*** OK - dumb question here. ***

[bkvette3]

What the heck is a power valve in a 2 stroke engine??? (go easy on me - I am a NOob here and I feel stupid for asking.) Is there such a thing in my '85 250R ATC??? I am thinking not. Someone school me here. Thanks.

[slashfan7964]

It basically changes the exhaust timing a little bit with the speed of the engine to give more low end grunt and power across a wider RPM range before that hit into the power band that everyone associates 2 strokes with. No, your 250R does not have one. No 250R had one.

[bkvette3]

It basically changes the exhaust timing a little bit with the speed of the engine to give more low end grunt and power across a wider RPM range before that hit into the power band that everyone associates 2 strokes with. No, your 250R does not have one. No 250R had one.

Thank-you, slashfan7964. Now I know.

[Ghostv2]

Aaaaand now I know too. :)

[Liquid-Darkness]

Doesnt a CR 250R or 500R have a power valve??

[DohcBikes]

Slash is referring to three wheelers, not dirtbikes.

To add to his explanation, the power valve does control exhaust by affecting the amount of flow and how long the exhaust port is open.

Not a fan of Wiki, but it actually has a good explanation of how a CR powervalve works so here it is.

Honda ATAC
ATAC System: The Honda Automatic Torque Amplification Chamber system works by effectively increasing or decreasing the volume of the exhaust system with a small butterfly valve located just before the exhaust connection. At low RPM a centrifugal crankshaft driven gear opens the valve into a small chamber and increases the volume of the exhaust by allowing the exhaust gases to flow through the chamber. At high RPM the ATAC valve is closed and the exhaust simply exits into the expansion chamber. A larger expansion chamber allows for more power at lower RPMs because of the extra time needed for the impulse to "bounce" back for the supercharger effect. It was used on their CR motocrossers, GP bikes and MTX, MVX, NS and NSR road bikes.

[RIDE-RED 250r]

Doesnt a CR 250R or 500R have a power valve??

That depends on how old they are. I know later 250's and 125's had them, but not sure about the 500. But why would the 500 even need it?? I had an '89 cr500 years back and it had PLENTY of low end grunt!

And I'll add the the often imitated but never duplicated Rotax R.A.V.E. (Rotax Adjustable Variable Exhaust) exhaust valves are hard to beat for reliable operation. Simple, functional, effective.

[yaegerb]

That depends on how old they are. I know later 250's and 125's had them, but not sure about the 500. But why would the 500 even need it?? I had an '89 cr500 years back and it had PLENTY of low end grunt!

And I'll add the the often imitated but never duplicated Rotax R.A.V.E. (Rotax Adjustable Variable Exhaust) exhaust valves are hard to beat for reliable operation. Simple, functional, effective.

x2....RAVE valves are far superior from all of the information I have read/people that have them. Hope to retrofit one on my 85 R some day.

[RIDE-RED 250r]

x2....RAVE valves are far superior from all of the information I have read/people that have them. Hope to retrofit one on my 85 R some day.

Yep, no linkages to keep clean and in adjustment... Just run exhaust valve friendly oil in your premix, pull em out and clean them now and then and they work. Also very easy to adjust to your liking. I have had many Ski-Doo sleds over the years and I had zero issues with their exhaust valves on everything from twin cylinder/single pipe to triple cylinder/triple pipes.

Somebody on one here or 250r.net has done Rotax powervalves on 250r's. I can't remember who, but I know I have read about someone having done it successfully.....

[c_hustle]

One day i WILL own a bad azz pv engine!

[barnett468]

Hello;



And I'll add the the often imitated but never duplicated Rotax R.A.V.E. (Rotax Adjustable Variable Exhaust) exhaust valves are hard to beat for reliable operation. Simple, functional, effective.
Here’s some trivia.

In 1978 Yamaha applied for a device to vary the timing of the top of the exhaust.

http://www.docstoc.com/docs/140811168/Two-stroke-engine-having-variable-exhaust-port-timing





not sure about the 500.The Honda CR500 never had a power valve.





