EzGo ST350 Redux – Big-Block, Lifted, and then some


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This all started several years ago... My then 83-year-old dad was complaining that the walk to his hunting blind at our ranch was getting to be a bit rough on his knees. It was then that I began the search for a suitable cart that he could use for his trip to the blind. I was first searching for an electric cart but I ended up purchasing this nice used ST350.

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This cart was bone stock at the time...and this was good enough for a year or so. After using it for a while he mentioned he did not like the pedal start (nor did I) and we REALLY did not like the rough ride of the stock leaf spring/shock setup. The ST350 has heavy-duty springs and you can really feel it!

Right after last years hunting season was over I hauled the cart back to my house and began the BIG transformation of the cart. It took me several months to complete, but that was mostly do to the amount of time I could work on it.

EzGo ST350 Redux-overall plan
There were two main complaints about the stock cart. First being the pedal start and second the lack of any “real” suspension. In addition to not caring for the pedal start...the stock Robin 350cc didn't really have enough power. This cart was intended to be a ranch cart...not just a hunting cart, so part of the Redux plan was to do a big block conversion to increase the power.

For the big block power plant I went with a Predator 670. I was able to pick up a slightly used 670 off of FB Marketplace (it was practically brand new) for less $350 back in the summer of 2019. The big block would solve the power issues, but there was still the suspension to deal with. The stock leaf spring/shock setup, both front and back, had to go!

For the front end my first thought was to fab up an A-Arm suspension using ATV components. For the rear suspension I really wanted to go with a 4-link setup with coil over shocks. I researched both of these ideas and found several folks who had done both of these exact things...so I started the design and planning for my cart.

As I got further into the designs, it became apparent that my desire for a 4-link rear suspension wasn't going to work out. Given the space needed for the engine cradle there just wasn't going to be enough space for a properly fitted 4-link...the engine cradle would be in the way of the triangulated links. The builds I had seen from others who had done a 4-link were using electric carts...so no issue with an engine cradle being in the way. Additionally after estimating my time & effort, cost of the ATV components as well as all of the material needed to build the support structures for the front end, it just didn't make economic sense to for me to build it myself. Due to these realizations I went back to the drawing board for the whole suspension.

I ended up deciding to go with a RHOX BMF 7” A-Arm front end.... which worked out great (with a few modifications needed to fit my cart)! For the rear end I ended up designing a 3-link setup with coil over shocks that incorporate a pan-hard bar to control lateral movement of the axle.

I will post separate threads for each of the main build groupings as well as several other custom designs that went into the overall build.

Hope you folks enjoy the build story...and maybe get a few ideas of your own from it... also jumping to the finished project so y'all can see the end result.

paint-1.jpg paint-4.jpg


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EzGo ST350 Redux - engine cradle and trailing arms
The ST350 wheel base is longer than other EZGO gas carts like the TXT, etc... This fact contributed to the design of the trailing arms and the engine cradle. Having a little more room made the build easier, in my opinion. Even so I still made a small modification to the frame in my build, most notably I removed the central cross member where the stock front engine mount was attached. This allowed me to have the front of new engine cradle attached at the same lateral pivot point as the trailing arms.

I adding a 1/4" thick 2" x 2" piece of angle iron along the full length of the front cross member as reinforcement and as an attachment point for the trailing arms tabs as well as the front engine cradle mounting tabs.

For the engine cradle itself, I had mulled over purchasing one of the various cradle kits available on the market...but once again economics played out for me. I already had most the material needed to build the cradle on hand; I only needed the front heim joint and a bung. As I was already ordering heim joints and bungs and other suspension components I just added one more set to the order.


The trailing arms as well as the front bars on the cradle are made of 1-1/4" diameter, thick wall tubing. I also incorporated the stock rear yoke (part of the original engine mounting setup) into my design, which made the attachment to the axle "like stock".

I’m not a welder or fabricator by trade, so please don't judge the look of the welds! LOL

I added the parallel c-channels with the slots cut into them as the actual mounting points for the Predator engine (after much carful measurement). The piece that attaches to the stock yoke is 1/4" thick 4"x4" angle iron and is welded to the base plate of the cradle which is also 1/4" thick steel. The whole think is solid as a tank and IMHO is many times stronger than any commercially available kit on the market.


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EzGo ST350 Redux - rear suspension
Due to the reason stated previously, I could not use the 4-link design I had wanted. Instead I ended up with a 3-link design (trailing arms) with coil over shock and incorporating a pan-hard bar setup. This pan-hard bar was needed to control any lateral movement of the axle. Had I been able to use a 4-link design instead the triangulated links would have accomplished this task.

I started by removing the original axle mounting brackets from the axle. This gave me room to weld on the lower mounting tabs for the coil over shocks as well the lower tabs for the trailing arms.

The most challenging part of this design was how to add the pan-hard bar setup and not make it look like an afterthought! The design I came up with was to weld a 2"x3" rectangular tube across the wheel well opening of the frame and then attach a drop bracket to it. This gave me some adjustability in the pan-hard bar configuration. I found the drop bracket online at some "off-road" suspension store. The other end of the pan-hard bar is attached to the axel with a bracket I fabricated from leftover pieces of that 4"x4" angle iron that was used for the engine cradle. The pan-hard bar itself is made from the same 1-1/4" diameter thick wall tubing as the trailing arms.

I re-enforced the existing top shock mounting points with 3"x3" 1/4" thick angle iron and then welded mounting tabs to them. This gave me the top mounting point for the coil over shocks.



