E v H top end differences?

[Fatguts]

G'day, my search-fu must be weak because I couldn't find anything on this topic, so apologies if it's been done before.

Will a H cylinder fit an E bottom end? Reason I'm asking is my 1990 KDX200 is coming home after a couple of years as a semi-basket case that I swapped a mate for something that I forget, then ended up swapping him a set of 4x4 wheels and tyres back for

It's mostly complete except for the KIPS - typical chewed valves where the reason I originally pulled it apart, but I have no idea if any of the assembly even exists anymore. The aim is to put it together as a farm bike that'll get ridden every couple months at best, so I'm finding it hard to justify dropping $300+ on new valves, and that's 'IF' I can get em. At best all it needs to do is beat the brother in law's 86 XR250 which shouldn't be hard

Alternatively what's the general consensus about running these without the valves. I generally understand the reason behind the KIPS but am after a bit of first hand info as to how rough they really run without em. Not looking for perfect here, just good enough to run WOT every now and then!

[pumpguy]

Can't answer your specific question about parts interchangability, but if you're just looking for a mild mannered bike to putt around the farm, you might look into setting up the engine with permanently closed KIPS valves. The only loss will be high RPM performance, but the gain should be the absence of KIPS rattle, and the (in your case) needless complication of KIPS valve linkage.

Sorry, I can't provide details on this modification, although I believe a site search here will provide some information.

[Julien D]

You can fit the H top end, provided you also use the H series clutch covers and the actuator rod for the KIPS valves. Someone here did it, quite some time back.

[Thrahl]

You can run it with chewed valves. Neither of my subvalves work and it is still a blast to ride, the top end just falls flat.
I ride pretty low speed stuff and prefer to short shift and put that KDX torque to use so having bad valves doesn't really affect me.
I don't know if you should run it without any valves at all. I imagine you would have terrible low end and your top probably wouldn't be as good either since the air flow would be all screwed up. Never tried it though.

[Fatguts]

Good info, thanks blokes. So the question is, run em closed or run em open? How much top end do you lose running em closed? It's mainly flowing fire trails where it'll be ridden, not so much single track or steep stuff. Conversely, how crook is the bottom end if they're open?

[6 Riders]

I'm pretty sure the head is "reversed" from the E to H models..... I think that the E models head mount is towards the back of the bike, the H to the front. Check just to make sure.

[bufftester]

Set it up just like you would if the valves were in good shape (closed when engine is off) and then just ride the piss out of it. If they are chewed to the point of not operating then all you lose is the top end.

[Roadhazardguy]

What exactly gets chewed up with the kips? Is it the valves itself or the mechanism behind the clutch case that gets messed up? If its the governor that's the problem would it be possible to actuate it with a small thumb lever like you would find on a xl600r for the decompression valve?

[Thrahl]

What exactly gets chewed up with the kips? Is it the valves itself or the mechanism behind the clutch case that gets messed up? If its the governor that's the problem would it be possible to actuate it with a small thumb lever like you would find on a xl600r for the decompression valve?

Haha that would be funny. Turbo boost button on a KDX
But no the shitty aluminum gears on the top of each subvalve strip since they are turning on a steel rod that tends to snap open aggressively.
The general consensus seems to be that after many hours of riding and the aluminum valves turning in the aluminum cylinder with aluminum bushings (brilliant engineering I must say) slop developes so that the valves tend to "catch" rather than spin freely. The steel actuator rod makes short work of them when that happens.

[Roadhazardguy]

Haha it would be different to use that's for sure! Gears seem easy enough to make, why not get some machine shop to pump out 100 or so of them then sell them on here and eBay.

[Julien D]

Haha it would be different to use that's for sure! Gears seem easy enough to make, why not get some machine shop to pump out 100 or so of them then sell them on here and eBay.

Get on it!

The gear is one piece cast into the sub-valve. In order to have a replaceable gear you would need to redesign the valve as well. Probably easiest to find someone who can machine the entire part out of brass or a better grade of aluminum.

[Roadhazardguy]

Well first off I think I would at least need a 89+ KDX and second didn't I see some sub valves made out of bronze some where, it seems like someone posted a link to a set or something? Its kinda funny how the first gen KIPs models don't have this problem.

[Julien D]

First gen lips subvalves are steel, no?

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[Thrahl]

It seems as if someone could make the gear itself out of brass and then press it on to a chewed valve.
You would have to remove the old chewed gear portion until it was just a perfectly round shaft and then press the new one in place.
Seems like it would be easier than machining an entire new valve.

[Julien D]

Then you just deal with the thin part of the shaft below the gear shearing off. I have had as many fail due to that as I have from stripped gear teeth. The barrel part is fine, but it needs to be cut off flush, drilled, steel shaft pressed in, and then a pinion gear with a set screw affixed to the shaft.

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[Jaguar]

to leave the valves open or closed depends on the port timing and type of riding you do. I did both street and dirt and since I also raced motocross I epoxied the valves open. But for most people probably leaving them closed is best for put-putting around and woods riding.

[Roadhazardguy]

Yeah I think the 1st Gen valves are steel.