Go Kart accelerating slow

Hello,
I have a Mancini Go Kart and I put a Predator 6.5 hp motor on it from Harbor Freight. I also put a mini bike clutch on it. When I first try to take off (accelerate) it takes a bit to get going. Any idea what would cause this? I work on just about everything but don’t have experience with motor sports stuff.
Thanks.

 

Where did the centrifugal clutch come from?

 

I got it sat a local bearing shop. BTW it’s a Manco Go Kart.

 

My first thoughts were, as Marq stated, the clutch. Either its bad or worn out or not the correct clutch for the application.
Then, how big a boy are ya? I mean, how much weight is the cart trying to move around?
Then, is this a new motor or an old motor that could potentially have problems (worn out)?

When you give it the gas from a stop, does the engine rev up, just not start moving very fast or does the engine not rev up?

 

On a cart like yours the number of teeth on the drive and driven sprockets are your drive ratio. Just changing by one tooth on the smaller drive sprocket (the one on the engine) can have a large affect on the gear ratio which will affect acceleration and top speed.

Another thing to consider is the amount of torque going through the centrifugal clutch. Some clutches intended for lighter weight mini bikes just don't clamp down hard enough to transfer the engine's power to get a heavier cart moving without the clutch slipping. The clutch engagement can be tuned by using different springs and/or weights but parts are often not available for the cheapest clutches.

 

The engine is a brand new Predator 6.5 hp. It rev's up when I give it gas, but doesn't accelerate for a bit. I'm thinking it's the wrong clutch? Maybe it should be a snowmobile type clutch like this one: eBay item CG-332710-12254.

My question about this one though, is it self contained or does the "Jack Shaft" need a bracket.

FYI- the model # of the Go Kart is: Manko 616B-09

Thanks

 

Also, this is a diagram of the Go Kart assembly the way it was new. When I replace the engine I did not have any of the clutch assembly from the original engine. This is the link to the assembly:

http://kartingdistributors.com/pdfs/...l_20050405.pdf

 

When you rev up your engine is the clutch engaging? Can you tell about what RPM the clutch engages? When it does engage does it just slip or does it grab solid but you just don't get any acceleration? The details of exactly what's going on are important to figure out what's wrong.



You can go to a variable clutch (belt torque converter) system though it is more complex and will require more figuring to make everything work. Whether or not you have or need a jackshaft depends on how you install it. If your cart's drive axle will fit then you don't need a jackshaft. They don't say anything about the bore of the second pulley though a couple photos do show what looks like a key. If your cart's axle won't fit through the pulley then you will need a jack shaft, brackets and a secondary sprocket to drive to the axle.

A simple centrifugal clutch can work very well if sized properly. I have run engines with much more power through simple centrifugal clutches so it can work. Depending on your sprocket sizes you may simply have the cart geared for higher speed and sacrificing acceleration. There are some tricks you can do by allowing a certain amount of clutch slip during acceleration which is OK if you are racing or not doing many starts and stops. If this is just a yard kart for kids then you want a more positive clutch engagement so they don't burn it up.

 

How tall are your tires?


.

 

I was under the impression that the "Snowmobile" type clutch I ordered is wheel to wheel with a belt, then a chain from one of the pulleys to the axle. What other info do you need to know? Axle Sprocket size? # of teeth? Is there an easy way to measure the sprocket? Diameter? I'll measure the tire diameter...

 

So, you've gone from a centrifugal clutch to a torque converter? Did you make sure the torque converter works with your engine shaft size and axle size including keyway?

As for the other details there is no "sprocket size" or "number of teeth" with a torque converter. There is with the clutch and sprockets in your photo but not with a torque converter. A torque converter is sorta a constantly variable transmission. It moves through a range of gear ratios depending on load and rpm depending on what you bought. Cheap ones only have one pulley that adjusts and it's usually spring loaded and controlled by torque only. With better units both the drive and driven pulley move. The one on the engine is centrifugally actuated and moves based on the engine's rpm's while the one on the carts axle moves based on torque.

Tire diameter on it's own isn't important. It is important though when trying to figure you overall gear ratio. A smaller diameter tire has the affect of putting your cart in lower gear. Better for acceleration but hurts top speed and provides less ground clearance. Larger diameter tires hurt acceleration but increase top end speed and provide higher ground clearance.

 

Thanks Pilot Dane,
Yes I did make sure the clutch I ordered would fit my 3/4 inch shaft. I did a lot of searching online and the engine it is mostly paired with is my Predator 6.5 hp. My Go Kart came factory with this type of clutch but I tried to do the quick inexpensive solution which was a Centrifugal Clutch. The link I gave above shows a diagram of my Go Kart assembly.

 

So, would you think that since my Kart came originally with a torque converter that installing one should solve my problem and run the way it was designed to?

 

I think chances are good that the torque converter will operate better than the clutch, chain and sprockets you tried.

 

I changed the clutch and it runs like a champ! I installed eBay item#