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EzGo ST350 Redux - front end
As can be seen the front end is a RHOX BMF 7" A-Arm kit. There were a few modifications I had to make, both to the RHOX kit itself as well as my cart, to get this to work.

First off the RHOX kit is designed for the post 2001.5 year models that have the 4-bolt steering setup. My cart was made pre 2001.5 when EzGo was still using the 3-bolt design. This design change by EZGO was more significant than just adding another bolt to the column...the entire steering assembly was changed, from the steering column mounting, steering rack, idler arm, tie rods... everything was changed in the later models. For me to use my existing steering column with this RHOX kit I had to fabricate a custom mounting bracket for the steering column to be bolted to.

Additionally, in the post 2001.5 year models EzGo increased the spacing of the mounting holes where the tops of the shocks are bolted to the frame. The RHOX kit uses these holes (along with the mounting points of the front leaf springs) to attach the kit to frame. I had to cut and re-weld a portion of the top mounting brackets on the RHOX kit so that the holes would line up with the older frame. This was relatively simple and the material I use was thicker than what I removed, and therefore stronger than the factory bracket...at least in theory.

The front wheel axle/spindles of the ST350 (and therefore the hubs as well) are quit a bit longer than the ones that came with the RHOX kit. The RHOX kit expects you to reuse your original hubs, since mine would not fit I needed to order a set of new front hubs. Ones from a post 2001.5 TXT model worked fine.

The only other mod I had to make to the front was the addition of 2" wheel spacers. The RHOX kit is designed for wheels that are 12" is diameter...mine are 10". Not wanting to spend more money on a set of larger wheels I just added these spacer, which worked great. Without the spacers that smaller wheels would not clear the axle/spindle arm that attaches to the tie rods.



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EzGo ST350 Redux - engine
The engine is a Predator 670. I'm using a comet 780 clutch and I fabricated a custom drive side alternator bracket and pulley setup.


EzGo ST350 Redux - engine & alternator
Here is the engine with the alternator setup installed. Since I was going with an alternator setup I would no longer need the built in charging system of the 670… so I ripped out the whole thing (charging coils, voltage regulator and all the associated wiring)



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EzGo ST350 Redux - alternator bracket/pulley
Here are a few pics of the alternator and pulley setup. I built the alternator bracket from a sheet of ¼” thick steel plate. I first created several templates out of cardboard… only after I was happy with the fit did I laid out the pattern on the steel plate. I pulled all the critical dimensions for the bolt pattern from an owner’s manual I have for the Predator 670. The v-belt pulley I found online… but did have to make some slight modifications for it to fit as I wanted.



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EzGo ST350 Redux - exhaust
I fabricated the exhaust header and the mounting bracket for the muffler. The exhaust header tubing is 1-1/4" and comes into a 1-1/2" collector. The muffler is a Walker Quite-Flow model 22229, which has 6" outer diameter. The clamps are TOTALFLOW 6" TF-600SS Stainless Steel Single Bolt AccuSeal Exhaust Muffler Clamps (usually used on big-rig exhausts). The whole exhaust system is relatively quite... which is what I was going for:


EzGo ST350 Redux - electrical control system
Since this project was turning into a total makeover... I did not want to forget about a new electrical control system. In addition to the mechanical upgrades I ended up stripping out the entire electrical system from the old cart. I don't have any pics of the new relay/fuse box, other distribution boxes or wiring harnesses... but I do have several of the new dash panel.


The only "old" electrical parts that stayed were the fuel gauge, fuel sender unit, headlights and tail lights...every other single wire, connector, switch, etc was removed from the cart.

I custom fabricated the dash panel from a 1/8" thick sheet of aluminum. I added the swirl pattern by attaching a 2" abrasive sanding pad to my drill press and just used it to scratch the surface in the overlapping pattern.

I also added some LED fog lights as well as LED light bar for the cargo area, which can be seen in the pics for final finished project.


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EzGo ST350 Redux - shifter
I'm pretty sure everybody noticed that shift lever right in the middle of that custom dash....:cool:

Another little annoyance that I’ve never have liked was that forward/reverser shift lever mounted below and in front of the seat... I never did like that. So, I decided to change it! After a little digging I ended up picking up this Kawasaki Mule shift lever from EBay for like $25...and a shifter cable for another $20.


I fabricated a mounting bracket out of 1" angle iron. And bolted the bracket to the frame behind the dash. The shifter cable was routed under the body and secured to the frame. I did need to enlarge the hole a bit that was in the frame to route the cable through, and lucky enough the cable length turned out to be just about perfect.


I had to fabricate a shift bracket for the transmission side and I had already built the anti-twist lever that goes from the transmission to the engine cradle.... I just needed to add that part to bolt the cable in place.



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EzGo ST350 Redux - paint and finished project
The cart is back at my ranch... and performing amazingly well. The cart has plenty of power to do chores around the ranch and the camo finish blends well when dad takes it out to his hunting blind.

The ride is a whole different story. Before, with the factory leaf springs and shocks, the ride was horrible... you'd feel every single rut, bump and gopher hole you drove over. At times you'd think the suspension was non-existent. Now the independent A-Arms in front and 3-link with coils-overs on the rear absorb most of that unpleasantness. I am very, VERY happy with the outcome of the suspension.

I also replaced the factory roof mounting supports with a custom roll-cage I built from 1-1-2" tubing.



So would it have been easier to just get him a side by side ? I mean it is impressive what you did, but your time and material costs just doesn't make sense unless you just like making one of a kind carts.