gearing

[buildinthrillz]

hello all sorry if this has already been asked. Im running a 30 series torque convertor and im having trouble finding drive sprockets for it. im using the 12 tooth it came with and a 63 on the axle the shifter karts a ton of fun but not fast enough, my question is how small of a sprocket can i run on the axle with a built up predator 212 and t/c i still want some low end torque but want a top speed more then the current 45mph i realize its a give and take change and i dont want to buy 10 sprockets to answer my question. my understanding is because of the torque convertor i can run a taller gearing any advise will be greatly appreciated thanks in advance.

 

[itsid]

Hi and welcome!

Well, first and this is somewhat important:
shifter karts means SHIFTER!.. no gearbox to shift, no shifter kart!
(FnR gearboxes don't count )

Now terminology aside:
we just recently had a highly modified 212 and series 30 combo that suffered from a similar issue.
(allegedly the series 30 has an issue with high powered engines and stops them from unfolding all their rpms somehow)

ideal gear ratio depends on wheel size and weight as much as on sprocket teeth.
(the wheel itself is as essential of a gear as the sprockets are..)

So we need more infos to properly suggest anything.
crack out your phone and visit:
app.kartcalc.net
click on Quick Calc and enter the numbers to get a conservative viability rating
(if it moans about too tall gear ratio you might need to adjust it)

on small wheels and light weight I think you can safely get away with a ~ 4.6:1 ratio
(55Teeth on the axle) but since we don't know the power of the engine, the weight of the kart (with you in it) nor the size of the driven wheels we can't really tell for sure.

'sid

PS If I'm assuming 18" rears you're engine bogs down at around 4100rpm..
which is where MrMonks had issues with as well
check the thread to see how he solved that. (juggernaut essentially)

 

[buildinthrillz]

Thank you for the quick response the overall weight including my self is around 315lbs the motor is almost built exactly as the 212 in the forum link you provided with out the head shave and I haven’t advanced timing yet. The tires are 10inches from floor to top of tire. The kart has a ton of torque it’s a donut machine and it gets to 45 very quickly. It’s does sound a lot like the t/c is holding it back as it did 45 bone stock and continues to go 45 after all the modifications to the motor I have a 53 tooth sprocket on the way I’m going to try and I’ll post the results but after reading the forum link you provided I’m not going to hold my breath. The only other thing I can think of is switching to a clutch as I’ve read they are overall faster top end but I didn’t want to lose all the low end next step would be Lifan 200 cc 4 or 5 speed and make it a true “shift kart “again thank you for the response I’ll keep you posted. Also I do not have RPM gauge yet but it sounds like there’s room left to go faster it does not lock down by any means it sounds like it red lines i’ve heard horror stories blowing these motors wants governors fully removed so I very rarely hold it open throttle like I said it gets up to 45 very quickly but then just stays there on bone stock motor and on hopped up motor

 

[landuse]

If you have loads of torque at the moment, I would try the 53T you have on the way and then see how that handles

 

[itsid]

10" rears?
Wow.. well in that case the engine is likely hitting max rpm already..
with 45 mph you need upwards of 7000 rpm to get there.
So no, the TC does not appear to be your problem.
(the rev limiting on the other TC stepped in at 4100 rpm or so)

53T sprocket isn't bad.. maybe a 51T would still work and give you a tad more speed even.

'sid

PS if you want to get a rpm estimation, record the audio of the running engine (at full speed),
load it into audacity and count the pops and you get a very good estimate

 

[buildinthrillz]

alright after about an hour of converting sound files and if im doing it right and or understanding you correctly im at around 5000 rpms,I remeasured my tire and i was wrong the tape says around 11 inches the tire size is a 12x8x6? I am new to these types of karts always built off roaders im going to go ahead and pick up a few different size sprockets it cant hurt to have some extras for other karts. I was debating buying a series x hub and sproket at a 36 tooth to try because i felt it had enough torque but ill hold of for now till i try the 51-53 ill post after i try them thank you for your time and knowledge. -will

 

[itsid]

with 12" wheels and 5000 rpm (assuming 5.25:1 gear ratio [as in 12 to 63 teeth])
you'll be running at ~38 mph not 45mph (that'd be 6000 rpm)
smaller wheels mean even slower speed thus more rpms to reach 45mph

Anyways neither of which is actually indicating a rev limiting TC *shrugs*
So we should be good on that patr at least.

I'd rather have you recount the teeth tbh,
but how about some pictures of the kart and setup instead..
that usually gives us some good idea and
also we just looove some nice kart images

'sid

 

[buildinthrillz]

12 front and a 63 tooth rear for sure I am using a gps speedometer? and my rpm count may be off I did fully remove the governor so my understanding is it’ll rev higher with valve float at 5500 so I have the 22 lbs springs in and bigger jet the pictures are from about a month ago I replaced the stock intake and now running pulse pump and steering column gas tank this is my first build for street.picked up the frame at a yard sale and slowly built it up last year learned a lot in the process I’m hooked and now working on my second now

 

[buildinthrillz]

Welp before I went to work this morning I had my helper drive the scooter next to me while I was driving the go kart top speed on scooters speedometer was 43 mph so GPS mph was a little off AnyWho I should be getting that sprocket today or tomorrow I’ll post results after I try her out thanks for all the knowledge -will

 

[JTSpeedDemon]

FYI, we STRONGLY recommend you upgrade to an ARC billet connecting rod and flywheel since you have upgraded the valve springs. At stock valve spring RPMs, the stock parts usually hold, but at speeds higher than that, there are no guarantees(lots of people have thrown rods).

