How to tell what kind of chassis?

[LiftedF350]

Hi all, New to the forum, Recently I bought a racing kart that had a crapy brigs 5hp, the owner before me said it was a yamaha shifter kart, but he switched to that motor to sell the chassis, Well it has yamaha disk brakes and on the floor board thing it says something about yamaha and they are not reliable or something, Well I could not find a part number but I did find a number on a plate near where the motor is mounted saying these numbers
787102486

Would any of you be able to help me figure out what it is? I will have pictures of it soon.


My plan for it : Kx80 motor, just got the motor mounts welded up today.

Still need to figure out how to rig up a rear sprocket? Any help on that? It had a bicycle thin sprocket on it and obiously thats not going to hold up the the abuse of the 80 motor.

 

[Kaptain Krunch]

Im horrible will chassis identification, but as far as the sprocket goes most shifter karts use 428 chain, and sprockets are readily available for 30mm, 40mm, 45mm, and 50mm axles. What size axle do you have? and what pitch sprocket front sprocket does the Kx have?

 

[LiftedF350]

Im horrible will chassis identification, but as far as the sprocket goes most shifter karts use 428 chain, and sprockets are readily available for 30mm, 40mm, 45mm, and 50mm axles. What size axle do you have? and what pitch sprocket front sprocket does the Kx have?

Im sorry, But I have no clue what you just asked! haha. But the size of the chain is literally like a bicycle chain, which what was on it, But the KX sprocket is just a regular sprocket? Thats the motor that is going on it, So i figured I would find a CRF50 or CRF70 sprocket and rig that up. But how do i tell the size of the axle?

 

[anderkart]

It seems many KX80's came with #420 sized sprockets. If yours is a #420 you can use a #40/41 style rear sprocket.
Heres some sprocket pitch/sizing info:
http://www.diygokarts.com/kart-parts/go-kart-chain.html

You'll probably find some #420 shifter kart rear sprockets for sale here:
http://www.google.com/search?source...US_enUS221US222&q=#420+shifter+kart+sprockets
But first you'll need to conform what diameter axle your kart has. I'd sugest using one of these to mesure:
http://www.google.com/products/cata...log_result&ct=image&resnum=8&ved=0CCwQ8gIwBw# (you can buy these most anywhere tools are sold for $10 on up, and you'll probably find they come in super handy for all kinds of other tasks when working with karts)

You'll find some good pics of a Yamaha race chassis to compare with yours at this link:
http://www.kartingarchives.com/index.php?option=com_jmovies&Itemid=58&task=detail&id=207
(if it wont let you veiw this Yamaha kart Brochure, you may have to join that forum first)

 

[LiftedF350]

It seems many KX80's came with #420 sized sprockets.
Here's a link to some #420 shifter kart rear sprockets for sale:
http://www.google.com/search?source...US_enUS221US222&q=#420+shifter+kart+sprockets

But first you'll need to conform what diameter axle your kart has. I'd sugest using one of these to mesure:
http://www.google.com/products/cata...log_result&ct=image&resnum=8&ved=0CCwQ8gIwBw# (you can buy these most anywhere tools are sold for $10 on up, and you'll probably find they come in super handy for all kinds of other tasks when working with karts)

You'll find some good pics of a Yamaha race chassis to compare with yours at this link:
http://www.kartingarchives.com/index.php?option=com_jmovies&Itemid=58&task=detail&id=207
(if it wont let you veiw this Yamaha kart Brochure, you may have to join that forum first)

Thank you for your information. I looked at the Race chassis, but couldnt find it in there, The problem with my sprocket is that I have a mount from where the orignal split sprocket bolted too, and was going to try to use that. and i will check out that tool

 

[anderkart]

At that sites page, you have to click on "Click here to view the document"

Because of the transmission, shifter karts usualy only run somewhere around a 20 tooth rear sprocket. These usualy mount directly to the axle and probably wont fit on your old hub cause they're so small. Here's another link you should check out: http://www.iwt.com.au/GSKARTS.htm

 

[LiftedF350]

At that sites page, you have to click on "Click here to view the document"

Because of the transmission, shifter karts usualy only run somewhere around a 20 tooth rear sprocket. These usualy mount directly to the axle and probably wont fit on your old hub cause they're so small. Here's another link you should check out: http://www.iwt.com.au/GSKARTS.htm

The thing about that was was that truthfully, im not going to be racing pro or anything, im just looking for tourqe to destroy the tires, but have the speed to corner well. So i was just going to try and find a sprocket that will bolt up weither I have to drill my own holes or not. haha.

 

[anderkart]

That's cool if you can accurately mod a sprocket. If you have to buy a rear sprocket anyway, you might as well just buy a #40 rear sprocket that bolts right on your old hub. And then I beleve a #40 chain should also mate to your engine sprocket assuming its a #420.

