Predator 420 on a Spiderbox

[TigerBuggy]

Has anyone successfully mounted a Harbor Freight Predator 420 on a Yerf Dog Spiderbox?

I'm in the process of bringing a Spiderbox back to life and will be attempting to mount the 13hp Predator 420 onto a modified Spiderbox swingarm.

I was hoping to get some tips or advise before I move into uncharted territory.

I put a bit of effort into attempting to find details on a successful 420 install on a Spiderbox, but did not come up with much of anything.

Feedback welcome.


This is my Spiderbox so far. What do you think?

[jmansracerocket]

if you still have the original gy6 motor ur better off keeping it over the predator.

[TigerBuggy]

I know the GY6 has a pretty big following on this site.

Is there no love for the 420?

It seems like a fun alternative to the GY6. Higher displacement vs. higher rpms

[xlint89]

GY6 bolts right up, no modifying needed

Reverse is easily installed on GY6

Internal as well as external gearing changes are possible

Many aftermarket parts available for the engine/trans combo


Those that normally do conversions, look into snow mobile or 4 wheeler engine/trans combos if you're going to go that deep into a conversion.

And if you use the Yerfdog Spiderbox as your platform, be prepared to make many reinforcements to the frame, ball joints, and spindles if you're going to be adding more HP. They have issues of cracking/bending with just normal 150cc HP.

[TigerBuggy]

Maybe I'll be the first pull off this type of install successfully on a Spiderbox and live to tell the tale.

We shall see.

[SYCARMS]

Much better off with the GY6. Build the engine, install a reverse kit you'll have a beast.

[ckau]

IMO only... These type of motors were intended to be used in a industrial application for mowers, snow blowers, fluid pumps, etc. Designed to run at one steady RPM to produce high torque. The HP rating is what the motor gives inside that narrow RPM range. HP can fall of dramatically above or below that RPM range. Don't be fooled by the advertised HP claim, you won't see it 90% of the time. The carbs, jetting, ignition advance, governor and linkages are all set up for optimum performance at one RPM, mostly wide open! So their not real suited for the RPM range used in a off road buggy. You can make them run, no doubt! The pavement karts have proved that but as you can see by several other continuing threads on the forum getting the power coupled up proves a real challenge in the dirt world. Clutch, gearing, torque converters all that stuff. Final costs after trial and error equals more than a brand new drop in GY6, If they out performed a GY6, you can bet your backside a whole lot of people including my self would be all over them!

[TigerBuggy]

The Predator seems to work pretty well on this setup.
(See from 13:30 on in this linked video for Predator 420 action)

https://www.youtube.com/watch?v=A2ufOpTjD0g

Thanks for the feedback!

[TigerBuggy]

deleted

[TigerBuggy]

Originally Posted by ckau

Don't be fooled by the advertised HP claim, you won't see it 90% of the time.

It's actually the increased torque that I'm after. I see the buggy weighing in a bit north of 700lbs while riding around in it.

[TigerBuggy]

I wanted to post my current progress on the Spiderbox. She's coming along nicely IMO.


Feedback welcome!

[x-bird]

Looking excellent! As far as tracks go, i've got 3/4 of an acre that i'm setting a 900+- foot long track in, about a dozen carts, all 5.5 honda engines.

[TigerBuggy]

Originally Posted by x-bird

Looking excellent! As far as tracks go, i've got 3/4 of an acre that i'm setting a 900+- foot long track in, about a dozen carts, all 5.5 honda engines.

Thanks for the compliment. The buggy is looking very nice when seen in person


Is your track(s) going to be on or off road?

[jmansracerocket]

dam that thing looks like it came off the show room, I don't know if your plans are trail riding for it if so, don't expect the front end to last long. theres tons of threads and info on reinforcing that front end.

[x-bird]

on road, too many liability variables and regulatory issues to deal with when it comes to an off road facility. PA is pretty strict with amusement ride regulations. I could set up some jigs and build the karts for 1/3rd the price, but getting them certified is a whole new can of worms.

[TigerBuggy]

Originally Posted by x-bird

on road, too many liability variables and regulatory issues to deal with when it comes to an off road facility. PA is pretty strict with amusement ride regulations. I could set up some jigs and build the karts for 1/3rd the price, but getting them certified is a whole new can of worms.

Karting on road courses is a real blast. My whole family loves it.

