YZ 250 Porting

Im looking for some specs or even some accurate advice one doing a port and poilish job on a 2005 yz 250 two stroke.

Personally, for $225, I'd send it to Eric Gorr.

I'd rather have a professional job on this type of work.

You can polish ports fairly easy with a dremel an polishing compounds, but when it comes to porting I half to agree, Eric's years of expererance is a deal for what it costs.

Start a port timing map. You will need a degree wheel to get started. Find your baseline and start pulling numbers. Go read on mac dizzy for a few weeks and get after it. By the time you buy the wheel, drum rolls and die grinder.....you are more than halfway to having a pro do it.

What do you want out of it?

Start a port timing map. You will need a degree wheel to get started. Find your baseline and start pulling numbers. Go read on mac dizzy for a few weeks and get after it. By the time you buy the wheel, drum rolls and die grinder.....you are more than halfway to having a pro do it.

What do you want out of it?

Im looking to get my feet wet on the porting venture number one, and aside from that just smooth out the fuel delivery for better response and feel before adding the flywheel weight....trying to make my 250 two stroke feel more like my 250 four stroke.

Start a port timing map. You will need a degree wheel to get started. Find your baseline and start pulling numbers. Go read on mac dizzy for a few weeks and get after it. By the time you buy the wheel, drum rolls and die grinder.....you are more than halfway to having a pro do it.

What do you want out of it?

Im not too hip on your slang homie (mac dizzy)lmao

I searched "noob" but im not sure of the relevance. would you care to elaborate on the fact that im on a forum looking for advice on things i do not know about? noob yes...this is my first port job and ive never heard of mac dizzy but you didnt have to be a "dick" about it. :thumbsup:

I did a search on U-Tube and only found a bunch of foul mouthed toothlees front people using a grinder on air cooled cyclinders. Not what I would recommend to watch if your trying to learn. The little that I know about two srtoke porting is this : It's not about just making ports bigger and wider,it is more of a science than just grinding.I know that might not be what you wanted to hear.It will be difficult to make gains and not cause damage to your cyclinder but not impossible, So if if you feel inclinded I say get as much info as possible and give it a try.

didn't Eric Gorr write a book on 2 stroke engine performance and porting? that's what I would be looking into to get started. check out his website

you have sleeve or plated jug ? its alot easier to learn on the steel bores, that way you dont have to worry about messing up the plating. you could just keep riding your bike the way it is and read some books in the mean time to gain more knowledge. then when you decide to rebuild it just have millenium remove the plating and send the jug back and you can grind on it, then send it back to them for new plating. could also buy a old crappy $100 bike from craiglist and practice on that. one of the first things you need to learn is how to chamfer the ports or youll snag the rings. i do all my porting, let me know if you got any questions

Edited by harryhandshake

I did a search on U-Tube and only found a bunch of foul mouthed toothlees front people using a grinder on air cooled cyclinders. Not what I would recommend to watch if your trying to learn. The little that I know about two srtoke porting is this : It's not about just making ports bigger and wider,it is more of a science than just grinding.I know that might not be what you wanted to hear.It will be difficult to make gains and not cause damage to your cyclinder but not impossible, So if if you feel inclinded I say get as much info as possible and give it a try.

No doubt...Im a tool maker by trade so the science of removing the steel in my art. Definitly wasnt looking to gain any substancial amount of power by any means, just want to clean it up, so im not looking to increase the size. I want to say the size the the engineers at Yamaha chose will suffice. I am now going to look for those foul mouthed toothies you were speaking of. I love youtube.

Edited by alloutmx

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