I had an '89 cr500 years back and it had PLENTY of low end grunt!The link below contains a brief history of "grunt". Editor Tim Webb calls the 83 KX 500 [which did not even have a power valve] "unrideable". This is the same bike I had to take my riding test on for Kawasaki at Saddleback.

http://www.dirtbikemagazine.com/ME2/dirmod.asp?type=news&mod=News&mid=9A02E3B96F2A415ABC72CB5F516B4C10&tier=3&nid=9F4F461E88C04C65858CDD3C382A19F5





But why would the 500 even need it??
Because if you’re man enough like Mike Larocco is[which I am not], you get your picture in magazines and get to ride around with this nifty number 1 on your bike for a whole year.

https://s-media-cache-ec0.pinimg.com/736x/19/e1/33/19e13370147eeafd6ec17f4ce423702a.jpg



Because if you are Ron Lechien, you get to spank Ricky Johnson on your way to winning both motos of the 1988 Motocross De Nations by around…well a mile. Oh…and you get your picture in magazines and get to ride around with this nifty number 1 on your bike. Did I mention you also get nifty little check for around $10,000.00.

https://s-media-cache-ec0.pinimg.com/736x/6f/f7/3c/6ff73c2f3558c754b8db2c9dbcf8cbf2.jpg

[barnett468]

What the heck is a power valve in a 2 stroke engine??? (go easy on me - I am a NOob here and I feel stupid for asking.) Is there such a thing in my '85 250R ATC??? I am thinking not. Someone school me here. Thanks.Hello bkvette3;

Here's some additional info. It’s an rpm controlled mechanical device that varies the effective size of an exhaust port. This allows for the use of “large” exhaust ports without sacrificing low end performance. There are two "types". one affects the height of the exhaust port and the other affects the width.

I was tinkering with combining both while I was at Kawi. Below are photos of what they ultimately did. It is one of the most exotic cylinders ever made. It is also all aluminum and Nikasil plated.

It also allowed for the uber powerful Kawasaki Tecate’s, which were already the undisputed horsepower leader in 84 and 85, to not only continue their domination over all other challengers but spank them by an even bigger margin in 86 and 87 even though it continued to have just a 5 speed transmission while the Honda whatchama call it and the Yamaha thingamajig both had 6 speeds.

http://www.freesmileys.org/smileys/smiley-laughing025.gif (http://www.freesmileys.org/smileys.php)



Below are just a few painful excerpts from an 86 Nationally distributed 3 Wheeler Magazine shoot out comparing all three.

MOTOR MOTION

The undisputed king of horsepower; the Kawasaki Tecate, held its crown for '86 and benefited from the numerous engine improvements that were made. We noticed both a significant boost in the midrange over last year's model and in Kawie's always-explosive top end.


THE BALLOT PLEASE

And the winner of the Race Bike Award goes to. . the Kawasaki Tecate! This tight, light, fast bike will win races, and it doesn't require a whole lot of effort to get the Kawasaki race-ready. Most everyone could sense the precise, tight handling characteristics of this race-bred machine, and they loved it!


RACE VIDEO

Here’s a cool video of an 86’ Championship 3 wheeler race with around 30 Tecate’s which was of course won by a Kawasaki. Enjoy the first 30 seconds as poor factory Honda rider Marty Hart gets SMOKED on the start by a sea of Tecate's, then is literally blown off of his bike buy the horrendous roost thrown at him buy these powerful machines as their as their rear tires spin wildly due to the abundant horsepower produced by their uber powerful engines.

http://www.youtube.com/watch?v=r9E9OaUllsY



Here's a nice magazine COVER SHOT of an ultra light, uber powerful 86 Tecate [NOT A HONDA] flying through the air with the the greatest of ease.


https://s-media-cache-ec0.pinimg.com/736x/04/7e/fa/047efa9fde9e7f1ba5ce88ead9ca5d6a.jpg



The "guillotine" regulates ex port height. The round valves control width by rotating which opens and closes the two small ports next to the large ex port. There is one on each side. The ex port is on the left side of the photo.

http://i.ebayimg.com/00/s/MTIwMFgxNjAw/z/FLkAAMXQlgtS-mDK/$_12.JPG

http://i.ebayimg.com/00/s/MTIwMFgxNjAw/z/AEUAAMXQVT9S-mDl/$_12.JPG

[RIDE-RED 250r]

Barnett, I never said ROTAX was first..only the best. ;)

Arctic Cat was still having issues with their mechanical PV's well into the 2000's, fussy and problematic.... Rotax got it right from the get-go. No linkages, no rotor to get gummed up and stick, no electronics. Very simple and easy for the consumer to tune to his liking. I have NEVER had a Rotax PV seize up.

