MOPED ARMY

By "raising" the exhaust port, the author means that you should take a handvile, dremel or whatever grinding tool you feel comfortable with, and increase the height of the port by 3mm. You don't need to wel any material on the bottom.

Removing any material directly below the window of the piston is a bit vague for me, I'd need to see the piston first. But my guess is that you need to cut a piece out of your piston, to increase the intake timing.

And there aren't any real step by step guides. Mostly because this isn't really something you learn from a guide, but rather by trial and error. Try it on some shitty cylinder you don't mind throwing away if it goes wrong.

Performance gain is hard to tell, as I have no clue how these engines run.

I don't know if the article you mentioned tells you to widen the exhaustport, but that's always a good thing to do. You want the absolute width at about 67% of the bore. So you would need to make a portmap to calculate how wide it whould be ;)

Hmm, you're wayyyyy off base trooper.

You have no friggin clue what this is all about, do you? :P

Ok, what is meant by intake is not the intake-manifold (The thing that bolts to the carb) but the intake that is IN the cylinder, in the bore as to speak. (I hope you know what the bore is). Never raise an intake, it will make you very very sad if you do. You can lower it (make it go more to the base of the cylinder)

By exhaust they don't mean your exhaustpipe, but the exhaustport. Again, it is in your cylinder, in the bore. You need to modify the window in your cylinder wall to the new specifications.

The transferports are ports that are in your engine-casing and in the base of the cylinder. They move the fuel from the crank-case to the combustion chamber.

But please, do me and yourself a favor... If you don't know EXACTLY what you are doing, don't do it. You can very easily turn a perfectly good cylinder into an ashtray.

Have you tried other tuning options yet? Like an expansion exhaust, bigger carb or high compression head. Try those options first, in this case it will gain you more MPH than messing with the ports.

Nice work with the 2 stroke tuners handbook.

There are a lot of things that you can do with porting. I'll post some pictures up here soon of my latest attempts.

what I posted on the wiki was on persons idea of a system for changing the windows on a motobecane av7-style cylinder.

It was scanned from an old french magazine.

That is not a guide of the definitive way to port a motobecane. It's just one persons porting that worked out for them.

Just buy some gasket material and raise the cylinder with base gaskets until it runs like you want it. then measure everything out to where it needs to go to have the port in the same spot, cut it out and fly. I've never worked on a motobecane engine, but thats what I do with my puchs and I gained about 5mph. I could've gone more, but I wanted to be on the safe side. Widening the intake and exhaust are harder to screw up than port timing.

Good luck,

Eric

haha thats exactly why im on here asking =P i said i wasnt gonna do anything hastily. im on here to collect some info =P

but thanks for the link!

Really just try your best to get the general concept- follow the guide in the wiki, expect that it won't be perfect, learn from that first experience and keep trying. I don't think understanding every element of the 2-stroke handbook is possible until you have run both good and bad cylinders of your own to compare. So get out there and make some good mistakes to learn from. Good luck.

how about somebody with a rough intake ride with it, takes notes, then smooth out the intake, ride it, take notes and then see if there is an actual difference at all. Both arguments sound convincing -but what actually happens from experience???? A lot of logical conflicting 2-stroke theory gets tossed around without real-life application.

This is only the second time I've seen this handbook.You nice folks must have had it read to you in the womb.I am an idiot .Idiots should be forgiven for they don't know any better.The part that said the price to of this is paid in reliability was a downer.I do understand (better) how rings seal against all that pressure without leaking.I realize now where I am compared to others on this forum.Oh the shame on me.Thanks for enlightening.