8fun 350 Watt E-bike Motor—First Impressions and a Safety Concern

8Fun 350 Watt E-bike Motor—First Impressions and a Safety Concern.

The new 350 watt 8fun motor. This shot from the right side clearly shows the black plastic cap that hides the axle threads from view. Not clearly seen is how the wires exit the motor from the housing and not through a hollow axle..

Just on the market is this new 8fun offering for the E-bike world.   I recently got hands on experience with three E-bikes with this motor and a visible feel for one other.   Here is what I found, plus I also need to expose a potentially dangerous problem that could exist depending on how it is mounted to the bike.

First off, I think the 350 watt motor is the optimum size for most E-bikes.   A 250 can seem kind of anemic, were as anything much bigger just really isn’t needed.   This is just my opinion of course.   The wattage rating of the motor is just one indicator of its performance, but usually the most important one.   Finding the right balance of power and efficiency is one important key to having an E-bike to fit your needs.

This size motor can easily hold your bike at the maximum allowed speed for E-bikes.   Its hill-climbing ability is strong and solid.   The range of the batteries capacity is well served with this mid-size rated motor.   The only other 350 watt motor I have ridden, the BionX also showed sufficient power and range.   I just don’t see the need for more power.

All E-bike motors emit a certain amount of sound during use.   Direct drive (gear-less) motors are the quietest with the BionX being completely silent.   Most of the noise you might hear will come from the reduction gears that are used on the majority of motors.   The gears increase the torque (pull that will help you climb hills).   The two direct-drive motors I am familiar with are the Pedego and the BionX, (I am sure there are more).

Both those companies have some systems with 48 volts (as opposed to the more or less standard 36 volt) to help those bikes have a little better hill-climbing pull.   One disadvantage to a direct-drive motor is that it can have increased rolling resistance (drag).   Geared motors are better in this respect due to a one-way (sprag) clutch that allows easier free-wheeling when the motor is not activated.

Of the three 8fun 350 watt motors I rode, one was quite noisy.   It seemed that at certain speeds (the lower range), it started getting a resonance (vibration from the gear mesh) going that translated into excessively noisy operation.   One of the others seemed to get noisier as the miles went by.   It never became as bad as the worst one, but it might have been on its way.   Gears in E-bike motors can be made of fiber or nylon.   Gears breaking or stripping is also an issue with a geared motor.   Whether or not lubricant is added on the gear teeth is a good question.

Also too, on that noisy motor I noticed twice that the sprag clutch didn’t disengage.   Definitely something bad was going on inside that motor.   It performed fine during many miles of testing, but it did seem that a premature failure is possible.   I am sure that any problems with the gears and clutch will be squared away by the factory, as this is a great motor company that has their products on many, many bikes.   Up till now, all 8fun motors I have ridden were 100% trouble free.

From the left side, you can see the threads in question. Here, with no rack installed, the thread contact is fine. But with a thick rack support under the nut, a problem will exist.

Now to the safety concern.   This too I believe will be taken care of, but in the mean time it is up to your dealer and you to make sure it doesn’t affect you.   I found that on three of the four motors I saw, the front axle was not centered correctly in the motor housing.   In almost every instance, this won’t cause any problems.   The danger could occur if accessories (like a front rack) is mounted under the front axle securing nuts.   This could cause the nut to not contact all the threads on the axle.

On most E-bike conversions, they use a torque arm to help keep the motor from rotating in its mounting.   E-bikes from the factory use a squared off groove in the frame or fork and a axle that is slotted.   Either way, it needs to be well tightened to prevent the vibration and torque from allowing it to spin, come loose (potential crash)  and twist the wires (ruining the wires and causing a short that could lead to a fire or damage to the electronic system).

This new motor has the wires coming out the side of the housing instead of through the end of a hollow axle.   With no slot ground in part of the axle where the wires exit, it does allow more of the axle threads to contact the nut.   This is as long as the nut screws onto the axle far enough.

This motor has a large size set of threads that are more than sufficient to keep your motor and wheel secured to your bike.   But like any nut and bolt combo, the threads need to completely used to maintain the strength of the connection.   In the one instance (during the front rack installation), I removed the thick axle washer and it was still not enough to allow all the threads to be used.

One other factor in this problem is that a black plastic cap can be in place that hides these threads from view.   It should be pried off to do a visible inspection of the correct thread contact.   Plus, all the axle nuts should be checked for correct (tight) torque when the bike is new and every now and then as the months go by.

 
If your bike (any bike, not just an E-bike) is having this issue, have it taken care of before riding.   Your wheels need to be securely fastened to your bike (this should go without saying).   Checking all the fasteners on your bike should be something to be done several times a year.   Take care of your bike and it will take care of you.

The final thing of concern I noted on the threads of these motors was some fine metal shavings.   Probably due to over tightening and / or dry threads, these shaving were once part of the nut and axle threads.   If too much of the material gets ground away (from multiple tightening or over-tightening) then the threads will fail.   I use anti-seize thread lube on many of the threaded parts of my bikes.   It prevents this problem and also helps to lubricate the threads so the correct torque setting is easily hit,   The anti-seize helps keep corrosion from the threads that might make them seize together and cause the bolt to strip during removal or tightening.   Make sure to clean the axle and nut well before coating them with a small amount of anti-seize during reassembly.

Well, there you go, a fine motor from a great company that might still need a few bugs worked out.

Torque your nuts, Turbo Bob.

“To be a real city rider, you have to learn the streets and neighborhoods.   You have to know which streets are better to ride on, which ones are safer at night.   This can’t be taught.”—Keith Mills.

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About Turbo Bob's Bicycle Blog

E-bike Enthusiast Vintage Bike Enthusiast
This entry was posted in Bike maintenance, E-bike general interest, Opinion. Bookmark the permalink.

7 Responses to 8fun 350 Watt E-bike Motor—First Impressions and a Safety Concern

  1. RBS says:

    Where do you buy these hub motors in the USA? I’ve seen them on their site, but I have yet to find a dealer that sells them. Bafang seems to have a presense in Europe, but not the USA.

    • RBS, I really don’t know. So far, the ones I’ve seen are on complete E-bikes from China. I will look into it a little. They may only be selling in bulk to the bike makers.
      Thanks for asking, maybe I can find an answer, Turbo

  2. eric says:

    Hi Turbo Bob, this is Eric from electricbike.com. I really enjoy your blog. Is the 250 watt and 350 watt the same diameter of motor? Diameter is important for me because I am considering using one of these as a mid drive motor in the middle of a frame I have.

  3. Phil Lepak says:

    Good info on the 350w motor. I’m considering building some bikes to sell and the 8Fun motor seems like a good choice. Phil

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