And you can tout your Tecates and slam the other 2 all you want... I like them just fine, they are very cool machines and a nice 2nd gen Tecate is high on my "gotta get" list... But sales numbers don't lie and Honda was first on 3 wheels...you can't deny that! Honda, makin' dirt dance since 1970....Funny how similar to a 3rd gen R a 2nd gen Tecate is.... That's because the 3rd gen R came out and Kawi had to do some major catching up! ;) See Honda's 3rd gen R came out and Kawi realized a radiator where the headlight belongs just isn't a good idea.... Where to put the headlight??? Oh yeah, we'll just stick on top of the rad... :naughty: HAHA!

But anywho....back to our regularly scheduled programming....


BTW: welcome back buddy! :beer

[El Camexican]

The link below contains a brief history of "grunt". Editor Tim Webb calls the 83 KX 500 [which did not even have a power valve] "unrideable". This is the same bike I had to take my riding test on for Kawasaki at Saddleback.
Great story. Seeing as this post has gotten as far from power valves as I am from the 49th parallel how about you keep it going by telling us more about your input at Kawasaki on the mighty Duckster, the steering rake angle of the KZ900, the design of the KX500 combustion chambers and the R&D of the infamous Tecate stators!:Bounce

[stoshu]

Great story. Seeing as this post has gotten as far from power valves as I am from the 49th parallel how about you keep it going by telling us more about your input at Kawasaki on the mighty Duckster, the steering rake angle of the KZ900, the design of the KX500 combustion chambers and the R&D of the infamous Tecati stators!:Bounce If he had anything to do with design on the starter for a KLT 200 he must know his chit. Sold one for parts yesterday, and the guy tells me the motor must be seized because his 450 cca battery in his minivan wont turn the POS over. He asks if I have a hammer to tap the starter. I say sure and go get the 10lb sledge. Hit the starter hard enough to move the trike 2 feet sideways. Boosted it with my old ford with dual batteries, fired right up. He walked from the deal because he didn't like the way I treated my stuff. Did I mention I was only asking $100. Sold it 20 minutes later to the next guy who looked at it.

[El Camexican]

If he had anything to do with design on the starter for a KLT 200 he must know his chit. Sold one for parts yesterday, and the guy tells me the motor must be seized because his 450 cca battery in his minivan wont turn the POS over. He asks if I have a hammer to tap the starter. I say sure and go get the 10lb sledge. Hit the starter hard enough to move the trike 2 feet sideways. Boosted it with my old ford with dual batteries, fired right up. He walked from the deal because he didn't like the way I treated my stuff. Did I mention I was only asking $100. Sold it 20 minutes later to the next guy who looked at it.

I gotta admit, there's not a lot of electrical issues that can't be fixed with a 10# sledge.

[RIDE-RED 250r]

I gotta admit, there's not a lot of electrical issues that can't be fixed with a 10# sledge.

Or a cold brew.... :beer

Electrical and I do not play well together.... I must have relieved myself too close to a cow fence one too many times as a kid! I guess it would have been better to have been dropped on my noggin... ;)

[El Camexican]

Or a cold brew.... :beer

Electrical and I do not play well together.... I must have relieved myself too close to a cow fence one too many times as a kid! I guess it would have been better to have been dropped on my noggin... ;)

You’re preaching to the choir buddy. I ^%#&*$ HATE electrical! All that “flows like water” crap. When's the last time taking a wiz into a pool of water ruined your ability to urinate for a week?

[barnett468]

.
Hello bkvette3;


I hope the power valve photos I posted for you helped you understand a little better how they work, and I also hope you find your thread entertaining.




BTW: welcome back buddy! :beerThank you very much and thanks for your support and the many times you have “thanked” my posts as well as other peoples posts. You and others like you are a great asset.




Barnett, I never said ROTAX was first..only the best. ;)Oh, I know. I just thought it was an interesting bit of trivia, especially since I don’t think they used a power valve for years later, lol.




No linkages, no rotor to get gummed up and stick, no electronics. Very simple and easy for the consumer to tune to his liking. I have NEVER had a Rotax PV seize up.I agree, it is a brilliant system and follows the engineers creed. KISS. I can assure you, it is EASY to over engineer something. Kinda like a Rube Goldberg cartoon, lol.