 

[itsid]

Indeed, you really want a billet conrod in there
(ARC or other doesn't matter.. stronger than original cast con rod DOES!)

Frankly.. whoever gave you the stupid advice to upgrade the valve springs without upgrading the connecting rod should be verbally punched in the face;
that is an catastrophic engine failure waiting to happen with the potential
of people getting hurt badly
on a rear engine kart shrapnel points towards the back of your neck and skull on most mini bikes it's aimed right at your testicles, so luckily with a side engine race kart chassis
you are at least out of the danger zone somewhat.. still a really crappy idea to not take precaution!

Flywheel is a good idea as well indeed,
it also advances ignition timing, which is what I think is holding you back at the moment.
a 4-8° timing advance would likely increase the performance potential at higher revolutions.

but first test the new sprocket (and for your own sake.. get a billet con rod!)
if you lack a bit of power and having a hard time to get the kart moving
you might need to upgrade the TC's garter springs maybe weights
to a tad higher engagement speed..
you likely will have to do that once you advance timing

'sid

 

[buildinthrillz]

Thank you guys for scaring me out of driving it for a while lol billet parts are on the way I’m slowly building another engine with all billet parts this one was temporary When I’m done with the other engine I was planning on doing the same thing with this motor for another cart had no idea that I was in danger very good info I value my life lol while I’m in the other engine I would like to change out the cam but have no idea which one to choose or if I even need to do so do you guys have any advice on cam selection and I may just put the other valve springs back in for now so that I can test the new sprocket without fear of blowing my engine or injury thanks again for the knowledge-will

 

[itsid]

Yes, pop the original valve springs back in..
that will more or less safely limit the rpm to around 5500 rpms (5100-5700 ish)
speeds the cast con rod should be able to handle rather safely.

there's always a risk that something fails, you forgot to remove the tiny washer behind the governor wheel for example and it wedges into the cam gear abruptly stopping the engine
(resulting in kablammo rogers tickling your chin with an asphaltum rubbing)

But we want to make sure that you are at least as safe as possible...
there's no fun in road rash, broken limbs or worse.
and at best in case of such failure you totaled the engine (also a bit of a downer, no?)

a billet conrod isn't expensive enough to take the risk.

'sid

PS I think the MOD2 cam is the goto "overall performance" cam.. not too violently increasing the max rpm, not causing a too massive loss of torque in the lower rpm band...
(well.. as far as I remember that is..)

 

[Wilson_Engine_Shop]

Hi and welcome!

Well, first and this is somewhat important:
shifter karts means SHIFTER!.. no gearbox to shift, no shifter kart!
(FnR gearboxes don't count )

Now terminology aside:
we just recently had a highly modified 212 and series 30 combo that suffered from a similar issue.
(allegedly the series 30 has an issue with high powered engines and stops them from unfolding all their rpms somehow)

ideal gear ratio depends on wheel size and weight as much as on sprocket teeth.
(the wheel itself is as essential of a gear as the sprockets are..)

So we need more infos to properly suggest anything.
crack out your phone and visit:
app.kartcalc.net
click on Quick Calc and enter the numbers to get a conservative viability rating
(if it moans about too tall gear ratio you might need to adjust it)

on small wheels and light weight I think you can safely get away with a ~ 4.6:1 ratio
(55Teeth on the axle) but since we don't know the power of the engine, the weight of the kart (with you in it) nor the size of the driven wheels we can't really tell for sure.

'sid

PS If I'm assuming 18" rears you're engine bogs down at around 4100rpm..
which is where MrMonks had issues with as well
check the thread to see how he solved that. (juggernaut essentially)

Is there a link to MrMonks thread? I'm having the same issue with my 30 series at 4100rpms on my Murray Explorer and i'd like to fix it.

Sometimes my belt slips when i'm going slow and punch the gas, it'll stall up to about 3,500 rpm until the belt grabs then goes back down to 3,000. Then i can get up to speed. I cant get past 4100 rpms. Even pushing the governor arm doesn't make it rev more

 

[buildinthrillz]

If you click the blue letters it takes you straight to the page very good info
Thought this was not my issue it may help you.-will

---------- Post added at 11:42 AM ---------- Previous post was at 11:41 AM ----------

If you click the blue letters it takes you straight to the page very good info
Tho this was not my issue it may help you.-will

---------- Post added at 11:46 AM ---------- Previous post was at 11:42 AM ----------

53 tooth sprocket installed did a test run and still had a ton of torque happy about that will post a top speed run after work today oh and factory springs are back in I’ll keep ya posted itsid thank you -will

 

[buildinthrillz]

Well I broke the sound barrier at a whopping 50mph lol think it’s time for a new motor thanks for all the info guys but a five speed is in Order for this “shifter kart” if it’s gotta stay on pavement it’s gotta be fast any recommendations on a motor choice. -will

 

[mckutzy]

Pick any 5 speed motorcycle you like..
Or buy a big twin Harley type transmission and mate that to your built engine..

 

[buildinthrillz]

Thank you for the information I have been looking for a transmission for a while never thought of searching Harley good info right there.

 

[jmaack]

Well I broke the sound barrier at a whopping 50mph lol think it’s time for a new motor thanks for all the info guys but a five speed is in Order for this “shifter kart” if it’s gotta stay on pavement it’s gotta be fast any recommendations on a motor choice. -will

what app is that? I cant find it in my play store.

 

[itsid]

what app is that? I cant find it in my play store.

looks like tacho55 on ios

'sid