Streaker Go-kart Project

Go-kart Project

After leaping headfirst into the world of go karts, I found an abandoned project. With a little bit of work it just might fund future karts. It looks like a Kenbar Streaker.

All the parts were there, just not together. The kart had been extended 11". The work was solid though not detail oriented. It came with a Briggs & Stratton engine that while advertised as unknown, ended up not working.
The tires were bald and dry rotting. The steering wheel plate was broken off, but I did get a clutch, chain, and plastic steering wheel.
The length is 5'-10" with a 52" wheel base.

Purchasing:
Engine 6.5hp 212cc - $100
5/16" x 3/4" 24 tpi bolt for output shaft - $0.18
5/16" fender washer - $0.18
5/16" lock washer - $0.18
Tires 4.1x3.5-5" - $7 ea. (2)
Tires 4.1x3.5-4" - $7 ea. (2)
Steel spacer sleeves - $5
#40 Chain - $10
Spindle 1 & Spindle 2 - $28

References:
DIY Go Carts forum
Harbor Freight coupons - don't pay more than $100 for engine
BMI Go Kart Parts
Go Power Sports Parts
OMB Warehouse Parts 
Northern Tool Parts
Kart Performance Estimator

How I bought it.

Introduction
I stumbled upon this kart after picking up three karts that had been sitting outside for a while (check that out here). This one needed less work so I started on it first. It seemed to be a quick job. It came with an engine that ended up not working. The gas and brake lines were cut, then had a second piece of rod band-aiding them.
The frame was cut with a smaller tube inserted into the frame and welded, then another piece of steel running the length of the splice and overlapping each side of the frame.
Expanded metal mesh covered the floor. The seat was plywood and foam covered in canvas.

I wasn't sure how much I was going to redo. Depending on price, I would redo the gas and break lines. I left the frame, but thought about replacing the mesh with sheet metal.

While it had a kill switch, there was no wire running to it. I was definitely going to remedy that.

Here is the info on the kart:

Engine: Briggs & Stratton 4 cycle 5 HP

Model: 130202 Type 0198 04 Code 80032706

It was a 1980 engine and it didn't last. Just in case you want some details on your old Briggs engine, here is an engine diagram page and an engine code key.


Rear tires: 4.1x3.5-5" (width x section height - wheel diameter)
Front tires: 4.1x3.5-4"

Clutch: 10 tooth
Sprocket: 48 tooth (8" diameter roughly)
Chain: #41 with a .5" pitch & 6.35 mm width between plates

Engine Check
The first step was determining if the engine would work. It turned over, but that was all I knew. The gas in it smelled okay, but I replaced it anyway. The oil level was okay and the oil didn't look bad. I went ahead and bolted it to the cart just to keep it still. I scavenged mounting bolts from my other karts.

I checked the air filter first, blowing it out with compressed air, but make sure you are blowing dirt out, not farther into the filter.
Then I checked the spark plug. I grounded it to the motor and pulled cord. I could definitely see spark. When you do this, make sure you aren't touching the spark plug or the engine.

If you don't see spark, remove the spark plug and hold the contact slightly away from the motor. If you see spark the plug is bad. If not, that's an issue I haven't had to figure out yet.

I checked the air mixture screw. I screwed it in, then two full turns out for the stock setting. I tried the engine and it made no sound that indicated it might crank.

An engine needs air, spark, and fuel to run. I had ruled out problems with all but one. I put a teaspoon of gas in spark plug hole, replaced spark plug and pulled the cord. The engine didn't even try to crank and on the third pull it locked completely up. With putting gas in the spark plug hole, you need to replace the plug and attempt a start kind of quick.

If the engine hadn't locked up and actually sounded like it might crank with gas in the intake, I would have cleaned the carburetor. Follow this example or this example. I may have done a carb rebuild, but it didn't get to that point. With an unknown engine like this, a rebuild could end up being a waste.

If you go the route of cleaning the carb, also remove tank and clean that and fuel lines, makes sure gas will flow all the way to the carb too. Make sure you clean the pick up filters for in the tank.

