Added a boost port tonight *pics*

even if I wreck my head, got a better one coming in the mail. so I can keep hacking on it for practice and see what gains I get before I ever start on the head I will be using for sure.
and when you mess with the stock transfer ports, would you just widen them and play with the angle of them or would you deepen them as well if there is enough material to safely do so?

Depends on what you want to do. If you want more top end then you would widen and raise the roof of the transfers, exhaust and the boost port. If you want more low end then use epoxy and narrow the transfers and steepen the roof. There is so much involved and it's impossible for someone to sit down and explain it all at once. If you have the extra head to play with then I think that is a great way to learn. Make your mods small, a little at a time and note the performance gains/losses.

I suggest reading this before attempting anything: http://ericgorr.com/techarticles/basic_two_stroke.html

Best way to learn this stuff is threw trial and error,i was never taught anything by anyone about engines when i was 16 i jumped into it and taught myself ..

Ive done alot of small things with this bike considering u can get a head for dirt cheap for um and a entire motor for under a 100 bucks sometimes on ebay.

This is a great thread, I'm new to this site but am a Top Poster on the v-Rodforum. You guys do a great job explaining all this stuff. Now, *** is a boost post, how do I do it, and where do I start. Let me start by saying, i took my 47CC Cag and did a BB, HP Carb kit, Carbon fiber reed valve, and a billet manifold, velocity stack. The bike screams, much more power all over the powerband. Probably could use the clutch springs considering I'm 6'2" 240. Anyway, I want more power, so help me out here. If someone has pictures post them so I can see, or email them to me.

it is a 3rd transfer port in the cylinder wall across from the exhaust port. as far as I know it is to increase the efficiency of A/F transfer from the crankcase onto the cylinder. I dont really know about tuning it or anything like how wide/deep/long or anything but thats basically hat it does. Ive seen kits sold that have 2 boost ports also, not sure which is better, I'm sure ones better for something as is the other setup.

Great thread is right! However, we're jumping right to the 52cc Big Bore kit. Mild porting is fine.. but nothing beats displacement and well tuned exhaust

again... thanks for the info, and you're right... 50 guys will have all different way to achieve more performance. We've got some of the best port'rs around keep'n our clients grin'n from ear to ear

Big bore will be my next purchase for the 3rd bike im gonna buy lol

oh also, for the epoxy you are talking of, if I was to use JB-Weld that is fine right, if I wanted like a bit of both could I just add the boost port, narrow the transfers and raise them a bit along with the exhaust and boost port. the reason for narrowing them is because air flows better with less surface area correct? so is it possible to cross some of the benefits of each technique with the other? Im gonna go read that as well right now.

just read it and got some good info as well as a little bit confused. when I make my boost port, sinec I will be copying the principle over to the bb head.I am gooing to do two shallow boost ports since thats what I will have to do on the big bore. and now I am going to try wiht the angling the tops of the boost port inwards towards each other for better low end scavenging. Im just wondering if its goping to hurt the top end alot, it says between 2k-5k is where the benefit is, but it must be a bit fdifferent dealing with 125's and 250's vs out little 38cc thing. seams it will naturally rev higher just cuz of its size...

anyways Im gonna quick talking cuz I really dont know what im talking baout here and I am just gonna experment and see if I can at least keep it running, hopefully gain power but thats a lot to hope for when youve never ported anything before.

You sound like you're on the right path. Trial and error is deffinetely a good way to go if you have the means. I would suggest for you stock head (don't hold me liable for this) to make your boost port about 3/16" taller than the transfers. Angle the roof about 45 degrees. You want the edge of the angled roof that touches the piston rings to extend the 3/16" past the transfers not the bottom of the angle. The boost port on the stock head can be deeper than that on the BB head. The double boosts on the BB isn't a bad idea. The fact that they will be shallower than the stock heads you will deffinitly want to extend them past the transfers hieght. How far will be up to you, but obviously not past the roof of the exhaust port.

As for the transfer ports: On the stock you can widen them a bit, but I found that just widening by rounding off the bottom is best. I wouldn't mess with the roofs, they are already at a correct timing for the exhaust. As for the transfers on the BB, DO NOT TOUCH THEM! They are already big enough, this info was passed on to me from Tyler at Adrenaline and from IP2.

