Two Stroke Power Valves.
Two Stroke Power Valves.
(OP)
Can anyone tell me where to find any info about power valve operation specifically on the Suzuki RG 250 of the late eighties?
I would appreciate any information at all on the different types of power valves used on two stroke exhaust ports (old or new), up to the types being used at the moment.
Thanks, Will.
I would appreciate any information at all on the different types of power valves used on two stroke exhaust ports (old or new), up to the types being used at the moment.
Thanks, Will.
RE: Two Stroke Power Valves.
you might want to check on the yamahas version the YPVS (i think) I had a RZ350 that had one of those and you could hear it when you switched the key. Its the same motor that is used in the popular banshees so I think you might be able to find a coulple of those around in parts to get a peek on the inside.
As far as operation I heard a bunch of different theroies, so I dont want to confuse you anymore then you might be. I am still riding the tuning bars with my R1, but long for the buzzing bees of a two stroke. I would be interested if you found information out pertaining to this.
Alex
RE: Two Stroke Power Valves.
I have a pair of barrels for an RG 250 and I see that he valves actually open up a chamber situated in the head (to enlarge the volume of the chamber at low RPM??).
I hear that the modern ones also effectively change the exhaust port timing, but I haven't seen any of these yet.
When I stopped riding bikes about 25 years ago, the power valves were just beginning to appear, and I didn't keep up with two stroke development, - now I hear that there is a very real chance of two strokes being banned, that's too bad, instead of just a blanket ban on two strokes, maybe they could ban all high polluting engines, then the two stroke could still stand a chance of being developed even further, making use of it's better qualities, and overcoming its percieved pollution problems.
RE: Two Stroke Power Valves.
Regards,
MB
RE: Two Stroke Power Valves.
So what actuates the valve? I know that the particular type on my Suzuki barrels is operated by cables, but what sort of mechanism actually provides the power? and what instructs it to move, - is it normally some sort of mechanical arrangement?
I did see somewhere a while ago that in some cases stepper motors were used, but there still needs to be something which tells them when to operate - an electronic sensor/controller perhaps?
Anyone else out there who has worked with these, or know where I can get any detailed info on them?
Thanks for the replies so far.
RE: Two Stroke Power Valves.
On my R1 this valve system is right before it breaks off into two underneath the seat. You cant hear it though, I hear if you go with another exh sys on these bike you have to toss the power valves.
I know quite a bit of people who are old school mechanics on bikes, some with two stroke experience. I will ask them.
They will never get rid of two strokes all together, I dont think. I read that 10% of the worlds pollution comes from two stroke lawn care equipment. If true that means there is a whole butt load of them out there, converting that many people and products, wheww....mind boggling
The variable intake and exhaust tuning is trick, I learned about that reading up on turbos. Very awesome.
Alex
RE: Two Stroke Power Valves.
Regards,
MB
RE: Two Stroke Power Valves.
As far as I know, the RG250 used the same mechanism as the RG125. This required a resonant chamber cast into the cylinder head directly above each exhaust tract. A simple plug valve was fitted between a hole in the roof of the exhaust tract and a hole in the floor of the resonant chamber.
At low rpm the plug valve was held in the open position, effectively lengthening the exhuast system and lowering its resonant frequency. At high rpm (typically 9000 rpm) the plug valve was rotated 90 degree into the closed position.
The plug valve was indeed actuated by a stepper motor and cable linkage. In the UK the RG125 was sold with no plug valve and no stepper motor to 'restrict' them to 12bhp. To remove the restriction, most people cut a length of copper household plumbing tube and hammered it into the hole where the plug valve should have been.
Early '80s Yamahas had a very slightly more sophisticated system. The power-valve DID change the exhaust port timing by adjusting the effective height of the top of the exhaust port.
This was achieved by having a gate valve shaped in profile like the 'sector' of a circle. This could rotate through about 20 degrees and alter the height of the port.
I say only slightly more sophisticated because until the TZR series of road bikes the movement of the valve was still either 'on' or 'off' at about 9000 rpm.
Later bikes were able to vary the position continuously with respect to throttle postion and engine speed.
Kawasaki and Honda had other variations on the theme.
What you have to remember is that Yamaha were first to patent their system, which has the simplest implementation of theory into practice. The other big three Japanese manufacturers then had to find ways around the Yamaha patent, which in most cases are less than optimal.
ZR
RE: Two Stroke Power Valves.
ZEDRIDER,
In the more modern versions,is the resonant chamber still used, (as well as port timing variations?)
RE: Two Stroke Power Valves.
I can't say for sure because I've not cracked the cases on either bike.
There must surely be some more info out there on the web for you to find.
ZR
RE: Two Stroke Power Valves.
I've had a few Suzuki RM's and RMX's and they are all powered in the same way, from the clutch, but the method of closing off the exhaust ports are all different.
RE: Two Stroke Power Valves.
The valve was cable operated, using an electric motor according to engine speed. A real weak link too. Most power valves coked up and got stuck. Even spraying WD40 (a.k.a. liquid engineering) into them didn't really work. The only solution was a regular clean-out - normally at each engine seizure (mine seized twice in the few years I had it!).
Here's a picture of the YPVS controller:
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RE: Two Stroke Power Valves.
Regards,
MB
RE: Two Stroke Power Valves.
RE: Two Stroke Power Valves.
The rgv250 uses a blade type powervalve (nothing like the RZ's YPVS system) and I believe the earlier ones used a 2 blade system, with the newer ones using a 3 blade system. They had big problems with the pins holding them together wearing out and breaking (dropping powervalves into cylinders)
There are also disc type exhaust valves (which I think are used on the rg500 and rd500) and kawasaki has one known as the KIPS system (which I think has a type of disc valve).
There are other types of valve that involve a secondary exhaust chamber.
There are another kind of valve (pretty sure it's a blade valve) used on a product known as the cheetah stroker kits (for banshees) that use some kind of system triggered by exhaust pressure.
John Robinsons "Motorcycle Tuning : Two Stroke" has some good information on exhaust valves.
RE: Two Stroke Power Valves.
RE: Two Stroke Power Valves.
A closed exhaust power valve simply lengthens the effective stroke.
2-strokes are amazing. We used to make the intake port so big it openened up to above the piston near BDC. Some of the charge shot right across the top and some stayed in the cylinder. Good for cleaning and charging. This all happened while the intake port would normally be closed. Overall it made a greater and more constant air flow through the carb. Another trick was moving the "points" plate with a little lever. Retard the timing at high RPM and the top end goes wild.
RE: Two Stroke Power Valves.