porting and polishing.

[odypilots]

Assuming we're talking 2 stroke here, ideally, porting would be done by someone with knowledge of that particular engine. It also should be done to suit a particular expansion chamber.

Polishing is flow matching to me. Not so much putting a mirror finish on a passage, but light grinding taking off casting flaws in the transfer ports, for instance. That can be done by a home mechanic, but if you start worrying that you're taking too much, you probably are.

A BIG second to nutz's advice not to bore it out to it's biggest piston right away. With a 2 stroke, I'd want to use the smallest piston that will fit a properly prepared cylinder, so the engine has hopefully 2 or 3 size pistons left for future rebuilds.

[bdkw1]

Originally Posted by evan

You can alter the piston on 2-smokes to play w/ the concepts. A $60 piston miscalculation is better then a $300 cylinder miscalc.

Unless your running a piston port motor from 1972, theres not a whole lot you can do to a piston in a 2 stroke to effect the port timing.

Everything on a 2 stroke has a resonant frequency, carb, reeds, transfer ports, exhaust port and expansion chamber. Get them wrong and you will have a sluggish pig. Get them all working in the same RPM range and you will have a lightswich motor that will be no fun to drive.

If you really want to get a good idea of what's going on, get copy of 2 stroke performance tuning by A graham Bell and read it.

[ruthlessxbeastx]

alright ill have to check that out for sure!
right now i have my odyseey it seems to be running flawlessly besides once i start it it seems jumpy like the belt engages then disengages. if i left it to sit still once started it would roll away it jerks. no better way to explain. any ideas on that? ya i was planning if i bored it out to only go up to the next available piston size so then i can gradually keep going!

[LiveWire]

If this is the 250 Odyssey we are talking about, it is piston port. The clutch available is the Comet 102C and the Comet 94C kits. They come with a wider belt and a new driven clutch.

I can't recall the amount of imperfections in an FL250 cylinder, but the FL350 cylinder has a decent amount of flaws if just smoothing things out. I just did a 2000 Polaris 600 triple. I am not familiar with the engine so I did not alter the port timing like I do on the FL350 cylinders. I assumed that a newer engine would have better ports. The amount and size of protrusions into the ports in the Polaris cylinder was horrible though. There were pretty good mismatches between the liner and the aluminum as well. The aluminum did not make it all the way to the bottom of the liner on more than half of the 12 tranfers. I could not do a lot with that. I have heard of people using epoxy, but I think it would fall off in that location.

[ruthlessxbeastx]

ya ive read about the clutches but still dont understand them.
any body have a link about how they work? also how to install and if anyone has used?

[evan]

bdkw1: Dropping the dome 1mm at the exhaust or transfer ports has the exact same effect as raising the port itseft 1mm. Pretty common mod by back-yarders.

[bdkw1]

Originally Posted by evan

bdkw1: Dropping the dome 1mm at the exhaust or transfer ports has the exact same effect as raising the port itseft 1mm. Pretty common mod by back-yarders.

It also does wonders for your ring life. Theres a reason the ring is that far below the top of the piston. Lowering the top down to it will have all sorts of drawbacks...... Not to mention what its going to do to your squish band. A very piss poor idea.

[ruthlessxbeastx]

so now kind of off the subject i was told updating my carb is a good idea. like getting rid of the stock and getting a flatside carb?! pros and cons?

[nutz4sand]

Cost. If you can find one cheap it might get a tad more response and a bit more power (the amount depends on several factors concerning your motors condition and any mods it may or may not have done.)

You can spend a lot of money for a tiny power increse. Its your wallet. Jsut be careful to not ruin any reliability it has now. A bit more power is no fun if it cause the machine to break down much.

[bdkw1]

If your looking at replacing the carb, I'd go with an oval slide from a CR. They are much more forgiving on the jetting and much easier to work on.