Well good luck and let us know the results. Try doing a little at a time, maybe first make the boost as tall as the transfers, run it, then maybe go up 1/8", run it, then go a little more or none at all. just try it and see how you like it. I run mine at about 3/16 and like what it does.

I got big gains off my portwork,I have my bike geared lower than stock now and it has a way higher top speed than stock.In fact I havent been able to top it out yet in any parking lot ive ran in.It just keeps reving and reving and reving. By far the best mod yet is going to town with the dremel. I did alot of mods at once to my motor,then it took a few days to tune and break in.Once i got it tuned its a rocket. I'm still running the stock pipe too.

Ported Zh1 head with boost port,notched piston,ported case,ported intake manifold,ported reed block with fg .5mm reeds,Ported carb w/jet kit,Rocket key,1.5 clutch springs,af and vs stack,stock pipe

I have the pos redline motorsports pipe its a total waste looks better is about it,i did my carb boring tonight also I tapered the bore coming in and going out and port matched the reed block to it,i also tapered my needle

Guess ill see how it works out lol

I got a black crome Rev Unlimited(poop pipe) but it wont fit my moded cag because there is a bar that goes across the frame right where the pipe goes. I wish i could run it on my mod bike cause it actually made good low and mid on my stock bike. I'm waiting for Rev Unlimited to come out with thier copy of the pacsales in black crome to put on my mod bike,it should clear just fine cause its routed like stock.

well, would I not even touch the transfers when I install the FCS crank? I would need to raise them just like I do the exhaust port wouldnt I, because the piston now travels further, so it can be transfering the mix for a longer duration and still have the same amount of stroke to compress it? or if I raised it would it transfer the mix inot the cylinder but since it would cover up the transfers late the compression would throw some of the mix back into the crankcase? If I practiced on porting the stock head in the same fashion as the B head, as in double boosts, raising the exhaust port, and transfers to certain distances from the TDC of the piston, and installed the FCS crank first, so I could port the head to accomodate that crank, would the same dimensions as far as transfer closing 1.25" before the piston hits TDC and the boost port being closed at 1" BTDC. would the same dimensions produce the same results with different bores? I would assume not since its a bigger volume to fill but it should produce "similar" results right? also I was wondering, where the reed block bolts to the case, if I were to leave it the same size but enlarge it just a bit inside and round it off, could there be any benefits there, cuz thats something I cant reverse.

I added a boost port to my 47cc go kart last night and it kicks azz. Id have to agree with making the boost port extend past transfers cause if you dont you are just adding crank case volume and reducing velocity which can be done by simply adding a spacer. Good thread though

Wow, I did not know that I would start such a heated debate with that question on the first page. Let's start another one, for those who did their boost port with a dremel like the pictures earlier in this thread, how come the port is square shaped? Most boost ports should be cut in with a round bit so that the air has a channel to escape. The next question is: how does the shape of the edges affect the boost port?? Meaning what difference does it make if it is a square groove or rounded groove? How does the angle of the edges affect what RPM the power will be made, for that matter how does changing the angle on the transfer ports affect the power delivery. These questions ought to prove who the real "porters" are and who are just experimenters. (it is a fact that every "porter" had to start out as an experimenter and most of us in the shops here have plenty of "ash trays" meaning screwed up cylinders to prove we were never right the first time)

Im just getting into the porting as i stated earlier ,i get alot of my information from my buddy that ports 2 strokes for a living in his custom shop.

I made my boost port go up a smidge higher then the transfer port im going to run it like that and see if i like how it feels if i dont ill pull the cyl again and work from there,when i first ported my cyl i didnt do a boost port and i said if im not happy with the gains ill pull it off and do a boost port i wasent happy off it came and i did the boost port lol if this isnt up to my expectations ill do more work.

My boost port isnt square i used a round bit.

I know you are just experimenting but the taper bore on the outlet of the carb won't do anything. However boring the throat completely through will but don't do it as big as your taper otherwise you get major leaks past the slide and it won't idle correctly, 14-15mm is good. The inlet side looks good, you can get away with tapering more and it should help increase air velocity like this:
http://tjtech.org/~CPF/darkzero/mini_moto/p&p_carb.jpg

I did bore the carb all the way threw but i added the taper to try to gain low end tq a striaght threw design provides all top end im just trying to see if i can get a lil of both.

I see. So does it? I'm curious too.