Gear ratio help

[Hollow45]

Hello everyone,

I recently purchased a manco phantom and a stock redator 420 with a go power sports 40 series torque converter kit. The kit comes with a 10T clutch sprocket. However, I do not know what drive sprocket to run with it. I have read that running the wrong ratio can burn clutches. It currently has a 60T sprocket with 420 KMR chain. The kart also has 22 inch tires. I dont plan on riding on the road to often. I plan on using it more for off road. I bought the engine separately from the go kart. I also plan on doing a stage 1 kit in the near future but want to get it running stock first. What sprocket do yall recommend I use?

 

[bob58o]

Kick the tires and light the fires.

What you have should be a fine starting point. You are set up for 39 mph at 3600 RPM, which is acceptable. It may not be ideal for what you want, but it is close enough for hand grenades. It is probably the sprocket ratio I would have recommended if somebody told me they have a 420cc, a 40 series TC, and 22" tires.

If you want more bottom end, you can see if they make a smaller jackshaft sprocket for your chain pitch and shaft size. I'm assuming you have a 3/4" jackshaft and are using 1/2 pitch chain. I'm not sure if you can find a 9T 3/4" bore sprocket for 1/2" pitch chain. Size of the bore can put a minimum on the number of teeth you can put on a sprocket. If the jackshaft is 5/8" you might have more options. If the jackshaft is 7/8", you might have less options.

Or you can put a larger sprocket on the rear, but if you are using 1/2" pitch chain, 60T is as big as the standard sprockets get. Larger than 60T are available, but a bit more expensive.

Or you can swap the driven pulley (7.5" 40D) for the larger pulley (8.5" 44D). Which will give you roughly 20% more torque than the 40D unit. This driven unit will require a longer belt, or tighter pulley center to center spacing.

But you should be ok. Test out what you have and then start to play with the ratio if needed. The belts in these systems take most of the abuse, so if the sprocket ratio isn't ideal for you the belt may wear quicker than expected. Make sure you post pictures of how you set up the 40 series. It is slightly more complicated than a 30 series. If the driveN unit isn't allowed to float (an inch or so) along the length of the jackshaft, the driveR unit should be mounted inboard on the crankshaft. Systems utilizing a backing plate do not allow the driveN unit to properly float, so these systems should have the driveR unit mounted inboard on the crankshaft.

 

[Hollow45]

Thanks for the suggestion bob58o, I will definatley try out the 60T drive sprocket and see how things work out. As soon as this 40 series comes in the mail I will post pictures on the setup and how things are coming along. I have only seen torque converters mounted one way and I'm not sure how the engine will fit my existing engine plate so we will see how this goes.

 

[itsid]

I so hope you have NOT picked the series 40 kit with the terrible backplate thing...

if you did, you will be in for some nasty surprises soon
(crooked belt, sticking tc.. premature beltwear.. and overall not too impressive performance because all of the above)
that was the worst idea GPS ever had!

if you can.. cancel the order and get a series 40 with std jackshaft instead and mount it properly!

'sid

 

[bob58o]

From what I have seen, the best way to install the 40 series with the backplate is like in this first picture.

The dirveR unit is flipped around compared to how it is "traditionally" installed. When installed this way, as the DriveR unit expands, the belt gets pushed away from the engine.

Looking at the DriveN unit, we will get the same thing. As the unit shifts, the movable sheave gets pushed away from the engine allowing the belt to slide down in the same direction.

When installed on a traditional jackshaft (using pillow block bearings or the like and NO backplate) you can set up like in this last picture. In this setup the belt moves closer to the engine as the TC shifts.

What is most important is that both driveR and driveN move in the same direction. Ideally, the driveN unit should be able to float (move laterally back and forth) along the length of the jackshaft enough to allow for perfect belt alignment at both idle and when fully shifted. The backplate doesn't allow for the driven to float. Careful design of a traditional jackshaft will allow for better alignment, longer belt life, longer bearing life, more efficient transfer of power, more fun, and probably less down time once installed.

Another option is something like this engine / jackshaft mount. But you have to consider pulley to pulley center distance. Belts are only offered in certain sizes that correspond to the distance from the center of the crankshaft to the center of the jackshaft.

Images may not be in correct order, but you'll get the idea.

 

[itsid]

now gearing..
the "phantom" I think you talk of is a 710E XTK
with a 13horse engine that technically renders it
a 713E

Anyhow.. looking in said 713 manual the 60 rear sprocket is fine,
the ten tooth driver sprocket is not!
You need a 9T TC sprocket to get to a 6.67: 1 gear ratio for that thing.

it's a pretty hefty piece of steel (475lbs curb weight) and
actually to keep the belt alive I'd recommend a 7.5:1 ratio tbh (68T axle, 9T TC)
but Manco disagreed and installed a 6.67:1 instead

if you can find an 8T TC sprocket for your jackshaft instead,
that would again get the kart down to 7.5:1 ratio so maybe worth a try,
although I'm not particularly fond of very small sprockets in this case,
especially if that offroading is not your nicely mowed golf lawn but the unkempt bushes of the nearby woods, I'd pick one up.
just saying.

And since you have to order a new TC Sprocket anyways.. you might as well order them both to try what feels better.

the original 710E (and 713E of course) had a seperate jackshaft plate under the engine.
No need to tell you that I think you'd be better off reusing that, right?

'sid

 

[Hollow45]

It did,

I noticed on my go kart mounting plate there is an old torque converter mounted with a 9t sprocket opposite of eachother on the mounting plate. Is this what you are referring to?

 

[itsid]

yes, exactly what I was referring to



'sid