tav 2 question

[happy_8637]

ok so i moved the secondary clutch spring one the right because it was lacking on top end power was that the right thing to do or no i have a 6.5 hf with the gov. removed and ported, polished and shaved head . tav 2 with 6:1 gearing on 18 inch tires.

 

[Half-breeder]

... w/ the driven turned so the 3 holes are 'under' the shaft opening... and moving the 'hook' to the right hole, will increase your initial torque, keeping the driven closed at a 'higher' rpm(that setting is recommended for off-road mainly).

 

[happy_8637]

ok so how do i get more power on the top end cause im not pulling any more than like 2500 - 3600 in the like 2nd gear when i shifts

 

[itsid]

(that setting is recommended for off-road mainly).

or really large tires

with a lower setting it's quite possible that the TC shifts too soon and prevents getting anywhere near top speed with tires that size.
(depends on the overall weight and road inclination etc.)

ok so how do i get more power on the top end cause im not pulling any more than like 2500 - 3600 in the like 2nd gear when i shifts

if your TC doesn't reach his highest ratio, then you might want to try the medium setting of the driven.
but you might need to increase your final gear ratio a little (maybe to 6.5:1 or 7:1) to get the best of both worlds (torque and speed)

'sid

 

[Half-breeder]

Im only guessing... the 'lack' of torque on the high end... could be due to the 'drag' of your wheel size(weight/traction)... maybe, due to 'possible' motor setup/build(more power on the lower rpms vs the upper... I think that's variable w/ the timing).

Im NOT sure... but Ive noticed that the design of the TC/CVT 'can' possibly limit the rpms of the motor due to the lack of torque above 3600 rpms(over drive). I 'can' imagine' that this can be 'over-ridden' by adding more HP... but im only guessing from my trial n outcomes.

 

[Half-breeder]

or really large tires

with a lower setting it's quite possible that the TC shifts too soon and prevents getting anywhere near top speed with tires that size.
(depends on the overall weight and road inclination etc.)

The 'way' you just explained it makes complete sense to me... (scarey)

if your TC doesn't reach his highest ratio, then you might want to try the medium setting of the driven.

Im only 'guessing' he's been running the 2nd(middle) position setting... hence he's trying the 3rd, cause he's not liking the response?

Im interested in seein his outcome... I have set 'mine' to the 1st setting(for when my motor is back together)... and will see how 'that' works... but if the 3rd position compensates it then the 3rd setting is the way ill be setting mine aswell(im 'missing' +7-10mph somewhere, and would like to know if it was the motor... the TC... or both.

 

[itsid]

shifting sooner doesn't make the kart faster,
like in a car, if you shift from first to fourth instead of using second and third...
it's not actually fast
Good point about the mid position.. it could have been the mid position previously as it is the std setting...

But I tried to find out (in a previous thread) and noticed something...
happy, you might have the wrong spring in your driven unit.

The Comet series 30 spring is GREEN, not red,
the Comet series 40 spring is red (reversly wound and stiffer than the green one)
I'm not sure that if they changed colors sometime, but I doubt it.

So as Tihm suggested try the first hole instead.

If your kart doesn't reach top speed
(~45mph or 72km/h .. @ 4500 rpm)
but about that rpm,

downgrade to the green spring again,
or upgrade your engine.
carefull though, you might cross the line that the series 30 can withstand power wise
and you'll start buying belts again on a daily basis

Check your spring first!
I think the red spring is wounded in the opposite direction,
(series 40 drivens are mounted inbound, not outbound like a series 30...)
so if it is indeed a red spring of a series 40 you MUST change the spring,
to either a green series 30 or a yellow series 40
(manco outbund series 40 same tension as red, but reversly wound)


'sid

 

[KartFab]

you really need to get a new belt, you will notice the difference immediately.

