I just finished installing a harbor freight predator motor in my Rupp Blackwidow. I saw a few people with pictures of it done on here, and ive seen a couple people asking about it, but didn't see anyone actually talking about what it takes. Its pretty simple so I thought I would go ahead and post up some info.
First off, the Predator motor is ~6.5 hp so there is a decent amount of extra power already in this motor. Ive seen dyno number through research that puts it stock more like 7.5hp. Go to Harbor Freight, grab yourself a $99 coupon and pick one up.
Once you get your motor, first thing is to take off the gastank (you have your own), Intake (it wont fit), and Exhaust (it wont fit). At this point it'll slip right into the stock mounting holes in the frame. From here on we'll take each task individual and go through some options.
Intake
You really dont have an option here, the intake on the stock motor is to big and you cant cut it down to fit in the frame. Your going to have to buy an adapter and run an aftermarket air filter. This will require you to re-jet the carb. Your better off just going to OldMiniBikes warehouse or nrracing and picking up a stage1 kit. These kits also come with a choke bracket, without it your choke lever will fall off. The original airbox is what kept it on.
Exhaust
Here you have a couple options, and is likely the hardest part to overcome.
1. You can flip the exhaust 180. This will allow it to clear the frame of the bike, but also put the exhaust facing forward. At this point you could cut the pipe, flip the muffler, and reweld in the correct direction. This is your cheapest option, bit it will bulge some.
2. You can make your own exhaust. This is what I did. I utilized the minibike builders kit from nrracing. I was able to get it to loop back into the frame and out between the seat and fender. It was super tight, you will need a welder and a buddy to help hold while you work on this. There is still a small bulge, its behind your leg, but Ive touched it while getting on and off (Its Hot!). Get some header wrap to help insulate the pipe and prevent it from melting your skin.
3. You can also get a pre-made pipe. No one makes one for our setup so your left getting on that sticks out the left side.
Clutch
I have heard people on here talk about getting a new clutch from OldMiniBikes Warehouse, but you dont need to. The stock TC-1 utilizes a 3/4" shaft which is what the predator motor has. You will need a 5/8" spacer to line up the front to the back. I used PVC as a temp solution until an aluminum one comes in that I ordered. It could likely be a permanent solution.
Throttle
Throttle is easy. There are three steps, first you need to find the nut that holds the throttle linkage all together. Remove it, and remove the flex washer underneath. Go to your local hardware store and find a standard washer to replace it with. Second, while you are at the hardware store, grab yourself a stiffer return spring. Then, you just hook it up, the predator motor comes with the hookups to run a remote throttle.
At this point you likely have a faster motor, so you may want to remove the governor. There are multiple youtube videos out there that walk through it. If you do, please ensure that you replace the flywheel and the valve springs. We dont want it to blowup and kill you. I clocked myself with this setup at 49.4mph running stock sprockets, wheels, and clutch. There was loads of power left, just out of RPM.
Hope this was helpful, if you have any questions ask and i'll do my best to answer.
First off, the Predator motor is ~6.5 hp so there is a decent amount of extra power already in this motor. Ive seen dyno number through research that puts it stock more like 7.5hp. Go to Harbor Freight, grab yourself a $99 coupon and pick one up.
Once you get your motor, first thing is to take off the gastank (you have your own), Intake (it wont fit), and Exhaust (it wont fit). At this point it'll slip right into the stock mounting holes in the frame. From here on we'll take each task individual and go through some options.
Intake
You really dont have an option here, the intake on the stock motor is to big and you cant cut it down to fit in the frame. Your going to have to buy an adapter and run an aftermarket air filter. This will require you to re-jet the carb. Your better off just going to OldMiniBikes warehouse or nrracing and picking up a stage1 kit. These kits also come with a choke bracket, without it your choke lever will fall off. The original airbox is what kept it on.
Exhaust
Here you have a couple options, and is likely the hardest part to overcome.
1. You can flip the exhaust 180. This will allow it to clear the frame of the bike, but also put the exhaust facing forward. At this point you could cut the pipe, flip the muffler, and reweld in the correct direction. This is your cheapest option, bit it will bulge some.
2. You can make your own exhaust. This is what I did. I utilized the minibike builders kit from nrracing. I was able to get it to loop back into the frame and out between the seat and fender. It was super tight, you will need a welder and a buddy to help hold while you work on this. There is still a small bulge, its behind your leg, but Ive touched it while getting on and off (Its Hot!). Get some header wrap to help insulate the pipe and prevent it from melting your skin.
3. You can also get a pre-made pipe. No one makes one for our setup so your left getting on that sticks out the left side.
Clutch
I have heard people on here talk about getting a new clutch from OldMiniBikes Warehouse, but you dont need to. The stock TC-1 utilizes a 3/4" shaft which is what the predator motor has. You will need a 5/8" spacer to line up the front to the back. I used PVC as a temp solution until an aluminum one comes in that I ordered. It could likely be a permanent solution.
Throttle
Throttle is easy. There are three steps, first you need to find the nut that holds the throttle linkage all together. Remove it, and remove the flex washer underneath. Go to your local hardware store and find a standard washer to replace it with. Second, while you are at the hardware store, grab yourself a stiffer return spring. Then, you just hook it up, the predator motor comes with the hookups to run a remote throttle.
At this point you likely have a faster motor, so you may want to remove the governor. There are multiple youtube videos out there that walk through it. If you do, please ensure that you replace the flywheel and the valve springs. We dont want it to blowup and kill you. I clocked myself with this setup at 49.4mph running stock sprockets, wheels, and clutch. There was loads of power left, just out of RPM.
Hope this was helpful, if you have any questions ask and i'll do my best to answer.
