Sun Kiss – Deadeye Monster DIY BBS02 42lb Single-Track Snow Machine $900 (w/o Batteries)


I added a Nexus 3 IGH to this bike after about a year of thrashing on it, and it was worth it. Review is here.

I went for a ride on my newest build and was incredibly happy with the results. This is my third BBS02 fatbike conversion and I have to say it is probably the best yet. Although the donor bike is a single-speed Deadeye Monster, I found that with the proper gears in the front and the rear, the motor had enough speed range that I didn’t really need to shift. Riding along on snowmobile tracks at 30 mph completely out of control can be fun, but it’s nothing like singletrack through the woods. When biking through powder that is more than 6 inches deep you need a lot of power. Although my singlespeed tops out at about 20mph on the flat, I never found myself wanting to go faster than that in the woods. At

‘It felt like what fatbiking through the woods in a lot of snow SHOULD feel like’

So far I’ve converted 3 Bikes Direct Fatbikes to a BBS02 drive unit. I purchased a Boris X9 and a Bullseye Monster with the intention of grinding off the BB and mounting a BBS02 on them. You can imagine my disappointment when both bikes showed up with a bottom bracket/chainstay intersection that looked nothing like the pictures. I blame it on frame sizing, since I am 6’10” I always order the biggest frame I can get. Since manufacturers always keep the chainstays about the same length, everything else on the bike has to change. This leads to bike that are more rear tire heavy than their smaller framed counterparts and the whole triangle gets pushed back towards the chainstays thus moving the chainstays out to the edges of the BB.

Looks p

Bullseye Monster looks perfect for an angle grinder and a stock BBS02? Don’t bet on it.

The Deadeye Monster is the only 4″ tire fatbike with an aluminum frame that I could find for <$400 shipped. I bought mine from Bike Island for only $300 since it had scratches all over the frame and the front brake was knocked off and the fork was pinched. The Deadeye Monster comes stock with a 68mm BB which is perfect for an unconverted BBS02. The bike arrived again with a Bottom bracket that looked NOTHING like the picture on the website. Luckily on my bike there was a dimple on the chainstay that was more or less exactly where the BBS02 had to rest against. Modifying aluminum frames is huge pain when compared to modding steel frames, but they tend to be much lighter than their steel counterparts.


Deadeye Monster, don’t expect your BB to look anything like what is shown on the website, it won’t. But it will still work for a BB02 drive unit.

The Deadeye monster weighed in at around 32lbs before I swapped out the tubes and the seat and added the 9.5 lb BBS02. The chain was nice and heavy and both the freewheel and the chain-wheel were both steel. Getting the BB off was a real pain. There seems to be a direct correlation between how cheap a bike is and how hard it is to get the drive side Bearing Cup off it. I couldn’t do it with a giant impact wrench and I didn’t want to use heat so I put the bearing cup removal tool tool in a bench vise and used the bike frame as a lever. That seemed to work, although there was so much force I ended up moving the entire workbench. Remember the drive side bearing cup is reverse threaded so you need to go clockwise to loosen. My Bearing cup removal tool was not deep enough to grip the threads so I had to borrow one with a longer reach from my partner in crime Larry at Boxy Bikes.

It doesn't quite fit, but it's good enough with the chainring dimple there.

It doesn’t quite fit, but it’s good enough with the chainring dimple there. Notice the BB/chainstay intersection does not look anything like the pictures above.

When mounting the BBS02 it won’t totally go all the way on, which is fine. You will need some washers to space out the mounting screws on the opposite side. The mounting plate must be flush with the BB housing. Also make sure the side of the plate with bumps faces in towards the BB. Use blue Locktite on everything.

The Non-drive side will need to have an offset crank mounted on it so that you can clear the chainstay without hitting it. I got mine from Doug at California E-Bike, although they are not listed on his website. They are slightly heavier than the crankarms that ship with the BBS02 so I would only replace the one on the non-drive side.

You need to grind down the cheaper adapters so the chain will settle all the way down on the teeth.

