I don't really know that much about power valves or what exactly they do ? Also what would be the reasons for and/or benefits of having a power valve service performed ? Could a broken piston skirt effect the performance or condition of the power valves ? Any insight and knowledge on this topic would be hugely appreciated !
Power valves ?
- Thread starter JBRoc01blaster
- Start date
Very interesting topic actually! Unfortunately, our little air cooled Blasters don't feature a power valve. But the power valve is a valve in the exhaust port that regulates the flow of exhaust gasses leaving the cylinder. You can adjust it for different timing of the opening and closing in the RPM range to alter the position of the powerband. But like I said, power valves aren't a feature of the Blaster. And actually I can't think of any air cooled engines with one. Most of the power valved engines are later dirtbike engines and some aftermarket cylinders on 2 stroke quads. If you want some more info shoot me a PM and I'll keep it up. Haha
Gotcha ... Now I know why I've never heard much about power valves or don't remember reading about them in my manual haha. That makes me feel a little better about my lack of knowledge on them. Thanks bro !
if your interested in the powervalve motors, i believe that the dt200 yamaha dirtbike engine is a powervalve/watercooled version of our motor. i think it puts out 5-10 more hp than a blaster motor. from the little ive read, i think you can adapt a dt200 cylinder to our cases, by adding the watercooling set up. if you look at the space above the blasters oil pump theres a space and coolant inlets that are blocked off from the factory.
theres a few people on here that have done the swap or swapped the whole dt200 motor. they would be much more knowledgeable on the subject.
theres a few people on here that have done the swap or swapped the whole dt200 motor. they would be much more knowledgeable on the subject.
There are two different types of powervalaves!
One changes the size and shape of the exhaust port itself (more modern dirtbikes) by having a "lobed" drum that rolls up and out of the way to raise the exhaust port and sometimes uncover triple exhaust ports.
The other older type (only used on Suzuki's LT's) utilizes a chamber cast into the case and a valve inside the exhaust port itself to affect the volume of the "chamber" leading to the tuned pipe.
Both systems work but the cylinder mounted powervalve that changes port timing is more effective and more stark improvement in power.
Really, combining the two together would be an incredible feat as it would affect the port timing and pipe tune together....
One changes the size and shape of the exhaust port itself (more modern dirtbikes) by having a "lobed" drum that rolls up and out of the way to raise the exhaust port and sometimes uncover triple exhaust ports.
The other older type (only used on Suzuki's LT's) utilizes a chamber cast into the case and a valve inside the exhaust port itself to affect the volume of the "chamber" leading to the tuned pipe.
Both systems work but the cylinder mounted powervalve that changes port timing is more effective and more stark improvement in power.
Really, combining the two together would be an incredible feat as it would affect the port timing and pipe tune together....
my buddie had a 87 cr250 with one of the older designed powervalves that you mentioned sicivicdude i noticed its nothen like the one you would see in a dt200.
i did a dt200 swapp to my blaster i have 2 actually
its better to use the blaster bottomend and swap the dt200 topend and waterpump cuz the blaster has tougher tranny shafts and better gears.
the dt200s use a electrical conection to run the PV and i elimitated that when swappin into my blasty but my dt200 has a working pv. it tends to help lowend power an keep topend.
i did a dt200 swapp to my blaster i have 2 actually
its better to use the blaster bottomend and swap the dt200 topend and waterpump cuz the blaster has tougher tranny shafts and better gears.the dt200s use a electrical conection to run the PV and i elimitated that when swappin into my blasty but my dt200 has a working pv. it tends to help lowend power an keep topend.
Does anyone know what dirt bike had some kind of wannbe power valve that was part of the pipe, and that always got removed when they got a aftermarket pipe... I dont remember 
and i was trying to find some pics of it..
and i was trying to find some pics of it..Yeah the dt200 swap sounds like it would be pretty sweet, I know a member on here ( Best ) did the dt200 swop and seems to be very knowledgable on that topic and with motors in general. He would be the guy to discuss in detail what all is involved/needed for the swop. And it sounds like there would be some good power gains if you could utilize both types of power valves in one motor ! Someone needs to get on that ! That would be revolutionary for 2 strokes, and would definately level the playing field against them fancy dancy 4 strokes ( sense the sarcasm haha ? )
best is very knowledgable about these motors and the swap But i know who actually did the swapp
the start of this thread is really on page4 but this is when the dt motor was fabbed up to use in a blaster
http://www.blasterforum.com/engine-mods-swaps-129/dt200-motor-swap-pics-43770/index3.html
this is the bike that was built later on to run the motor in
http://www.blasterforum.com/full-rebuilds-128/dt-parts-blaster-build-46409/
remember the PV wasnt hooked up becuase dt wireharness is needed which wasnt avaliable at the time.
we do have a pv system ready to go now just waiting for next build
Does anyone know what dirt bike had some kind of wannbe power valve that was part of the pipe, and that always got removed when they got a aftermarket pipe... I dont remember
No, the powervalve has to be right up by the cylinder to work.
