15 HP Engine, what is a good gear ratio? Thanks

[thunderstorm]

Hi everyone,

Its my first time here. My uncle gave me his 15 hp horizontal shaft engine. I have no experience building go karts but it seems fun. I dont know what gear ratio I should use. I'm looking at gear from Azusa Parts. Will I burn my clutch if I have a 2;1 ratio? 7 or 8 inch wheels.

Thank You.

 

[itsid]

Welcome
yes you will burn your clutch with a 2:1 ratio!

but before telling you what ratio you will need, we need to know what ratio you will likely need first ... err...

you know, what'll be the overall weight of the kart with passenger(s?) what wheels will be mounted to the rear axle, what terrain is it going to be dealing with etc.

the best advice for now is still (as always) 6:1 ratio for medium sized kart with I'd say up to 15" rear wheels for the 15horses you have.

but in the end, without weight, wheelsize etc, it's nothing but a guess...
2:1 though will NOT work, no matter what.

'sid

 

[thunderstorm]

I will burn it even with 7 inch wheels? The online gokartspeed calculator says top speed would be 35 mph.

I plan to have 7 inch wheels, offroad. Its hard to tell the wight, im a heavy person. The engine weighs 87 pounds. So no less than 400 pounds.

Will I need to buy a clutch for this? Its a 15HP Lifan 420CC engine.

Thank you

 

[itsid]

there are NO 7" wheels... dolly wheels yes.. kart wheels NOPE
you need kart wheels.. smallest 11".. smallest off road (knobby) 13" IIRC..
common road 11-13" common offroad upwards 16".

Oh we talk tyre outside diameter here not WIDTH or RIM diameter or something.

yes you will need a clutch.. I'd say you will need a torque converter even to make it reasonable.

'sid

 

[landuse]

A centrifugal clutch for that engine will need a 1" bore, and they are over $100. A torque converter will be about the same. You will need a 40 series TC, as a 30 series is only rated for 8HP

2:1 will NEVER work, no matter what you do

Oh....and welcome!!

 

[Poboy kartman]

Nope...that's a 30...only good for about 8 hp. You'll need a 40 series.

 

[thunderstorm]

Thanks everyone.

So this must be it https://www.amazon.com/gp/product/B0...A1UY2YMGL7FILQ.

I guess I need to buy the other parts separately?

I need a belt and a jackshaft

 

[bob58o]

Well the two pulleys can be found as a set on eBay for close to $95-$100 free shipping.
I got a broken Amazon link (OH NO the Amazon Link is broken again)
The belt is like $25-$35.
The Jackshaft sprocket is like $15.
The locking collars are a few dollars each. You need 4 or 6.

You need bearings, bearing holders, a shaft....
There is a engine mount with jackshaft kit availbale somewhere. Two people are using it for a 420cc engine and 40 series TC.

---------- Post added at 11:42 AM ---------- Previous post was at 11:39 AM ----------

http://www.bmikarts.com/Motor-Mount-Plate-with-Jackshaft-and-Bearings_p_1051.html

---------- Post added at 11:45 AM ---------- Previous post was at 11:42 AM ----------

I plan to run 420cc with 5.4 : 1 and 40 series TC with 18.5" Tires.
Total weight 550 - 600 lbs.

Should do around 30 -35mph at 3600 RPM and and 50 -55mph with no governor.

Should have Lots of Torque.

 

[thunderstorm]

Here is the link again

https://www.amazon.com/gp/product/B019SL0LUK/ref=ask_ql_qh_dp_hza

Thanks

 

[bob58o]

Here is the link again

https://www.amazon.com/gp/product/B019SL0LUK/ref=ask_ql_qh_dp_hza

Thanks

looks good to me.
The belt you buy depends on where the jackshaft goes.
The pulley center to center distance determines what belt to buy.

I think 9 3/4" and 10 1/8" are two common pulley center to center distances, with both shorter and longer available.

 

[thunderstorm]

I understand. With the motor mount link you gave me...

So I mount the engine on it. Than the jackshaft goes through the 2 holes and is held in place by the bearings. I buy a 10 tooth sprocket and assemble it. Thats it right?

Whats weird to me is, the belts have teeth, but the torque converters driver and driven shafts dont seem to have places that the belt fits into?

