How to MOD a Flat-Head Briggs For Offroading

[@tonyktx44]

Good job young man, you're gonna be a hell of a mechanic one day....

[@tonyfremont]

Yepper, he sounds young, but he's on the track to excel at engine performance tweaks. He already knows it's all about torque, not horsepower.

[@2stroketerror125]

This is actually working the motor unlike just removing the governor. Great video you sound pretty knowledged for your age

[@960wattoffgridrv]

I recently swapped to a bigger engine on my 20" lawnmower/brush cutter. I spent most of the night and into the afternoon buttoning up the new motor after some slight porting, repaired a cracked intake tube and eyebrow shave. I also ported the head to get more flow around the valves. when putting the valves back in, check the valve lash particularly the intake valve. not sure why the intake lobe on the camshaft has a slight bump that holds the intake valve open on part of the compression stroke. aside from the compression release mechanism on the exhaust lobe, it's also a good idea to check the valve lash on the compression stroke. I usually take close to half a millimeter off the end of the valve stem to get increased compression. turn the flywheel by hand, slowly and observe the action of the intake and exhaust valves. I managed to keep the function of the compression release mechanism this time. I usually shorten the exhaust valve stem 1/2 millimeter to have full compression. I leave the governor off and put a direct throttle control to the carburetor. I only learned of porting and shaving the engine a couple years ago. I've been playing with these small engines for most of my life. they can cut a tree stump if you know what you're doing

[@europeanman6506]

Thank you for this, will be implementing this in my lawn mulcher build. Cheers from New Zealand👍🏻

[@recklessrust2001]

I believe that the intake port(s) on an engine are supposed to be rougher in order to mix the air and fuel

[@mechanicalmonster2115]

Nice job kid! I built racing carts when I was younger, little trick I learned was to make my own head gaskets out of manila folders. Thinner than real gaskets and they let more heat into the head. Very cool vid.

[@volvo09]

AirborneBadass how long did they last? I was thinking of using paper gasket (soda / beer package) when I had my push mowers head off. the area of concern is where flame would touch but anywhere else is cool enough.

[@mechanicalmonster2115]

Oh I gotcha! Its been awhile but if I remember correctly, I think we would changed them out after 3 passes. We had T-handled head studs too make it a quick swap. But I have used similar materials on my small engines over the years, those green, thicker sorting folders are nice. I used one of those in an early 80's Sears push mower, that I could not for the life of me find parts for. It was in there for a years worth of yard work, with no problems. I think people have this idea that there is a Street Fighter fireball trying to come out of the cylinder, but its really not like that. Not alot of flame going on. And you can always use a very small amount of high temp RTV , closer to the outer edge of the head also.

[@ianduijsens]

volvo09 you could asow make a copper one (its cheaper to buy one) or make one from a beercan and make tiny dimpels in it to make it seal

[@aspenwells8240]

I have used aluminum foil, more compression and cheap also won't burn like paper or manilla folders

[@arkman8109]

we built these things when I was a early teen and raced them on wood grain alcohol, man they would fly, with the prettiest blue flames when you let off!

[@WBatte1]

kid knows his stuff . and shows better restraint than I did as a youngster . because I used to switch the heads shave them and use the copper gasket . I'd also under gap the valve lash . typically I'd have to use the electric start in conjunction with the pull cord to fire it up . I also used old smog pumps to supercharge small engines . I never could afford any of the go fast parts like racing cams back then those were around 30 or 40 dollars .

[@donaldpatton1560]

So I been looking for this kind of info for a long time now on how to do free or cheap mods myself. Great info and one of the best I have seen. Thanks and well done sir.

