Has anybody played around with opening exhaust ports and intakes and transfer cases on the china 110cc atvs?????

what were the results???
if you have done so please post what you have tryed and ad the number of material removed.
this way we can all gain from it.

thanks

 

Are you talkin about 2 or 4 strokes? You said 110cc china quads.
Porting is usually done on the 2 strokes to get about 3 times the power out of a piped, modded 2 stroke. On a 4 stroke porting is far more complex, and you would need other mods to open up the choked up intake and exhaust to benefit at all.

 

also your top 2 stroke engine builders wont give you details on their porting jobs. porting makes the motor so most keep very tight lipped and try and keep other builders from stealing their knowledge. i know one mini quad builder that will port you a cylinder like no other and it only cost $800.

Mark

 

yes i am talking about 4 stroke china

i have been doing some small 2 stroke for remote control boats that run gas 26cc engine
the porting that i have done is nothing major . just match most ports open exhaust ,intake and raise timing a bit.
in the boating community we normaly share and learn from each other.

4 stroke for me is anew ball game thats why the question.
if you have some links to webs that show how to post them.
we can all learn.

thanks

 

Engine theory 101

2 stroke and 4 stroke engines are very very different. A 2 stroke engine has port windows on the side of the cylinder and by changing the size of those windows or openings you can actually change how soon they open, how long there open, and when they close (intake and exhaust timing). In a 4 stroke engine you have valves, an intake valve and an exhaust valve in the Head. It also has a cam shaft. The cam shaft has lobes or bumps on it and they control when the valve opens, how much it opens, and when they close. To make things more complicated you also have something called rocker arms. When the cam lobe goes up it pushes one end of the rocker arm up which pushes the other end down against the valve, opening the valve. So in order to change when the valve opens, how much it opens and when it closes you have many factors. Minor changes can be made by adjusting a screw at the end of the rocker arm this is called adjusting the valve lash. Some cam shafts have the gear on the end of them that can be adjusted this would be cam shaft timing. But to get major changes you have to change out the cam shaft itself to one that has different lobe sizes and shapes and where the lobes are in relation to each other exhaust vs. intake. You can also put bigger valves in a head but that usually is done by just putting a whole new head on. You really asked about porting, so in a 4 stroke engine that is just smoothing and minor reshaping the tunnel that leads to the valve in the head. That doesn’t generally get you big gains in HP but racers that are looking for every little bit will be doing it. You can actually lose HP if you don’t know what you are doing, the size of the tunnel effects the velocity of the air and fuel moving through it, so a big tunnel slows down the air and fuel and they don’t mix well together. So unlike a 2 stroke engine there is no one that can show you a picture of where to remove a ¼ inch of metal and open up a port window on a 4 stroke engine that is going to give you a lot more HP. If you read some of the post here on the forums you will find advice on things you can do to get more HP out of your engine (like air filters, exhaust pipe mods and jetting). But if you want big increases in HP from a 4 stroke you have to spend some money for parts like bigger piston & cylinder, heads, cam shafts, carbs, and exhaust pipe. This is the first time I have ever tried to explain the difference in a 2 and 4 stroke engines so it might be more confusing than helpful. I hope it has helped.

 

hey:
thanks for the explanation, it didnt confuse a bit. but now i know what areas i will have to work on.
so i will start by making my own
cam shafts and start playing with the size of the lobes on them and go from there. i like making my own parts. this way i can say i did it.
the fact that it is a china motor. doesnt really push me to go spend some dollars for parts. and i think they are none existant.

but if you have a lynk post that up too.

thank you so much.