Your top speed (stock rpm) should be 35.7 mph

 

[Half-breeder]

shifting sooner doesn't make the kart faster,
like in a car, if you shift from first to fourth instead of using second and third...
it's not actually fast
Good point about the mid position.. it could have been the mid position previously as it is the std setting...

But I tried to find out (in a previous thread) and noticed something...
happy, you might have the wrong spring in your driven unit.

The Comet series 30 spring is GREEN, not red,
the Comet series 40 spring is red (reversly wound and stiffer than the green one)
I'm not sure that if they changed colors sometime, but I doubt it.

So as Tihm suggested try the first hole instead.

If your kart doesn't reach top speed
(~45mph or 72km/h .. @ 4500 rpm)
but about that rpm,

downgrade to the green spring again,
or upgrade your engine.
carefull though, you might cross the line that the series 30 can withstand power wise
and you'll start buying belts again on a daily basis

Check your spring first!
I think the red spring is wounded in the opposite direction,
(series 40 drivens are mounted inbound, not outbound like a series 30...)
so if it is indeed a red spring of a series 40 you MUST change the spring,
to either a green series 30 or a yellow series 40
(manco outbund series 40 same tension as red, but reversly wound)


'sid

... Mines red... From BMI new, last Christmas... Maybe their fault?

 

[exenos]

Try marking the clutches with a marker to see if they are fully shifting out. If all the marker is rubbed of then its shifting all the way, in that case just keep tightening the secondary spring until you see some marker left on the primary sheave. Once that happens you can either back off the spring one hole if a lot of marker is showing, leave it if less than 1/4" is left or add a few teeth to the axle sprocket if you want to get the absolute most out of your engine.

EDIT: Or if you really want to go nuts start removing some weight from the primary clutch, that will both increase the engagement and delay shift out. **DISCLAIMER: NOT recommended unless you know what the consequences are and are prepared to buy new weights if you mess up. Just added for info**

 

[itsid]

... Mines red... From BMI new, last Christmas... Maybe their fault?

that's odd!
Comet or clone?

Anyways, if you got it this way it shoud be the correct one.
I highly doubt they change the springs just for fun at BMI
So it's more than just likely the stock spring in there, which will work as intended.

thanks for letting me know.. *mindmap updated*

'sid

 

[Half-breeder]

that's odd!
Comet or clone?

Anyways, if you got it this way it shoud be the correct one.
I highly doubt they change the springs just for fun at BMI
So it's more than just likely the stock spring in there, which will work as intended.

thanks for letting me know.. *mindmap updated*

'sid

China clone... however... in the link u posted on the other TC post... look down at the Asymmetrical Systems section(lil past halfway down page). They 'say' no red for 20 series... but 30 seems to have 'red' and 'green'... but when I go over to BMI for a replacement... they only have 'yellow' and 'green'.... hmmm.

Thought the china copy and Comet used the same parts/color guidelines...?

 

[rocketkart]

China clone... however... in the link u posted on the other TC post... look down at the Asymmetrical Systems section(lil past halfway down page). They 'say' no red for 20 series... but 30 seems to have 'red' and 'green'... but when I go over to BMI for a replacement... they only have 'yellow' and 'green'.... hmmm.

Thought the china copy and Comet used the same parts/color guidelines...?

thats cus it's China. I think there color blind or somthing. http://www.youtube.com/watch?v=gNy2pbHxXpg sorry

 

[Half-breeder]

thats cus it's China. I think there color blind or somthing. http://www.youtube.com/watch?v=gNy2pbHxXpg sorry

I forgot bout 'that' part of the movie...

...but BMI probably 'puts' the packages together... and I 'think' their stationed in Ohio...(northerners) and the guys at GKS , that supplied the info specs for the springs, sid's link, are in LA(Louisiana)... (Gulf-coasters) lol.

Either way... Im Japanese(we are not ALL like Mr. Sulu... I 'think' he's color blind too), and Im NOT color-blind...

Either way... forgot bout the Chinese color-blind thing

....sorry for hyjacking the thread...