I ended up getting the Predator 212cc engine from Harbor Freight.

Engine Replacement
You can't beat the 212 cc Predator engine. It's a lower cost knock off of the Honda GX200 engine. It has a compression Ratio of 8.5:1, takes fuel type: 87+ Octane. The engine oil capacity: 0.5 Quarts which is 16 ounces. Fuel capacity is .9 Gallons.

It's a 3/4" output shaft with a 3/16" keyway, which matches the clutch that came with the project. The Predator does come with key stock.

I read a lot of posts like this one and this one that the factory spring is insufficient with a kart throttle cable. I loosened the tension nut on the throttle and while it would move freely, it wouldn't return. I loosened it even more and it easily returned with the stock spring. It comes out of the box with the nut tightened down. Keep loosening it until the throttle returns automatically.

The Predator engine has a low oil sensor, but in a kart, just taking a corner can trip the sensor and shut down the engine. The oil sensor can be simply unplugged. It's a yellow wire coming out of the relay box that has a connection to a yellow wire going into the crank case. The wire from the relay can be connected inline to ground with a momentary push button or toggle switch to use as a kill switch.

There is a cable clamp for the throttle cable and a cable anchor for the cable.

Engine Break-In:
After mounting the engine, fill the oil and check the level. The Predator takes 16 ounces. Give the pull start a slow pull to make sure everything turns over okay. Check your engine max throttle screw because the factory sets it pretty low. I left mine all the way in. Fill the tank with gas.

To start the engine, just turn the red knob to ON, turn on the gas valve with the black lever, turn the grey lever to choke and pull the rope. While some recommend a 3 hour break in, I rode the kart for about two hours and changed the oil.
I leave the choke on for just about a 10 seconds, then shut it all the way off.

During my break in period, I noticed oil on my frame. Two crank shaft cover bolts were missing and two were very loose. This was the reason my oil was leaking. I searched my yard, but couldn't find the missing bolts. I tightened down the bolts I did have, filled it with oil, and ran the kart again. The screws didn't loosen, leading me to think the screws were not tightened to start with.

Harbor Freight has a 90 day warranty, so I returned the engine after draining the oil and gas. They will ask you multiple times if you've drained them, and you do need to.

Speed Calculator:
The question is always, how fast is my kart. Here is a speed calculator. Of course weight is a factor, but based just on gearing my kart will go a max 27. With the extra weight and the fact I have the throttle screw all the way in, I'm probably going 15 mph or so.

Here's the long math:
3600 max rpm (governed 212 cc predator) / 4.8 (gear reduction for 10t and 48t)= 750

750x12" (tire diameter) x3.14 (pi for circumference)= 28260

28260/12 (inches to feet)= 2355
2355/5280 (feet to miles)= 0.446
.446x60 (minutes to hours)= 27 miles/hour.

Steering / Steering Wheel
The steering wheel bracket was gone. I happened to have a round 3.5" plate and welded it to the steering shaft after sanding it down to bare metal The thickness is the same as what my other karts had.

If I hadn't had the round plate, I would have cut a 3" by 3" square, and then kept making small cuts to round it, finally filing it to be smooth. That might be more effort than it's worth but I pay attention to details.

The tire rods were obviously salvaged from something else, possibly a lawn mower. A tab was welded to the pit man arm, seemingly for these shorter tie rods. Also the spindle arms had been bent in.

Came with lawn mower tie rods

The steering radius was much larger than a kart should be. I replaced the tie rods with some from another kart to dial the turning radius in. I ended up keeping the plate on the pitman arm as I could adjust these tie rods quite long enough. One end was rusted in place.
I also ended up replacing the spindles. This changes dialed the turning radius in right where it needed to be.

Kill Switch

The kill switch on the kart still worked. Here are two kill switch installation examples. I ran a wire from the engine low oil sensor wire, which i unplugged and capped on the engine side. On the relay side, I connected 14 gauge wire from the kill switch, using the same cover. My switch is self grounding, but if your toggle switch has two blades, you would connect the wire from the relay to one, and then run a wire from the other blade to a screw on the kart.