[@mattprice37664]

Little dudes like this are the ones who go Powersports and those guns should be helping out

[@bryanst.martin7134]

One thing you didn't mention was port matching. The intake runner from the carb should also be ported to match the intake port. Same for the exhaust. Steps in the flow cause resistance. But contrary to that, since this is a low RPM motor, instead of matching the carb runner to the intake port, is to make a preswirl effect by grinding grooves in the carb runner in a rotating pattern to induce a pronounced swirl of the fuel/air mixture. This would look something like rifling. It may take a few try's including reversing direction, depth, patterns, etc. But carb runners are cheap compared to heads and blocks.The idea is to get the fuel/air mixture thoroughly mixed prior to compression. Once you have gotten peak performance from the carb runner mods, the last step is matching the intake port to the carb runner mods to get the maximum yield from your modifications. While a fine polish on the intake is desirable, the exhaust should have a fine grit to it. Maybe 300-400 grit. This is to allow some carbon buildup to act as an insulator and reduce heat build up in the cylinder head and surrounding block area. You can also grind some of the exhaust valve guide to enhance the flow, but don't get too thin, and leave a finish to allow some insulating carbon buildup to protect it too. Make sure there are no sharp edges anywhere in the combustion area. This causes hot spots and preignition. Once this is done you can move to tweaking the carb jets and timing advance. Final recommendation, is to run two stroke engine oil in your fuel. TCW3 at 100 to 1 ratio will help prevent excess carbon buildup in the exhaust and from collecting on your piston. At that ratio you should hardly see any smoke. Sorry for the long post, but you're a sharp young man, and I think the information won't be wasted. Congrats on the busted finger, that's man style. Style that too few men will ever earn. Other than that a Bandaid will shut them up. ;-) Keep at it, Bryan

[@styga1969]

Bryan St.Martin true !! I do a little 2stroke oil in both my kids mini bikes. Just a small cap fulll.

[@bryanst.martin7134]

The TCW3 has a cleaning agent to reduce carbon buildup. Use the TCW3 when the engine performance starts waning. But take advantage of the port mods They were handed down from Smokey Yunik via a NASCAR Mechanic of the Year, who taught me to build.

[@connorssmallengines6663]

Carb runners are expensive for me since I work on 5hp Briggs and usually make them use tecumseh h50 or h60 carbs. I can get whole engines for 50 bucks MAX. Most of them I get are free. But carb runners are 45 bucks! I don’t have a welder

[@jackrabbit7389]

Very nice young skywalker you got the fundamentals. Now to learn the darkside of force.

[@FretsNirvana]

Excellent video and instructions young man. Can I ask if you have any reference to how much more compression you got as a result of these modifications? Any reference to increased torque? Thanks …keep it up …smart young people like you are what we need in this world.

[@lescobrandon2202]

Exhaust port surface does not matter so much, but to keep it cleaner for longer it does not hurt to polish it.

[@dieselman2000]

tip on sanding (lapping) the cylinder head. Instaed of just sanding in a circle, use a figure eight motion. this insures the entire surface is flat.

[@trevinskiking2165]

That cutting back of the cylinder wall between the valves & the cylinder itself not lower than how high the top ring travels up is called " relieving" & improves the breathing significantly...you even hear it in the Jan & Dean song: " she's ported & relieved & she's stroked & bored" pertaining to the Ford Flathead where they used to put the mercury 3/8"th stroker crank in it & bore & port the block...Jan & Dean wrote most of the Hotrod songs like in American Grafitti but people mistook them for the beach boys...songs like "dead man's curve" etc ...Trev New Zealand 🤗🇳🇿

[@scootergeorge9576]

You don't relieve the block? In the past, standard procedure with the flathead Ford V-8 was to slightly grind the top of the cylinder between the piston and valves to increase power. Some compression is lost but is made up for by better flow.

[@MVP11489]

The connecting rod isnt going to "blow" from too much power lol. The rod or piston will blow from the detonation from the fuel pre igniting. You either run higher octane fuel such as premium, race gas, E85, ethanol, or methanol. Or you go with a larger cam to bleed off the compression. Your measured compression ratio based off bore, stroke, cylinder head CC, piston head CC, deck clearance, and head gasket thickness, is your static compression ratio. Your dynamic compression ratio is affected by valve overlap, which has to do with cam duration and lobe separation. The bigger the cam, the less dynamic compression you will have, but in turn, a higher RPM range you will have. Going with a stronger rod, will just mean you will melt a hole in your piston. Pre-ignition is like a hammer, and generates an enormous amount of heat. Yes, the closer to detonation you run, you will make a little more power, but that's not what blows parts.

