GOTTA have a 415 TRIKE/Industrial chain- half the weight and smaller plates- 415 size otherwise- BIG difference rolling- and if you can feel that much difference peddling- the motor's gotta be feeling it too-
Is your kit new?- I think they do get a little easier rolling with break in.
I personally also like to have a bike as reasonably equipped to something built to ride distance on- i.e. lightweight wheels- most important- fairly narrow tires, and a newer lighter cruiser frame- the vintage diamond ten speeds don't have a long enough top bar for a tank there and normal peddlin- but you can get a rear rack tank
I'm always sayin that my two builds probably pedal better than MOST regular bikes out there
Both are single freewheels now- I found I wasn't using the seven cog and rear derailleur on the one, here in flat Florida, and riding almost exclusively within several miles of home- so I dropped that weight and took those off.
I've done a number of things to keep the kit weight down- no tensioner, trike chain, alloy sprocket and bolted to hub so there's no rag joints with plates and rubber and heavy bolts- smaller tank- titanium bolts for the motor covers
It all adds up, peddaling especially, just like normal cycling