I would think that certified pre-built karts is definitely the way to go with an operation like that

[TigerBuggy]

Originally Posted by jmansracerocket

dam that thing looks like it came off the show room, I don't know if your plans are trail riding for it if so, don't expect the front end to last long. theres tons of threads and info on reinforcing that front end.

Thanks jman! Yep, reinforcing the front end is likely in the kart's future.

[TigerBuggy]

My axle parts arrived the other day, and this is basically how things are going to be arranged.

1.25" axle, 70t sprocket, etc.

Additionally, the unfinished axle assembly has not yet been mounted on the unfinished swingarm.

(Pics below)

[x-bird]

What's that, a 50T sprocket? If you go with a comet setup, you should be able to run a much smaller driven sprocket.

[TigerBuggy]

Originally Posted by x-bird

What's that, a 50T sprocket? If you go with a comet setup, you should be able to run a much smaller driven sprocket.

It is a 70t steel axle sprocket which will be mated to a Series 40 torque converter capable of running a 10 or 12 tooth sprocket on the torque converter. I will be running the 10 tooth on my setup. The acceleration and general pulling power of the vehicle should be quite impressive even with the Predator 420 in completely stock form (oil sensor bypassed of course).

I honestly get a little giddy thinking about it. The setup will be simple, effective and brutal

[x-bird]

yep. but wondering what top speed is going to be with that ratio. that's wall crawling material. )

[TigerBuggy]

Originally Posted by x-bird

yep. but wondering what top speed is going to be with that ratio. that's wall crawling material. )

The buggy should top out at about 30 mph using this particular arrangement.

This is the top speed I want for my particular application.

[TigerBuggy]

Well, Christmas is now over and I finally got a chance to work on the Spiderbox again. The modified swingarm has been completed (for the most part), axle and engine are mounted, so I bolted everything back together and fired her up. The 420cc Predator is an absolute beast and sounds wonderful!

Unfortunately, I didn't have a chain for her on hand (no test ride), so I intend to pick one up on the way home today. I will be taking a spin in the buggy TODAY for the 1st time ever (for me anyway) if things go according to plan. See pics below.

Feedback welcome

[SYCARMS]

Nice looking buggy.

[TigerBuggy]

Originally Posted by SYCARMS

Nice looking buggy.

Thank you

[x-bird]

looking good. My one suggestion would be to utilize the swingarm to build a pair of vertical tubing triangles or frames on either side and send tubing down to an additional bearing hangar close to the wheel to take some stress off the axle. you've got a pretty looooong extension from the old mounts to the wheels.

[TigerBuggy]

Well, I took the Spiderbox 420 for a spin and it is a blast! I also installed a set of LED lights on top for increased visibility. At this point the project is pretty much complete and I could not be happier with the results. I'll have to let you guys know if I run into any issues, but the setup is pretty simple and I don't foresee any problems.

Take a look. As always, Feedback is certainly welcome

(I'm not sure why these pics are posting sideways, but if you rotate your screen 90 degrees you will be able to see them properly, LOL. Or just check my later post below.)

[TigerBuggy]

Originally Posted by x-bird

looking good. My one suggestion would be to utilize the swingarm to build a pair of vertical tubing triangles or frames on either side and send tubing down to an additional bearing hangar close to the wheel to take some stress off the axle. you've got a pretty looooong extension from the old mounts to the wheels.

Great observation! My rear hubs can be moved along the 1.25" axle and then locked into place in order to adjust rear track width. I find the current position to be the most pleasing to the eye, stable and quite close to the track width of the front wheels (but jumping the buggy is out of the question in this configuration). This is basically my neighborhood / street cruising rear wheel arrangement.

I intend to slide the wheels inboard a bit before any serious off-roading in order to greatly reduce the bending moment on the axle. But, I still may have to modify the swingarm further in the future to increase its strength as you're suggesting. Time will tell!

Thank you for the feedback!

[TigerBuggy]

Got a few breaks in the rain during this New Year's Holiday weekend that were long enough to take the buggy out a few more times and let a few folks ride. The buggy has no problem riding around with just over 300 lbs of rider(s) onboard.

Take a look at the finished product now that I got a chance to snap a few pics of it outside without rain pouring down

[TigerBuggy]

The rain finally cleared and we took the buggy out a few times in the cool sunny weather! My son gives the setup a thumbs up.

Good times

I posted a few more pics for those interested.