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So I thought I'd share my precious go kart project with you guys. More info can be found at the DIY Go Karts forum here:http://www.diygokarts.com/vb/showthread.php?p=535987#post535987
I got this thing off Craigslist for $60 on New Year's Day this year, not really knowing much about go karts, and so with what little I knew, I got to work.
Whenever I looked up a question I had, the search engine would always direct me to DIY Go Karts, so I eventually joined, and that was an excellent choice.
It's a 70s Bird Engineering Starbird, a real classic in the world of go karts. It still has the factory original front wheels, tires, and seat back!!!
It's powered by a 1985 Briggs and Stratton 5 HP flathead 4 stroke engine, that I hopped up with a racing header, and am currently upgrading with a racing connecting rod(so I can remove the governor and increase max RPM).
I sanded off most of the rust and redid the black paint in flat black. The previous owner modified it horrendously by doing stuff like adding a terribly ugly roll hoop(which I removed), so it feels good to give this classic a better shot at life.
First pic is the condition I got it in, and the others are the latest glam pics I took.
I have a series of videos on my Youtube channel that can tell the story much better than words alone.https://www.youtube.com/channel/UCQZBmyTrZ9dxpA2uFfEdDog
Enjoy.

Nice job JT, keep tinkering
And don't get run over on the street by a Big Texas Truck

Heheh, thankfully the brakes and engine kill switch work well. And there's not many big trucks in my neighborhood. And I always wear my DOT approved motorcycle helmet.

That's great! It made me reminisce about the one I had in either the late 80s or really early 90s that looked kind of similar. My father surprised me with it one day, and we fixed it up together. I drove it a lot, and even have video of it on a tape somewhere.

Cool! If you can find the video, try to get a still and post it up! I'm 90% sure I can identify it!

Unfortunately the footage is on old Hi8 camcorder cassette tape. Nearly all video recordings I have from back in the day are on that medium. Over the years I've periodically looked into converting the tapes into a modern digital format but the price of equipment has always been the hindrance. I haven't looked in a long time to see if anything has changed. Maybe prices have finally come down some. It's about time I look into it again.

Great job! Just checking your YouTube channel

Finally finished the connecting rod upgrade and governor removal, got a verified 38 MPH at approximately 5400 RPM!
I love it! I can actually hear the valve float at top speed.
That feels REALLY fast on this kart. It actually handles and stops quite well even from top speed.
Now I have to tackle the leaky carburetor. It's between putting more money into this old unit, or upgrading to a performance Mikuni carburetor. The Mikuni will be more expensive, but there will be parts support, it'll probably be more reliable, and it'll increase performance. Just waiting to hear back from the local powersports dealer on how much they want for a manifold for my engine.*toetapping*

Ok an update is due.

I had to open up the engine to reorient the piston rings, since I messed up the first time, so now that's fixed, everything is holding up great!
The wheel bearings have been giving me issues with extreme play on the front right wheel(that side smacked into a curb once), and when I pulled the wheels off today to inspect and measure, I made a shocking discovery!
The outer front right wheel bearing is THE WRONG SIZE!!
It's a 3/4" ID instead of the 5/8" ID it should be, so it gave excessive play, giving camber to that wheel and causing uneven tread wear. And on top of it the bearings are trashed. I'll be getting some new ones in the next few days. I am NOT driving it until I get that fixed and hopefully some fresh tires as well, because I don't want to be going almost 40 MPH and have a bearing or tire fail! Ouch!

When you say "reorient the piston rings", are you referring to the relative positions of the gaps?
I had a friend back in the day that hopped-up a Techumseh 5hp motor on his Rupp mini-bike. He fitted a performance rod and forged piston, lightened and gas ported the piston to improve the seal and milled the head to increase compression. It ran on aviation fuel and it performed pretty well as I recall. Those little motors can be a lot of fun to tinker with.

Yes, the relative positions of the gaps.

When I upgraded to the Raptor connecting rod, it slipped my mind that the 120 degree rule also applied to the 3 piece oil ring. So the two rail rings ended up lined up, allowing blow by and oil leakage. I know for sure the oil leakage was happening, but blow by was probably happening too. When I opened it up I found a puddle of oil on the piston.....
I've never wanted to mess with a Tecumseh, they're notorious for finicky carburetors, plus the hop up part market is pretty limited. Even the OEM parts are expensive, no one produces them any more. At least Briggs and Stratton are still in business!

I'm thinking about someday upgrading an engine like this one to have an AMR 300 supercharger: https://www.ebay.com/itm/AMR300-mini-Roots-supercharger-Compressor-blower-booster-Turbine-0-5-1-3L/264330982535?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D40719%26meid%3D20cef6459f3946808d34ec53e78c5f3a%26pid%3D100675%26rk%3D3%26rkt%3D15%26sd%3D193133587424%26itm%3D264330982535%26pmt%3D1%26noa%3D1%26pg%3D2380057&_trksid=p2380057.c100675.m4236&_trkparms=pageci%3A75ab7130-2133-11ea-b436-74dbd1801434%7Cparentrq%3A16903bdd16f0ad4cf4732f84ffb80696%7Ciid%3A1
Forced induction karts are pretty exotic, mostly because of the numerous technical issues people encounter and the high cost. However, most people have done turbochargers, and I think a supercharger would be much simpler, since the AMR 300 is filled with oil(these small engines have splash lube), and there is minimal electronics and plumbing. Plus there wouldn't be turbo lag.

But that won't happen to this engine. this one is completely decked out with heavy duty, high performance parts only rivaled by certain Raptor racing engines. I plan to keep it as a reliable, mildly modified, naturally aspirated engine.
This thing has dual ball bearings on the crankshaft, a steel bore, heavy duty valvetrain, electronic ignition, and a high compression head! From the factory!! Plus it has the rare Flo-Jet updraft float carburetor. I'm impressed on how well this engine has been preserved, the previous owner didn't even know what brand it was!!

However, I do have a 3 HP flathead that's quite plain, it might be a good test bed to work out the kinks of a forced induction engine. It will be going on a wagon rod I have.