To speed or not to speed.....this is my first build

[adsum]

Saturday starts the first day of my adventure. Im planning on running the kart a few times around the parking lot before I decide what I want to do with it. Im torn between a 600cc swap, building the internals of the Tecumseh power sport thats already attached to the kart or swapping out that for a 250cc dirtbike motor.

My goals:
-reach speeds of at least 60-70mph
-build a reliable and safe kart
-build it right. Nothing peace mealed. Do it once and do it right (to the best of my knowledge)

Motor ideas:
-4 stroke 250cc dirtbike motor
-600cc Yamaha r6 motor $450 comes with only ECU. No harness
-Tecumseh 6 hp motor (build internals and change the gearing, remover governer?)
-Predator series motor 220cc or greater with built internals and change of gearing

 

[KartFab]

That kart already has a sweet setup. Performance intake/exhaust and a torque converter. Should be able to take it to 40 mph with no problem the way it is. Have you checked the governor yet? Making a direct throttle and removing the governor will get you closer to your goal.

I'm not a fan of tecumseh engines, and other people can chime in about it as they seem to be alright. I have had the worst carb trouble and weird power issues when accelerating with all tecumseh engines I have owned.

 

[adsum]

That kart already has a sweet setup. Performance intake/exhaust and a torque converter. Should be able to take it to 40 mph with no problem the way it is. Have you checked the governor yet? Making a direct throttle and removing the governor will get you closer to your goal.

I haven't looked yet because I pick up the Kart on Saturday. If the governer is still installed that'll be my first project.

 

[Axx3d]

40 mph on a kart feels like you are flying as it is..

I'd wait until you get it and run it prior to wanting more out of it..

 

[adsum]

40 mph on a kart feels like you are flying as it is..

I'd wait until you get it and run it prior to wanting more out of it..

"Supposidly" this kart can already do 40mph. Im not sure whether I believe that or not. It was kind of an impulse buy because it seemed like the exact kind of kart I was looking for. I guess we'll find out!

 

[KartFab]

Can do 40 vs what it's geared for right now may be two seperate speeds. Best way to verify is to get a speedometer app(free) on your phone, and/or get the following info:

rear tire diameter, #of teeth on Jackshaft and axle sprockets. And... Assume engine does 3600 rpms under load. Ungoverned it should go higher

 

[karte_m0lim]

Looks like realy beauty, do not destroy it ...

 

[BirdFanatic]

Go get your self a 4 stroke 420cc or 390cc engine either honda or predator mount it on that kart pull the governor off gear it to about 5 to 1 and you can easily hit that speed

 

[firemanjim]

Go get your self a 4 stroke 420cc or 390cc engine either honda or predator mount it on that kart pull the governor off gear it to about 5 to 1 and you can easily hit that speed

Too much weight to balance.....

 

[adsum]

Well, I couldn't wait any longer.... I'm picking up the Kart tonight!

 

[Hybridyne]

I did about 90mph and my more experienced friend did 135mph in this custom Kart I built years ago.

 

[Young One With A Manco]

Good luck! Do you have it yet? How about now? Now? Now? Can you post pics yet?

 

[Badot]

60-70 mph should be reasonable with a 125cc 2 stroke dirtbike engine, right? Should be pretty small and light, and (depending on your area) you can expect to pay about what you would for a larger displacement predator engine.

I wouldn't do a 600 bike engine unless you're looking to hit 140+ mph. Too heavy. Maybe an engine off of a Nighthawk/Rebel 250, or a Ninja 250 if you want to get a little crazy, but they'll still be much heavier than a comparable dirt bike engine.

I'm very unimpressed with my Tecumseh. Although it runs decently, the design has blatant corner cutting and a few minor problems stemming from it. No way I'd trust it with the revs/torque required to push a kart to 70.

 

[rmm727]

Not too many performance parts for the OHH Tecumsehs. ARC does make a rod for them. They just don't last un-governed.

 

[BirdFanatic]

60-70 mph should be reasonable with a 125cc 2 stroke dirtbike engine, right? Should be pretty small and light, and (depending on your area) you can expect to pay about what you would for a larger displacement predator engine.

I wouldn't do a 600 bike engine unless you're looking to hit 140+ mph. Too heavy. Maybe an engine off of a Nighthawk/Rebel 250, or a Ninja 250 if you want to get a little crazy, but they'll still be much heavier than a comparable dirt bike engine.

I'm very unimpressed with my Tecumseh. Although it runs decently, the design has blatant corner cutting and a few minor problems stemming from it. No way I'd trust it with the revs/torque required to push a kart to 70.

Yea and you will pay out the butt for the engine not only that but the cost to maintain it lol

 

[BirdFanatic]

Too much weight to balance.....

