Yerf Dog not performing w/ Predator 212

[BMRbrnSNRbrd]

I recently installed a HF Predator 212 in my son's Yerf Dog 3203. The cart did not run before the swap, so I have nothing to compare it to, but it seems like it is under-performing.

How fast should I expect it to go with a total rider weight of about 240? I was only able to pull 17mph according to two different GPS. Does that sound right? If not, what should I look at first? I have the chain tightened to spec but the belt seems pretty loose (new chain, old re-used belt). Could that be my power robber?

 

[ross1998]

I recently installed a HF Predator 212 in my son's Yerf Dog 3203. The cart did not run before the swap, so I have nothing to compare it to, but it seems like it is under-performing.

How fast should I expect it to go with a total rider weight of about 240? I was only able to pull 17mph according to two different GPS. Does that sound right? If not, what should I look at first? I have the chain tightened to spec but the belt seems pretty loose (new chain, old re-used belt). Could that be my power robber?

You should be getting around 30mph on it, we might be able to help you more if your told us your gear ratio. I think your gear ratio might be your problem.

 

[modestmouse]

 

[OzFab]

Also, pics, lots of pics.

If the belt is on a torque converter, it's meant to be loose... Pics will confirm

 

[landuse]

Pics pics pics

 

[BMRbrnSNRbrd]

The kart has the OE sprockets: 10t and 60t.

I've attached a picture of the way the belt sits with the chain tightened to spec. Please ignore the oil spatter, that was due to a previous incident (i.e. I didn't tighten the oil fill plug down...whoops!)

http://i269.photobucket.com/albums/...YuzlHRpGyeDgoWyw4H2bZcmom8KQY_zps4bda5363.jpg

 

[OzFab]

Yeah, that looks about right to me, wait a bit for others to confirm...

There are several things to consider when looking for speed such as:
-engine performance; since it's a new engine, we could rule that out but, not yet...
-gearing; if it's over geared, you'll have great acceleration but a low top speed. If it's under geared, you'll have a high top speed but lousy acceleration.

Let's start with the engine: Will it easily free rev up to governed speed? ie: With no load, you open the throttle & it revs quickly & smoothly until the governor kicks in. Now, does it do the same thing when you're driving it?

Next, gearing: Count the teeth on the driven clutch & the axle sprocket & report back. Also advise us as to the height of the rear tyres...

 

[mysteryboy28]

That belt looks pretty worn to me. It shouldn't be sitting so low inside the driven (secondary) pulley. Get the part number off the belt and order a new one. A narrow belt will get snagged inside the secondary pulley and cause performance issues. Also, a 212cc motor is really only enough power for a small kart with a lightweight driver. Even a 9hp motor struggled up hills on a light single seater manco dingo kart with my 250 lbs on it. 11hp or bigger for an adult size kart is my suggestion. The 420cc Predator with electric start is a decent motor, but you'd also have to upgrade the clutch to a comet 40 type ($200!).

 

[Doc Sprocket]

good eye, Mystery- that belt IS sitting too low in the driven- waaay too low.

 

[OzFab]

I missed that, nice catch

 

[Flash550]

Just a thought, but check for a brass governing spacer on the shaft of the driver. The previous owner may have put one on to limit the top speed.

 

[mysteryboy28]

that's the first I've ever heard of that... brass ring to govern TC top speed...

 

[landuse]

Just a thought, but check for a brass governing spacer on the shaft of the driver. The previous owner may have put one on to limit the top speed.

You absolutely need a brass bushing. It is an integral part of the TC. If you do not have it, it will not function properly and start binding up

 

[Flash550]

that's the first I've ever heard of that... brass ring to govern TC top speed...

You absolutely need a brass bushing. It is an integral part of the TC. If you do not have it, it will not function properly and start binding up

I didn't say anything about removing it. When I bought my cart, the previous owner had put in a much larger bushing in order to limit how far the moveable face of the driver would actually move, and not allowing it to shift to higher gear ratios, thus limiting top speed. After I installed the right bushing my top speed nearly doubled. I did run it for a while with no bushing and it worked fine, no binding.

 

[qtband]

This is so simple, you may have missed it. The HF engines have a limiter screw on the throttle plate. Make sure it's turned all the way out for max rpm's.