CSC 20" rear 7-spd geared 36V eBike kit issues
 

I've bought a CSC brand 20" (NOT-fat) rear 7-speed geared 36V 500W kit on Aliexpress.com (because I couldn't find a good domestic source for a normal-width 20" rear kit that I liked) for a Sun EZ-1 steel-frame 3x7-speed recumbent bike. Everything appears present in the box. I'd recently assembled a 26" rear geared 36V 500W kit from ebikeling.com onto my Sun EZ-Speedster with little difficulty, so I thought I'd upgrade my wife's EZ-1. I have problems (apologies if I misstate part names).

1. The original wheel with 7-speed cassette fit great of course. Removed & I place the new hub motor with spin-on 7-speed cassette with freewheel into the dropouts, the smaller-outer 14T gear rubs against the frame, even with 2 washers on each side of the motor axle inside the frame. The spin-on is snug very tight. I don't really want to file away frame metal or introduce a 3rd inside washer there.
2. Experimentally I spun-off the 7-speed 14T kit cassette & spun-on a DNP 7-speed 11T cassette. Because the 11T is smaller diameter than the 14T, the gear clears the frame nice, but the cassette hub lightly rubs the dropout. I think I can file a little off the cassette hub edge to get decent clearance from the dropout. I'd really like to use this 11T gear so that pedal assist is still possible at higher speeds (too many teeth make it impossible to pedal fast enough to help at higher speeds.
3. The main baffler is the wheel is way offset from left-right center of the frame with 2 washers inside each dropout. I have linear-pull brakes, I'm no expert, but can I adjust the pads to brake a wheel very much off-center? I've double-checked, the original wheel sits perfectly centered.
4. I think the empty, unsprung rear dropout width is about 133mm. It's a steel frame & with little spreading effort, the hub motor +2 +2 washers fit OK.
5. I'm guessing one way to get the wheel centered is to use a cassette of fewer gears. I'd never need the largest gear on my DNP cassette. Can it be disassembled, largest gear removed, reassemble it all & have a 6-speed cassette that is roughly 0.25" less wide? I could use that narrower cassette & washers to properly center the wheel. Can my DNP 7-speed cassette be modified to be a 6-speed? Please advise or point me to instructions/videos. Or let the bike shop mech tweak it for me?
6. I'm not allowed to post pics yet, but trust me, I've got the pics.

If the rear cogs spin on it's a freewheel, not a cassette.

Thanks for clarification !

I'm in an email dialog with the CSC Store contact now. He suggested I can correct the wheel off-center with an extra washer on a side, but it's already pretty hard to spread the dropouts enough to fit the 4 total washers I have on there now. I may consider the threaded-rod/washers/nuts cold-set process of gradually stretching open the dropout spacing, but I don't think making room for a 5th washer is enough.

I think dimension-wise, this hub motor + 7-speed freewheel combination is just too wide, by roughly 1/4".
I don't see a potential solution other than a freewheel that takes up less width, so the wheel/tire can move to center.
I don't care that I loose some hill-climbing ability in a gear I won't miss.
I could order a 6-speed freewheel, but can't find one with an 11T gear (yet).
I'm going to drop by my bike shop & inquire about disassembly/reassembly of my DNP 7-speed freewheel less the largest diameter gear.
I think I'll have some exposed hub that I can grind-off near flush & have a working solution maybe today.
Wish me luck or throw me some advice/comments, thanks.

1) You can move the wheel over by tightening the spokes on the side you want to pull towards and loosening the other side. Very easy as long as you adjust both sides equally.
2) It's possible to locate 6-speed freewheels with smaller gears; they'll be NOS and may cost $50 - $ 100 on ebay.

den458, although I'm reluctant to ever disturb an alloy frame, I'd have no problem adding a washer to the hub to clear the freewheel on a steel frame.

What you need to do is called "dishing" the wheel. It's a term made by wheel builders to move the rim over. Anyway, loosen all the spokes on one side 1/4 turn. Tighten the other side 1/4 turn. The rim will move surprising far. You might have to add a little more on the tightened side to keep tension. Be methodical and it's not bad. Many people try to keep the tone on both sides the same, when a spoke is rapped with a tool, as a means of determining the tension.

In the past, I'd often try to mount a wheel skewed in the dropouts so the rim would be centered between the caliper pads. After I learned about dishing, I saw how little I knew about wheels.

Hopefully it will move over enough. If not, they screwed up when they built the wheel, as the spokes usually have to be different lengths to center the rim for wheel that includes a cassette or freewheel.

You can check Sheldon Brown's tutorials or go to utube if you need more instruction

Update on my EZ-1 20" rear geared build: I'd shared earlier that my rear wheel with freewheel was not well-centered in the frame. I'd hoped to address that by disassembly & reassembly of my DNP 7-speed freewheel, such that leaving out the biggest ring & spacer would result in a thinner but useful 6-speed freewheel. I had it apart & reassembled as a 6-speed but the design wouldn't allow me to fully snug the gears tight using the lockring, due to limited hub thread depth.

I've searched pretty exhaustively for a 6-speed freewheel with an 11T small gear. IT DOES NOT CURRENTLY EXIST to my knowledge. I contacted DNP about my wish for one, they acknowledged my request, said they'd get back to me, we'll see.

Plan-B, I used a threaded rod, nuts & washers to stretch the dropout width by 10 mm so that additional washers needed to better center the wheel would fit. The wheel is still not perfectly centered, but way better. It remains to be seen if the center-pull brakes can be adjusted to accomodate the wheel location, or if I will still need to "dish" the wheel some, or not. More as time permits...