go kart with motorcycle engine

[kartingfan]

Hello to everybody,
I just joined this forum because I am atemmpting to build fast kart with 125cc 2 stroke engine(with gearbox),otherwise known as shifter kart.
My major dilemma is regarding the width of the back axle and front tire holder(the steel pipe on which ends are front tires).
My go kart will be overally 190cm long and distance between front and rear wheels will be 150cm.The width of sitting part of frame(where I will put chair)will be 60cm.
So,should I put 80cm axle or 100cm axle.Since it will be live axle,I read that if I make kart narrower,it will be better in turns.Is this true?

 

[landuse]

Whatever the length of the axle, make sure that you have your wheels mounted as close as you can to a axle bearing. This gives your axle more support and less prone to bending if you crash

 

[kartingfan]

And here is my second dilemma.You know how racing karts have front part of the chassis(the part that is near the front wheels) narrower than the back of the chassis(the part that is near the rear wheels).Example is this image.

But,many homemade karts use straight chassis(like this one):

So,my question is,does the design with narrower front has any advantage over the straight chassis design?

 

[landuse]

I actually have no idea, but it must have some advantage as all racing karts are like that. Wait for Anderkart to chip in. He is the racing kart guy

 

[kartingfan]

I think this way.If I want do build it,I want to build right!

 

[anderkart]

This link has info explaining how wider or narrower track widths can alter the handling and grip characteristics of race karts:http://www.racemates.nl/PKinfoTech_kart chassis setup_2.html#_Toc529198884

Modern Sprint or Shifter karts typically use front track-widths of between 45.5" to 46 inches wide (that's measured from the outside edge of the tires) They use extra-long front spindles and have a stack of spacers that can be moved to the inside or outside of the front wheel hubs to adjust front track width.

Rear track-widths typically range between 50" and 55". Rear track width can be easily adjusted wider/narrower by simply loosening the rear wheel hub clamp bolts and sliding the hub in or out further on the axle.

Most modern 125cc. shifterkarts use 50mm.-diamiter axles that are 41" long. Rear wheel hubs are typically sold in 3 different lengths to further expand the range of adjustment.
_____________

If its any help, heres some frame measurements from my Biesse B3 Sprintkart.
A 125cc Biesse shifterkart would use the exact same frame, It'd just have front brakes added.

There's more pics of this kart at this link: http://www.diygokarts.com/vb/showthread.php?t=3664

My Chromoly frame rails measure 33mm. with a 3mm. wall thickness.

 

[kartingfan]

Thanks for the link and explanation.
But,regarding the frame itself(not wheels),does narrower front end of the frame design has any advantage over straight frame design?
Example is in attachment.The part marked with blue is narrower than the part marked in red.Does this kind of design has any advantage over the straight design?Imagine that whole frame is the same width.

 

[kartingfan]

OK,maybe a stupid question,but how do I mount sprocket on axle?I know how to mount bearings,but it seems that mounting a sprocket using of hammer is not a good idea.

 

[OzFab]

OK,maybe a stupid question,but how do I mount sprocket on axle? I know how to mount bearings,but it seems that mounting a sprocket using of hammer is not a good idea.

Umm, probably not. Do you have a sprocket hanger? Is it compatible with your axle? If you answer yes to both of these questions it should just slide on

 

[oldbikerarlo]

Thanks for the link and explanation.
But,regarding the frame itself(not wheels),does narrower front end of the frame design has any advantage over straight frame design?
Example is in attachment.The part marked with blue is narrower than the part marked in red.Does this kind of design has any advantage over the straight design?Imagine that whole frame is the same width.

The narrow frame at the front allows the frame to flex, (twist). keeping better tire contact.

 

[kartingfan]

The narrow frame at the front allows the frame to flex, (twist). keeping better tire contact.

Thanks,I decided to go narrow design.
I'll make a drawing and send it to local pipe bending company.

 

[kartingfan]

On my own frame design, the ratio between the rear part of the kart(where the seat and engine are) and the waist of the kart is 2.Is this OK?Or should the waist be narrower or wider?

 

[kartingfan]

Anyone? I would really like to start project as soon as I can.

 

[anderkart]

I'd say your 2-1 waist design is a good plan.

 

[kartingfan]

I managed to shorten my go kart to 150cm.This will make it more agile.Also,I need to find some medium tyres because I want to drive both on road and off road(grass,not mud though).

 

[kartingfan]

I know that this is REALLY stupid question,but can you put 8" or 10" tires on a racing chassis(instead of 6" tires)?

 

[landuse]

I know that this is REALLY stupid question,but can you put 8" or 10" tires on a racing chassis(instead of 6" tires)?

It all depends if your frame has enough clearance for larger tyres of that size. You are going to have to do some measuring. Measure from the spindle bolt to the edge of the frame. Subtract about an inch for clearance. This is the maximum tyre that you can use. Just keep in mind that it may fot, but may not be able to turn properly (I got this from someone elses post. I think Toystory)

 

[anderkart]

I know that this is REALLY stupid question,but can you put 8" or 10" tires on a racing chassis(instead of 6" tires)?

Did you mean tires that are 8" or 10" wide? Or tall?
Or tires that are made to fit rims that are 8" or 10" in diamiter?

 

[OzFab]

Did you mean tires that are 8" or 10" wide? Or tall?

Does anyone make go kart tyres 10" wide? Around here that's the widest legal tyre size for cars

 

[kartingfan]

Did you mean tires that are 8" or 10" wide? Or tall?
Or tires that are made to fit rims that are 8" or 10" in diamiter?

tall

EDIT: One more question.I could get a good deal on a 100cc tag kart engine over here in my town.Can you put some kind of tranny(maybe cvt) with on that kind of engines(since I see that people drive these engines with clutch and only single gear)?
BTW,I am having a really hard time finding motorcycle engines over here in Croatia.Only ones that are for sale are 50cc.