H series EFM Autoclutch into an E Motor

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dfeckel
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H series EFM Autoclutch into an E Motor

Post by dfeckel »

I recently bought a used EFM autoclutch for an H series KDX with the hopes that it would fit the E series motor in my hybrid. When I saw it pop up for sale, I did a bunch of parts fiche scouring to see if the H series and E series clutches were too different for this to work. The major parts which mount to the clutch, i.e., the transmission input shaft, crankshaft output gear, and the kicker gears were all the same part numbers between the E and H series motors, so I took a chance and bought the EFM assembly. Thanks to JoKDX220r for the sale, and also for including a set of fiber and steel clutch plates. :grin:

Here's a pic of the two assemblies side-by-side. As you can see, the H series on the right is significantly larger in diameter than the E assembly. Plus, the EFM pressure plate adds about 1/3" to the height of the assembly.

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In this picture, the H series basket is in place. Lo and behold, it fits!! All the gears mesh exactly as they do with E series basket.

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I was pretty nervous about the larger diameter of the basket interfering with the inner clutch cover. You can see that the clearance is tight, but I think it's adequate.

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If you're not familiar with EFM auto clutches, they add a custom pressure plate that has a ring of ball bearings that operate centrifugally. It's a nifty system, but it adds about 1/3" to the height of the clutch assembly. As a result, you have to add a spacer so the clutch cover clears the EFM pressure plate. Here's the major snag in my plan. The H series clutch cover is larger with a different hole pattern. The H series spacer definitely won't work.

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Plus, the H inner clutch cover must be a little deeper than the E also, because even with the H spacer resting on my inner cover, the outer cover won't reach. I'll need a bigger, E-specific spacer to make this work.

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There is no way to make the original clutch pushrod mechanism work with the EFM, so I may remove the clutch actuator shaft needle bearing and its seating area on my clutch cover to get it to sit further over the EFM.

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It's that needle bearing area that bottoms out on the EFM pressure plate. Even with that area relieved, I'll probably need a bigger spacer to get everything to clear.

I'm encouraged. I think it'll work as long as I can get an adequate spacer for the clutch cover. I'll have to call Garry at EFM and find out how thick the usual E series spacer is. I may just be able to use that off-the-shelf part instead of having one made.

So anyhoo, there ya go. I'll update as I get further along. I'm splitting the cases this winter (something in the tranny is spitting out a lot of metal--I probably damaged the little needle bearing on the end of the input shaft when I replaced it the first time--sigh), so I likely wont' have a ride report any time soon.
Last edited by dfeckel on 03:00 pm May 01 2018, edited 1 time in total.
David Eckel
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SS109
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Post by SS109 »

Thanks for the update and the excellent pics! I have a question that I hope you might try to answer just based on your observations. Do you think a stock H series clutch setup would work in the E and it's stock clutch mechanism?

Definitely keep us posted on what you learn!
Youtube Channel: WildAzzRacing
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Current KDX: '98 KDX220
Old KDX: '90 KDX200 -White/Blue
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dfeckel
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Post by dfeckel »

Good question. I don't have the stock H pressure plate, so I can't verify for you. However, I think it would work. I measured how far the fingers of the clutch baskets extend out from the inner clutch cover when the outer cover is off, and it is the same between the E and the H baskets. The only question in my mind is whether the pressure plate push rod rests in the same relative position for both the E and the H. If so, then you should be able to just bolt up a stock H assembly and use it with the E actuator arm.

One thing I didn't try is to fully seat the outer cover over the H basket without the EFM pressure plate in place. I'll try that next time I'm in the garage. If it fully seats, then I think the stock H clutch will work in an E.

This might make for a more economical auto clutch route for us E owners. Pick up a good used H clutch assembly and get a Dyna ring
David Eckel
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Post by SS109 »

>|<>QBB<
dfeckel wrote:This might make for a more economical auto clutch route for us E owners. Pick up a good used H clutch assembly and get a Dyna ring
I was thinking the same earlier but after you buy the H series basket, clutch plates/discs, and the Dyna Ring it would be about the same as the EFM.

The reason I say this is that I searched Ebay and there wasn't even one H series basket on there. Hell, there was only one for an E! So that leaves only new factory or aftermarket baskets as the only real option. :sad:
Youtube Channel: WildAzzRacing
AZ State Parks & Trails OHV Ambassador - Trail Riders of Southern AZ
Current KDX: '98 KDX220
Old KDX: '90 KDX200 -White/Blue
'11 GasGas EC250R
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