You need to grind down the cheaper adapters so the chain will settle all the way down on the teeth. The more expensive adapters from California E-bike will not need to be ground down to fit a 32T ring.

The chain-wheel that comes with the bike doesn’t fit quite right on the chain-ring adapters so you’ll have to use a grinder on the chain-wheel or the adapter to make it fit. The 32T steel chain-wheel that comes with this bike is a very good match for trail-riding and 6-8″ of snow. Use the 22T rear cog unless you want a street machine, for a  higher speed commuter you can use the 18T rear cog that comes with the bike.

You will need one offset crank on the Non-drive side.

You will need one offset crank on the Non-drive side. Notice the washers used to space out the mounting plate.

Singletrack 32T front/22T rear ~15mph top speed chains or deep tread tires(like the Lou), get the 4×100 model from Slipnot and add the spacers with the repair kit and they will work, or better yet build your own for about $15). You will have enough torque to climb a 10 degree incline at about 8 mph. You will only pedal on really steep inclines, most of the time the motor will spin too fast.

Road high Torque 42T front/22T rear ~19mph top speed

Road high Speed 42T front/18T rear ~22mph top speed

Road higher Speed 52T/18T rear ~26mph top speed fried mosfets.

Have it all – Nexus 3 IGH high 20’s top speed, tons of low-end torque.

Read it and weep, battery not included

Read it and weep, battery not included. Wow look at that pile of bike crap on the table! Do people really live like that?

I’ve tried all kinds of configurations for trail-riding but there is none that compares to the BBS02 (see why here). The problem with going with a single-speed is that you lose all the benefits of having a mid-drive unit. For another $350 or so you could throw in a Nuvinci rear CVT hub. I’ve heard that the Nuvinci was only designed to deal with about 60nm of force and the BBS02 can put out about 120nm. I recently purchased a commuter fatbike that I plan on installing a Nuvinci N360 on and will post a build thread when it is done.

The Deadeye monster has a pretty narrow front fork, so don’t expect to put anything bigger than a 4.5″ tire on it and still have enough room for chains. I was able to squeeze a Surly Lou on the back which is the king of fatbike tires. Because the Lou has a 7mm very aggressive tread pattern you will not need chains with this tire. It is slightly heavier at 1585g than the Vee-Rubber Mission 4, but well worth the weight. A great list of fat tire weights can be found here.

The best rear tire I have tried. No need for chains with this beast on.

Surly Lou, The best rear tire I have tried. No need for chains with this beast on. It won’t fit on the rear of the Boris X9 or Bullseye Monster, but plenty of room on the rear of the Deadeye Monster.

With everything except the battery my bike weighed in at just under 42lbs. Figure another few pounds for a LifePo4 16S2P pack and your are still under 50 lbs, a featherweight for an electric fatbike. You should get about 90 minutes of riding unless you are plowing though a lot of powder then your riding time could be cut down to 45 minutes or less. Deep snow has an insatiable appetite for Watts.

For a battery pack get something that is 48V and puts out at least 30Amps continuous. The highest I’ve ever seen on my watt meter for the BBS02 is 26Amps, but you don’t want to stress your BMS (if you use a BMS at all which is recommended). 12S2P Lipos from Hobbyking are a good option if you know what you’re doing. If you don’t really know what you’re doing, then I’d go with a 16S2P Lifepo4 pack as they don’t explode as easily when mishandled. A nice 25R frame pack from em3ev is another excellent choice for a little more money. The only Chinese vendor I recommend for the 750W BBS02 is Paul at em3ev at $499.

For instructions on how to mount a Bluto onto a Deadeye Monster which does not have a tapered headtube check out this post.

For step by step instructions installing a BBS02 look no farther than here.

UPDATE: The newest Deadeye Monsters ship with a 100mm BB & 80mm rims (ignore the specs on the website). Your best bet is a BBSHD 1000W system.

Ride On.

