Doodlebug of Doom: Saving a Superpowered Minibike


This helped, quite a bit, but it uncovered our next problem: the throttle cable hadn’t been lubricated in ages and was sticking in its sheath.  We removed the cable and sprayed in some WD-40 and ran it back and forth a few times.  After about 10 minutes of lubing and stroking, the throttle cable slid freely.  Once reinstalled, the throttle was a lot smoother.  Awesome!  The builder of this bike was smart enough to add a handlebar kill switch, very helpful if this bike ever runs amok. 

The chain guard is custom made and incorporates one of the mounts for our large capacity fuel tank.  We'd like to add a guard over the clutch, not only to keep our squishy meat parts away from the spinning clutch, but also in case that clutch decides to self-destruct.  It was definitely not meant to handle this kind of power!

Next, we turned our attention to the chain.  Our bike came with a chain, but with the motor out, the chain was not installed.  We looped the chain back on and found it was too short (this bike has seen a number of different gear ratios and this chain was obviously meant for one of the top-speed gearing options).  This wasn’t such an issue as the chain in our hands had seen better days. We picked up a new 10’ chain from Hot Rod MiniBike, a cool site that sells all sorts of minibike hop-ups.


The new chain was way too long and needed to be cut to length.  You can buy a special chain breaking tool, or if you have a grinder and a punch you can grind off the rivets and punch out the link like we did.  There is enough chain to make 2 and for us this was very helpful as we accidentally cut out first chain a link too short.  D’oh!  Our second attempt worked a lot better.  The chain is a basic #35 chain.  If you need your chain NOW, it turns out Tractor Supply has a nice stock of chains and master links.
Adjusting the chain tension is done manually with this idler pulley.  Setting the tension too tight will prevent the clutch from fully disengaging.  Setting it too loose will throw the chain.

With everything set, we finally went for a ride.  HOLY HELL THIS THING IS NUTS!!!  Barely crack the throttle and you’re doing 20.  On the first pass we found the brakes didn’t really work, so we turned back and tightened the cable.  We also adjusted the throttle cable to remove a dead spot that made rolling into the throttle impossible.  After a bit of tweaking, we were able to settle things down a little, but man this is one hair raising bike to ride.  Remember, you’re squatting over a tiny little frame with barely any brakes and no suspension.  You’re always on the lookout for bumps and holes because hit the wrong obstacle and you WILL go flying.  After a few minutes of riding, we never found what full throttle felt like.  We did however figure out where we need to spend money next.  


Getting the larger fuel tank installed is high on our list.  All things considered it is very nicely made, with good welds and solid construction that can handle trail riding.  There is only one real mount though and the previous owner's solution of “lots of big zip ties” really isn't good enough for us.  

First, we need new brakes.  We found a hydraulic brake kit that replaces the cable handle and caliper with a hydraulic one.  This should give us a good improvement in braking torque.  We also need new tires front and rear (our rear tire is nearly bald and our front tire has a slow leak).  We also need to install that bigger fuel tank as this is a very thirsty engine.  The carb needs some major tuning (the bike runs very rich and stumbles at WOT).  The throttle cable still sticks, but the housing and ends are all custom made for this engine, so we will need to modify a stock throttle cable to work.  We would also like for those lights to work so we can ride this thing with some semblance of safety (the wiring for them needs to be redone and of course we need to somehow power the lights which will likely mean a standalone battery).  Really though, this bike is everything we expected.  It’s crazy, fast, and just plain insane.  It’s a lot of fun too!  And once we get the gremlins figured out, we can surprise the crap out of scooter riders.

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