And you can tout your Tecates and slam the other 2 all you want.As you know, the Kawi guys are outnumbered here by around 10,000:1, so I like to take the opportunity on occasion to let the Honda guys know that there are OTHER good bikes besides the glorified Honda, lol. Believe me I love them all and I have had many Hondas. We used to race the Z50’s in the perking lot after the shop closed.




they are very cool machines and a nice 2nd gen Tecate is high on my "gotta get" list... But sales numbers don't lie and Honda was first on 3 wheels...you can't deny that!Oh, I agree Honda is a GREAT company with many, many great bikes even though the fastest production bike in its class is still a KAWI. Don’t forget the old H2’s. Kawi’s motto back then was, if we make them fast we don’t need to make them handle. Kawi street and dirt bikes used to handle like cr_p. You were almost takin your life in your hands every time you rode one.

As far as Honda being the first 3 wheeler, we all know it was not exactly, however, they certainly were the ones that made the market and Kawi and a few other companies obviously jumped in and benefited from it. I assure you that EVERYONE at Kawi, including the management have a great respect, appreciation and reverence for Honda even though Honda hates us, lol.





Funny how similar to a 3rd gen R a 2nd gen Tecate is.... That's because the 3rd gen R came out and Kawi had to do some major catching up! ;)Actually that’s not the case at all. From the beginning, Kawi planned to make a new version after 2 years but they certainly did not know they would be lowering the radiator etc.. Kawi literally threw the first Tecate together. Most of it was done by one engineer in our shop who had only seen pictures of a Honda and was a motorcycle engineer, not a 3 wheeler engineer. He drew it all by hand WIYHOUT a picture of a Honda and I never saw dimensions of a Honda on his desk. We had no cad program, lol. Once an engineer got good at his job in Japan, they would transfer the guy to a different section. It drove us nuts.

I swear on a 3 wheeler magazine that the only water cooled Honda I ever saw until AFTER I finished the 86 Tecate prototype was only in a photo. The 86 Tecate was a very rough pos prototype when they turned it over to me. Once I was finished, we bought a new Honda [nice] and compared them.

I was a pro motocross rider so I made the Tecate perform as well as possible on REAL MX tracks like Carlsbad and Saddleback because I liked MX a LOT more than sand and slow riding. The tracks were also never prepped so they were nasty. The Honda was NEVER tested on an MX track. The wussies tested it on girly tracks. I know this for a FACT because one of my friends worked at Honda R and D at the time, lol. Anyone can make a bike work on a smooth surface or in the sand etc.. The Honda is a WAY better trail bike than a Tecate but we didn’t want a trail bike so we didn’t design it that way.




See Honda's 3rd gen R came out and Kawi realized a radiator where the headlight belongs just isn't a good idea.Hey Kawi’s idea was a great one [that was painstakingly thought out] because it allows capable riders like multi Championship winner what’s his name, lots of room to move around on the seat as they pass Honda's left and right on the track. Below is an illustration. Besides, unlike Honda, Kawi had the foresight to realize that the higher a lite is mounted on a vehicle, the farther it will project. This is evidenced by lites mounted on the roof of the Baja cars and trucks.

They also had the foresight to realize, that because the Tecate, which was the highest performance production 3 wheeler ever made, was virtually race ready out of the box, many people would also race it on tracks where a lite is not required, therefore, they made it so it can be easily removed and installed. You can also mount them on top of each other for even greater nite time visibility. We even offered a helmet mounted accessory.

http://atvscene.com/images/white3wheeler.jpg



PS I just typed in “cdi” into the search engine. It reached its storage limit at 500 posts regarding cdi’s. I looked through the first few pages until I got tired and did not see a single one pertaining to a Kawi ignition failure of ANY kind. See the search below.

http://www.3wheelerworld.com/search.php?searchid=8837791

No Kawi ATV stator ever failed during testing while I was there. The Tecate stator endured a few hundred hours of testing under SEVERE conditions. I also used the production stator that had over 150 hours of test time on it in my race bike and it never failed. I had nothing to do with the stator design. Since that seems to be the ONLY fault ANYONE can find on an 18 year old dirt bike, it doesn’t sound all that bad to me.