Stretch the frame to = the weight out or just like my dad used to do with paper air planes add weight to the front of it (he used a penny but you get the idea)

 

[rushking19]

Saturday starts the first day of my adventure. Im planning on running the kart a few times around the parking lot before I decide what I want to do with it. Im torn between a 600cc swap, building the internals of the Tecumseh power sport thats already attached to the kart or swapping out that for a 250cc dirtbike motor.

My goals:
-reach speeds of at least 60-70mph
-build a reliable and safe kart
-build it right. Nothing peace mealed. Do it once and do it right (to the best of my knowledge)

Motor ideas:
-4 stroke 250cc dirtbike motor
-600cc Yamaha r6 motor $450 comes with only ECU. No harness
-Tecumseh 6 hp motor (build internals and change the gearing, remover governer?)
-Predator series motor 220cc or greater with built internals and change of gearing

You should probably just look for a honda gx260 or a Briggs and Stratton 6.5 hp ohv since its the cheap version of the animal motor, or a harbor freight predictor motor, they should all have performance parts cheap and easy to find, and 40-50 mph is fast enough for your first build, and like the others say a r6 engine is going to be expensive to buy to setup and to maintain ,and it would be way too fast for you and could kill you, now a 250 dirt bike motor could possibly work but it would be hard to setup though

 

[Badot]

Yea and you will pay out the butt for the engine not only that but the cost to maintain it lol

If you're making a kart that can go 60-70 you'll need a good bit more power than a 6.5. Dual HF 6.5s with dual torque converters might be doable for a little under $400, a HF 13 hp with torque converter will be about the same. And honestly, I'm not sure how the torque converters would cope with spending so much time in the slip range.

Or you can go to the local junkyard and pick up a functional engine (2 or 4 stroke, whatever your fancy) pulled from a wrecked big 4 bike for well under that $400, including a real clutch and multi-speed transmission, with obvious weight and size benefits.

Of course, when you back it off to 40-50 mph, that's reasonably doable on the street with a single 6.5 and TC, so that would become much more practical.

 

[itsid]

Well I think I said it before, but I'm happy to repeat that..

mathematically you need at least 12Hp to push 150kg to 60mph,
and mathematically means: no imperfections, no gear friction or slip etc.

So... technically I'd say 15-17hp should do.

that frame looks home made.. I would go near a 600cc engine with it.

even worse, I wouldn't want to push that kart to 60mph at all..
I think that should be the 'magic line' where you should have front brakes, and a set of those can easily draw 400 bucks off your pocket alone

For speeds like that, a proper built shifter chassis is the way to go IYAM.

Yes, some DIY'ers are able to make a chassis that's good enough, but that doesn't look like one of those to be honest.

remove the governor, tweak the engine so it reaches 5000 rpm under load and run a high ratio (it'll chew on the belts, so be careful with that)
but a 4:1 ratio (12-48) will get you to 45mph (kart+driver weight 150kg or less)

KartInfo by kartcalc.net:

[FONT="Verdana"]
[B][U]KART[/U][/B]
[INDENT][I]RW diameter[/I]: [B] 27.94 cm | 11 in[/B]
[I]Total weight[/I]: [B] 150 kg | 330.69 lbs[/B]
[/INDENT]
[B][U]ENGINE[/U][/B]
[INDENT][I]Original HP[/I]: [B] 6[/B]
[I]Asummed HP[/I]: [B] ~6.67[/B]
[I]Torque[/I]: [B] 11.87 Nm | 8.75 ft lbf[/B]
[I]RPM[/I]: [B] 5000[/B]
[/INDENT]
[B][U]TRANSMISSION[/U][/B]
[INDENT][I]Final ratio[/I]: [B] 4:1[/B]
[I]TC type[/I]: [B]  series 30 6" driven[/B]
[I]Lowest ratio[/I]: [B] 10.8:1[/B]
[I]Highest ratio[/I]: [B] 3.6:1[/B]
[/INDENT]
[B][U]PERFORMANCE[/U][/B]
[INDENT][I]Max Wheel Torque[/I]: [B] 128.2 Nm | 94.56 ft lbf[/B]
[I]Min Wheel Torque[/I]: [B] 42.73 Nm | 31.52 ft lbf[/B]
[I]Acceleration[/I]: [B] 3.47 m/s² | 11.39 ft/s²[/B]
[I]Top Speed[/I]: [B] 73.15 km/h | 45.45 mph[/B]
[/INDENT]
[/FONT]

'sid

 

[Badot]

Sid, I'm curious to the math (mainly the assumed values) for the 12 hp - 60 mph 'rule'. Care to elaborate? I feel it may be a bit too generalizing.