[@lostforevermore7150]

awesome video kiddo. You have improved this engines efficiency significantly :)

[@Hinckley_Stickshift]

Im 16 and I do the exact stuff u do but I also have a buisness around small engine the whole idea u had will sand paper and the head is how u get leaks ive never done that personally but my neighbor did and ruined the head I have a milling machine so I dont have to worry about it but just was saying gotta watch and good for u getting into the hobby we need more kids that still do this stuff

[@zombieresponder]

I've never seen anyone polish an intake tract smooth on an engine that doesn't have direct injection. If I remember correctly, you want to remove sharp corners, casting flash, etc., but the walls need to be a little rough or the fuel/air mix can separate. As someone else mentioned, "shaving" the head is best done in a mill or a lathe. Doing anything more than a light polish to remove burrs or scratches with sandpaper stands a good chance of getting the surface out of square. If you are polishing on sandpaper to remove scratches, make a figure 8, otherwise you will remove more material on the side you are moving towards(right side for a clockwise circle). I'm sort of wondering about changing the shape of the ridges around the valves to direct flow and change the velocity of the incoming/exiting gas. On two strokes(at least the ones I've had apart), the intake and exhaust ports are tapered, with the smaller side at the cylinder. On the intake side, it compresses and speeds up the incoming fuel/air mix. The opposite is true on the exhaust. If the exhaust velocity is too high, it will pull more of the fuel/air mix out the exhaust port. If it's not high enough, it leaves spent gasses in the cylinder.

[@Thepockets88]

Good vid kid, a port and polish should be the first step to any engine mod, one thing id like o add though, if i may, is that when shaving the head and using thinner gaskets, make sure you watch the depth left on the combustion chamber, shave too much and your plugs gonna contact the piston head.

[@billbergen9169]

Could you use a washer between the spark plug & head?

[@DriveShaftDrew]

always nice to share info good job

[@jasonGreenVw]

when raising compression it a good idea to use high octane fuel to prevent detonation

[@v-g-z3689]

There is a lot of room before that happens on these engines. Adjusting the ignition timing (not possible on all engines) is usually the first thing to do.

[@connorssmallengines6663]

They don’t have high compression ratios

[@trevinskiking2165]

@@connorssmallengines6663 No but their prone to pre-ignition at a lesser comp ratio than their OHV counter parts of the same displacement & compression ratio 8.5:1:is about your limit for pump gas. Trev New Zealand 🤗🇳🇿

[@connorssmallengines6663]

@@trevinskiking2165 yes but the compression ratio is only 5.5:1 so there’s lots of room

[@trevinskiking2165]

@@connorssmallengines6663 I know that: 5.6:1 to be precise....Trev

[@drubradley8821]

Good job kid!!!. I actually enjoyed watching this video, it brought back lots of childhood memories, Thank you for that! Do every thing you can to keep your channel going for the next several years, with as much passion as you have with an old B&S, I can't wait to see what or how crazy you are gonna go on you vehicles power plant... lol... again, good job kid, keep up the good work!

[@thereelmaster]

one more thing ive found is that if you shorten the valves (not very much, a couple mm at the most) you can get even more compression, there for more power

[@redlinemotorsportts]

Nice talking to yea last night. I like the tips with the shaving, should help out and prolong the life of it. I'll do this to my opposed when i start upgrading it.

[@ShainAndrews]

Not sure how old you were when you posted this, but I'd have to compliment you on your speaking, nomenclature, and of course subject matter. Better than most of the crap I see kids posting. One thing to point out though. You shave the head, or swap heads you need to check and adjust the valve lash. Carry on. I'm sure you've progressed quite a bit in the two years since posting this video.

[@HSPOVgames]

wrong, wont change valve adjustments at all

[@ImpenetrableSilence]

When you do the eyebrows, you should to cut them even with the valve surface. I did that with my flatty 5hp and it works great.

[@pauls466]

offroad unlimited you sound like a young guy but I'm surpriced by your knowhawe. waw keep up the fun well done

[@bigboytoys98x]

Thanks!

