2008 EZGO ST 6 - Predator 670cc conversion

[trarex]

Documenting the process of swapping a Robin 295 engine for a Predator 670cc and 8:1 gear swap based on my ongoing project.

I picked up a low hour 2008 ST 6 seater about a year ago in great condition. Our cart is used as a beach town runner spending most of its time plowing through loose sandy beaches for hours on end with a couple good size Texans aboard.. At any rate last summer after about a 25 mile stretch of loose sand and 4 Texas size passengers we developed an oil leak somewhere on the fan side of the motor. The leak caused the fan to spray oil droplets back and onto the exhaust fogging out the beach. Upon seeing this we stopped and investigated, obvious the general area the oil was coming from but not the exact source so we had it towed home to explore further. long story short the cart would run great until it got hot ~30 minutes into a trip and then start the whole process over again. Although we felt justified contributing to mosquito control in the area its time to do something.. We had local techs look at it who thought they knew what it was (crank seal) and quoted outrageous prices to replace I had other plans in mind. After a few months of selling my wife on the idea it was time to do a big block swap..

Option #1: Pull the engine and trans from my old shaft drive 1500cc Kawasaki Nomad and do a custom 5 speed swap with a trike rear end.

Option #2: Not do that..

Reluctantly I went with option #2 and ordered a Predator 670cc install kit from Ivan at Vegas Carts, rear disk brake set from Amazon, and a 8:1 gear set off ebay.

And so it begins.

[trarex]

Once all the parts came in it was time to get started. I pulled the engine, fairly self explanatory with very basic hand tools and some mechanical / electrical knowledge. Remove air cleaner box, exhaust, generator, wiring, cables, belts, some skin, etc. Then support engine and remove motor mounts bolts. you are then able to lift up leaving the cradle in place. The Robin is not very heavy and was fairly simple to remove overall. Once removed I unbolted the cradle from the front frame and the u-bolts around the rear axle to drop out the whole assembly in two pieces.

[superpro56]

You wont be disappointed by the big block.

[trarex]

The goal now is to remove the trans-axle as simply as possible. I disconnected the remaining parts from the trans-axle (mostly governor linkages, and old mounting hardware we wont need) then removed the center nut from the forward / reverse control bracket and pulled off the assembly in one piece. With the cart on jack stands I removed the tires then brake cables from both back drum brake assemblies. I then removed the 4 nuts & bolts retaining the leaf springs and unbolted the two bottom shock nuts allowing the trans-axle and leaf springs to be dropped down with a floor jack and rolled out from the back.

[trarex]

At this point I need to get this transfer case open to see what is needed for the gear swap.. I remembered seeing a post on here talking about leave the driver side tire on and stand up the rear axle when you open the case. After draining the fluids (before dropping) and breaking all the nuts loose on the trans-axle housing I stood the axle up on the drive side tire and tapped the casing all the way around with a dead blow until it started to separate. I then gently pried the two sections apart. As I did one bearing dropped down into the case, it is set into the passenger side of the housing, the other one stayed in place.. I have seen before people talking about these bearings and fits being different tolerances. I found that the two drive bearings that needed to be removed were both different. The smaller gear bearing fell off in disassembly and the larger gear bearing (sorry i know there is a name for these gears) took prying with several screwdrivers to finally get it off. Anyway this is probably the most difficult stage so far in disassembly making sure that everything is correctly orientated with lots of reference pictures. So once the case is apart and the bearings are removed the larger gear has 4 bolts that need to be removed. I used and impact to keep the axle assembly from spinning while trying to loosen. Once removed installation was just the opposite procedure. There is a governor arm on the trans-axle housing that interferes with the bearing placement when putting the housings back together. It takes a bit of fineness and alignment to get both halves to line up again but wasn't that difficult. I cleaned everything up and checked all my work, cleaned off the old gasket material, laid some gasket maker silicone on both sections then worked the two back together aligning everything back up. Overall not that hard, i just made sure I took lots of pictures as i tend to remember things slightly different than reality sometimes.

