crankshaft has no keyway

[mhostetler]

Hello, Iam new to the karting world and need some help. I have a Honda Gx140 that had a 6 to 1 reduction box on it, I removed it and the crankshaft is set up to connect to a gear only, no keyway. How do i make this work with a torque or clutch?

 

[toofarnorth]

Is it going to be long enough to fit a clutch? You might have to turn it down to the proper diamiter then use a grinder to cut a new keyway, a machine shop could do this but you'd likely have to remove the crankshaft and it'll cost you, in which case you might be better off buying a new crankshaft.

 

[toofarnorth]

Or if the reduction unit is still good you could use that and make your kart belt drive you'd just put the same size pulley on your output shaft as your axle and rig up a belt tensioner as your clutch.

 

[Kenny_McCormic]

Some of those reduction boxes have(very good) clutches in em, you just run a 1:1 or so from the box to the axle.

 

[mhostetler]

i didnt know there was a clutch in them. This came off a cement mixer and there is a 6'' pully on the reduction box shaft that i cant get off. so if i use the puley on there can i use a real small puly on the axle? last thing i want is a slow kart.

 

[mhostetler]

ok i called the machine shop they want $100 bucks to grind it and ket it. And i will need to remove the shaft. I think i will just try the reduction unit as is with the same size pulley to drive the axle. I just fear that this may make the kart slow. Do you know if it will slow things down? i would like to go at leat 30mph.

 

[anderkart]

If you post the height of your rear tires, one of our gearing-gurus here might be able to calculate the approximate top speed you could expect from this setup. (post your motor pulley width and axle diamitor too, so we could research all avalible axle pulley sizes)

If you cant come up with the gearing you want you could always add a jack shaft setup to end up with any final gear ratio desired.

 

[r_chez_08]

you can use the speed calculator
you would need about 16" wheels to go 29mph.
iv heard that these 6.1 boxes are quite rare, u could sell it for a new crankshaft and clutch.

 

[freakboy]

or he could just keep it and the crank and use it. instead of wasting time selling it and gettin new parts.

 

[toofarnorth]

okay if you use the 6:1 reduction unit here is what you do to determin the speed of your kart go to the speed calculater http://www.diygokarts.com/speed-calculator.html pick what tire size you want, enter in 600 for engine rpm because that should be the output shaft rpm, you have a 6" pulley so multiply that by 3.14 to get the cercumferance would be 18.84 so enter that in for the # of teeth on the clutch, then you can play with the axle pulley size to get the top speed you want just remember to multiply the diamiter by 3.14 then enter that # like a 5" pulley would be 15.7 and if you use 14" tires your speed would be 30 mph

 

[frederic]

Most of the 6:1 B&S gear reductions I've seen do not have a clutch in them. It's straight gears. Maybe something changed recently, - I have no idea.

I would turn the snout of the crank down and machine a keyway, then use go-kart parts for a normal, easy to service/maintain/operate system.

 

[motor_head]

if its 6:1 use it if it's geared lower maybe not

 

[mhostetler]

thanks to all for the info. After reading all the negatives on the net about expensive belts breaking a lot i have decided to take the crankshaft out and have the gearportion ground off and the tapped to hold a clutch. Last night was a learning experience for me, i was suprized at the simplicity of the valve, cam,and pushrods assembly. This is a Gx140 Honda and i took off the Govenor that was insid the engine, i will use new 18Lbs valve springs now. Tonight i will tackle removing the crankshaft. I will let ya know. Thanks guys.

 

[Rickracer]

Shop around a little bit, I had the very same thing done to a Honda GX240 crank a couple of months ago, and it was $25. Now the machinist is a buddy, I take him all kinds of work like that, but still, you should be able to find someone who will do a good job for a lot less.

 

[motor_head]

?????????????????
belts aren't expensive

if you were looking at torque converter belts thats not what you would need you would need a regular v-belt