[@garymiller1706]

Any fluid dynamics class 101 tells us very little mass flows along the walls, thus no air-fuel mixing . However, we still encounter wall resistance ,hence , a higher reynolds # . The smooth wall is the only way to go.

[@styga1969]

Great vid! Love to see the young kids with black and blue nail bangs doing vids like this. When I was your age I use to grind down in between the valves to head like a V shape from both valves to cyclinder. It would burn rich because of the flow. .

[@styga1969]

Also use to shave the head also. But no joke.. grind the block where both valve are like a V towards the piston.. don't go to deep. Make it like a chamber.. maybe like 10 thousand of an inch.

[@mrcodesteez1211]

I love this video here every young man should have these things instilled in there minds great job bud take more stuff apart and figure out how it works it's a great quality to have

[@sonyacarrier4942]

Hey just my 2 cents is the NOT completily "polish" the intake but DO polish the exhaust, but the turbulence in the intake mixes the air and gas better. Any thoughts?

[@droptheblades895]

you don't want to polish the intake port too much, you want it rough so it makes the air and fuel mix better. if you polish it, it can decrease torque.

[@zolljaboy]

do you use a torque wrench when putting these back together? I have a 5hp briggs that i wanna tear down and re-build but i dont have a torque wrench or the torque specs. if you could reply that would help a lot

[@bbsmyname]

I own a torque wrench but i dont bother with these smaller motors. Ive never had a problem. Thats just me though.

[@ephenj]

Just a heads up if you go with close to a mirror like finish porting the intake you will actually loose power. Its o.k. to open them up and get rid of the poor castings but if your using a dremel or air tool, leave the little scratches it makes for better Atomization of fuel. You can read up on it, At first I thought the smoother the better but that ended up not being he case, You also have a high velocity fuel side flow and low velocity side flow side on the intake valve and depending on the shape yo go with can make a huge improvement to.

[@fischermann5279]

Polishing the intake wont hurt anything and if you see pro ported heads they are very smooth. The shape and volume is what will effect flow. Intake doesnt atomize the fuel. Everything here is just guesswork. Why not cc the heads and if you know stroke, bore, thickness of head gasket and head volume you can get your true compression. Then you can see the effects of milling head, thinner gaskets, etc... will have. Also when we ported heads the areas that affected flow the most was unshrouding valve area, cleaning and radiusing valve angles and thinning valve around the seat contact. That will change flow dramatically as valve first opens. Flow bench is necessary if you get serious about porting. Good vid tho!

[@chrisradla]

thanks for showing both heads side by side

[@darrenstevens.7520]

Good job young man, your video was awesome an very informational. I'm going to try the copper gasket. keep posting your knowledge Of small engine's.

[@trevinskiking2165]

Darren....thin copper head gasket is a cheap way of doing a head milling without the expense, get the thin copper sheet from an arts & crafts store & use the original head gasket as a template & cut out with a pair of sissors..Trev New Zealand🤗🇳🇿

[@emmettcarr2988]

Hey great video buddy, would you mind linking me to where you can find them copper head gaskets you were talking about. I've been trying to find some for my 42 ci Briggs twin cylinder boxer

[@jimmccarthy1698]

love your work

[@PaulieDetmurds]

Great info, thanks a lot kid!

[@fh276]

Perhaps a valve relief, would help? Between the valves & the cylinder, for the 11 HP head conversion. It would help, drop compression & increase port flow on both intake & exhaust valves

[@josephmahoney9646]

I was always told, rough intake to help atamiz the fuel?

[@proxismog9896]

To get a bit more compression besides using the other head, you can check your intake valve to see if it stays sealed throughout the whole compression cycle. Some Briggs I have come across the intake valve doesn't fully seal until about 1 to 2 inches from TDC. You can make it seal a bit sooner by milling down the valve stem end ever so slightly. This will increase your compression giving you a bit more power and torque. Also a good old over bore doesn't hurt. I like mine at about .20 over.

