Power friggin' valve?

[Colorado]

Power friggin' valve? FOLLOW UP

I ride an '80 KDX175, '78 Yamaha IT400, '75 Yamaha MX400B and have a '79 Yamaha MX175 for my daughter to ride.

My best friend has a couple of mid '80's Honda XR200s that he and his son have been riding, but last weekend he picked up an '86 KDX200 for $350. It runs, but needed a few things right away, and he now has about $500 in it. He thought I would be his 2-stroke guru to get it all dialed in, so I stopped by yesterday to look it over.

1986 had much more technology than I am experienced with working on! I understand the basic old 2-stroke, piston port, air cooled bikes, and this one is air cooled --- but it already has systems I don't have a clue about. On the right side of the cylinder there is a 'push rod' of some sort, in a rubber sleeve, which seems to push a lever into a wheel (the lever and wheel are in a cover on the side of the jug), and on the left side is another cover that I haven't taken off.

I know that some Kaws were rotary valve, and am wondering if this one is, or if this is the 'power valve' that I've seen posts here about. I figured the power valve was something on newer, water cooled bikes, so have always skipped those posts, as they didn't apply to my bikes. On the other hand, if it is a rotary valve, I don't really understand how that would work on a 2-stroke either. Does it somehow use a valve instead of transfer ports for intake and exhaust?

Could someone give me a basic rundown on what a power valve is and does, and how a rotary valve functions in a 2-stroke? If you could kind of compare it to the piston port systems I'm familiar with it would help.

Also, he has the carb torn down soaking in Berryman's. He called me a little while ago to say that there is only one adjustment screw on that carb --- the idle speed screw (which happens to be turned all the way in) ... no pilot screw, no air screw. Doesn't the thing have any adjustments?

I told him to buy a Clymer's, but no one has one locally in stock. Any help you can give me is ap0.preciated.

 

[John Cena]

The 86 uses a Power valve similar to the 89-94 KDX 200.

86 Power Valve Picture

The Carb does have a pilot jet and a main jet that can be changed.

Here's a good read on what power valve does. http://www.dirtrider.net/justkdx/kips.html

 

[Colorado]

Thanks John
That's just what I needed.

 

[Colorado]

I have a couple more questions about the KIPS. We pulled the right side cap when I was at his house on Thurs., and everything was pretty splooged up with exhaust carbons/oils. Looking at the picture John provided above, I can see that the shaft (#49406) runs through to the other side, and that removing the left side cap will provide semi-internal access to it. If I've got it right, two sets of parts (#12005 and #92143) drop into two holes in the top of the cylinder, resting on that shaft and actuated by it. To remove or replace those parts it looks like at least the head has to come off, and maybe the cylinder has to be turned upside down to shake them out.

Do I have all of that right? Does that also mean that correctly cleaning it and inspecting all of the parts requires the top end to come off? My friend doesn't want to pull the cylinder right now. He's had the carb soaking overnight and plans to put it back together and go riding this afternoon, and is hoping that eliminates the hessitation it had at 1/4 throttle.

How much KIPS cleaning can he do without pulling the jug? It looks to me like he can remove both right and left cover/caps and at least use a spray cleaner to de-gunk everything at both ends of the shaft. It also looks like he has to leave the shaft in, or the parts that drop in from the top will drop too low and make it impossible to get the shaft back in short of pulling the top end. Do I have that right?

Thanks again in advance.

 

[glad2ride]

Hi.

It is a power valve, not a rotary valve. The KE100 had a rotary valve engine, but thankfully you didn't ask about it. :-)

The power valve opens or closes (can't remember right now) two subvalves in the cylinder around 6,000 RPM to help make more power / widen the powerband.

There is no pilot screw or air screw on that carb. Check out www.buykawasaki.com under OWNER INFO, then Parts Diagrams for complete diagrams and part numbers (microfiche basically). It's a huge help.

Taking off the left cap won't do much for you beyond cleaning.

Taking off the right cap, you will see a screw. Take that off (carefully, as it may have had 20 years to get stuck). That keeps the rod from coming out. After taking that off, I think you lift the two gears up about 3/8 inch, then slide the rod out.

When reinstalling them, there is a dot on each valve. Point it toward the front upon reassembly.

If you are not going to take the cylinder off (only a $5-ish gasket more of parts replacement), then I would not try to get too happy with rinsing carbon and oil gunk down into the bottom of the engine / crankcase.

If he didn't finish up, I hope this helps.

 

[DirtDawger]

I would highly recommend pulling the cylinder and doing a thorough cleaning of the power valves as this will make a huge difference in the power delivery. Also you will be able to inspect the cylinder piston and rod. I would be willing to bet this baby needs at least a piston an rings. The last thing you want is an old neglected piston coming apart and ruining the engine.