"el Terror de Tejas"

[jamyers]

It got that name after my 13yr-old daughter and her bff ran it into a rather large oak tree at full boogie last year, very nearly tearing the RF wheel/tire/steering clear off the frame.

Thankfully they weren't hurt other than a couple of bruises and some soreness - and hopefully a lesson was learned.

It started off as a "Thunder Kart" with a Briggs "Fun Power" 5hp driving one wheel. I learned to hate the Briggs Pulse-Jet carbs / fuel tanks with that engine...so last winter we took it off, extended the frame and put on an old Briggs 8hp I/C (196437) engine and live axle we had around the farm, then added a battery and electric starter. The tires that were on the axle were too tall, so I put the old rear tires on the wheels and that helped, but it was still a little slow to start (but went plenty fast on the top end).

Anyways, the old 8-hp Briggs seized up, so it's on the bench to be torn down and rebuilt if possible. If not, I've got a good Briggs 5-horse and a Wisconsin Robin that I think is either 4.5 or 5-horse (will start another thread w/ pics to id it).

We left the old axles in place just ahead of the tires, and mounted the battery / starter relay on the old engine plate.

Front end after the repair. Note the huge gussets and new front "bumper". Still have to straighten that tie rod...

Steering wheel with start button and kill switch.

Rear axle sprocket. The hub has 5.25" bolt centers, with an Id of 4.55-4.6 inches by my measurement. From googleing, it looks like sprockets for this hub are common - are they?
It's geared too tall, I need either get a torque converter, jackshaft, or bigger sprocket. I'm thinking the cheapest and most flexible way would use a jackshaft, then I'd have way more options with the gear ratios (and could avoid a huge axle sprocket running in the dirt).

My immediate plans are to get an engine back on it, then figure out the gearing. Then I'd really like to start planning a suspension of sorts, right now it's a pretty rough ride unless you let almost all of the air out of the tires, and then the rears like to slip around on the wheel (not good for the tubes, I know).

 

[porsche930dude]

cool hopefully you can get the 8hp going . i had a peg leg kart with a 7hp tec on it and it was very fast and fun as hell. you wont need to worry about gearing with that much torque either. then you can put the bigger tires back on so you have some bounce. you can do away with the pulsajet carb and put a tecumseh carb on the 5hp. just have to make up a manifold

 

[jamyers]

Out of curiosity, would the float-bowl carb off the 8hp be a good candidate for the Briggs 5hp - assuming no governor and a header?

 

[Bluethunder3320]

Out of curiosity, would the float-bowl carb off the 8hp be a good candidate for the Briggs 5hp - assuming no governor and a header?

i assume its adjustable, so yes.

ive put a 8hp briggs carb on a 6hp tecumseh with a custom manifold. ran sweet.

 

[jamyers]

Just updating and consolidating pics/stuff...

Tore the engine down, found a trashed conn rod (no oil will do that, grrr).

Getting an extended-reach sparkplug to bring the gap/spark out of its hole and into the chamber:

Ported the block / ports:
Briggs 8hp Horizontal Flathead w/ cast-iron cylinder liner. Not a racing engine, just one on my kid's kart. I've done my own "street/strip porting on my Buick 455 and Ford 200, so it just seemed the thing to do to this engine once I had it apart anyways.

I used my air-powered die grinder with a 3/8" carbide round-nose burr for the rough cutting, with sanding rolls for cleanup. The carbide cuts quickly, so if you use one be SURE to brace your work and self or it can go through aluminum like you wouldn't believe. I've got a lot more polishing and cleanup work to do, but here's the progress so far.

The Chamber: I've cut the "eyebrows" (I think it oughta be called the "mustache", but I'm the new guy so...) down nearly to the level of the top of the valve seats. I didn't cut it down completely flat, but left a kind of a "hump" between the valve and the cylinder. My thinking is that a curve is better than a corner. I chamfered the very top edge of the cylinder liner, being VERY careful to stay well above the highest point the rings can get - which was obvious after using a ridge reamer. On the intake side (which curves inward), I went out to the head gasket, but on the exhaust side just eyeballed it - didn't want to remove too much material, and from what I gather the exhaust doesn't need near the help that the intake does.

The Ports: The only other place I've seen this much casting flash, bumps, and obstructions in an engine is inside my Ford inline 200 with the integral log intake 'manifold'. Sigh...

I didn't try to enlarge anything any more than necessary. My main goal was to just remove the casting flash, goofy seam irregularities, and smooth out any huge bumps in the port walls. The only place I tried to get technical was on the short side radius (the "inside of the corner" where the flow goes from horizontal to vertical to get past the valve. I laid that radius back, giving as smooth a transition as I could.

On this engine, the valve seat ID's are noticeably smaller than the block, leaving quite a ledge under the valve. I VERY carefully undercut the intake seat a little bit, just to take that edge off the underside. If I knew what I was doing with epoxy (and was trying to go for broke on this project), I'd add some to make it a smoother passage - and in the outside/bottom corners of the bowl area as well.

Here's where I'd add epoxy or something, from down in those corners to up under the valve seat. Make it a nice, rounded bowl instead of a 2-cornered mess.

Exhaust Port exit, looking inside at the bowl. The valveguide was sticking up 1/2", there was so much casting mess in there that it's a wonder anything ever got out of the engine. I also removed the threads, making it a true 1" exit port (the stock muffler has a .8" inlet, no wonder they're so restrictive). I'll fab up an exhaust pipe/header later on, and do a good deal more polishing in there as well.