[trarex]

Now then with the trans-axle back together and all the nuts torqued down I reinstalled the axle assembly back into the cart reversing the procedures to remove it. The axle is heavy and very awkward to maneuver, a floor jack and some scrap wood is very helpful. I found that aligning the leaf spring mounts on the back of the cart one side at a time and holding with a bolt allowed the other side to be maneuvered into place. once both back bolts were reinstalled the front was easy to align back up. I then reinstalled the shock nuts and torqued everything down. Now with the trans-axle in place i can address the drum brakes. The disk brake kit is fairly explanatory but they are directional, if anyone needs help let me know. After aligning everything and torquing down the mounting hardware I then reinstalled the brake cables on both sides of the axle and adjusted the tolerances and movement via the brake adjustment nuts under the brake peddle. Adjusting the cable tension so that the brakes are not dragging but also close enough to engage quickly and with full travel.

[trarex]

Now it is time to start the install of the Vegas Carts V Twin cradle kit. The installation was fairly simple following the directions however, i noted several examples where the information and pictures in the manual did not align with my carts layout. Leave everything loose until the entire cradle is installed then align your level on the cradle before tightening everything down. Aligning everything probably took the most time just going back and forth in adjustments. With all of that I still had an issue where the Anti-wrap bar was too short for my application. I could not make the adjustments in the cradle or axle to adjust for the shortage. After reevaluating everything I decided I would make a replacement anti-wrap bar out of the skid plate removed with the robin engine to make up for the difference. I just traced the provided bar and added another 1/2" to the design. I then cut the metal out with an angle grinder and cut off wheel followed by drilling the holes to align trans-axle housing studs and bolt hole on the cradle. I later verified that the install was correct with Ivan at Vegas Carts. Not sure if the ST 6 seater is a different design but I would plan on having to do the same thing on that make and model. I then installed the aluminium engine mounting plate withe the provided hardware and reinstalled the shifter linkage verifying correct operation.

[trarex]

Now is the fun part.. I stopped by my local HF to pickup a Predator 670cc engine with my 10% off coupon, which included predators. Once in the store the only only remaining 670 left was an open box on the floor that looked like it fell off a truck and someone kicked it all the way to the display area. It was in bad shape.. Surprisingly with the manager we opened the box and the only damage we could find was some denting to the muffler, which will not be used anyway. I told the manager what I was doing with the engine and I didn't want to have to pull it back out because it was damaged. Long story short she agreed and ended up offering a considerable discount for the damage and condition of the packaging. I ended up getting the 670cc for $400 and bought the two year warranty for $250 for a total of $650. Once i got the motor home i couldn't find any additional damage or issues and everything appears to be in great condition.

Still following the Vegas cart directions I unbolted the muffler, throttle box, disconnected the wires from the engine to the throttle box and installed the torque converter and key. After torquing the torque converter down I unbolted the engine from the plywood that it is shipped on in the box and prepared to drop the predator into the cart. After 3-4 bourbons I mustered up the courage to try to drop that heavy bitch into the tight engine compartment. I have to say it was more like a slightly controlled descent to its cradle. I defiantly recommend getting some help to install that engine, its no lightweight especially when your dropping into a tight area.

[trarex]

At this point I am caught up on progress so will post updates as they happen. Just wanted to make sure I got it down while its all still fresh in my head. May help someone along the way like this forum has helped me.

Funny when you tell people that you are upgrading an engine from 9hp to 22hp in your golf cart their first response is either "why?" or "how fast will that make it?"

If your question is "why" sorry we can't be friends anymore, go away..

If your question is "how fast" i'll explain mechanics to you but will judge you forever after.

With all of that there is a cool speed calculation tool on this forum that I have used with figuring tire size, gearing, and rpm calculations. example I drive this cart for hours on end in loose sand with frequent starts and stops. I don't want to be at 4k rpm for hours on end to maintain a steady speed but would rather change gears and tires to maintain a good RPM range while keeping torque loss in mind.

[rjwenter]

Wow nice looking project and great deal on the motor. That two year warranty is nice to have, but hopefully won't be needed :) Good luck the rest of the way!