[@oldboatclub]

Nice job on the video. When lapping a head or any other flat surface, be sure you use an absolutely flat surface (1/4" plate glass works great) and do a figure 8 pattern Not a circle. By doing a circle, you will end up taking most of the meat off the leading edge. You can also "relieve" the block by milling away the bridge between the "eyebrow" as you call it - and the cylinder.

[@TheBossKelso]

you are so wrong about the intake... the intake should never be smooth!!!! because the air/fuel will mix worse!

[@mr.gutterwater4479]

Same with 2 strokes never polish intake just port but exhaust you can port and polish it

[@bigboytoys98x]

+Boss Kelso yes i agree, as far as in the intake manifold goes, yes when it is smooth it docent atomize as well instead it beads up but fuel atomization docent happen in the head/intake port

[@scootergeorge9576]

Airflow adjacent to the port wall is slower than the the bulk of the flow. This is known as "boundary layer" effect. And because of this, the size and shape of the port has a greater influence on flow than texture.

[@mattmoilanen3813]

Scooter George Ya not so much big guy. A slightly rough texture will cause flow turbulence that will extend into the bulk of the incoming mixture and increase atomization therefore promoting better fuel burn. The theories you speak of were thought to be true 30 years ago. Any quality port optimization will include a rough intake surface. This is done on all engines intended for performance use as it is not an aircraft wing trying to minimize flow separation.

[@stanleydenning]

Pros & cons about polishing intake ports. In this case, I think it won't hurt. Won't help either. Enlarging the port would help, but polishing is little difference. The run from the base of the carb to the valve opening is rather short. So, condensation should not be a problem.

[@hughjass1835]

Great video Bud!

[@marcchaffee7751]

a hardcore guy would remove the exhaust threads , good for around half a horse .

[@johnsavoy4784]

made some good points, however take the ridge off the head, more compression is good,,, use plasti gauge or other method to ensure you will have valve clearance on full load at high temps, do remove the governor, when you port the intake,create some dimples to help in atomizing fuel air mixture, then to really wake up this engine do some work to the cam,grind away the easy spin start feature B&S incorporates into it, more compression is good, using braze build up a few thousandths and grind smooth on both lobes increasing lift this is when you really pay attention to valve stem expansion, giving it adequate clearance at high RPM's and high temp. and last using a round file elongate the holes on magnetron ing. and advance the timing by a few degree's the significant difference in power will leave you in awe ! All of this can be done with household tools,a brazing torch is the only specialty tool needed

[@timerickson2141]

While I watched this I was thinking about when guys hotroded flat head v8s they used to shave a dished area in the block a passage between the cylinder and the valves to really make the airflow much better not much like 40 thousands of an inch just a thought

[@lescobrandon2202]

Intake channel should not be smooth because of the micro turbulence effect. Surface should be ideally golf ball -like, a bit rougher side for the maximal gas flow.

[@fastcobra8]

Btw I'm not meaning to be mean but ur supposed to port the intake and leave it rough and the exhaust port it and make it as smooth as possible. The reason u want to leave the intake side rough is it helps w/ur air/fuel mixture. Just to let u know bud. But nice job.

[@fastcobra8]

yes sir u want the rough texture so that the fuel doesn't puddle or pool in the chambers.

[@wintermachine]

lightly sandblast the intake port for fuel mix. you have ported too big. remove the eyebrows by the valves. maybe you can get by without a head gasket, use hi temp rtv. go to Brian Miller's pulling site for more info. get a ball hone for the carb and open it up. you may have to enlarge the jet.

