Sherco

[Anders]

Originally Posted by tm_enduro

Hoping that Sherco is the company that finally brings a stepper / servo motor on PV to market. This could greatly reduce the 2T hit and possibly give the engine a 4T like smoothness.

servo controlled power valves is nothing new. My wife's 1986 RD350YPVS has exactly that. I wasn't into dirtbikes in the eighties, so I don't know if the dirt Yamahas of the period had the same system.

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[twowheels]

Originally Posted by Anders

servo controlled power valves is nothing new. My wife's 1986 RD350YPVS has exactly that. I wasn't into dirtbikes in the eighties, so I don't know if the dirt Yamahas of the period had the same system.

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I think the DT200 of the day did (neat little dual purpose, liquid cooled 2T), and later Honda took a swing (and a miss) at it.

[tm_enduro]

Originally Posted by twowheels

I think the DT200 of the day did (neat little dual purpose, liquid cooled 2T), and later Honda took a swing (and a miss) at it.

As far as I know, the previous attempts have been two-postion (open / "close") type operations. I have to believe that a 3 or 4 stage opening would smooth out the power nicely. Short of figuring out how ot make a trombone pipe work, this may be our best chance getting rid of the hit, yet being able to tune a 2T for broad power.

[Clay]

Just picked up the 300i Race from the airport. The United States Department of Agriculture had the bike for three days. Maybe someone in the USDA rides offroad and wanted to look at the bike? Anyway....I will try to get close up photos loaded on the website as soon as posible. This bike is so sweeeeet!

[pscook]

Originally Posted by tm_enduro

As far as I know, the previous attempts have been two-postion (open / "close") type operations. I have to believe that a 3 or 4 stage opening would smooth out the power nicely. Short of figuring out how ot make a trombone pipe work, this may be our best chance getting rid of the hit, yet being able to tune a 2T for broad power.

The RZ (and other YPVS motors) have a servo motor that opens the PV based on RPM. You can get a custom CDI (or programmable) to adjust rate and timing of opening if you so desire. It's a very simple system and works very well. I am really surprised that it is so uncommon on 2T dirt bikes as it's light and can be mounted out of the way as it uses a cable to operate the valve.

http://www.zeeltronic.com/index_datoteke/ppv-rz.php

[Marco]

Does the TM 125/144 have this feature or does it differ to what is discussed above?

[tm_enduro]

Originally Posted by pscook

The RZ (and other YPVS motors) have a servo motor that opens the PV based on RPM. You can get a custom CDI (or programmable) to adjust rate and timing of opening if you so desire. It's a very simple system and works very well. I am really surprised that it is so uncommon on 2T dirt bikes as it's light and can be mounted out of the way as it uses a cable to operate the valve.

http://www.zeeltronic.com/index_datoteke/ppv-rz.php

I stand corrected, thanks for the info.

[pscook]

Originally Posted by tm_enduro

I stand corrected, thanks for the info.

And I know nothing about PV's on dirt bikes, and can only imagine the abruptness of a light switch in there. On my RZ350 I wired the darn thing open (after installing it backwards and wondering why it ran so poorly...), but I can only imagine the gains from having a truly "adjustable" rate of opening and timing. Mix that up with a SmartCarb and you could have a real winner on your hands.

[farmerj]

Originally Posted by Clay

Just picked up the 300i Race from the airport. The United States Department of Agriculture had the bike for three days. Maybe someone in the USDA rides offroad and wanted to look at the bike? Anyway....I will try to get close up photos loaded on the website as soon as posible. This bike is so sweeeeet!

I also wish you'd take that bike out and ride it! I'm curious as to how the acclaimed "long-stroke motor" changes the power delivery.

[Clay]

Originally Posted by farmerj

I also wish you'd take that bike out and ride it! I'm curious as to how the acclaimed "long-stroke motor" changes the power delivery.

I've ridden it around the parking lot and in the yard here. It seems to have a lot of grunt for an engine that small. I think the 6 speed really helps. I will prolly ride it tomorrow.