Buying a old used karting

[itsid]

well tapered shaft can do without keyways actually..

as opposed to a straight shaft,
where there's always play between the shaft and the bore;
a taper will -at one time- have zero play and the rest is friction

The bad thing about that.. it needs to be a perfect match, and zero tolerance is really exhaustive to machine; so we're back at adding a key

'sid

 

[Miky]

While I'm waiting for the clutch, sprockets and chain I setup the brake line. I putted two springs because spring in the brake assembly is not doing it's job.

 

[itsid]

Miky,
remove the lever again and before reinstalling it; make sure the slopes are free of dents
then add a bit of white grease;
that way the lever will snap back more easily

'sid

PS the springs you added might do the job, but it's the job of the compression springs to push the lever back and grease will help them doing so

 

[Miky]

What is life without problems...
So I ordered new chain and sprockets yesterday, today package was delivered but I made a huge mistake ordering it, I didn't check diameter of big sprocket. Normally it's bigger than it needs to be, my tires are 275 mm and sprocket is 310 mm plus chain.
Question in this is can I put 9 teeth sprocket on the clutch and 52 teeth becouse this 52 sprocket is 216 mm? Next sprocket is 60 tooth and diameter is 249 mm so it has only 13 mm to the ground because the tires are 275 mm...

One picture of the kart with my kid

 

[itsid]

tyre diameter will be even less I'm afraid.. (11" are 275mm of course, but compression due to weight will reduce the effective diameter by a bit )

Anyways.
IF you find a 9T sprocket for the clutch... yes that still should work (5:78:1 seems okay'ish)

but there are drawbacks, a small sprocket stresses the chain mor than a bigger one;
also the power is transfered using fewer teeth so the sprocket sees more abuse too.
(4 instead of 6 doesn't sound like much but it's a 30% decrease.. thus 30% more abuse)

it'll still work,
but frankly.. you'd be better off buying a proper clutch/sprocket chain set (#35)
(12T clutch, 72T axle) if you ask me.

oh btw.. what size sprocket did you buy? 310mm... that's much more than a 64T

'sid

 

[Miky]

Here is one sprocket with 72 tooth but I don't know what size it is, which chain goes on it, ad says distance between sprocket teeth is 10 mm, that is for 3/8, right? http://www.njuskalo.hr/moto-dijelovi-ostali/zupcanik-karting-72t-oglas-4411287

 

[OzFab]

Correct, meaning it's a #35 sprocket...

You can safely run less than the "recommended ball park" 6:1 ratio with those small tyres; my kart has 10" tyres & runs 5:1 with no problems...

 

[itsid]

10mm is NOT 3/8" .. (that'd be 9.5something)
and since I've just seen odd metric chains I've never seen before (4mm and 5mm pitch)
I cannot say there is no such thing as a 10mm pitched chain...

I don't know if it's a measuring error (likely) or not.. diameter should be 224mm for a 72T #35
he says it's 223mm... again likely it is 3/8" but I can't tell for sure

'sid

 

[Miky]

Thanks guys, I ordered it so we will see

 

[OzFab]

10mm is NOT 3/8" .. (that'd be 9.5something)

9.252mm to be exact

 

[itsid]

9.252mm to be exact

cough cough.. EXACT??
check your math Tony.. 3/8 is .375
(so any result will either have a zero or a five as it's last digit.)
quick head conversion:
25 is 100/4 (the 25 mm)
so 37.5/4 (9.375)
and 4 times .0375 [the .4mm] (.15)
added up...
9.525mm

and my calculator says I'm correct (just checked for whatever reason )
(where's that tongue smiley when you really need it )

'sid

 

[OzFab]

My bad, you are correct Alex... I knew it was one of the two

 

[itsid]

At least you haven't been too far off
I tend to misplace the decimal every now and then.. and that's where it get's nasty

'sid

 

[Miky]

Question, 35# chain, will it hold becouse kart, engine and me together we have approximately 170 kilograms?

 

[KartFab]

well tapered shaft can do without keyways actually..

as opposed to a straight shaft,
where there's always play between the shaft and the bore;
a taper will -at one time- have zero play and the rest is friction

The bad thing about that.. it needs to be a perfect match, and zero tolerance is really exhaustive to machine; so we're back at adding a key

'sid

I didnt follow this thread to know too much of the background, but even the ARC billet flywheels do not "need" a key once they are mated with the crank. The procedure for getting a good mating surface (for flywheels) is to put some valve grinding compound on the shaft, and work the flywheel left/right pushing it into the crank, clean it all up, and properly torque it down. Once mated/torqued, the friction is more than enough. Problems happen when its not torqued to spec. No idea if this is even relevant, just thought I'd share.

 

[Miky]

I'm having trouble getting 72 tooth sprocket so I thought building a jackshaft. I have 12 tooth on the clutch, I will order 48 t sprocket for the axle and 30 the sprocket for the jackshaft in and 20 the sprocket for the jackshaft out. That gives 6:1 ratio, right? Also if I find 72 tooth sprocket hole for the key is on opposite side so I need to cut new keyhole. For the jackshaft I have an axle and bearings.
Today i got 12 t sprocket for the clutch, chain, bearings for the front wheels, spindles and axle.
That big sprocket is 72 t but it is not 3/8.

 

[itsid]

Sorry Miky,
I have to say it..

Go and just buy a setup from the US..
omb isn't that expensive at all, shipping is a pain I admit

but frankly, this is now what your third try to save shipping fees;
and all you did so far is burning money for things you didn't want.
(yes, that'd be 6:1... btw)

Know what call istra karts
www.istra-kart.com

IIRC their smaller karts run chain setups too.. they'll know a source or likely even have a spare you can buy.
if that fails
try
www.kartcross.hr
(still istria...)
and ask the same.

I think not much longer and you spend the "shipping fees" on parts you'll never going to use.

'sid

 

[Miky]

Thanks sid but buying isn't fun, building it is

 

[Miky]

Today got the last parts for the jackshaft. Next step is cutting peace of steel plate 30x40 cm. It will go under the engine and towards the seat. For the axle sprocket I will use old sprocket, make a seat for the new sprocket and bolt it down.

 

[Miky]

Started cutting 4mm steel plate for the jackshaft.
As pictures shows it goes under the engine and jackshaft goes behind the seat. And yes, that is Coca-Cola air filter, it is not finished yet