Briggs and Stratton.

8-) seriously, ... perfect for the newbie

that was my 8th grade project. Kids today don't get that experience

Note: Manufactures add too many parts to small engines, that's why there is always some left over after wrenching on your bike as a kid..........:rolleyes:


Wanna New Engine Tweeking Experience?


My thought. A two stroke ATV quad.

I've had 14 of them over 25 years. 3-4 major builds


1st quad - yamaha Blaster. 200cc stock. Port/polish put a pipe on it. you can buy one for all day long on Craigslist for $1500 running quad.

2nd quad - 350cc 4 stroke Warrior. Did a big bore / stroker kit and high lift cam for 400cc. It died a Glorious death in Oregon sand dunes after rod pin started tapping and seized. Putting lower rod thru two new holes in the case. Big smoke cloud as oil poured forward. I got off quad and laid in sand looking at pretty clouds in blue sky over head.....sigh.

3rd quad - called White Lightning. stock Banshee Twin 350 two stroke. Big bore sleeved pistoned with .25" stroker crank = 404cc. Major carb work with intake spacers for longer throat/torque. Toomey t-5 pipes with CSFX quiet muffers. (92dB noise limit in dunes) +4" trailing arm to keep nose down. Stock is ~38 hp? I was putting down around 65. hooking up PADDLE tires in the dunes and bangging gears = many bent shifter forks. Too Lean = several 4 point seizes of pistons during tuning runs. (locking up rear tires at 50, cool down start , go home)



4th quad. Predator 500cc 4 stroke. Jet hot coated Tuned Supertrapp exhaust with Drilled re-jetted carb . awesome all around family performance machine.


That was 15 years ago, Everything is sold now......:(:(;):D but my Twin Black 500cc Predators.




https://cimg1.ibsrv.net/gimg/atvconn...418110cdcd.jpg


https://cimg3.ibsrv.net/gimg/atvconn...8c2e5ae0ee.jpg

https://cimg6.ibsrv.net/gimg/atvconn...ee0f6a9254.jpg



A dozen other my ATV pics playing in sand dunes. ST Anthony's Idaho and Florence Oregon:

yes they were an honest 350-400 foot talll............in baby powder soft sand.....man that robs the power.

click. comment.



https://atvconnection.com/g/album/4235348

Don't forget bull- nosing / knife edging crank throws, optimizing the oil pump for reduced 'pulsing' , windage trays, crank scrapers. All are very important even in a mild street engine.

While later gen engines like Mazda or Honda are also good platforms, the machining, materials and oil control are very good because the manufacturers have already addressed sloppy machining and heavy / inefficient components. What's the lesson there?

The SBC offers real world challenges with simple improvements machining-wise. Think budget, not cheap horsepower - as in work with what you have - just like engineering.

You are absolutely right. Stay focused on the intended purpose which is learning as much as possible and choose the platform that will maximize that opportunity.

So much of the answer will depend on what use he will have for the final product when done. For sure building a Briggs & Stratton is way easier than a small block. But will there be a use for the engine when done?

A small block will drop right into a ton of different car projects. No doubt more 32 Fords have a 350 Chevy engine than Ford engines. And there are a zillion old Chevrolet vehicles from Corvette to pickup to 4 door cars.

It takes lots more space for a car, but in the end if he ends up with a car he can drive and sell, he will have learned a lot of very practical knowledge.

40+ years farting around with cars and never heard of a crank scraper. In my defense they are fairly new tech. No more than 90 years old.

Googled and they can make them out of teflon (inserts) with as little as a few thousandths clearance.

Rods still throw up plenty of oil so (from read) not as restrictive as some windage trays.

Learn something new everyday.

^^^^^ Yes, low tech really - in a typical short block layout where the rotating assy is exposed, the scraper is sandwiched between bottom of block / oil pan rail and oil pan. The protruding 'forks' are very close to each crank counter weight throw surrounding the edges to scrape the liquid off.

You wouldn't believe how much drag and slosh the liquid has on the rotating assy.

AFA blueprinting I don't think there's much more bang for the buck than an H-4 air cooled motor. The case halves are machined and bored whereas V8's are simply line bored for the crank and cam, and the block surfaced square to the bore, but the block is a single lump. The H-4 has the additional setting of the cylinders that have to be at the same height to fit the heads right. This would be true with many motorcycle engines.

When getting to rod length and wrist pin height all multi-cylinders are pretty much the same. And then there's balancing. Believe it or not, a single cylinder engine can be balanced to a certain degree.

When I was racing karts a huge amount of time, effort and money was spent to get more HP out of a stock out-of-the-box engine. The ubiquitous Yamaha KT100 was good for another 2 HP with modifications strictly adhering to the rule book which did not allow timing changes to the ignition nor the 2-cycle ports. The differences between motors shipped out of the factory were subtle but they did differ. And the tolerances could be improved on. Mainly squaring the cylinder to the crank, establishing the ideal piston clearance and making sure the ports were right on the money. Plus CC'ing the head, as well as balancing. By doing all the work with ultimate precision, 15% more HP could be found. A really good motor would turn another 1000 RPM over a bone stock box motor.

However, 4-cycle engines have more things to play with, mainly the cam and valve train that a 2- cycle motor doesn't have. And don't forget flowing the heads.

I've seen some nasty B and S motors on karts that were way beyond mowing the lawn.

I ran a bone stock 350 cheby 2 barrel on a bare engine dyno, applying a varying hydraulic load


If I recall, it took 12 horsepower to idle, pushing mechanical mass and fluid resistance.

Crank Scraper - Mopar calls it a windage tray..keeps the oil down in the pan and keeps it from sloshing around all over the place.

If you want some air cooled fun. Type 1, and type 2 engines are as easy as they get. Splitting the case is the hardest part. I think small 1 and 2 piston engines are pretty easy too.

THE LAWNMOWER RACER'S HAVE SOME INSANE b&s MOTORS MODS
INC TURBO'S ON V-TWINS

Not the same. Scraper is profiled around the throws of the crank. Windage tray is below that. Both are important for oil control. http://forums.pelicanparts.com/suppo...s/beerchug.gifhttp://forums.pelicanparts.com/suppo...s/beerchug.gif