[@hardtop123]

i used to race ride on mowers. i modded a 28 series 12 HP flat head and it went like stink……what i did was mounted the head in a lathe (i used a long piece of round bar with a spark plug thread on it, screwed that into the head and spun it up on the lathe) and i machined about 120 thou off it. i used a standard head gasket too. next i retarded the cam timing 1 tooth. this brings your torque range down lower and into a more useable rpm range. the governor was still used to control top speed. i did nothing to the porting on this engine, except for a 3 angle valve seat and new valves. i run this engine on premium fuel too. pulled like a train at low rpm, and got me out of the corners quick….would be what you need for offroad stuff…..hope this info helps…cheers

[@lelandlewis7207]

If you are looking for torque, keep your intake work minimal and concentrate on smoothing, not increasing size. A smaller port enhances port velocity at lower RPM, which promotes cylinder filling and torque. Also, as has been mentioned, do not polish the intake port, leave a sanded finish. Polishing the exhaust, on the other hand is very important. Also, concentrate on the short radius on the port roof where the port turns to the valve seat, this is a critical area for flow. A back angle cut on the valves can be a large help for flow.Lastly, size your exhaust pipe diameter and length to promote scavenging at the RPM you are most likely to use. A smaller diameter will once again promote velocity and length tunes the RPM, so matching them to the engine has a big affect. Megaphones can also be used for fine tuning.

[@ericschulze5641]

Polish intake like a mirror, then glass bead it or gently sandblast ,Polish exhaust and leave it,tulip intake valve

[@lelandlewis7207]

@@ericschulze5641 Pretty much what I said. Polishing and then bead blasting will work, but is a lot of extra work for minimal, if any, gain over a good sanding roll finish. Knife edging the valve guide bosses to split and direct flow, which I forgot to mention, will also be a big help. Both valves need to be backcut to maximize flow.

[@thatonedodge]

Hey so you did good but you should have kept the intake the way it was after rough sand paper but so it would atomize the air and fuel

[@lloydcisco3027]

Nice work keep it up!!

[@stenbladh6153]

Scooter George relieveing is a classic thing I do that at my Harley flathead and I don`regret it.

[@fleamine]

If you want more power and torque, bore out your cylinder to .030 to .060 over.reseat your valves, bigger piston and over-sized rings. To raise compression, boring oversize, give your new piston and rings a tight fit within the cylinder. Not too tight as the starter wont be able to crank it over. Then, find a bigger carb to put on to increase gas flow.ex: If your building a 11hp engine, go with a 12 hp or 15 hp carb. It can be done, as i have done this in the past. (certified small engine mechanic) For all things described, it may run you under $100 for the parts, you will also need a honing tool to bore out cylinder and the use of a drill to power it. Hope this helps anyone...

[@crazybob1954mo]

A .030 bore on an engine this small is Useless and Very expensive!!!! Forget the larger Carb. He clearly said more Mid-Range torque is the desired result. Duh... " you will also need a honing tool to bore out cylinder and the use of a drill to power it. ""???? WTF are you talking about????

[@hernanjavierlopez306]

How much power can be obtained by modifying? (I have a flat head English 4.5 hp. It has 76 gauge and 100 career)

[@trickyricky12147]

It's good to know there are still ppl at your age working on small engines instead of being on the Xbox all the time :) eh em the millenials u listening?

[@slippery396]

Why wouldn't you remover the governor ?... we always use to take that off and we never had a problem with throwing a rod. . . . .

[@TRX450RVlogger]

great job kid! I'm impressed I give you respect. awesome work.

[@davidabraham3873]

when your connector rod blows is that from high rpms or is it from high rpms and that the piston is putting to much pressure on the rod thanks

[@bigboytoys98x]

it can be both but mostly from high rrpms

[@michaelau5159]

An old video with so many comments that show how little many commentators actually know about engine design. Porting is good if the engine requires or is able to use the extra air. What you should be looking for is air speed not outright airflow. As an exagerated example a port that flows 100 cfm (cfm = cubic feet per minute so it is a volume measurement) at 300 fpm (fpm = feet per minute so it is a speed measurement) is bet.etr than a larger port that flows 110 cfm at 250 fpm. To big a port will slow down air speed and you will kill torque in the lower to medium rpm range. With regards to polishing well let's just say that polishing is an old fad that did very little to help produce torque and hp. The theory was the better the polishing the faster the air could flow. The problem was, as some have pointed out, polishing disrupted fuel atomisation into the airstream. So the way around that is to keep some texture so that the fuel atomises better in the air stream. With modern CFD, 5 axis machines, and airflow benches it has been recognised that dimpling (like a golf ball has dimples) the port helps both airflow and fuel atomisation. I like the rounding of the edges near the valve inside the combustion chamber. To go further with that idea take a look at videos for Ford V8 Flathead performance and see that some people also cut a shallow channel from the valves to the cylinder. It will decrease compression ratio slightly but improve low lift air flow potentially increasing volumteric efficiency (which is what you really want to do).