Read SiCivicDude's description carefully, the powervalve acts like the top edge of the exhaust port window.
It might be possible to drill an aircooled cylinder to fit one, but then you would need a means to operate it.
Triplecrown (who did the DT200 swap himself, not me) ran into that problem. The DT200 uses an electronically controlled servomotor.
Most MX bikes use a centrifugally controlled mechanism. It needs to be rpm controlled.
The only purpose of the powervalve is to fill in some mid-range torque while allowing more radical exhaust port timing.
It makes for a more broad powerband, not more peak power.
Triplecrown's "stuffing the intake box" experiment seemed to make nearly as much mid range torque as the DT200 powervalve.
See the "improving Velocity!" thread.
Imagine we combine them both?
Steve
best is very knowledgable about these motors and the swap But i know who actually did the swapp
the start of this thread is really on page4 but this is when the dt motor was fabbed up to use in a blaster
http://www.blasterforum.com/engine-mods-swaps-129/dt200-motor-swap-pics-43770/index3.html
this is the bike that was built later on to run the motor in
http://www.blasterforum.com/full-rebuilds-128/dt-parts-blaster-build-46409/
remember the PV wasnt hooked up becuase dt wireharness is needed which wasnt avaliable at the time.
we do have a pv system ready to go now just waiting for next build
well maybe if you guys could stay away from the kegerator long enough the next build could get on its way lol
Apparently you dont understand what im talking about, so i will try to make it simple... There was a very very early type of power valve that i think was on smaller cc bikes that bolted between the cylinder and pipe, and it increasing and decreasing the volume of the exhaust. But i dont think it worked very good because it was not used with a aftermarket pipe, so most of them got thrown away..:-/
Yeah, ya gotta use crayons and finger puppets to get thru to me!
If all else fails, draw me a picture.
Not familiar with these at all, can you give me any examples, any years you remember seeing them or what type of bikes they were on?
I am pretty familiar with sleds and offroad bikes from 1974 on.
KTM used a chamber device on the 380 and 300 in the1990s, shown here:
Suzuki LT's had that system. The valve was inside the exhaust port "tube" (not near the exhaust port itself) and acts on the tune of the pipe by opening into a chamber cast into the front of the cases.
A couple more pictures of the KTM chamber system:
I actually have 2 similar KTM cylinders, one has this chamber style powervalve.
KTM stopped using them about 1999. I cannot find a reason why, although some claim they did not work.
I find it hard to believe they would make it in the first place if there wasn't good research behind it.
Cover off, you see this big oval port into the roof of the exhaust port, above the powervalve flap.
When the powervalve flap is down at low speed, it uncovers the port into the chamber.
Nothing seals very tight, everything is more of a flow diversion nature.
The round holes with the red "O" rings are water passages.
This is a view down the exhaust port. You can see one of the two "triple ports" in the side of the exhaust port. It comes with a rotating spool that opens and closes with the powervalve too.
I actually have 2 similar KTM cylinders, one has this chamber style powervalve.
KTM stopped using them about 1999. I cannot find a reason why, although some claim they did not work.
I find it hard to believe they would make it in the first place if there wasn't good research behind it.
Cover off, you see this big oval port into the roof of the exhaust port, above the powervalve flap.
When the powervalve flap is down at low speed, it uncovers the port into the chamber.
Nothing seals very tight, everything is more of a flow diversion nature.
The round holes with the red "O" rings are water passages.
This is a view down the exhaust port. You can see one of the two "triple ports" in the side of the exhaust port. It comes with a rotating spool that opens and closes with the powervalve too.
Our LT's power valves are just to 'make the pipe longer'. In other words changing the pulse timing coming back out the pipe and allowing us to run a fataz pipe and keep good bottom end. But I'd much rather the 'flap' like it RM, KX engines that actually alter the exhaust port timing. With our bikes we can mate an 87 RM top end onto our 87+ bottom ends ad have a 'real' power valve. All its there for is to give you better low range power and let's you be able to run a shorter pipe with more aggressive cone angle. The blaster has good bottom end pull so I don't see why it would be needed. Unless it was one that actually changed the exhaust port timing. Then that would be sick as hell lol
