Middrive GNG Gen2 (2015) something is wrong, help please.

[gman1971]

I've been commuting on my newly built ebike for about 2 weeks and today at the end of the ride I noticed the motor was making a weird noise. So once I got to work I realized the motor wasn't easily moving backwards anymore, it used to be super smooth to move the bike backwards but now it feels like something is jamming it. Any thoughts? Where can I find replacement parts for this motor?

I run it with the stock GNG controller @48v, 12S, 12000mAh LiPo batteries.

Any advice would be appreciated. Thanks.

G.

 

[gman1971]

I can see when it comes to this things you're basically on your own... thanks for the great help! I figured the problem and turned out to be a broken motor shaft; which a local machine shop fixed and I am back on the road. Other issues were discovered after putting the motor back together, but I'll solve those as well.

G.

 

[Jackrabbit]

Broken motor shaft? Not a very common problem I would say. I've been running a couple of GNG kits over the last 2years and had no issues with them even at 2kw. What were the other problems you found? My brother has just completed a build using a GNG motor and a modified lightningrods kit so it would be good to know. Thanks.

 

[slowhands]

There is another discussion going on about this kit. In that one, the crank broke. This kit sounds like garbage.

Could it be that they are using very inferior materials? When the only thing you care about is low price, you might buy the cheapest not realizing it would break easily in normal use. Buy the cheapest, and you get to pay double.

 

[gman1971]

I fixed it; took a lot of effort and money but is now fixed and fixed well. I had to re-engineer a fair amount of the kit...

The first problem was the motor shaft; yes, shaft broke... why? Because someone in their infinite wisdom decided to use a 12mm to 6mm shaft step down to hold the massive amount of lever from the thing; and of course that little 6mm shaft end snapped, twice, so I had my local machine shop drill me a 10mm threaded hole inside the shaft and then push me a 10mm hardened socket bolt in there and then cut the socket head. Along with the 6mm shaft POS, the motor can used 2 el-crapo 6x15 mm bearings on the back end, so I replaced these with 4 new 10x15mm ceramic bearings so my shaft is now longer and the motor sounds a heckuva lot better than even when brand new! Haven't had any issues with the axle breaking since then. I also ordered a 12mm blank hardened steel shaft in case this 10mm shaft end broke, but looks like it is going to hold forever.

Then, after I fixed the motor shaft, then the square keys that allow the sprocket and the planetary clutch to mate/couple with the shaft sheared off, clean shear, both: first the one in the sprocket and then the one in the planetary gear. To fix this I made a dutchman round keyway and the motor is been handling the power like a champ for the past 2 1/2 weeks now.

Then the freewheel crank broke, so I had to replace it with a Cyclone 3 chainring freewheel... that one is been working like a charm.

The original BMX chain that came with the kit was crap and broke off; so I replaced it with a KMC chain and its been rocking without a hitch ever since.

The throttle hall sensor came undone, as in, one of the legs broke off and I had to order a new throttle to fix it...

Draw your own conclusions.

G.