Vanguard V twin engine modded for minibike

#21
I'm not sure that Chinese trashed engines are any cheaper than the Japanese they copy, nor are any able to just unbolt the trans and add an input sprocket. Substantial cutting, machining, and welding were required on the few I've seen done. The 2-stroke single would have a clutch, oil-tight trans with integral clutch, and would only require adapting a sprocket to replace the stator, removing the rod and pressing crank back together, adding a couple welds. Slip a sprocket on the ditch pump, and away ya go.

http://rover.ebay.com/rover/1/711-5...0001&campid=5335845805&icep_item=283310288518
 
#22
I'm not sure that Chinese trashed engines are any cheaper than the Japanese they copy, nor are any able to just unbolt the trans and add an input sprocket. Substantial cutting, machining, and welding were required on the few I've seen done. The 2-stroke single would have a clutch, oil-tight trans with integral clutch, and would only require adapting a sprocket to replace the stator, removing the rod and pressing crank back together, adding a couple welds. Slip a sprocket on the ditch pump, and away ya go.

http://rover.ebay.com/rover/1/711-5...0001&campid=5335845805&icep_item=283310288518
So...can you still leave the crank intact or do you have to replace it with a solid shaft?
 
#23
So...can you still leave the crank intact or do you have to replace it with a solid shaft?
The rod would have to be removed, but the rest is fine, after a static-balance session. Or, one could turn the OD to accept a tube that both cheeks are welded to. Depending on the primary drive gear retention method, it may be possible to replace with a shaft of drill rod or similar. Splines are tougher than a simple milled slot, of course.

My personal build with a CR125 lower end will have the tube method, with a sprocket in the center so a chain can go up to the crank coupler sprocket for the little powerheads I'm using. 6 speed, wet clutch, water pump, CDI ignition, primary kickstart, all in a tidy little package. 8 40cc crossflow 2-stroke cylinders firing opposing pairs every 90 degrees will sound much more impressive than the combined 10.8hp that a pair of stock Zephyrs will make. I'll tune them up a tad, but they're over 60 years old and the rods are brittle alloy castings.
 

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#24
The rod would have to be removed, but the rest is fine, after a static-balance session. Or, one could turn the OD to accept a tube that both cheeks are welded to. Depending on the primary drive gear retention method, it may be possible to replace with a shaft of drill rod or similar. Splines are tougher than a simple milled slot, of course.

My personal build with a CR125 lower end will have the tube method, with a sprocket in the center so a chain can go up to the crank coupler sprocket for the little powerheads I'm using. 6 speed, wet clutch, water pump, CDI ignition, primary kickstart, all in a tidy little package. 8 40cc crossflow 2-stroke cylinders firing opposing pairs every 90 degrees will sound much more impressive than the combined 10.8hp that a pair of stock Zephyrs will make. I'll tune them up a tad, but they're over 60 years old and the rods are brittle alloy castings.
Ok. So how exactly would I go about modifying it to accept drive power by an external engine such as a Vanguard V twin?
 
#25
The rod would have to be removed, but the rest is fine, after a static-balance session. Or, one could turn the OD to accept a tube that both cheeks are welded to. Depending on the primary drive gear retention method, it may be possible to replace with a shaft of drill rod or similar. Splines are tougher than a simple milled slot, of course.

My personal build with a CR125 lower end will have the tube method, with a sprocket in the center so a chain can go up to the crank coupler sprocket for the little powerheads I'm using. 6 speed, wet clutch, water pump, CDI ignition, primary kickstart, all in a tidy little package. 8 40cc crossflow 2-stroke cylinders firing opposing pairs every 90 degrees will sound much more impressive than the combined 10.8hp that a pair of stock Zephyrs will make. I'll tune them up a tad, but they're over 60 years old and the rods are brittle alloy castings.
http://rover.ebay.com/rover/1/711-5...0001&campid=5335845805&icep_item=113311401380
This one seems good. It has a 4 spd trans which would work. It doesnt run but that doesnt matter.
 

65ShelbyClone

Well-Known Member
#31
The rod would have to be removed, but the rest is fine, after a static-balance session. Or, one could turn the OD to accept a tube that both cheeks are welded to. Depending on the primary drive gear retention method, it may be possible to replace with a shaft of drill rod or similar.
I may do this myself with an old Yamaha 250 engine. One big concern I have is a possibility of the crank halves being through-hardened. I expect the ends to be since both are threaded and one is also splined. Since it's a full-circle crank about 6" in diameter, shaving off that much hardened steel would be a long, miserable job.

The whole point of this build is to do it as cheaply as possible
Then either get a complete Chinese v-twin bike engine and be done with it or scrap the idea of a gearbox and go with a CVT. Your goal is lofty to begin with, but trying to do it dirt cheap is inviting failure IMO.
 
#32
I may do this myself with an old Yamaha 250 engine. One big concern I have is a possibility of the crank halves being through-hardened. I expect the ends to be since both are threaded and one is also splined. Since it's a full-circle crank about 6" in diameter, shaving off that much hardened steel would be a long, miserable job.
In my experience, the crank cheeks aren't hardened through. I've spun a bunch on my little 0" Jet. Many seem to be induction/flame hardened at the pin hole, so between that and the interrupted cut, I'd consider as large a diameter center tube as practical. Or,,, hit that B with an angle grinder and cut-off wheel to rough it in as a hexagon/octagon. I'm not bright enough to calculate the capacity of the taper fit at the flywheel end to determine if feeding the power in to there is viable.



*I left a chunk of counterweight because this one got a stepped 10mm stroker pin, longer/heavier rod and big bore heavier piston.
 
#33
OP looks to have deleted his Youtube channel and Instagram. Hopefully he gets in to a trade school, vo-tec program, apprenticeship, something, before he gets hurt.
 

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