(agent orange special) What could possibly go wrong?

well the little 29cc bike is being retired. it is a sad day.

BUT, dont fear, my projects always come back better.

in this case, i have an almost brand new 5 hp briggs. it has less than an hour of use, and looks factory, no dents not even any dirt packed in the fins, it just happens, that it will fit in the frame of the old 5 speed bike. now i know what you all want to know, and that is, it it gonna have gears? that is a definate yes. i feel that with this power, the gears are gonna be fairly shallow, but i have an idea to combat that. it is gonna be a street bike, as much as that pains me, but the casette doesnt have a creeper gear. i did the math, and i need a 6 to 1 for dirt use, but that will be very hard to make. i can make an about 5.5 to 1. (with a jackshaft) which should work ok. im gonna have about 65 ft lbs of torque, and with pedals, you can make more, so i hope i wont break the chain. its gonna have a centrifugal clutch, because there is no room for a cub cadet, or belt clutch. im gonna leave the governer in, and leave the engine 100000% stock. i need help connecting the throttle cable, on the below tank bracket. i really need a picture. speaking of pictures, i have mocked up the engine. let the build begin.

I am open to any advice, from the people that know about high power, and gears.

 

[redneckracing674]

Any ideas on how to increase the chain tension on a deraileur? The SIS shifter is on there, cause it fit. I have a tourney, and an early Deore, which could be forced to fit on this bike if necessary, but they dont appear to have any tension adjustment, and I really dont want this chain falling off at mach 3.5 (750 rpms), not for fear of it turning into a chain whip, but it catching in the spokes, and locking up at 47.8 mph. I may make some little 3d printed inserts, to catch the chain, like driveshaft safety loops in a race car.

 

[Sidewinder Jerry]

Any ideas on how to increase the chain tension on a deraileur? The SIS shifter is on there, cause it fit. I have a tourney, and an early Deore, which could be forced to fit on this bike if necessary, but they dont appear to have any tension adjustment, and I really dont want this chain falling off at mach 3.5 (750 rpms), not for fear of it turning into a chain whip, but it catching in the spokes, and locking up at 47.8 mph. I may make some little 3d printed inserts, to catch the chain, like driveshaft safety loops in a race car.

Build a 4-speed freewheel this'll reduce the amount of lateral stress on the chain and offer bigger jumps between the gears.

Thread '4 Speed Freewheel' https://motoredbikes.com/threads/4-speed-freewheel.58615/

 

[Sidewinder Jerry]

You can tighten the draw-back tension by tightening the draw-back spring. You'll have have to drill another hole for the spring.

 

[Chainlube]

Any ideas on how to increase the chain tension on a deraileur? The SIS shifter is on there, cause it fit. I have a tourney, and an early Deore, which could be forced to fit on this bike if necessary, but they dont appear to have any tension adjustment, and I really dont want this chain falling off at mach 3.5 (750 rpms), not for fear of it turning into a chain whip, but it catching in the spokes, and locking up at 47.8 mph. I may make some little 3d printed inserts, to catch the chain, like driveshaft safety loops in a race car.

If you use a bigger chainring it will create more tension, all your gearing is in the back anyway. You might want to adjust the deraileur so it only shifts on the first couple of gears, that keeps more pressure on your chain.

 

[Chainlube]

@redneckracing674 thanks for posting that previous photo, you solved a mini bike issue for me.

 

[redneckracing674]

what minibike issue? thanks. i can post more detail photos tomorow if need be

 

[Chainlube]

what minibike issue? thanks. i can post more detail photos tomorow if need be

I'm trying to make a chain guard and the way you put the plate on the engine is ideal for my mini.

 

[redneckracing674]

bike is rideable. it is fricken fast, and if you could power shift it (4000 rpm+) it would be as fast to 45 as my cvt scooter. it needs more top end gearin. it is super smooth, and is fairly quiet with the current muffler. it does second gear wheelies. i had to 3d print a governer bypass, cause it wouldnt cooperate. it is kinda hard to start, because the throttle it on the opposite side than the pull starter. it does gain throttle response that way. the gear ratios are perfect, if you stay below 3600 rpms, but if you are really gettin in it, you want to double shift after 3rd. the rotating assy caries so much weight, around 10 lbs, that you just let off, and it shifts for you, without having to rev match, or slam. the downfall, was pulling the rear axle out of the carriers. i made some plates, to keep it there. lastlly i had some issuses with the chain getting alittle excited, and bouncing, so i put another wrap on my cheapest, shifter, and if it breaks, i dont care. this worked fantastic. it bounces a bit in 6th and 7th, but im not on it hard in those gears anyway

 

[redneckracing674]

top speed in second gear, at a reasonable rpm, is about 13. this gives you more than enough torque, and i doubt i will ever have to change the clutch, atleast due to shoe wear, in 7 th gear, it goes about 45. it has the power to do this up a decent hill, so i prolly could get away with a 11, or 9 series briggs, since theyre lighter and smaller.

 

[redneckracing674]

than disaster strikes. im motorin along, 6th gear, to the bar, when i grab 7th. when i do, the chain overshifts, and grabs on something or another. i let off, but the weight in. the rotating assy, tries to rip the wheel out of the carriers. when it cant, cause it is blocked in there, instead, it bends the frame into an S shape. this in turn slams the tire against the opposite frame tube, locking it up, and slamming me into the handlebars. i managed to recover it, and didnt wreck, (see im not an unskilled driver), but the skid mark is like 50 feet long lol. i had to carry it about a mile back. also destroyed my brand new tire. broke the chain for the second time.