Demise of yet another HT, considering Flying Horse electric start


Oct 30, 2011
Seattle, WA
Happily broken in, my fairly new HT 66cc was performing very well, carrying my 250# self up very steep inclines and running smoothly overall, when 2 head bolt holes became stripped out. After ahell-coil repair of said holes, I proceeded to brake a piston ring during reassembly. I replaced that and was satisfied with my work, the head bolts took the necessary torque and thus I began my first ride post repair, the engine started, I released the choke & as the engine began to rev, thee was a sickening sound & the engine gasped and stopped. The piston is totally fused to the cylinder, thus far I've been unable to free it, but furthermore, the clutch seems to have failed as well, I get no repression from the motor, the wheel & chain spin freely. In other words, this particular iteration of the "riquimbly Dervish" model 3.3 is sadly gone. I have this one & 2 other complete (though disassembled) engines that I'm considering attempting to fabricobble a single working engine from. Maybe. Or maybe I'll scrap the whole thing and get a Flying Horse Bullet Train. I've heard good things. I'm frustrated with the unreliable nature of the HT, at one point tardiness due to maintenance actually cost me a job! I understand these are not motorcycles, and we're subjecting bicycle frames to forces they were never designed for, coupled with the nature of the cheap manufacture methods of the motors, lacking in any meaningful quality control, adding to all that the questionable adherence to EPA regulations and dicey, arguable legality of importing these things, none of this points to quality, reliability or consistency. Needing to keep project construction costs as low as possible, options are scarce. There are inexpensive 4 stroke options, but those are at 49cc for the most part, weighing what I do and the enormous hills I live nearby calls for greater displacement. There are the Harbor Freight 212cc 4 strokes and kits to adapt them, but at that much displacement it's just too damn close to a motorcycle, and all the insurance and registration and license headaches. Electric options are very attractive, but battery prices must come way down first. I believe that batteries are in fact becoming more affordable but they are still outside of my grasp. Whizzers, Cruzzers and the like cost far too much. I've read a lot of good things about the 2 stroke Flying Horse 66cc Bullet Train, centrifical clutch and electric start. Adding my horn, turn, brake and headlights and quite possibly a sound system seems doable on this kit. It hasn't been on the market too terribly long and I have yet to see parts and accessories available. The $300 price tag puts it way up at the higher end of possible for me. I'll take the opportunity to upgrade my fork, brakes & handlebars, but the chromoly mountain bike frame from my 1985 Fat City Cycles, "Fat Chance" model is up to the task of housing the power plant and accessories.
Well this was a bit of a longer ramble than I had initially intended, sorry about that, though thanks for reading & please let me know your thoughts!


Well-Known Member
Mar 15, 2012
Santa Barbara, CA
You should know that not all HT engines are the same. Watch these videos from Fred at CR Machine as he explains the differences.

I prefer the PK80s to the GT5s personally. They have the shorter caged connecting rod and the lower wrist pin location on the piston. They allow for a smaller squish gap and more compression. Check out the F80 ones at thatsdax (scroll down this page to see them):
Also, if you notice that Dax can call them 69cc instead of 66cc, with a 40mm stroke instead of 38mm stroke. They have balanced cranks with less vibrations.They are just better engines. Also, Dax checks them out before sending them out and they use decent bearings, plus, you got to respect a man who answers his own phone and is more than reasonable to work with. I have over 1700 miles on my engine and it's running better than ever.


Well-Known Member
Sep 30, 2012
not sure PK80s are still being produced with the 38mm rods - my last order had PK80 stamped on pallet, but had 40mm rods like the A80 - nice motors tho