I had nothing to do with the Duckster graphics. I have no idea why that was even brought up.

The 83 KX was an “Exploder”. I had nothing to do with its design since it was a production bike at the time I started at Kawi as I previously mentioned, therefore, I have no idea why this was brought up.

Most of the other later years of KX500's would ping/detonate to some degree under certain conditions, however, since none of them "grenaded" during testing, and the only practical cure was to reduce horsepower, Kawi elected to simply let them ping away. Other than some occasional pinging, they seemed to run well enough to win several races and Championships, therefore, who cares if it pings as long as it wins. Below are just a few examples.


Magazine excerpt

“For over 20 years it was generally accepted that if ant bike made more power than a Kawasaki KX 500 it was impractical. The KX was seen as the upper boundary of sanity.”


85 - Voted best bike in class.

Won on STOCK PRODUCTION BIKES!

88 Motocross Des Nations - Lechien
89 500 National - Ward
90 500 National - Ward
92 500 National - Keidrowski
93 500 National - Larocco.
93 Dutch ISDE – Davis
95 AMA Enduro – Davis
91, 92, 93, 94, 95, 96 San Felipe 250
87, 90, 91, 92, 93, 94, 95, 96 Baja 500
88, 89, 90, 91, 92, 93, 94, 95, 96 Baja 1000


ALL the street bike design and testing was done in Japan. US R and D never had a street bike. I also have no idea what KZ900 steering has to do with anything.

The only “street bike” testing I did was on the police bikes because we had several police bike contracts. That was an entertaining job!
.

[barnett468]

Sorry..I forgot.

:beer

I still have no edit button. http://www.freesmileys.org/smileys/smiley-laughing013.gif (http://www.freesmileys.org/smileys.php)

[barnett468]

PS – I also did a “submersion” test on a Tecate stator…well it was actually the whole bike while it was still running and I determined a few things.

1. It will quit running.

2. It will turn upside down and the tires will keep it floating for “easy” retrieval providing the water is not flowing too quickly.

3. None of the electrical system will get damaged including the stator.

4. The flywheel magnets will NOT fall off.

5. Engine cooling is greatly increased.

6. Detonation is greatly decreased.

7. It will start right up again if you drain the water out.

[LastFoolerInVA]

PS – I also did a “submersion” test on a Tecate stator…well it was actually the whole bike while it was still running and I determined a few things.

1. It will quit running.

2. It will turn upside down and the tires will keep it floating for “easy” retrieval providing the water is not flowing too quickly.

3. None of the electrical system will get damaged including the stator.

4. The flywheel magnets will NOT fall off.

5. Engine cooling is greatly increased.

6. Detonation is greatly decreased.

7. It will start right up again if you drain the water out.

I've done the "submersion" test on a Honda with the exact same results...Sounds like Kawi & Honda have something in common after all... :lol::lol::lol::lol:

[RIDE-RED 250r]

I still say the headlight was mounted high on top of the rad to prevent rocks thrown by the Hondas out front from shattering the lenses... ;) BA HA!

Honda riders could remove their headlights for race day just as easy, if not easier... 4 quick release rubber straps and a light plug... But that's ok, some guys like riding around with what looks like a submarine periscope sticking up above the bars! LOL!

But all ribbing and ball breaking aside... Didn't the Kawi water cooled bikes of the time have the rads mounted on the front of the tank?? I know that would have been pretty early in water cooled bikes.. But if that was the case, just curious as to the reason to mount the rad to the triple clamp? Better air to the rad with the wider trike front end out front??

[DohcBikes]

I had nothing to do with the Duckster graphics. I have no idea why that was even brought up

Are you sure?....


A stock bike was used by and the designer "camoed" it up by hand 50 feet from my desk, lol. I thought it was pretty cool.

Maybe he was trying to hide it from you so you wouldn't put the headlight in a weird spot.......

:Bounce:lol::Bounce

[El Camexican]

Maybe he was trying to hide it from you so you wouldn't put the headlight in a weird spot.......

I just laughed rum out of my nose.