61 thoughts on “Sun Kiss – Deadeye Monster DIY BBS02 42lb Single-Track Snow Machine $900 (w/o Batteries)

  1. Nice ride! I’m thinking that the mac hub motor might be a better match for the single speed, unless of course you intend to change your gear ratios manually as you mentioned.


  2. I have heard of some one mounting a front derailleur to a bike with a BBS02 so that they could have 2 or 3 different ratios even though they only had one gear in the rear.

    Karl, have you done any experimenting in that area?


  3. This has really been a great read. Thanks. I am going to try a nexus 3 speed igh…if you dont shift under power it might work. Dont know what gears to run because the spread is wide for this IGH. The Nuvinci works but is not very efficient. I think a puesdo fat bike frame with a single speed converted to some IGH would work…If the fat E bike market takes off I am sure they will make a 3 speed strong enough. I am in Florida and would do all my riding in the sand…..much like snow I imagine. Thanks again for the great read!


  4. Talking to very smart people… is what I believe…Tesla is the reason they all say the E motors are a waste with gears for hub motors. Tesla spent millions on testing a two speed…..they are back to a single speed because of the E motor characteristics. Constant torque is the big reason. So if was going to have a hum motor it would be at least be a geared motor with lots of amps thrown at it… a MAc with 1500 watts…..would not need any gears….but I dont like the wheel lacing pain etc…..I think the bafang with a few gear selections would be the best and least hassle……..I have one I will try soon with that IGH…Thanks again


  5. Karl, I think this is your best and most important article so far! Awesome work. You’ve done all the research for the builder, and provided all the details to copy it. This combo would be my number-one E-fatbike recommendation.


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  11. Thank you for the post Karl. I found this after I ordered a Deadeye (3″). This is my fourth build so my only problem was getting my chainline straight. I managed to get it spot on. I am just waiting on my battery and I’ll post some pics.



    • I bought myself a deadeye (non-monster with 3″ tires) because I have tons of 4″ tires laying around and it was only $250 from bike island. Going to build a commuter with a nuvinchi drive on it and if I don’t destroy the nuvinchi using it for street use I’ll try it on the trails. Will post a build thread in a few weeks. Stay tuned.


      • Guess that’s what I’m going to try for the moment, too. The Monster is sold out everywhere (???). So I better start with a not-so-fatty with less watts.


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  17. Hi Karl,
    Tanks a million for sharing. Your personal blog is very inspirational, too.
    Thanks to you my e-fatbike plans are finally taking shape.
    Too bad the Gravity Monster is out of stock. Need to settle for a regular Deadeye.
    Want to couple it with a Nuvinci and a Bafang.
    Still got loads of ???
    BBS01 or 2 or BBT?
    How much Watt, battery voltage and Ah (flattish muddy environment for the most part) would you recommend?
    Offset crank needed?
    Please keep on typing as much as screwing, riding and building,
    Love & peace,


    • The regular deadeye will only support 4″ tires in the front and rear. The monster will fit a 4.8 in the rear barely but just a 4.0 on the front fork. Both weigh about the same. The 3″ tires that come with the regular deadeye are not really fatbike tires, I would put some decent 4″ tires on it if you want to really ride it.

      Nuvinci are heavy and the only one that will take the 120N of force is the N171 which hasn’t been made for about 6 years. The new N360 will only work with 250W or less otherwise you void the warranty. BBS02 750 No question. Unless you want to commute just use the rings and cogs that come with it. Get a cheapo adapter Ballarat Ebikes is the cheapest ($25). You will be fine in the woods. For battery any 48v battery from em3ev will work well, I would get the drive unit and a Samsung 25R frame pack from Paul. $975 before shipping You will need a slightly offset crank for non-drive side. About $20-25 from Doug at Cali-ebike or Chris Lectric Cycles.