Frame
The top of the frame had been painted. The bottom half wasn't touched.  I didn't worry about painting it.

I considered replacing the gas and brake rods because I just didn't like how piecemeal they were. Sure the frame looks the same way, but these were easier to fix. Ultimately I left them.

After running the kart the first day, a stress fracture occurred where the seat frame and extension reinforcement bars are welded, just in front of the engine.

I ground/sanded the area to bear metal and used a big bar clamp to pull the frame together to weld it in place.

Throttle & Brake Cables
I didn't need any cable, but bicycle cable for the throttle is cheaper. Use kart brake cable for brakes. You don't want to cheap out on brakes.

The gas pedal stop should hit exactly at full throttle, match them up when connecting the throttle cable to the engine.

Clutch
This project came with a clutch I hoped would work. It's a 3/4" shaft with a 3/16" keyway. This matches up to the Predator engine perfectly.

The engine comes with keystock, though I had to shorten to 1" for my clutch. If you need keystock, try a local welding shop.

The bolt for the output shaft 5/16-24, 1.5" long for output shaft of engine. My clutch hangs off the output shaft just a bit to line up with the sprocket, otherwise get a 3/4" bolt. Also get a lock washer and fender washer in either case.

Oil the clutch bushing before you install it.

The keyway is the slot on the shaft/clutch. The locking part is the key. A piece of 3/16"" keystock is what's typically used. It's just square steel rod that is cut to desired length.

Sprockets & Chain
I cleaned the chain then soaked it in motor oil so the oil could penetrate all the rollers.
Allow between 1/4 inch and 3/8 inch flex for proper adjustment, if you have more than 1/2" flex it needs to be adjusted. Loosen the engine mount bolts and slide the engine to reduce slack, or add washers to the bolts to lift the engine.
Adding two links made it too loose, but adding only one was too tight. I needed a half link, but didn't have one on hand.

My engine was already 1/2" away from the seat, so I added spacers to lift it up. I had frame bolt washers from an old Nissan pickup truck. That raised the engine just enough.

I had #41 chain that ended up being two links short. I bought #40 chain, mixing up what I had but #40 still works. I used this chain guide to make sure the two could interchange. I pressed out the chain studs with a punch and nut. When installing the master link, the opening should point towards the back of the kart.

Gearing:
My gearing is 4.8:1. Commonly recommended is  6:1 for a fun kart. I wasn't going to change the ratio. While the kart can be slow to take off, it isn't terrible. Though inclines can be a problem.  I wouldn't recommend any shorter gearing.

Clutch: 10 tooth
Sprocket: 48 tooth (8" diameter roughly)

Brakes
The band brakes were in good shape.

Wheels & Tires
The front wheels weren't wide enough for the spindle. While the spindle was threaded, it wasn't threaded far enough. Instead of adding a bunch of washers, I added a steel spacer sleeve. I used 3/4" EMT conduit, which I had on hand and was the perfect size. I added washers, just to protect the wheel from the spacer.

Rear tires: 4.1x3.5-5" (width x section height - wheel diameter)
Front tires: 4.1x3.5-4"

I replaced the tires with studded tires, what came with the kart was bald.

Seat
I wanted to upgrade the seat so it didn't look like a quick and dirty job, which is exactly what it was. After riding it, the foam is not enough. This seat needs a lot more padding when bouncing around.
I recovered it and discovered upon tear down, towels were the only padding in the seat. I already had 2" upholstery foam from another project. I spray glued the foam to the existing plywood backer, then wrapped it in fabric. I used polyester curtains. I stapled the top of the material to the back of the plywood first, then pulled it tight and stapled it to the bottom. Then I did the sides. The corners I pulled tight trying to remove wrinkles or fold over the excess.

Conclusion
I bought this kart to fix and sell to fund my other three karts. The engine locking up hurt the profit margin, but I knew it was an unknown. All in all, the project wasn't too bad. I had fun fixing the kart.