TE/TC Often wondered?.?

[Bigbill]

I often wondered why they never used a cable adjustable operated power valve? Rather than take power from the engine.

 

[racemx904]

Operated off what?

There's some electric p/v but the amount of power loss is very small

 

[juicypips]

By cable adjusted you mean rigged up to the throttle?

 

[jimspac]

The oil pump for the Yamaha Autolube in the 70's was one cable at the throttle and split into 2 cables. One cable went to the carb slide and the other controlled the metering of the pump. Very synchronized and efficient that allowed straight gas in the fuel tank. So it has been done before, just not to a power valve. That would certainly eliminate the need for electronics unless it needed to be synchronized with fuel injection.

 

[Trenchcoat85]

I often wondered why they never used a cable adjustable operated power valve? Rather than take power from the engine.

I'm guessing it's 'cause the power valve position is rpm-dependent; and throttle position isn't an issue.

 

[Tetley]

Exactly, the power valve is mostly RPM dependent, and has little to do with throttle position. It's all to do with the resonant frequencies of port timing and the expansion chamber. RPM is by far the dominant factor, but throttle position, temperature, altitude etc do have a small effect. The only way this could be properly incorporated is to have a mapped ECU controlled power valve. So, easiest, cheapest and most reliable solution is use RPM as the driving force.
I'm sure once the new wave of FI 2 strokes come in, the power valves wil be ECU controled.

 

[ohmygewd]

Electronic powervalves have been around for years but not on dirtbikes. Yamaha YPVS on the RD/RZ, Kwaka KIPS on the KR's, Honda RC Valve on the NSR's..2t's with electronic servo's or something...that's was almost 40+ years ago and l can't believe that modern day manufacturers couldn't build a PV that somehow can work of the rotation of the alternator or even a simple rpm sensor to the countershaft.
I know 2t and majority of dirt guys hate more electronics but (showing my age), 40years ago electronic PV's were in place and we're still yet to see it on the dirt????

 

[shawbagga]

Sherco n TM use electric servo/cable Pvs.

 

[letitsnow]

Honda CR250R?

 

[Norman Foley]

Sherco n TM use electric servo/cable Pvs.

Last version of the Honda CR250 used this.

 

[troy deck]

AND YOUR FORGETTING THE 87 250CR WISH THAT HAD TURNED OUT BETTER WOULD HAVE BEEN A BIG FEATHER IN HUSKYS CAP BACK THEN

 

[justintendo]

Electronic powervalves have been around for years but not on dirtbikes. Yamaha YPVS on the RD/RZ, Kwaka KIPS on the KR's, Honda RC Valve on the NSR's..2t's with electronic servo's or something...that's was almost 40+ years ago and l can't believe that modern day manufacturers couldn't build a PV that somehow can work of the rotation of the alternator or even a simple rpm sensor to the countershaft.
I know 2t and majority of dirt guys hate more electronics but (showing my age), 40years ago electronic PV's were in place and we're still yet to see it on the dirt????

yup troy is most certainly correct...the swedes had it on the 87 husky cr250...right before the italians scrapped all the swede 2 stroke designs..i understand why they did it but they were about to evolve with a new case design.

 

[Norman Foley]

yup troy is most certainly correct...the swedes had it on the 87 husky cr250...right before the italians scrapped all the swede 2 stroke designs..i understand why they did it but they were about to evolve with a new case design.

Too bad Gustavsson and the boys weren't interested in developing the Swedish 2T bikes too, when they started Husaberg....

 

[justintendo]

Too bad Gustavsson and the boys weren't interested in developing the Swedish 2T bikes too, when they started Husaberg....

im betting they could only go with one or the other, and there was more promise to the thumper tech that was mostly unavailable to anyone else at the time.

 

[troy deck]

yea but it still sucks i bet say a 92 up Husaberg 2t would been a fairly bad mamajamma and still plenty fast today for must guys haha an 87 husky with 5 years of evaluation hell good enough for me

 

[lankydoug]

Funny that this conversation would come up. I was at a 2 day 200 mile woods ride this weekend and a bunch of guys were sitting around the campfire wishing for a big bore air cooled engine with a modern transmission in a modern chassis. Simplicity and light weight with a narrow tank and no chance of smashing radiators. Some modern spark curve mapping and carb.... they might be on to something. Of the 200 mile course 70% was bar width single track and it poured rain for the first half of the first day so linear power with good traction was better than tons of horsepower. There was a lot of vintage bikes and "vintage riders" and the median age was probably 45 years old, so most guys had let go of their expectations of winning a GNCC.

 

[Trenchcoat85]

Funny that this conversation would come up. I was at a 2 day 200 mile woods ride this weekend and a bunch of guys were sitting around the campfire wishing for a big bore air cooled engine with a modern transmission in a modern chassis. Simplicity and light weight with a narrow tank and no chance of smashing radiators. Some modern spark curve mapping and carb.... they might be on to something. Of the 200 mile course 70% was bar width single track and it poured rain for the first half of the first day so linear power with good traction was better than tons of horsepower. There was a lot of vintage bikes and "vintage riders" and the median age was probably 45 years old, so most guys had let go of their expectations of winning a GNCC.

Man, I would love everything about this...

'cept:
I want a 175-200cc, 6 speed, power valve, reed valve, 80Watt alternator, barely street-legal, with OIL INJECTION [and maybe an engine oil pump with filter; fittings in case you wanted to add an external cooler. but maybe not]. electric start? nope- probably not. no battery.

weight would be <200lbs. hp would be about 25, maybe a bit more. lotta torque.