How do you port and polish

So what exactly do you do when you port and polish your exhaust, I'm still waiting on my throttle and fuel line that wasn't packed in the box before shipping so I have time to do a few things before I get it going. This site is great and I'm glad I found it and joined up.

Porting and polishing loosely refers to ensuring that your exhaust port, exhaust gasket and exhaust manifold all are of the correct shape and size and are very smooth. Here is a quick how to. Take your exhaust gasket and place it up to your exhaust port on your cylinder. Do they match? Probably not. Take a dremel tool or knife and make the exhaust gasket match the exhaust port. Now that your exhaust gasket matches the port. Use it as a template to start machining the exhaust header on your pipe to match the gasket. Once that is done you have now ported your exhaust. Now you can polish the exhaust manifold and exhaust port to make them very smooth. You can repeat the process for the intake but skip the polishing part. Intakes work better when they are slightly rough, it helps atomize the fuel air mixture. Hope this helps.

I'm no expert, but I can tell you the initial stages are pretty darn easy - it doesn't even require cutting on the head:

1) Match exhaust port to "exhaust manifold" and gasket. Ideally this should be a header pipe for an expansion chamber pipe, but the stock pipe will benefit as well. The actual engine port is much larger than the exhaust header pipe flange (exhaust manifold) - put the factory gasket on alone and see what I mean. First make a gasket out of Mr. Gasket HD gasket exhaust gasket material (do it with heavy card stock first to practice). This will be your template. Now match this up to the header pipe and mark the metal you need to remove with a Sharpie. Using a Dremel tool and small size 80 grit drum start grinding, you'll need 3 or 4 drums. When the metal is gone you have achieved a perfect transition. Switch to a 120 grit drum and make it really smooth. It's actually a bit easier with the pipe kits because you can install the little header and feel inside with your pinkie. If you feel a step, take more material off. Make it baby but smooth when you are done.

2) Repeat the basic step above for the intake tube manifold, plus grind all the weld lumps out at the inside upper end bend and where the flange is welded to the tube. This one you can make a gasket from regular gasket material and I smear blue RTV on both sides for a good seal on the final install.

3) Make sure you do the sanding/grinding well away from your work area and clean the parts really well be bolting them on.

I'm sure I forgot some things but the other guys will jump in……it's really quite easy.

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For those who have matched their exhaust/intakes/gaskets, do you notice an improvement? If you are on the boarder of saying yes, then it's a mental thing and no improvement was noted...so anything? On paper you should notice a difference, but is it real?

I can tell you, it makes a difference. Combined with a new pipe, a HUGE difference. The stock parts are really made for the 49cc engine, so they choke the 67cc.

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Thank you that is way easier then I thought it would be, I think I'll go start on it now. Learning more every time I check in.

It does make a difference. Just look at your bike. My muffler flange covered the exhaust port by at least 25%. Just think about it the faster and smoother the exhaust can leave the engine the faster and smoother new air/fuel can enter...

Alright, ill give it a shot and see what happens. I use this thing almost every day, so ill be able to tell quickly if it makes a difference.

1.) Another question, well I guess I'm looking for some tips. I got my motor mounted up and it was a little tight inside the frame on my mountain bike. well the thing is I'm going to have a really hard time getting my plug out with a socket and I'm not sure I can get a box end wrench between the cooling fins. I could just cut the plug off with a cut off wheel, but then getting the new one back in is the same problem. any Ideas?

2.) Also I was taking the nuts off of the head studs and the whole stud came out, well not thinking when I put it back in I added an extra washer and well there wasn't enough threads catching and I pulled the first three threads out of the engine(great haven't even started it yet). Well I got the capped nut off of the stud and put a bb in it and tightened it on the stud and then worked the stud back in past the stripped threads. I got about 1/4 - 1/2 inch in before the nut and washer touched the head, it tightened down fine, will I have any problems down the road. Kinda long post, sorry.

what kinda mb do you have? replace all your studs with 1/4-20

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