my 125cc shifter kart project

[justang90]

Hi folks

i recently buy a kali kart frame on the pac in my region for only 120 buck ! so i got the idea to take the engine from a chinese 125cc dirt bike and transplant it in the kart. here is some picture.

 

[OzFab]

Nice colour

Since I don't see an axle sprocket, can I assume it's not running yet?

 

[fourtogo]

You could use a Mikuni vacuum fuel pump $20-25. Then fuel tank could sit of floor below steering wheel .

 

[justang90]

you got the eye !

i have ordered last week a mikuni fuel pump for 25$ with shipping and a #428 21T 40mm slipt sprocket from 7th-gears.com

now the only thing i have to do is a adapter for my 30mm axle to accept a 40mm sprocket. i plan to put the sprocket inside the 2 bearing casset on the engine side. i think its the stronger place on the axle. but im not sure about my engine mount... on the 2e pic you can see i have made 4 hole for the engine but i have redrilled 2 hole to make the engine more close to the seat. is this enought strong to handle 12hp ? cause the engine normaly mount on his top but i used the 4 bolt that mount originaly the foot peg on the dirt bike. its 4 10mm bolt and its screw about 3/4 inch in the engine.

oh! and ps: as you can see im a french canadian and my english is like a 10 years old

 

[justang90]

on the first pic you can se how i mount the engine on the second you can see how i fix the shifter cause i had try to search how to install it but i found nothing so i made 3 plate of stainless steel and bolt it with the floor plate to strengthen the floor so it will not bend under hard shift.

 

[OzFab]

Umm, you can't mount the sprocket between the two RH cassettes, unless it's a small sprocket in which case, it will probably be overgeared

Nice work on the shifter

 

[justang90]

so that my math on the gearing

first its good to know that the original pit bike with the engine on and the kart with the engine its aproximatly the same and the pit bike was totaly overpowered on gearing ! and the bike in 4th have enough power top pop a wheely:arf: and hit easily 45mph on top speed with shifting none stop

so i want my kart to go 50mph with 14/21 and 11 inch tire
the pit bike has 14/41 with 18.5 inch tire and did 45mph easily

so if the pit bike have 18.5 inch tire it can do 45mph with a gearing of 14/41 i have calculated that the maximum countershaft rpm in 4th gear is 2400 so now we know that the engine if the maximum rpm is 9500 and the 4th gear have a ratio of 0.958:1 the engine have a primaly gear reduction ratio of 4.130...

so 2400 max countershaft rpm with 14/21 and 11inch tire give a top speed of 50mph and shifter kart normaly have 17/26 for large oval racing and its aproximatly the same as 14/21

i think my head overheat loll to much math

 

[CaptCanadia]

That's a cool kart, you got it for a good price too!

Those **** French Canadians and their English.

 

[justang90]

Loll i learn my english in diablo instead of learning the colour in french highschool my english is enought to teach the english in canadian french highschool

 

[justang90]

That's a cool kart, you got it for a good price too!

for the moment the kart cost me :
Frame 120$
shifter assembli + seat 60$
cable,bolts and steel 20$
mikuni fuel pump 25$
sprocket 25$
bearing 10$

total for the moment : 260$ but i already had the engine so i would say its 100$ more value..

360$ + a lot of love = 2000$ shifter kart

 

[CaptCanadia]

Wow vous etes tres chanceux. Souhaite que je pourrais trouver quelque chose comme ca ici!

Sorry I don't know the accents -_-

 

[anderkart]

Welcome to the forum justang90, cool kart

Your gearing sounds fine to me, but how are you going to adjust your chain tension?

Your motor mounting plate looks fine, I'd just bolt it onto a racekart style motormount, so you could simply loosen those 2 clamps on the bottom and adjust your chain.

seventh-gear.com has some motormounts in stock or you can usually find prices as low as $35 on ebay.
The motor mount shown in my to-2 pics below is made to fit a 5hp briggs or 6.5hp Honda/clone.

I cut my adaptor plate out of 1/2" thick aluminum, then bolted it to that motormount for this huge 406cc. Honda engine:

More info/pics at this link: http://www.diygokarts.com/vb/showthread.php?t=3664

 

[justang90]

For the chain tention ive thinking to make a braket that will hold the dirt bike's chain guide to take the slack but if im lucky and have the chain fit with the right tension with just shim the engine with some washer...

 

[anderkart]

Ok you sound like a very knowledgeable guy, but I've seen quite a few karts that only had tensioners/guides for adjusting chain tension. Most of those guys ended up having constant problems throwing chains and regretted not installing an adjustable motormount right from the start...

 

[justang90]

When i buy the kart it come with some parts that i think its the engine mount you talking about but i think i didnt have all the parts.. I will follow your advice and put a movable engine mount but i will make some test run with my engine mount and see how it run.
This kart will be use on street and parking lot with my friend. I dont plan to make laping with it so is my concept (including brake) will be fun and not a hazardous mini bomb.

 

[fourtogo]

you got the eye !

i have ordered last week a mikuni fuel pump for 25$ with shipping and a #428 21T 40mm slipt sprocket from 7th-gears.com

now the only thing i have to do is a adapter for my 30mm axle to accept a 40mm sprocket. i plan to put the sprocket inside the 2 bearing casset on the engine side. i think its the stronger place on the axle. but im not sure about my engine mount... on the 2e pic you can see i have made 4 hole for the engine but i have redrilled 2 hole to make the engine more close to the seat. is this enought strong to handle 12hp ? cause the engine normaly mount on his top but i used the 4 bolt that mount originaly the foot peg on the dirt bike. its 4 10mm bolt and its screw about 3/4 inch in the engine.

oh! and ps: as you can see im a french canadian and my english is like a 10 years old

I run a CRF450 50-53ish horse power drive sprocket sits on the inside to the left of the second bearing carrier on axle. Eric at 7G is a great guy

 

[anderkart]

When i buy the kart it come with some parts that i think its the engine mount you talking about but i think i didnt have all the parts..

Post a pic of it, you might just need the 2 clamps. 7th gear might have some or you could buy them at most any racekart shop, they're sold here -> http://www.out2win.com/catalog/mount_chassis.html#clamps

You need to make sure your mount and clamps fit your frame,
good info about that here: http://www.out2win.com/catalog/enginemount.html

 

[justang90]

I will post a pic of what i have after work.. But the thing im not sure is the braking power of the kart. I didnt try the kart yet cause im still waitin for my sprocket but im wondering if i will have enought braking power for street use.

 

[OzFab]

As long as it's set up & bled correctly it should be fine

 

[anderkart]

Yeah your brakes will probably be fine, but if you post some close-up pics of your caliper and rotor we could give you better advice.