  18. Hi Karl,
    Thanks for all the cool tips.
    Tire size is OK with me though front and back could be swapped (fat front).
    For the rear I have got a very knobby NOKIAN GAZZALODDI 3.0 from a previous experimental hybrid built. On a 80mm rim it should be huge enough?
    Found an NV171. Am taking the advice seriously as I have ruined an SRAM 5-speed with 32 teeth in front previously.
    Why BBS02?
    Adapter? What do I need an adapter for?
    Watt-wise I’ll probably settle for 500W.
    Why 48 instead of 36W?
    How much offset will the crank probably need?

    Thanks & wride on!


    • The N171 is heavy, mine is 8lbs
      BBS02 is the best thing I’ve found, 750 only, don’t waste your time on the 500 (same unit programmed for lower power). Only 48v. Small offset crank, it’s only about 2-3 cm of offset.


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  24. As of at least 11/12/15 the Deadeye Monsters now have 100mm BBs, larger indents in the chainstay so there is no contact with a BBSHD and there is no longer any need for an offset crank arm on the L/H side with a BBSHD. Plus everything fits with no need for spacers or shims. It was like the bike was built for the BBSHD: Plug and Play, no mods or extra parts beyond a longer chain (7 links IIRC). I got a black bike and it all looks factory made, NOT kit like at all.

    BTW the Luna Cycles triangle bag with their 52v triangle battery was a very tight fit on a 17″ frame, but ended up being perfect after I removed the screws from the bottle mounts. Smaller sizes beware: the 20ah battery might not fit.


    • The rear cog is quite close to the chainstay already. I looked into doing that, but I don’t think it would work very well. Your best bet is to go with a Narrow\wide chainring and keep the chain tight. It won’t fall off. Much.

      I lose mine about once a ride which is about all I can tolerate. Usually on steep climbs.


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  27. Karl, I just repeated your Sun Kiss build with a 2016 Deadeye Monster (17″) from BikesDirect and a BBSHD / 52v shark battery from LunaCycle. The bottom bracket on this 2016 Deadeye Monster is indeed 100mm and the 100mm sized BBSHD slid right in with no hassle. Even removing the existing BB was cake. I’m pretty handy but I’ve never worked on bikes much. I bought a $50 bike tool kit and it had everything I needed to do the conversion. The shark style battery fit on the downtube using the water bottle mounts with only a very minor mod to the supplied battery holder.

    Thanks a ton for figuring out all of the hard parts of these conversions and documenting it for all of us to benefit from. My new Deadeye Monster/BBSHD build is a blast. I’ve looked at a lot of manufacturers e-bikes and this build is better than any prebuilt bike I’ve found for way less money. I’ll probably add the Nexus 3 IGH and Bluto shock at some point soon and then I’ll have near perfection.


    • Do the Nexus 3 conversion first. You can probably use the same spokes if you go from double cross to single cross. It only costs about $125 for the whole shebang and it is worth every penny.

      Bluto fork is nice but has major problems in the extreme cold. There is an article about adding the Bluto on a Deadeye monster using a cane creek bearing adapter, read that before you buy a Bluto.



    • David, do you have pics of how you got the shark battery to fit on the mounts? I have a dolphin pack that I want to fit, but it’s just too large. However, I think altering the battery holder might do the trick if i could slide it in from the side.


      • Joshua, The Shark battery holder mod was very minor and really all I had to do was drill one new hole so I could position the holder about 1/4″ higher so that my battery could slide all the way to the bottom of the holder and lock.

        ——— Nexus 3 Internally Geared Hub – Install notes ———–
        I added the Nexus 3 IGH this weekend to my 2016 Deadeye Monster 17″ and man it rocks! It has all of the pluses that Karl mentions in his post and I love being able to pedal along at higher speeds. My wheel came laced as a 3 cross and after reading up on lacing wheels I decided I wanted to keep it that way. I figured I’d have to get my spokes shortened and re-threaded (50 cents each from my local bike shop), but in the end only a few of the spokes protruded slightly above the nipples so I was able to just grind those down flush with the top of the nipple. I laced the wheel myself but I had my local bike shop true the wheel for $15 which was money well spent. The drive side spokes on my wheel are a few mm shorter than the other side, so keep them separate when you breakdown your wheel.