They make a few diferent OD's/bolt patterns of sprocket hubs and I'm still not sure which one you have. This link has a bunch of hubs with the sprocket mounting dimensions, you could compare these to yours to make sure you buy a sprocket that bolts right on: http://www.bmikarts.com/shop/?cart=1963277&cat=172&

Did you ever get that Yamaha kart Brochure to open and see the pics? http://www.kartingarchives.com/index.php?option=com_jmovies&Itemid=58&task=detail&id=207

 

[Kaptain Krunch]

The problem with using any sprocket you find is the speed will be so low, that you will be redlining in 6th just to hit 40, which is a lot of shifting. With a KX80, you will be able to roast the tires and do 60 easy, I suggest just buying the right sprocket, even if its just for messing around.

 

[anderkart]

Kaptain,
I wasnt sure. Would a #420 driver, a #40 rear sprocket and #40 chain all work together?

 

[Kaptain Krunch]

Dont quote me on this, but i believe 420 is wider, I've found out the hard way its always better to get matching sprockets and chains, even if it will fit. For my shifter i used a few #50 sprockets, a 530 drive sprocket on the engine, and 530 chain, they looked the same but 530 is just slightly wider than 50, and its a little sloppy on the sprockets. Once this chain/sprocket combo wears out i'll do it the right way with all #50 chain and sprockets.

 

[anderkart]

Cool thanks.

 

[LiftedF350]

I looked at the site and am still looking, sorry its taking so long, I have been busy working on it. I think the axel is a 32mm. I measured it and it was 1inch. And I will also take a look at that site to see what they have.

NEWS: I talked to my neibor and he said since i have the original sprocket, if i get another, i will be able to give it to him and he can mill it for me.
I got the motor halfway welded up, the welds arnt pretty, but it will hold, and I also got it running. One problem that I have is the exhaust. I ****ed up the expansion chamber, well the part where it connects the head port - to the expansion chamber pretty bad, so i will have to cut that out, and weld a new piece in.
Also got it running Now i need to rig up the clutch, shifter, gas tank, sprocket.


ANOTHER QUESTION: If the gas tank is below the carb, will it still create enough of a vaccum to suck in the gas? What im asking pretty much is that will I need a fuel pump of some sort?


Thank you very much for your help and replies. they all have been extremly helpful.

 

[anderkart]

Stock KX carbs don't have any fuel pump built into them. Unless you mount your fuel tank high enough to gravity feed, you'll probably be needing a good pulse fuel pump: http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4DMUS_enUS221US222&q=pulse+fuel+pump

They operate off the pulse signal generated by your intake manifold or crankcase. I'd suggest installing a barbed fitting to conect a 1/4" hose to your intake manifold.
Like this pic: http://www.affordablegokarts.com/cg...Code=A&Product_Code=AGK292&Category_Code=GPPX

Here's a couple DIY threads with more pulse pump info:
http://www.diygokarts.com/vb/showthread.php?t=5139&highlight=pulse+pumps
http://www.diygokarts.com/vb/showthread.php?t=5091&highlight=pulse+pumps

 

[LiftedF350]

Stock KX carbs don't have any fuel pump built into them. Unless you mount your fuel tank high enough to gravity feed, you'll probably be needing a good pulse fuel pump: http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4DMUS_enUS221US222&q=pulse+fuel+pump

They operate off the pulse signal generated by your intake manifold or crankcase. I'd suggest installing a barbed fitting to conect a 1/4" hose to your intake manifold.
Like this pic: http://www.affordablegokarts.com/cg...Code=A&Product_Code=AGK292&Category_Code=GPPX

Here's a couple DIY threads with more pulse pump info:
http://www.diygokarts.com/vb/showthread.php?t=5139&highlight=pulse+pumps
http://www.diygokarts.com/vb/showthread.php?t=5091&highlight=pulse+pumps

**** dude your good, your nailing the questions head on. Thank you.

 

[anderkart]

Yer welcome, I got lots of free time nowadays and enjoy helping. If your interested, I still think we can track down a rear sprocket that'll bolt right up to your old hub. (meyby for $20 or so)

You just need to confirm what chain size your KX80 sprocket is: -> http://www.gokartsupply.com/chain.htm
And figure out what bolt patern and sprocket ID fits your curent hub. Is your hub made for a 6 bolt sprocket with a 4-9/16" ID and a 5.25" bolt circle?
(that bmikarts link I posted above shows the sprocket mounting dimensions of other style hubs for comparison to yours)

 

[LiftedF350]

Picked up a sprocket, but looks like im going to have to drill new holes in the hub. and its a 6 bolt sprocket.

 

[red arrow]

lifted f350,
i joined this forum because i came acreoss this post while searching for yamaha rc100s info. stop what you're doing and evaluate your kart. without seeing your kart, i can guess that you may have a rare early yamaha rc100s from 1977-79. it does not sound like you have the original rare straight shaft kt100 engine with rear facing exhaust (as it came), but the chassis with the serial number begining with 787...... tells me it more than likely is, as mentioned above. if this is the case, the chassis is rare and hard to find in original straight form. more so than people think. and original parts are hard to get. at least thats what i have experienced. i hope its not to butchered up, but if you can, lets see some photos. you may have a rare find. the serial number will defintely uncover more detail, but i have never found a breakdown on the serial numbers, which i am still seeking. these early yamaha karts are collectors for sure, you may want to look into it.