[@20079037]

Thank you so much ... l've been looking for the shape of the chamber to L-head engine for my thesis. THANK YOU!

[@TheKutia]

porting a low rpm engine wont do anything that would only help with high reving engines... also i think that hurts air/fuel mixture in those small carb engines correct me if im wrong

[@motovatedbros9897]

INVISIBLE SUN you are correct when we raced dirt oval karts 5hp Briggs flatheads on alcohol even the modifieds didn't use much intake port work it was slim to none

[@windshear33]

surely the only way to increase the compression ratio is with a longer stroke or an oversize piston, unless you have a supercharger? Air drawn in at atmospheric pressure will only fill a given space, therefore the ratio stays the same.

[@nickarrigo8797]

While you are correct about a naturally aspirated engine only taking in as much air as atmospheric pressure would allow, your compression ratio would still be increased by shaving the head or changing to the head that has the smaller chamber.. more "squeeze". same thing as a longer stroke or a domed piston.

[@claytonm8434]

Dont polish the intake it needs to be rough so that it atomizes the fuel the exhaust needs to flow free for max efficiency

[@stevenlamphear1945]

nicely done and explained. Thank you.

[@preston121068]

I like the video, some decent tips. Just one thing though... you shouldn't completely make your intake that smooth. On these small engines it actually hurts the fuel atomizing process.

[@drewdprix2]

Sorry but from u saying u want to gain more power and torque at low end rpm ranges... porting the intake actually decreases power and torque at low rpm if ur not pulling enough cfm to create any velocity... it only helps if ur increasing ur rpm ranges for top end.... thus eliminating ur governor

[@drewdprix2]

Im not making fun of u btw just being constructive

[@matthewdirks3893]

Does this work with Tecumseh flat head engines too

[@thefieldsgarage6380]

the intake should always be rough because it mixes the fuel and air together

[@Xxcody3232xX]

polishing has no effect. Has basically 0 increase in power.

[@ClumsyCars]

I also notice you didn't shave the eye-brows, I hear that can help flow dramatically.

[@ClumsyCars]

You want the roughness in the bottom of the intake port, it's to keep the fuel from puddling up on the bottom of the port.

[@erickrivera3923]

Ive worked on mopeds for while now and usually im able to just remove the headgasket completely and slap the head back on to raise the compression. Is that something I would be able to do to the briggs motor without it making the plug hit the piston? any help would be appreciated thank you

[@erickrivera4891]

+leopold klop I guess is something I can only do to 2 strokes lol Thank you

[@tribulation138]

+Erick Rivera I do that to old chainsaws.. works really well. raised to comp to 150psi to 180-200psi

[@icekoolkueb8299]

good video although never polish the intake port and get the static compression to like 1 to 9.5 otherwise ur going to have to get a gridle plate if u run on methanol or alky other than that awesome video

[@nkaratzas]

Im building a racing mower and it has an 11 HP briggs flathead, the governor system is all wacked and I wanna just do away with it, if I set up a finger throttle from the butterfly on the carb, will it blow if I rev it above 3500 RPMs for too long? Great vids, Nico

[@bigboytoys98x]

you can go ahead and rev the motor higher than 3600 rpm especially with a briggs. just not too much. you should be able to listen to to the motor and hear when its revving TOO high. you could also forget the gov and just put a solid limiter on the throttle, but only if you have a gas pedal. if a load is put on the motor with a constant throttle, and no gov the egine will slowly idle down becouse there is no opposite reaction from the load slowing the engine sown

[@nkaratzas]

Offroaders Unlimited Great Thanks, I swapped motors instead cause the carb was junk and it needed work, thanks for the info though!

[@patrickspinks2166]

m

[@bigchad007]

When shaving the head down.. you have to make sure it's on an extremely flat surface like on a piece of glass.

