Really Cheap Trail Rider.

Thanks everyone!
Spent a bit of time working with the derailleur last night to get the shifting to work out. Having such a small sprocket in front required experimenting with chain lengths the make it possible to get the lowest gear. The derailleur didn't have the rise to get the chain over the 28t low cog. Had to lengthen the chain a bit more than would be normal to get the lower idler just above the cog when selecting. Seems to shift all gears fine statically, dynamically may be another thing. Have to wait and see. If not I will use it as a five speed which it seems to do more easily. Was looking forward to a stump pulling 31:1 low gear. However using second will still yield a 29:1 ratio for good pedal less take off. Have to add at this point Im not much of a derailleur fan. Its gotta be the Rube Goldberg of transmissions. The IGH is like from another galaxy!

I think these engines will turn 9k rpm? that would give nearly 44mph. I doubt the little fella will pull that high a ratio at that speed, but if it makes 2.5hp its got a bit on a CG and I have seen claims of similar speeds from them. Don't really care 35 is plenty fast for me.

This bike is REALLY light! Don't know how much the tires will weigh but that's about all that's left to add. Will weigh it when finished.
I noticed on ebay that the 2stroke pocket bikes seem to be a thing of the past with all the new ones coming with a Honda clone 4 stroke. The mini dirts still seem to be 2stroke, but bet they will go the 4stroke route soon. Its nice to be green while plowing mother earth with knobby tires.
Guess I will lay in a few CAGs in the future build department if this one works out well.

OK got a bit of time to relieve a little stress working on the bike. Fabbed the cables, for the rear brake and throttle, hooked up the kill wires and mounted the tires.
Got a few heat cycles on the CAG at a 32:1 break in ratio. Engine was very rich initially. Dropped the needle to the highest slot and it basically straightened it out. It will need a smaller jet to be right. This maybe be the fact I am running the can muffler. I bought a cheapie pipe to try to fit, looks like with a bit of bending it will.
I Got a quick ride in and the shifting worked perfectly until I hit 6th and the derailleur must be out of limits as it threw the chain. Will reset the high limit a bit. The bike rides well. The ratios are pretty right on and very close, each gear sounds like a new first.
The can muffler is a bit loud being a side exit. I intend to add a down pipe, copper water pipe fits the stub well. The little engine runs well and is definitely banded, probably more so with the pipe. Definitely has good power as it bands up. Cranks easily and after the needle drop idles well. The bike is in the rough stages but will tweek up nicely when time allows. Primary chain is off in the pics to allow various rpm during run in.

Thanks Map! Its to the point where fine tuning of the shifting is the next order of business once I get more time on the engine. I need to pull the jet to see what size it is and go one leaner I believe. The little motor is a willing rever once on the band. Its also smoother than I imagined. I am almost inclined to go ahead with the pipe install as that's the way the pocket bikes are configured to run so maybe it will be closer on running than with the can muffler. Cant be too much louder than the can muffler. Will have a shot at it as time allows

Ok, got a chance to tinker with the bike a couple of hours to blow off a little stress. Set the limit on the derailleur. Had no issues shifting. Engine seemed to run a bit better, was still running the can muffler. This little bike is plenty fast. I really think it only needs 4 of the 6 speeds. It will easily pull from stop in 2nd or 3rd. May set the limits for 2 thru 6. 1st is real low and rpms out fast.

So I went ahead and installed the pipe. It took about an hour of careful tweeking and it fit great. That was all dumb luck, didn't really think it would be that easy. WOW! What a beast it turned it into! Its rips through the gears as fast as you can shift and gets going way too fast way too fast. Reminds me of a highly modded motocrosser I had deep in the last century. Immediately turned me into a hooligan! This thing is definitely NOT neighborhood friendly. Pipe sounds great to an old(too old) 2 stroke race rider blasting through the close set gearing, but not to the general populace. The original plan was to load it on the bike rack and head to the outlands for trail riding. There I can enjoy the little brute in solitude.

Ok my thoughts on a CAG bike. If you want to go fast with an engine that has a definite power band and rips for its size then this is the engine. It will yield a light weight bike. This one weighs 36lb. The engine so far seems reliable, starts easily and idles well and consistently, especially since it has little time on it. It and its parts are certainly cheap enough, and theres plenty of mods should one want to raise the band even higher. I swear it wouldn't take much effort to have a 60mph bike. Spend any money for hi-perf mods on brakes!!
If you want a slow torquey plonker look else where. The can muffler helps civilize it a bit but its still bandy. The little thing does exactly what it was designed to do and that's offer plenty of high strung rpms!

I really LOVE it! I have bikes from one extreme to the other now.

Chain guards are in the works. Thanks for your concern. Im prone to take chances on early rides just to see how it goes.
I haven't locked out the low gear yet. But I would have to load the bike on the rack and drive several hours north to find a suitable incline to require the use of the first cog. Life on the coast is rather flat.

Sorry! Even the little stock engine is a ripper. Its a willing runner but it defines the meaning of hyper. I too was looking for more of a sedate little engine. This thing would be fun on a BMX track.
Don't give up on the idea. The small 4strokes that are showing up in large numbers would probably be ideal. They mount in a similar fashion, and use the same gear reduction/clutches, and I doubt weigh a lot more.

Curt there are two types of common(entry level) pocket bike engines I believe. The Cag type and the piston port which looks al lot like a weedeater engine(now 4 strokes too). The engines are 47cc and 49cc. I believe the 49cc PP engine is the more useable of the two for things like FD and such. Its much less peaky. They also generally cost more though. One of these would probably make a much more usable(tractable) engine for something other than hauling butt.
If you remember the little factory made bike the Zipper, it was a lovely shifter bike using only a 26cc engine maybe! There are vids on youtube. I believe a similar thing could be made using the 49cc PB engine.
I have been riding the Cag bike a bit when the neighbors are at work and its really fun, but that's my view. As a trail bike its high strung. It will do well on the miles of open desolate sand roads in the outback of this area. In the woods it would be like riding a full bore M/C bike when what you need is a much lower tuned torquey Enduro bike. You can do it but you are picking your way through the trees twice as fast. I have done that when younger and stupid!
Bottom line is a cag is a great engine if one wants to go fast on what ever its on. Would make a great top speed bike, particularly with gearing.

Yeah the paint mode! Some how that's mode seems to take as long as the rest of the build. Though I did enjoy descaling this bike and just blasting it with flat black.

The Cheapy has been doing well except for the occasional tossing of the secondary chain. Always from the small front chain ring. The result is a rather unspectacular dumping of the chain which trails harmlessly along behind the bike. Rather than figure out the dynamics I added a chain keeper. Its made from a 2" PVC pipe coupling. Im suspecting the fact it only happens in the higher gears is due to the lack of derailleur tension as it retracts to take up slack. If I shorten the chain to add tension it gets harder to get the lower gears. Hopefully this is a fix. It designed to tear away if the chain gets badly bunched.

I have ordered a jet set for the Cag. It is overly rich. I run the carb out of fuel when done riding. As it runs out it leans to the point that it goes from a decent idle to almost clutch engagement before it dies. My jet drills are lost in the abyss of moving so I have no idea of the original jets size. I think this is adding to the overly banded nature. Maybe leaning a bit will add tractability.