150cc dirt bike engine in go cart

[killawatt]

im sure its been covered several times but i couldnt find any post on the subject anyway i have a brand new 150cc lifan dirt bike motor that was given to me and a two seater yerf dog go cart i already welded a mouting bracket for the motor and have run into my first problem how to make the shifter since the transmission shifter goes up and down and the shifter ill be mounting goes back and forth. i was hopeing that someone had a simple solution that would save me some time and frustration. thanks guys

 

[anderkart]

Take your engines shift lever off and reinstall it pointing up or down.

 

[killawatt]

ok that makes complete sense i dint think about that.... i knew there was a simple solution to it. what gear ratio do you recommend?

 

[redsox985]

What was the size of the bikes rear tire? What was the ratio on the bike? What did the bike weigh? What do you think your kart weights? Probably a few more teeth in the rear than the bike had because the kart is heavier.

 

[anderkart]

We'll need to know how tall your rear tires are,
and how many teeth your current engine sprocket is,
and if you'd prefer to have better acceleration/climbing ability or a higher top speed.

We'll also need to find some way to figure out what your Transmission's final drive ratio is in high gear.

 

[killawatt]

the bikes rear tire was 24in from top of rubber to bottom of rubber. my carts is 22in. the ratio on the bike was 3 to 1. the bike weighed about 100 pounds my cart is probably closer to 125. probably close to 275 with the motor and myself in it. my axle already has a 38 tooth on it and id like to try and use it because its a pain in the *** to change but i will change it if i have to. the current sprocket on the motor is a 10 tooth and i want it for more off road and climbing

 

[killawatt]

thanks for all your help so far too guys
Alex

 

[redsox985]

What did the bike have on the rear? That is probably a decent setup for the motor but to get better climbing you would want to add some teeth in the back or lose them on the motor.

 

[killawatt]

uh you mean tire wise or tooth wise? it was a 24in tire and a 30 tooth sprocket i think. iv heard of an 8 tooth sprocket do you think that would cut it? do you think it will have enough power to do some pretty decent off roading stuff?

 

[anderkart]

Man those are some tall rear tires for a kart but you could just give your current gears a try and see how it does.

I found some gear ratio info for your tranny here: http://www.pccmotor.com/lifan-150cc-oil-cooled-engine-mo150.html
Looks like its got a pretty low 1st, and then 4th overdrives a bit so if you find it goes faster in 3rd than 4th you could try that 8 tooth driver if you dont wanna mess with swapping the rear sprocket. (although i've heard that those tiny driver gears tend to wear out much faster)

 

[killawatt]

i like the look of the tall tires and plus i have to cross a creek and some rocks and deep mud so i want as much ground clearance as possible and im ok with replacing the sprocket every now and then. i cant wait to see what kind of power it has. also how hard would it be to add an electric starter

 

[killawatt]

ok so i was working on the cart a little today and im going to have to go with a jack shaft so know that i have even more playwith the gearing what are my options?

 

[modelengineer]

I'd probably do all the reduction on the first chain from the motor to jackshaft, then have a 1:1 to the rear axle. That way you can use a smaller rear axle sprocket and gain some ground clearance.

 

[killawatt]

so run like a 10 tooth sprocket from the motor to a say 40 tooth sprocket on one side of the jack shaft and then just run a 38 tooth sprocket on the oppisite side to the 38 tooth sprocket on the axle?

 

[modelengineer]

Yeah, but I'd probably do 20 tooth to 20 tooth on the other side of the jackshaft to get more ground clearance.

 

[killawatt]

yea but theres already a 38 tooth sprocket on the axle and its a live axle so id have to take the whole rear end off to get to it but its not a bad thought at all and may be worth the effort do you think a 1:4 ratio is low enogh for what i want? im just second guessing myself i want a good bit of tourque im not looking to do wheelies but i wnat to have enough power to putt up hills and do some decent off roading but nothing too crazy

 

[modelengineer]

Mine has 22" tall tyres with about 3.6:1, but you can't really compare different bike engines in this way because they have different primary reduction between the engine and the gearbox, and different ratio's within the box. If you already have the sprocket I say just whack it on and see how it goes.

If possible I'd avoid the jackshaft though.

 

[killawatt]

well im not sure if i can the original motor in the cart was stupid and now the new one is like the typical. basically what i mean is the original motor had all the drivetrain componants on the oppisite side to the motor i have now...... i guess i could try just flipping the rear axle...this is carts though nothings ever that easy

 

[killawatt]

and with that set up how is your torque and off roaad power like?

 

[killawatt]

also any ideas for a carby now what im fixing to suggest may be a sin... but i do have a 6.5 clone carby in the shed now i havent tried to see if it would even fit just a suggestion though. terrible idea?