Dark Matter – Bullseye Monster Pro DIY Biktrix BBS02 46lb Single Track e-bike $2049 w/ out Battery


Dark Matter – this Bluto BBS02 build provides the ultimate street legal trail-riding experience

I have been procrastinating for months about buying a Bluto Front suspension fatbike to convert. When I finally broke down and did this build the results were astounding. The biggest problem I have found with the Bluto fork (review here) is how hard it is to go back to all my other rigid framed bikes for trail-riding after several weeks of riding Dark Matter.

When riding on snow you can carve up the trails like butter and when there is a few inches of powder everything feels like you are just floating on silk (until you wipe out). When the snow melts and you go back to hit the single-track every bump makes you feel like your teeth are going to rattle out of your skull. Deep inside you miss that feeling of miles of endless powder.

The Biktrix converted drive unit ships with it's own BCD104 adapter shown here with a 34T Raceface narrow\wide ring

The Biktrix 100mm converted drive unit ships with it’s own BCD104 adapter shown here with a 34T Raceface narrow\wide ring

I decided to spring for the cheapest Bluto forked fat-bike I could find, the Bullseye Monster Pro for $999 at Bikes Direct. When you consider that the Bluto fork is really overpriced at $650 retail ($500 street price) this bike starts looking like a pretty good deal. Although I prefer the Boris for the much lower stand-over height and the higher end components I didn’t want to spring for the extra $200 for a Boris X9 Bluto. Yes I really am so cheap that I will save $200 to repeated smash my nuts on the toptube.


The Bullseye Bluto Pro sports a X7 derailleur and BB5 cable brakes which is the cheapest level of components I will generally trail ride with

The tires that ship with the Bullseye Bluto Pro are the ill-famed VeeRubber Vee 8 which has the dubious distinction of being my least favorite fat-bike tire ever. I swapped the front out with a 120tpi Vee Rubber Bulldozer and the rear is a 72tpi Surly Nate (both ghetto tubeless). These tires are a vast improvement over the stock tires and generally run about $100 each.

I'm not crazy about the C961 mostly due to it's lack of a watt meter

I’m not crazy about the C961 mostly due to it’s lack of a watt meter, the C963 is my favorite.

This build was done with a 34T Race Face Narrow\Wide ring but would work well with any front ring up to 42T. I like much lower gearing because I’m often climbing up impossibly steep grades. If you were using this setup more on the road for commuting a 42T Lekkie Bling Ring might be advised. If you opt for the Lekkie you should spend 90% of the time singletrack trailriding in the 36T granny so as not to tax the BBS02 unnecessarily. On the road you can use whatever gear you want as long as the pedal cadence is fast.


It’s all about the fork, nothing else currently on the market can hold a candle to Bluto

The cheapest you’re going to get away with on a build like this is around $2049 not including shipping and battery cost ($1049 for the Biktrix 100mm drive unit and $1000 for the bike). I would plan to spend another $200 for decent tires if you plan on taking the bike anywhere except on pavement. With fat bikes it really is all about the tires.

Featherlight for a Bluto forked bike at 46.5 lbs without the battery.

Featherlight for an electric Bluto forked bike at 46.5 lbs without the battery.

When I finally weighed the bike I was pleasantly surprised at it’s weight. For the benefit of having 10 gears it’s not too much heavier than my lightest build, Duh Banana Bike. When it comes to sourcing the battery I would recommend a 48-52v pack that can do at least 25 Amps sustained from Eric (of electricbike.com) at LunaCycle.com. His US built packs are very competitive with Chinese packs, and much cheaper when you factor in the outrageous shipping when buying batteries from China.

Looking back I wish that it hadn’t taken me so long to buy and test a Bluto fork. This bike has changed the way I look at single-track trail-riding with fat-bikes forever.

Dark Matter … Why in the world did I call this build Dark Matter?

Does it really matter ?

Ride On.

23 thoughts on “Dark Matter – Bullseye Monster Pro DIY Biktrix BBS02 46lb Single Track e-bike $2049 w/ out Battery

  1. I did a similar , less expensive build .
    gravity bullseye monster pro , scratched but new $ 949 shipped
    generic yescomusa – 1000 watt brushless direct drive motor – $195 shipped
    LYEN 12 FET controller- $129
    48 volt – 22AH lifepo4 shipped/ new $420 { 30 amp constant- 60 amp bursts}

    so for around $1700 total, it can do top speed of 36 mph on flats and with me programming the LYEN controller to handle 60 amp bursts , I have enough power to ascend all the local inclines on our roadsystems , some of which are 4% grade or more.


  2. You mentioned you would like the Motobecane Boris more, would it be the same parts and performance-wise as the conversion on this bike? This is literally what I’ve been seriously looking at doing, between a Bullseye Pro and a Bluto-equipped Motobecane. I’m not so familiar with all the hardware compatability, so I appreciate your article 🙂 Thank you!


    • The Boris has a lower standover height so when you’re riding in powder and have to put your foot down and it goes through a foot of powder your nuts don’t take a beating on the top tube. The Boris also looks a lot nicer. The component spec between the Boris and the Bullseye is pretty similar which is why I went with the Bullseye Pro. I have no intention of taking my precious Bluto fork out in the snow.


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  7. Planning on this build with BBSHD. Would the 100mm or 120mm be a better choice. I have already built a hardtail up with the standard size BBSHD and love it so much I want a fatty now.


    • This is my current favorite ride. Every time I go out on it I have so much fun. 100mm BBSHD will work fine. Right now the best option for chainrings is the Luna Eclispe. You will have to space it out a few mm. Make sure to pair it with a 52v pack for the maximum punch. The 52v shark pack with the high power pf cells is a good match.


      • Thanks for the reply Karl.

        I’m gonna try and save money and use the battery from my hardtail-52v 20ah from Luna, maybe buy a smaller 52v pack at a later date. I’m still waiting for my Eclipse to ship from the last build. I haven’t had any issues at all with the stock ring on my hardtail so maybe I’ll leave well enough alone and use the Eclipse on the Monster when it arrives. Would a Bulldozer fit on both front and rear of the Monster? We have tons of snow right now.


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  10. Okay Karl,
    Im doing the checkout on the luna bbshd, 52v ga shark.
    Now i need to decide which bottom bracket. 73-100 or 100-120??
    The standard display good enough?
    42 tooth gear?
    gear sensor?
    programming cable?
    charging unit?
    If I am going with your preference.. I might as well get all of it..:)


    • I would buy the 42T luna eclipse ring and if the BB is 100mm then go with the 100-120mm unit.

      I did an article on the gear sensor, I don’t like them that much but other people swear by them, programming cable is a must and get a luna charger if the GA shark does not come with a charger.


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