After reading how a ported intake can give you up to 4 HP on a stock motor I decided to give it a try. To start off, my motor it internally stock and this was the first time I have really even looked at the intake. Before removing the intake I noticed that when the factory installed it they did not allign the ports and there was a ~.040 step from the intake to the head. That alone has to rob HP. The ports were very equal but it just takes a little care when installing the intake to line the ports properly.
What I did was I opened the carb side to 45mm and polished the ports to a smooth shine. I was amazed at how rough the casting was from the factory and immediately understood how polishing it out could help. I was careful not to take any more material then necessary off around the opening for the head because as mentioned, that opening was almost perfect.
I took it out to my local dirt area to test out the difference and found that it revs a bit higher and feels like the pull at higher revs is improved. I think it was a success but the real test will be at the dunes where I can compare it to other quads that I have raced in the past.
This is definately cheap hp.

 

you said you "polished" it. I hope you didn't put a mirror finish on it. It need a finish of about 120 grit sand roll to help keep fuel in suspension. So you think it was worth while? I will have to give a try next. I have done lots of port and polish work before, but just got my ds so have not touched it yet. Sounds like its time to get the die grinder and carbide burrs out again.

 

Hey,

Just to elaborate a little on what sled head1 had said. You dont want a mirror finish on the intake side, you need a rougher surface to help atomize (spelling) the fuel. Although, on the exhaust side, you would want a mirror finish, because the exhaust will not build up on a polished surface and it will flow faster. Just my 2 cents.

Gary

 

When I did my porting the head ports were quite a bit smaller than the manifold ports. I polished my manifold to a mirror finish and it was wouldn't even start unless I gave it half throttle, even when it was warm. Went back and roughed it up with a carbide burr and it started soon it as soon as I touched the button.

Also, the stock exhaust gaskets and rubber carb boot stick out and restrict flow.

 

Yah I overstated the shine a bit... my bad. I finished with 80 grit slapper type sander you know the one that looks like a wheel but is actually multiple pieces of sand paper stacked on top of each other. At high speed it leaves a purfect finish. When I say "shine" I'm comparing it with the way it started out.
No problem with starting after assembly, it started the same as it always does. No negative effects throught the RPM range either.

DCryder,
I was amazed at how close the ports were. I expected a big difference in size and was prepared to port the head to match if I had to. Luckily I didn't have to go there. The rubber carb boot wasn't a problem at all. It was actually about .020 larger then the carb. It may be because I'm running a TM42 carb which has a slightly larger o.d. flange and that may be enlarging the center portion of the boot so that it is out of the way.

Sleadhead1,
If youve ported before it will take you about 45 minutes with the right bits. definately worth it. I used a 1-1/4" carbide burr to open up to 45mm. Made quick work out of it and the large bit made it easier to keep a perfect circle.

I recommend this for those who have ported before. If you havn't and want to try your hand, I suggest that you get some practice on something else first. Im not sure what the intake costs but you certainly don't want to ruin it. There, you have my disclaimer.

 

I ported my intake and also matched the ports to the motor. I took some rubber out of the ridge in the rubber boot too so it flows better. My intake is on my pics page.

 

My buddy has a ds that he ported the intake himself very smooth and put a tm45 without accel. pump on it. It is very hard to start when cold, but starts fine when warm. Is this the nature of the best or could this possibly be because his intake is to smooth?

 

polarisfreak,
As you read above, if the manifold is too smooth, you could have starting problems however I think your buddy just needs to increase his cold enrichment (choke) jet or simply increase his mixture screw 1/2 turn CCW. New carbs almost always need some sort of adjustment in these circuits.

 

Ok thanks, I'll have him try that!

 

When I did mine I matched everything, including the rubber. At first Majorecho polished her up for me but I lost my low end torque that I loved. So then I took it and toook a cutter ball on a die grinder and let her rip, roughed it up real good then went back and smoothed it over some and the power was bacl pluss some. The difference went from needing a 175 DJ jet to a 185-190.