Part 1 on building a 5HP Briggs (Raptor 3) from scratch, 90% NOS / New parts, this video is showing most of the mods i did before assembly. Next Video will be engine assembly and test run. Thanks for Watching!!!
As always, love your videos man. Aside from the engine modifications, I really liked how you used that mirror to shine light back up into the muffler. A little trick like that, so simple and useful and I can't believe I didn't think of it myself haha Definitely have to remember that one. Thanks for the videos!
Great work, and some of those simple idea's can make all the difference. Have you tried polishing the head combustion surface to a mirror finish? I did that mod on a few bike motors many years ago, the idea being there is less surface area to absorb heat out of the flame, and being more reflective gives a hotter flame front. It also helps reduce carbon and soot buildup as it's harder to stick to. Anyway, thanks for posting a cool video, cheers.
Check into an NGK BU8H surface gap spark plug, it has a circular ground electrode all around the outside, and it increases compression slightly. It worked fine in the 2 horse cylinder of my Briggs 5432. Great vid about building a Raptor, I bet my son has watched this vid for sure!
I've got a little 3HP side shaft Tecumseh I got from my neighbor I tore half apart to paint. It came off an edger and ran great. next thing I know I'm going hog wild porting the intake and exhaust ports. They were really restricted and sharp corners. Widened up the holes and rounded the edges a lot to improve flow and reduce turbulence should help it out. I notice the Tecumseh doesn't have any eyebrows to shave. That engine also has the same diameter intake and exhaust valves, except for the seat angles. I gotta hog out the updraft intake the best I can, that stupid thing is half the size of the carburetor venturi and intake port. No wonder they don't make as much power as a Briggs lol. I figure it's best to experiment with a crappy engine before ruining a good Briggs. I think I will make a fire slot in the head and shave it down a little to increase compression.
@@fnaguitarplayer9 I painted the block and some tin pieces today and shaved the head down a bit and cut the fire slot. Looks pretty good. I figure the little bit I shaved off to increase compression compensates for the fire slot. I also found a couple plugs that will index perfectly with the fire slot when tightened down. Now if I can keep that connecting rod from breaking with all the extra torque it should make lol.
I hear ya! It should balance out the compression and maybe even add some, never know. This engine has so much compression it is hard to crank over. Part 3 is uploading now so it should be up in 1-2 hours. Thanks for Watching!!!
Hi, a hawe a question, i’m tuning a old briggs 8hp with a updraft carburetor and i’m looking to convert to delorto, its going on a off road go kart, wath do you think 26 or 28 ? Great video by the way i’m going to do that also!!! Or what mods do you recomend on that engine?
Hello Frank, like what your doing on the Raptor engine, Just don't port the intake side to much, sometimes them ruff edges and ridges help with the air and gas mixing better before burn. Can't wait for the next video 👍
Thanks. Yeah I didn't do to much at all really, just knocked down the real bad spots on both, part 2 (of 3) is uploading right now, should be up in a hour or 2. Thanks for Watching!!!
My 4hp head has a different bolt pattern and bigger bore. Not sure if you are aware but they make copper indexing washers. Cut off the stock ring washer and add copper ones til it is exactly where u want it.
They do make another coil for these, but most people actually run the stock coils, they say its not a huge difference, I'd like to run a external can type coil (auto style setup) on one, but it would have to have points/condensor. Thanks for Watching!!!
E3 is the worst spark plugs to buy, I've have had them fail on me, the center electrode likes to move under high heat conditions, I'd recommend Bosch spark plugs either with the 2 or 4 grounding electrodes.
I have recently had bad luck with E3 as well, in certain engines they do good, like my 2 cycle pocket bike (47cc) it ran 100% better with it, but in a 12hp briggs i had problems, I ended up using a NGK in this raptor build and it runs great on it, haven't tried anything else. I will check those out! Thanks for Watching!!!
I disagree, a spark does not "shoot" a spark' you cannot "aim" it. A "hotter" plug tends to contribute to detonation so that is not necessarily a good idea but you can maximize the stock plug by increasing the gap a couple thou (no more). He is 100% correct stating not to expect MUCH from small engine mods--these tricks are most effective on motors that rev 5000+ rpm and your Briggs 5 will push it to MAX 3400 without grenading. Flatheads are low revvers by design so it is much easier to get more power from even a stock OHV or better yet an OHC the same displacement. Of course, expect to pay more too. The beauty of an L-head is its simple design.
What I meant was the E3 brand plugs claim to make the flame "shoot" out of the plug instead of out and around the standard plugs, I kind of doubt it too, but i have noticed certain engines seem to like them better, but it just depends. Yes, you can only get so much out of them. I still love the old flatheads, its just a simple / dependable design. They do seem to have more torque the ohv at lower rpms. Thanks for Watching!!!
@@fnaguitarplayer9 I LOVE 'em : ) and yes, I am a fan of the greater torque too. These critters had an incredibly long and successful production run. Great video, I'm subbed!
@@royledford5673 thanks for the sub! I'm all the time working on these flatheads. I've always liked them, the 1st engine I ever worked on was a 5hp briggs.
@@fnaguitarplayer9 Last year I built a motorized bike board-track replica using a stock 2.8hp Baja Doodlebug L-head and a 26" bike frame. Turned out pretty darn cool if I do say so my self, never fails to draw a crowd in public. 32 mph top end is plenty fast enough with NO suspension!! Would really enjoy building another and of course--bigger is better...not that I'm in a hurry. Someone just gave me a Briggs 5 minus the carb and gas tank. 1) I plan to adapt the carb for a 5hp Tecumseh snow blower (new) and clean up both ports, nothing fancy. 2) Fire slot the head just as you demonstrated. 3) Shave the valve "eyebrows" in the block for smoother flow. 4) Rather than shave the head to recover compression loss I want to TRY lapping the block and head surfaces then use a .040" copper head gasket with 2.70" piston hole diameter. (I have a new stock head gasket that measures .071" thick). 5) Stock NGK plug with +.002 gap. 6) M/C tank up on the frame like the other bike. If all this works maybe I won't need the blower & nitromethane : )
@@royledford5673 so you mean to tell us that the 5 hp Raptors only turn 3600 rpm? ha ha. my clutch dont engage until around 4000. itll easily turn and make power up to around 7200. itll turn 10000 but it's out of the power band