Intake Port: The carb / 'manifold' bolts straight to the block, then the intake port makes a quarter-left-turn inside the block to get to the bowl. I cleaned this up a good deal as well,, and gasket-matched the opening. I'll do some more cleanup, but not going to polish this port. Now that I think of it, I might cut a wedge out of the intake to get the carb aimed same as the port - have to look at that...

 

[jamyers]

Used muriatic acid to get the aluminum remains off of the crankshaft, worked like a champ! After some light polishing, it mic'ed out to just above the Briggs reject size, yay!

 

[jamyers]

Used a piece of window-glass set on a table-saw table to get a flat surface, then lapped the head's gasket surface flat with valve-grinding compound. It wasn't bad, but you could easily tell where each head bolt pulls down. It's FLAT now, confirmed with a machinists straight edge.

Then I did some preliminary cleaning/polishing on the head, those corners are a pain to get to - but I'll get them in the end.

 

[jamyers]

Ordered new parts through Tulsa Engine Warehouse and saved $50 over the next best online deal and $100 better than paying the local dealer price.

New Piston / Rings, Connecting Rod, both Valves, all Gaskets and Seals. Piston/Rings are standard size, the bore measured within .002 of new (hooray for cast iron bores!). Conn Rod is also standard size, it's going to be withing spec - at the loose side - but within spec. Local machinist wants $80 to turn a single crank throw...grr...

New Rod vs. Old Rod...

 

[jamyers]

BTW, this gem from Harbor Freight does an outstanding job impersonating the $16 Briggs & Stratton valvespring compressor tool, and it looks like it'd be right handy on GM door springs as well! I got mine for $5, but $7.99 is still a deal, imho.

 

[jamyers]

After lapping the new valves and deck surface of the block (and another good degreasing/rinse), I used lots of hot, soapy water to wash away the abrasive. You might want to do this when nobody else is at home...

And get it out of there and get that bore oiled up IMMEDIATELY after the rinse cycle - raw cast iron will rust just from moisture in the air, let alone a box full of water.

 

[jamyers]

A little history...here's the complete Kart before the engine melt-down. That's my nephew Hal with his maniacal grin, fabbing up a front bumper / bush-whacker.

 

[Bluethunder3320]

thats a great engine, and youll have plenty of power with those upgrades

what would make it killer is a torque converter

 

[jamyers]

I've got my eye out on evilbay, craigslist, etc for a deal on one.

 

[jamyers]

I got the Briggs engine reassembled with the new parts, and all was well until I got the side cover on and the crankshaft held in place. Everything moved smoothly until the piston was halfway up on the compression stroke, then it had a "tight spot". So off came the side cover, and lookie there:

1. The connecting rod bolt retaining strap's upper ear was *just* contacting the exhaust lifter on the compression stroke, but not on the exhaust when it was opened by the cam. I bent the ear out of the way, and then noticed that:

2. The strap bows up between the bolts (bolt holes are not slotted, grrr), *just* enough for the strap to be contacting the camshaft between the lobes. You can see in the pic where it's been pushed back toward the rod. I went ahead and gave it a small bend, just enough to move it closer to the rod and away from the cam.

It's the little things that will drive you crazy....

 

[South Kart3377]

I got the Briggs engine reassembled with the new parts, and all was well until I got the side cover on and the crankshaft held in place. Everything moved smoothly until the piston was halfway up on the compression stroke, then it had a "tight spot". So off came the side cover, and lookie there:

1. The connecting rod bolt retaining strap's upper ear was *just* contacting the exhaust lifter on the compression stroke, but not on the exhaust when it was opened by the cam. I bent the ear out of the way, and then noticed that:

2. The strap bows up between the bolts (bolt holes are not slotted, grrr), *just* enough for the strap to be contacting the camshaft between the lobes. You can see in the pic where it's been pushed back toward the rod. I went ahead and gave it a small bend, just enough to move it closer to the rod and away from the cam.

It's the little things that will drive you crazy....

Hit them with Needle-nose Pilers and a flat head screw driver. Did that to mine. Briggs will sell you every part but the intake tube, and Choke-o-matic carb.

 

[jamyers]

Yup, a twist with needle nose and a smack with a hammer did wonders.

 

[jamyers]

Got the engine all together, and after some initial troubleshooting (see this thread for details) , we got it back on the kart and running again - for a little while at least.

...more on that in a minute...

I'm pretty sure that the engine was only making about half-power before the rebuild, because it was a bit sluggish taking off, especially with two kids or one adult aboard. I knew it was an older (worn) engine, but I had no idea...
When we tore the engine down we found:
1. a blown head gasket,
2. both compression rings had their gaps lined up directly over/above each other, and you could see where the blowby had discolored the cylinder bore.
3. both compression rings had ring-gaps of at least .25". Yes, that's a quarter-inch ring gap.

I'm betting that it was lucky to be making 4hp...

Anyways, with the newly-rebuilt engine, the kart has PLENTY of power now! On the upside, is has NO problem spinning both rear wheels and cutting donuts in the gravel parking lot (something it wouldn't nearly do before).

On the downside, it also has enough power to spin the wheels inside the tires and shear the valvestem clear off of an innertube.

 

[jamyers]

Updates: Swapped out the tire/tube with a used slick that's slightly taller but much wider, and did the old drag-racer's trick of self-tapping (#8 x 1/4") screws through the wheel into the bead of the tire - which works rather well so far.

 

[jamyers]

Here's the engine layout, the battery is sitting where the original Briggs 5-hp sat. I'm not thrilled having the gas tank that close (2 inches clearance) to the battery, but that's another project...

The white wire going across the recoil starter leads to a remote kill switch.

 

[jamyers]

Left side of the engine. Large see-through fuel filter, fuel lines zip-stripped down to clutch-shield bolts, and your basic Ford starter relay.