Am I wrong?

 

[Poboy kartman]

I understand. With the motor mount link you gave me...

So I mount the engine on it. Than the jackshaft goes through the 2 holes and is held in place by the bearings. I buy a 10 tooth sprocket and assemble it. Thats it right?

Whats weird to me is, the belts have teeth, but the torque converters driver and driven shafts dont seem to have places that the belt fits into?

Am I wrong?

Well...other than timing belts or blower belts...(which aren't V belts) teeth or not ....V-belts operate by friction on the sides of the belt...not the "teeth" which help give the belt more strength while still allowing it to be flexible.

The way torque converters work is that the sheaves close in and make the circumference the belt rides on larger...effectively continually changing gear ratio...This can only happen on the sides of the belt....not the inside where the teeth are.

 

[thunderstorm]

Hey guys, I'm doing some shopping.

I ordered 72 teeth and 12 teeth sprockets. And the torque converter, but I'm not sure what belt to order.

I see this:
https://www.ombwarehouse.com/comet-40-series-torque-converter-belt-40-120.html

40CD setting 11-1/2â€
44CD setting 10-9/16â€
Outside 40.5'''

I'm not sure what 11-1/2 means. I assume its the distance between the 2 shafts.

Also, when everything is installed, is the belt suppose to be loose?

Thanks

 

[landuse]

With the 40 series you buy the belts according to the center to center distance of the driver and driven. I think the 11 -1/2 is the distance.

The belt should be reasonably loose when installed

 

[Joe-405]

Your easiest way would be to buy the go Powersports Bolt on 40 series for your engine. Then you don't have to make a jackshaft. You also don't have to do any welding or fab work. It's a direct bolt on.

 

[bob58o]

looks good to me.
The belt you buy depends on where the jackshaft goes.
The pulley center to center distance determines what belt to buy.

I think 9 3/4" and 10 1/8" are two common pulley center to center distances, with both shorter and longer available.

I can't tell you what belt to get cause you didn't tell me what the shaft center to center distance is.

 

[thunderstorm]

Thats because I didnt even get the torque converter or anything yet. But thanks.

So I get to choose the distance by installing the jackshaft right?

Or buy one and choose the distance appropriatley?

 

[aham2003]

Your easiest way would be to buy the go Powersports Bolt on 40 series for your engine. Then you don't have to make a jackshaft. You also don't have to do any welding or fab work. It's a direct bolt on.

Are you a GPS rep? LOL. It would be crazy to buy that thing. You can get a jack shaft kit, 40 series pulleys, and belts for about $175. If im not mistaking, they want $400 for that kit. So they want $275 bucks for a $30 belt and $30 piece of steel.

 

[thunderstorm]

Are you a GPS rep? LOL. It would be crazy to buy that thing. You can get a jack shaft kit, 40 series pulleys, and belts for about $175. If im not mistaking, they want $400 for that kit. So they want $275 bucks for a $30 belt and $30 piece of steel.

I agree.

 

[bob58o]

Thats because I didnt even get the torque converter or anything yet. But thanks.

So I get to choose the distance by installing the jackshaft right?

Or buy one and choose the distance appropriatley?

Yep, get the jackshaft positioned about where you want it,
then measure where you are at in relationship to the engine.

Make fine adjustments until the distance is one of the ones in the chart.

Make sure the pulley fits.
Make sure the sprocket fits.

If you must go in between two sizes, get the bigger belt.

Search for replacement belts in that size just to make sure.

---------- Post added at 03:11 PM ---------- Previous post was at 03:10 PM ----------

Are you a GPS rep? LOL. It would be crazy to buy that thing. You can get a jack shaft kit, 40 series pulleys, and belts for about $175. If im not mistaking, they want $400 for that kit. So they want $275 bucks for a $30 belt and $30 piece of steel.

What do you know about crazy?

We have lots of Go Power Sports Reps here!

Want to know how to get 10 Percent off your next purchase?
I'll tell ya for 8 percent.

---------- Post added at 03:16 PM ---------- Previous post was at 03:11 PM ----------

There may be a discounted one for sale that needs a DriveR and Belt.
http://www.diygokarts.com/vb/showthread.php?t=34238