
October 20, 200915 yr Author Hi, Found out the bike is de-restricted already - so when it's run it, it just needs the powervalve opening. Think i'll leave it shut for the time being though!! Cheers, Paul.
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