Hi from South Africa

[Jaundre46]

Hi guys my name is Jaundre and I'm from South Africa, I recently bought a oval track kart with a 100 cc pcr engine but the piston and crank is damaged the chassis looks similar to a tony kart frame but I'm unsure, anyways I thought of buying a new engine for the cart saw on the internet that the gx390 looks like a fun and powerful engine, so I found a clone engine and im buying it the end of the month. the problem I'm having is that I don't know how I'm going to fit the engine to the chassis, and the other problem is the sprocket on the axle won't line up with the engine. any advice will be appreciated
thanks in advance

 

[OzFab]

Not that it's a bad idea but, a GX390 may be a bit excessive, both in power & size, you may have trouble fitting it between to side pods & the seat; the upside is you already have a mount, to which you can bolt an engine plate for the GX390 at any point you wish...

The problem with the sprocket alignment is a common one, due to that pesky rear crossmember; the only two choices you have are to move the rear crossmember or incorporate a jackshaft...

Welcome to the forum

 

[Jaundre46]

Not that it's a bad idea but, a GX390 may be a bit excessive, both in power & size, you may have trouble fitting it between to side pods & the seat; the upside is you already have a mount, to which you can bolt an engine plate for the GX390 at any point you wish...

The problem with the sprocket alignment is a common one, due to that pesky rear crossmember; the only two choices you have are to move the rear crossmember or incorporate a jackshaft...

Welcome to the forum

Thanks for the reply, the reason I thought of the gx390 is I don't want to regret later that the kart is to slow, so I thought let me put the big fella in and that way I know I already have a decent powered engine? How is the 9.5hp compared to the 13hp? Also how does a jackshaft look?

 

[landuse]

Welcome to the forum. Another South African!! We are going to ounumber the Texans soon .

I would have to agree with Tony that 13HP is a bit much. Not only the fact that you will struggle a bit to get it to fit nicely, but also that you are going to have to spend a large deal of cash on getting a clutch for the thing. What were you thinking of using for a clutch?

A 9HP engine is obviously not as powerful as a 13HP, but you could do a few simple mods like a free flow filter and exhause that will give you an extra HP or 2.

How is Klerksdorp nowdays? I havent been there in years since i lived in Benoni

EDIT: You asked about a jackshaft. It is where you use several sprockets to achieve compound gear reduction. It eliminates the use of large sprockets to save space. It also allows you to line things up nicely. Have a look at THIS thread for an example of a jackshaft. It is on a minibike, but the principle is the same for a go kart. From about post #2 you will see what one is

 

[Jaundre46]

Welcome to the forum. Another South African!! We are going to ounumber the Texans soon .

I would have to agree with Tony that 13HP is a bit much. Not only the fact that you will struggle a bit to get it to fit nicely, but also that you are going to have to spend a large deal of cash on getting a clutch for the thing. What were you thinking of using for a clutch?

A 9HP engine is obviously not as powerful as a 13HP, but you could do a few simple mods like a free flow filter and exhause that will give you an extra HP or 2.

How is Klerksdorp nowdays? I havent been there in years since i lived in Benoni

EDIT: You asked about a jackshaft. It is where you use several sprockets to achieve compound gear reduction. It eliminates the use of large sprockets to save space. It also allows you to line things up nicely. Have a look at THIS thread for an example of a jackshaft. It is on a minibike, but the principle is the same for a go kart. From about post #2 you will see what one is

Hi landuse nyc to see a south African on here,

Ok so 13hp is too much on the kart and as u say fitting is going to be an issue then I might have to go with a 9HP, will it be easier to fit than the 13hp? Klerksdorp is nyc I grew up here , I worked in Randburg for 3 years and then moved back to kld...

I was thinking on a 14t centrifugal clutch like the one in the picture? Thanks for the clarification on a jackshaft

 

[Jaundre46]

Otherwise will a 150 scooter engine be better than a 9HP lawn mower engine?

 

[landuse]

I am not too sure how easy a scooter engine would be to mount and use. Maybe one of the other members can help you out there. A 9HP would be easier to mount because it will have a smaller footprint. The holes in the existing plate you have might even line up.

The thing with clutches to remember is the bore size. A 9HP engine might have a 1 inch output shaft. That means you will need a 1 inch clutch (which gets a bit pricey as they are not as common). A 3/4" bore clutch is common and cheaper (like the one you posted a pic of)

A general gear ratio (depending on tyre size) to aim for is 6:1. With your tyres that should be fine. Using a 14T clutch means that you will either need a rear sprocket with 84T (14x6), or you will need a jackshaft to allow for smaller sprockets that will give you the same ratio. A 84T sprocket will probably have a diameter that is too big for the clearance you have on your kart. It will be scraping on the ground.

Using a jackshaft you can use a number of combinations of sprockets. To work out the ratio for a jackshaft, the formula is:

(JS In/Engine) * (Axle/JS Out)

You will also have to make sure that the pitch of all the sprockets are the same

 

[RASSIE]

welcome I got a 100c Yamaha kt100 motor just needs a carb rebuilt let me know

 

[Jaundre46]

I am not too sure how easy a scooter engine would be to mount and use. Maybe one of the other members can help you out there. A 9HP would be easier to mount because it will have a smaller footprint. The holes in the existing plate you have might even line up.

The thing with clutches to remember is the bore size. A 9HP engine might have a 1 inch output shaft. That means you will need a 1 inch clutch (which gets a bit pricey as they are not as common). A 3/4" bore clutch is common and cheaper (like the one you posted a pic of)

A general gear ratio (depending on tyre size) to aim for is 6:1. With your tyres that should be fine. Using a 14T clutch means that you will either need a rear sprocket with 84T (14x6), or you will need a jackshaft to allow for smaller sprockets that will give you the same ratio. A 84T sprocket will probably have a diameter that is too big for the clearance you have on your kart. It will be scraping on the ground.

Using a jackshaft you can use a number of combinations of sprockets. To work out the ratio for a jackshaft, the formula is:

(JS In/Engine) * (Axle/JS Out)

You will also have to make sure that the pitch of all the sprockets are the same

thanks for the info i will go and check out the size of the 9.5hp engine today, i understand what you mean on the gear ratio and the sprocket sizes with the ground clearance i have and etc...

 

[Jaundre46]

welcome I got a 100c Yamaha kt100 motor just needs a carb rebuilt let me know

hi rassie i sent you a pm thanks

 

[OzFab]

Welcome to the forum. Another South African!! We are going to outnumber the Texans soon .

You'll have to outnumber tha Aussies before you go anywhere near the Texans

How is the 9.5hp compared to the 13hp?

If we're talking industrial engines (Honda GX type engine or similar), the 9hp & 13hp are built with the same block, crank, etc...

A general gear ratio (depending on tyre size) to aim for is 6:1.

Take it from me, 5:1 should be ok...