        I added 3mm of spacers to the right side of my bottom bracket to slide the BBSHD over so my Luna Eclipse chain ring had enough clearance. After adding the spacers, the two sprockets line up very nicely and I didn’t have to make any adjustments to the rear wheel at all.


        Liked by 1 person

    • Hi David and Karl,
      I was all set to follow the sun kiss build too, with either the older 68mm bb monster (I have one), or the newer 100mm bb version, paired to a Nexus. But then I saw Karl’s update at the bottom of this article suggesting the BBSHD DOES NOT WORK with the Nexus. David, did you try this with the 100mm bb monster? Have you encountered any chainline problems with your setup? Karl, is there a tried and tested monster (old or new, or other fatbike?)/IGH/motor combo that definitely works well? Thanks very much for posting such great information!


      • Karl’s Update here: Update: I’ve spent many hours trying to get the BBSHD to work properly with the Nexus3 IGH on a Deadeye Monster with a 68mm BB and have finally given up. No matter which chainwheel I use and how I try to line up the rear cog I can’t get the chainline to work well enough so that it doesn’t fall off at least once per ride. You might have better luck, but I doubt you will as the 100mm version of the Deadeye Monster is going to have a chainline that is even worse. I cannot recommend the Nexus-3 with the BBSHD on a fatbike frame, although it should be fine on a normal bike frame.


      • Wait…I’m an idiot…just saw David’s later post. Seems like the 3mm spacers are the key…?! So best build is: 100mm Deadeye Monster + BBSHD + Nexus with spacers! Right? Any suggestions on alternatives before I start this? Karl, did you find a 170mm bike that works well with SA?


      • Josh from Lunacycle also had a Nexus-3 on a Deadeye Monster. He ground a little bit off the case with the dremel to clean up the chainline. Seemed to work fine. There is a sprocket for the rear for the Nexus 3 that has a guard on it, which I find helps to keep the chain from falling off. Part # CS-S500 comes in 18T or 20T

        It’s about the cheapest build out there that is good, at this point I’m in love with the Ludacris 50Amp Luna BBSHD controller. Running it at 60 amps and still no failure. Unfortudently you can only get one when you buy a BBSHD bike from Luna.



      • Thanks Karl. Do you know how these set-ups fare in subfreezing temperatures? Can the bike be parked outside in subfreezing? Guessing not a good idea to freeze the battery – easy to remove? Can motor be left outside in the really cold stuff?


      • I’m very happy with my 100mm bb Monster, BBHSD & Nexus 3 setup. The chain does fall off occasionally so I guess I don’t have perfect chain alignment even after the 3mm spacers. After reading about Josh from Lunacycle grinding down part of the Nexus 3 case with a Dremel to get better alignment, I may do that too. Here are a dozen pics of my build shared on dropbox;


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  31. David I am just starting the identical build as yours. Can you post here (or email me if you cant post) a couple photos of your build? Specifically interested in the 3mm spacer on the right side of bottom bracket and the Nexus install/alignment/spacer configuration in the rear dropout? Thank you, Scott


    • Hi Scott,

      I took a bunch of pics but don’t have a place to upload them just yet. Regarding the spacers; I just stopped in my local bike shop and picked up 3 of their 1mm spacers. I slid off the bbshd and put them on the part that slides into the bottom bracket. Then I put the bbshd back on my bike and the alignment was great. I learned that I needed the spacers the hard way. The new chainring chewed into my aluminum frame a bit before I caught it. I can send you some pics if you’d like.


    • Sorry Scott, I don’t have any of those forks. The Wren is good and does not have the cold weather problems. Tested extensively by Roshan @ Biktrix. The RST renegade is a great budget fork that is tapered, there is an article on my site for mounting a tapered fork on the Deadeye. That ebay fork looks generic, it is also a 1 1/8″ tube and the deadeye is 1 1/4″ HT so you will need a different headset. I would do the RST or Luna fork with a cane creek headset adapter.


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