How To Port a Cylidner Head: Small Engine Mods 101 

On my heads, I tend to remove a lot more material blending the short side radius. I also remove material from the walls of the runner to try and blend and smooth the transition from the bowl to the runner.

Great video! One the best I’ve seen regarding porting! Very clearly captured and explained! Thank you!

Still educating to this day, i used your video as a guide to do my yx160 head and it worked out great! thanks

I appreciate your time. I'm gonna give it a go! Very well explained...best I've seen!

this is the best video about the subject on YT. THanks

Great video. Thank you for explaining it properly for use .

Great video! Awesome fundamentals

Another awesome vid. Thanks!

thank you, informative !

what a simple and exactly accurate what and why porting the head.

Simple explanation of a stage one porting well done sir thanks for sharing

Thanks

Good stuff. You did a nice port job, that looked really good. Yes, be very careful to not knick the seats or you will need to get them cut again at a machine shop. Sometimes if I feel nervous about that happening , I’ll put some thin strips of tape over them. It can be fussy to apply though. It doesn’t add a lot of protection from causing a knick, but it makes you aware of them. If you’ve got your head off for work, clean up that casting flash in the ports. it’s not much more work.

On my riding mower with a 13.5HP Briggs, I opened up where the air comes into the filter and made the path to the head as streamline as I could. Smoothed (just broke) the sharp edges where the ports transition into the bowl on both the intake and exhaust side. Also done a half shaft mod to the throttle and choke shafts in the carb. On the intake side. The intake itself has a gasket, lip, then the port. The lip made a dark ring and the gasket made a slightly shinny mark on the head. So I opened up the intake port of the head till there was only 1/4th left of the dark colored ring. Going no more than 50% into the port towards the bowl and blended it to the OEM sized port. I didn't do a whole lot on the exhaust side. The exhaust manifold port was much smaller than the port on the head and I wanted to open the exhaust manifold up till it was slightly bigger than the port on the head. Unfortunately, there wasn't enough metal. But I was able to get the exhaust port and manifold port to the same size. I originally had a 1.2 ratio rocker on the exhaust and a 1.88 ratio rocker on the intake. Measured and remeasured to confirm the ratios. They are correct. I swap them around. With all that was done and a spark plug opened up to.042in with the ground strap cut back, I've noticed the following. More power in the mid range to upper RPM's with no ill effect in the low RPM's. Throttle response is also much better now too. It needs a rejet since it runs rich at any RPM above idle. But I'm happy with the gains made with the governor still on. I'd be lying if I said it didn't feel like I got 3 or 4HP gain.

Thanks for another informative video,still waiting for parts on my baja heat so i can put together a torque converter/jackshaft set up, did you have any trouble with the back wheel moving with the tensioner, mine was stripped on the brake side... I had it all tight so i thought, i will get new one if they will hold up ok

love it

Very helpful, me thanks you

Good info Grant!

The only thing i might add is port matching the intake manifold /head connection and head / exhaust pipe connection.

informative

You need to do a better job on the intake's short turn radius.

Do I have to get a larger carburetor and less restrictive exhaust to get perf. gains?

Good day kart fab where can I buy racing heads for 18hp block, thank you.

That area your porting would be the mca. It should be at least .85 of the throat😎

Great

I have a Cam in my mini bike now with 265 lift and 236 duration. It's an aggressive cam and i just paid like $125 bucks on Ebay for a Ported head that comes with the valve assembly and 22 lb springs and it's supposed to go very well with an aggressive cam that has 265 lift or more. I also ordered a bored out carb to go with them as well. I'm really hoping when i get all this put in my bike i notice a nice difference in power and performance but we shall see. It's only a 196cc engine so i dunno how much more power it can possibly produce but should be somewhat better. I've done all the usual mods to it already and as of now it goes around 45 mph. I'm hoping that after the stuff i ordered is installed it will go over 50 atleast. 🤞🚲

You look high lol, nice video

What are the name of tools that u are use in porting?

Terimakasih master enjin

I got a few lawn mowers, ready to do some port work on them and see how it goes...

On thing you can do to increase power is to port and polish your oil return galleries as well as pressure galleries because those casting imperfections will decrease the oil flow with ultimately translates to power loss.

can you reuse the head gasket if the engine has never been ran before and no heat has ever been built up?

Do u need to upgrade your valve springs wene you port and /or polish ?

Interesting...

I think I asked you already but can you do CG 250 engine

why is there no throat? now i want to remove mine

Polishing the exhaust is a good idea, but polishing your intake is not, keep it rough.

I read that grinding the intake side reduces low end torque

Very good video, but... That only covers OHV. I am in the process of doing a "Stage 1" (Homemade Exhaust Headers) on my 1991? Kohler Magnum MV18 (Vertical Shaft) Engine. Model#MV18S Spec#58560 . Is this engine even "Port-able"? There are no casting "reminents" or intrusions in either the Intake, or Exhaust Ports... I have been "suggested" to Upgrade to a Larger Intake Valve (1.500"), but the Stock one is 1.373", and I really don't know what to do, or what expensive Tools I need to aquire (for a One-Time job)... I hope I'm not "overwhelming" you with questions, but I can't get a Straight Answer from anyone. Feel free to Message/PM me if that would be more efficient. Or pass me to someone who KNOWS Kohler Magnum Opposed Twin Engines if you can. Thanks for the Awesome Education!, -Thomas (12) Port Orchard, Washington

wait has anyone done this to a 142f for a bike

its wonderful. i port every small motor i get for even miniscule gains from the losses cuz of high altitude/less O2 in the air= less power. 3.5% loss of power for each 1000' in elevation? 1% loss in power for each 10*F over 60*F so i am already behind at 3000'... 13%? runs RICH with stock jet= BLACK spark plugs from soot of too much gas. they make BIGGER jets, generally NOT smaller jets for high altitudes/less O2

Sou ds grt ,,but u missed .ost important part 2 do most of all

I’ve seen some idiots hogging out the exhaust ports 😳 don’t! They don’t seal to the exhaust gasket

I have bob Ross vibes~

Soooo...no gains?

I start hacking at my ports with a die grinder until the ports are as big as possible = 30 hp

cubic feet XD

High percentage of ignorant comments here. Lol!

Ok..them lil shite engines....they got sum pep in they step...so....lets say...we do this to a ....Ughhh...250cc with 17lbs torque and 12hp....what's the % in Gains?

Bro don did it

bro why? take it to a machine shop

Don't need u porting nothing of mine,,o,, boy find flow bench,u,ll learn quick ,what a difference, u need 2 do!!!!