[barnett468]

I still say the headlight was mounted high on top of the rad to prevent rocks thrown by the Hondas out front from shattering the lenses... ;) BA HA! Uh, yeah…but that’s only because we knew the Tecate, being the fastest production 3 wheeler ever made, was so incredibly SUPERIOR to the Honda that we would EASILY be lapping them. :lol:




Honda riders could remove their headlights for race day just as easy, if not easier... 4 quick release rubber straps and a light plug.Oh, now there’s some quality hardware right there. We actually used things like REAL bolts and stuff, and the Tecate was STILL several lbs lighter than the “The Big Red PIG”.

84 Honda PIG . – 293 lbs
84 Kawi Tecate – 286 lbs
86 Honda PIG . - 291 lbs
86 Kawi Tecate – 280 lbs

Wow the 86 Tecate lost 6 lbs in two years and is 11 lbs LIGHTER than the 'PIG" even though it has a more rigid chassis, massive 41mm fork tubes and a swing arm built as strong as a bridge compared to the Hondas spindly little 39 mm tubes and “massive” [not] swing arm.

How did that happen?

Ok, granted, the Honda did have a counter balancer [because it needed one] and a 6 speed trans [because it needed one of those too] that added some weight.

Oh my God!
http://www.freesmileys.org/smileys/smiley-laughing025.gif (http://www.freesmileys.org/smileys.php)




But that's ok, some guys like riding around with what looks like a submarine periscope sticking up above the bars! LOL!Please see reply above.




But all ribbing and ball breaking aside... Didn't the Kawi water cooled bikes of the time have the rads mounted on the front of the tank?Umm…maybe.

Actually the real answer is Yes and No.

83 KX 125 – No
83 KX 250 – Yes
83 KX 500 – No
83 CR 125 - Yes
83 CR 250 - Yes
83 CR 480 - No
Brilliant, huh? http://www.freesmileys.org/smileys/smiley-laughing013.gif (http://www.freesmileys.org/smileys.php)





I know that would have been pretty early in water cooled bikes.. But if that was the case, just curious as to the reason to mount the rad to the triple clamp? Better air to the rad with the wider trike front end out front??I don’t remember exactly but I do think the main reason was that he thought it would get more air flow.

We had a horrible overheating problem with the prototype and everyone was freaking out because it would be hard to make a big change at that point. We stared at the front one day and one of the guys said, “Hey, lets take the screen off and blow some air through it with an air nozzle.". Well we did that with around 100 psi from 1’ away and almost NO AIR came out the back side. We had some other chicken coupe type screen laying around and tried the same test and lots of air came out so I stuck that on and the overheating was gone.

The prototype screen was flat narrow metal that was installed at an angle. The air hit the angle and was deflected to the side. Well there was another angle deflecting air in the opposite direction so the air collided and caused turbulence that greatly reduced air flow.

:beer

[DohcBikes]

Usually I read the whole post before a response, but I have to say I knew the "[we had already lapped them]" thing was coming:lol:

Must have been the uber powerful Team Green engine, fueled by prefabulated amulite and high levels of ZDDP;)

[barnett468]

.
Hello bkvette;

Here's some more info as requested in your message.




Are you sure?Yes, however, I did formulate the actual paint that he used and made it up in our “science” lab




Maybe he was trying to hide it from you so you wouldn't put the headlight in a weird spot...:Bounce:lol::Bounce
. . . . Smart

http://t3.gstatic.com/images?q=tbn:ANd9GcQ1IzYeD5qO82tmeutAY7DxhA9Puyd6A WI7oAx7F9Jh2C_7eUGGd7gV54q6aQ


. . . . . As_

http://t0.gstatic.com/images?q=tbn:ANd9GcSMk2WD9_fNszno1IAe2ikRln-dJ4JVV21u5V-BvhhUo6MokuOhtPseZUE2Pg

Actually, I told him we should test its “camo” effectiveness by taking it out in the woods, having someone hide it, then see if we could find it. http://www.freesmileys.org/smileys/smiley-laughing013.gif (http://www.freesmileys.org/smileys.php)




Must have been the uber powerful Team Green engine, fueled by prefabulated amulite and high levels of ZDDP.
Actually the Tecate’s engine was already so powerful in box stock form that the use of Prefabulated Amulite Racing Fuel simply created such a substantial increase in the acceleration rate of the rear tires that the coefficient of friction between the tires and the ground was reduced to such an enormous degree that the vehicle simply failed to accelerate.




and high levels of ZDDP ZDDP is one of the best anti wear agents known. It acts as a sacrificial barr…