2 Stroke porting/polishing

[Groundworx]

I am rebuilding my 85 TRI-Z. I was wanting to have the head/cylinder ported and polished. I talked to my local shop and he doesn't do it. He told me he had it done on a dirt bike once and only to port the exhaust side, not the intake side. He also told me that the cylinder would have to be reworked after this is done. Has anyone ever had this done or know what part of this is true. The owner of this shop wasn't 100% sure about all of this, but said that is what he did. It is actually a street bike shop, and he doesn't know all of the little tricks of 2-strokes.

[StangLX302]

Now I don't know if this applies to larger engines, but, I'm into RC cars (a tiny 2-stroke basically) pretty heavily and I've always been told to port more on the intake side and just a minor clean up on the exhaust side. The reason being is that if the exhaust flows too much volume, the unburnt mixture will blow out of the exhaust port before it is used as energy by the combustion process. I hope that makes sense.

Matt

[J La]

I Know that you want to have someone do it that knows what they are doing. If it gets messed up it will never run right. It is definately worth the money to do it. It makes a hell of a difference.



'01 CR250, '85 250R '85 350X, '93 YZ80, '93 TRX90, '84 TRI-ZINGER

[Groundworx]

There is a guy here in town who build race heads for cars. He does porting and polishing on car heads. My dad knows him real well and I was going to ask him to do it.

Here is what is going on. It bottom end of my Z is trashed. My top end only has about 10 hrs on it. I bought another bottom end that is supposed to only have 50 hrs since new. I have a full DG pipe. I am looking at a 86 model carb. It is supposed to be a 34mm as opposed to the 32mm on the 85. I might look at like a 38 mm flat side. I am putting in Boyseen power reeds. I went down 1 tooth in the front sprocket and up 2 in the rear. That should give it more low end. And then I was going to do a port and polish job on it.

Do you think I should trust a head shop that mainly works on cars to do the port and polish?

[3WheelsForever]

I dont think I would, unless they've allready ported 2 strokes. A 4 stroke is completly different than a 2 stroke. If a person gets ahold of a 2 stroke cylinder and ports it wrong it can mess up port timing etc. On a 4 stroke you dont have to worry about port timing.

[smokinwrench]

A guy in Ok is the best at 250r porting from what I've heard. I know his trx is unreal fast. CHAINSAW had his Z ported by him and was very impressed with it what little he has ridden it. You might pm chainsaw to get his info, I can't seem to find it right now. This guy goes by SandTrix on the net.

[plkmonster2]

You can port and polish a 4 stroke by yourself, but 2 strokes take special machines to measure the flow, flow angle, and all that other stuff, including timing. Changing the flow angle can determine where you motor makes its power. Along with changing the angle, it gives the most advantage. but, I wouldn't do it myself. You need real machines that measure it constantly, not your dusty protractor and compass, lol.

[Groundworx]

I will ask Chainsaw and see if he has that info. I know some racers around here who might know someone too. I knew it was different, but I didn't know that it took special machines.

[CHAINSAW]

I am rebuilding my 85 TRI-Z. I was wanting to have the head/cylinder ported and polished. I talked to my local shop and he doesn't do it. He told me he had it done on a dirt bike once and only to port the exhaust side, not the intake side. He also told me that the cylinder would have to be reworked after this is done.

What kinda shop does he run?? lol

The exhaust side 95% of the time just gets a polished job. Thats the polish on a port and polish job. Very little polishing goes into the intake side. As for having the cylinder "reworked" I assume he means have the ports touched up. As in where they go into the cylinder. You leave a rough edge, and your gonna scar that piston up fast. Any notable porter will do this for you as part of the job.

As for Sandtrix. His site is gone for some reason, but he is still doing port jobs. For a 250R, I would put his work up against anyone in the world.. the guy is unreal! Ive seen a few of his machines run, and they are nothing to play with.
As for the job he did on mine, I am very impressed. He busted his collar bone when he was half way done with it, and still picked up the tools and finished the job hurt. Before my bike would wheelie the first few gears when draggin, but now It lifts the tire up in every gear, and thats with a +6 swinger. Thats the first time he had even tried a YZ cylinder.
He is known for his 250R work. Ill get his email address and let you talk to him.
As for head work, some people mill the head to get more compression.

[mbg75]

there are no special tools needed to perform the wrench mods on a Z. all you need is a die grinder, dremel, and drill to take care of the cylinder mods. as far as milling the head, any local machine shop can do that.
as long as you follow the directions exactly, you should have no problem at all.
i ported the cylinder on my old Z, and also on my sisters blaster. just go slowly and resist the urge to take more out.

[CHAINSAW]

dont take advice from a shade tree mechanic Groundworx. There has been a lot of updates and changes since the ole wrench report mods were published. The newer port maps will outshine a 1985-86 dirt wheels article any day of the week.

It does take special tools to port a cylinder. You cannot get up in the boost ports with a dremel. A correct and professional job should only be attempted by a professional. Some joe blo in his garage at night will not have a machine that comes close. If he is lucky, it might run as good as a stock machine. Most home made port jobs end up in an unrealiable machine, and poor performance. There are a lot of factors to consider when you are the port man,.. grabbing a dremel and start grinding isnt gonna get you anything but bad results.

[CHAINSAW]

some pics of his work.

[CHAINSAW]

exhaust port

[CHAINSAW]

the flash makes it hard to see, but this is a drag port.

[mbg75]

chainsaw,
my the boost port wasn't done with a dremel. pilot hole was drilled with a drill, then opened up with the die grinder and a long carbide bit.
as far as some joe blo in his garage at night, how can you make an accusation like that when you don't even know someone!
all i was trying to say was that the wrench report mods CAN be done by anyone who is mechanically experienced. i'm sure there are new updates to the porting out there. 95% of porting is done by hand w/ a die grinder. the research for port mapping is what the machines are needed for. wrench report has these specs already avaliable for you.