[@jasonstalder5208]

mums coffee table ......

[@DonovanBryant92]

This is helpful now that i got one of these engines

[@jesse1136]

Polishing your intake is counterproductive when you understand fuel atomization.

[@2aklamath]

You want the cylinder head surface to be a little rough to seal the gasket.

[@hankhill5860]

nice job, but you might want to hone that cylinder it's got some scoring

[@timorum]

Have you got some measurements on how much you can take off head?

[@bigboytoys98x]

Sorry no but you usually mill the head down until the section that sits over the piston has no ridge on the edges

[@walkaway6353]

Use "playdoo" between the head and piston to get an idea. You can go to far and have to much comp. or bang parts together. Remember moving parts and hot parts are closer together than cold on the the bench parts.

[@kierankay100]

theres alot of cool things you can do to these engines .. i would do these mods and and change to a pitbike carb ... remove the gov ... add a oil cooler and oil pump lap the valves but take more time on doing it and when driving you will get more of a pull and speed but try ad a re stricter to stop it from full throttling

[@crazybob1954mo]

Duhh... Remove the governor.... but add a restrictor to prevent full throttle?????? WTF!! Raising the compression is a great idea as it increases mid range torque and promotes a cleaner running engine!

[@kierankay100]

Bob Duvall i meant like when it full throttles they can snap the rod so try add something so it throttles off after abit goveners prevent good acceleration aswell as high revs

[@bubsiesiegel]

Great vid bud! Hey Im going to send you my build on Diykarts if thats okay! Thanks brother!

[@tommyacuna6384]

haha im 14 and i love small engines i have two go karts and how you work on small engine is just like how i do it i kind of mod them myself just removed my govnor on my briggs 5hp thanks for the helpful mods

[@tabbimerten9815]

Tommy Acuna removing the governor on a small briggs is a leading cause of throwing a rod. the internals werent designed for much higher that the factory set rpm

[@goldwingman1500]

We call it a Side Valve engine in Australia .

[@mtwseneca]

Next time you whack a finger (or pinch one) squeeze it on and off for about 2 minutes- keeping the blood flowing in and around the bruise. It hurts, but you will never get one of those throbbing black finger nails and pinches do not result in blisters. 'Been doing that since my grandpa told me that 60 something years ago. Mike

[@legowarriorsadventure3613]

What hp is yours?

[@Liamautomechanic]

good vid.

[@MrShagwell73]

A+ Great job!

[@jonusfarm]

where can you buy the head gaskets?

[@davidsymalla]

Good job young man.

[@stevepapadakis3287]

your one smart kit. you kinda sound 15 and well im 14 to :p i always work on these just to lazy to make vids on it. my dads a race mechanic for drag raceing and from over time iv learned that you should never polish the intake. use the grit rolls up to 230 or 340 or something like that. on in exaust if you got a good amount of metal you can get a carbide bit and take some away and then port it like the intake then polish it. when polished carbon and over all just hte exaust wont get stuck. i can keep going but this is put in a way that if people really dont know how porting works if you guys want me to say it detailed then just leave a comment and il tell you in detail but nice job on the engine buddy :)

[@MechanicalMikesRoadsideRepair]

I might have a mower shop do this with my 10hp tecumseh now man

[@noahdement9271]

A billet rod would allow you to modify the motor a little more. I however have never had a problem with the stock rod breaking, even at 6500 and above :-)

[@nkaratzas]

Thanks for the input! Im building a racer and am doing away with the governor but I was second guessing my idea, but now i think i should go for it!!!

[@noahdement9271]

No problem! Glad to see people my age with an interest in small engines :)

[@nkaratzas]

Noah Dement You should check out my channel! Im not a pro at small engines but I definetly know my way around one enough to race and mod! btw I subbed!

[@noahdement9271]

I subbed to you!!!

[@bigboytoys98x]

well as i said in the video there small mods for offroading you can do without swapping to a billet rod

[@artyberkhoff8878]

Cams are much more important then compression look up khk harley modified by jerry branch if you want to learn something.