 

[happy_8637]

well i moved it to the 3rd hole as it was in the second or middle. it made a slight difference but it still seems to lack a little speed. PS. if you wind the spring the wrong way the belt. when the secaondary engages all the way it tends to lock up the rear wheels, just saying it was a cold day when i was working on it and i go the belt off and unstuck and back to the shop so it wasnt that big of deal. My clutch came from bmi went and picked it up myself it has the red spring, in it so idk i might try to get a green one or something to see. it is a brand new belt on the kart just put it on the other day.

 

[happy_8637]

The 'way' you just explained it makes complete sense to me... (scarey)



Im only 'guessing' he's been running the 2nd(middle) position setting... hence he's trying the 3rd, cause he's not liking the response?

Im interested in seein his outcome... I have set 'mine' to the 1st setting(for when my motor is back together)... and will see how 'that' works... but if the 3rd position compensates it then the 3rd setting is the way ill be setting mine aswell(im 'missing' +7-10mph somewhere, and would like to know if it was the motor... the TC... or both.

And i also am missing the speed and rpm somewhere i think i am gonna try to put smaller tires on the kart and run it and see if makes a difference if it does them im gonna stick with them for good

 

[itsid]

No no.. sorry.. if you have a red spring in it when you bought it.. it's all good and changing to a greeen one won't make any difference.
My fault! The only red spring I had in mind was from a series 40,
yours is what you need, what you want, what you wanna keep

smaller tires are a good idea to test.

I'm sure you aligned the driver and driven once and for all
to not chew on your belt again, so I'd rule that out to drain energy.
Check if your brake's in order (free) and your axle bearings to move free as well.

Then see if the smaller tires help or not.
if you're missing rpm, then it's a gearing problem.
4500 is(should be) doable with just the governor removed
and maybe a high flow airfilter and exhaust.

I punched in some numbers,
theoretically the kart on 18" wheels and a weight (kart plus passenger) of not more than 200kg (441 lbs) should hit top speed within 8 seconds.
I don't know the weight not of your kart nor yours, so I used a rather big number to be on the safe side
see the result here:


as you can see in the raw data on the left you need no more than just 46Nm to keep the kart moving and you still should be able to provide ~150% of that

'sid

 

[happy_8637]

well it does have exaughst and intake on it. we took the gps on my friends kart which i did the same mods to as mine it topped out at like 5500 rpms. yea im not sure the actual weight of the cart and stuff either

 

[itsid]

5.5k is great, getting almost dangerous without billet parts but a nice number

But then again, it's getting harder to estimate the correct speeds, since we talk about serious wind resistance already, and apart from "not?" knowing the exact weight,
I have close to NO CHANCE to know the actual surface area, cw index etc.
So everything up there is nothing more than a good guess

But the point of the above calculation is basically this:
You should be able to reach said speed (or a least something very close to it)
it's perfectly okay to not reach max rpm at max speed because the actual torque drops in the upper rpm band again.
Maybe down to a value that is not high enough to accelerate the kart further.
Again, friction in the drivetrain, wheels to road, road inclination, wind resistance.... too many unknown variables to even try to calculate more exact values.

But the values I used you should reach, ~45mph @ about 4500 rpm.
just get a free speedometer app for your smartphone and see what you end up with.

If you DO in fact reach 45mph or more your TC is in good working condition,
and you do not need to tweak it.
And if that's not enough, it's the engine you should care about (improved carb jetting, further increased airflow things like that)
Only if you reach a number much smaller than this (say just 30mph) you have a problem with the TC you should fix

'sid

 

[exenos]

Something with that math doesn't seem right sid. I cant see a 400lb kart with a clone doing the equivalent of a 10s 0-60 time.



EDIT: Just mark the clutches with a marker and take it for a top speed run. That will tell you just as much if not more than a gps reading. You very well could be getting full rpms out of the engine but the torque converter just wont shift any farther because the gearing is too high.