race porting / port matching

atomikpunx · Post by **atomikpunx** » Sat Aug 20, 2005 3:17 pm

i notice everyone says get the pollini corsa instead of the bigger 100cc kits
due to the factory race porting, and how you have to port match, the others.

ive port matched throttle bodies, intakes and exhaust for d series (honda sohc) engines, what is differnt in port matching the cylender?

im just wondering the only upside on the corsa is it being factory race ported.

i work in aerospace tooling, and machine precision sample parts within .015 of an inch tolerance, but i havent built a 2 stroke, yet.

but i have 2 spree's lined up this next month to get, and im working on finding the elite swap, for a daily driver to work, college i live about 10min between them, and could use the extra pep in arlington, tx where speed limit is 45 on main roads and people drive 55mph.

im googing and howstuffworks etc right now, but if you have some insight, please share.

burnt_toast · Post by **burnt_toast** » Sun Aug 21, 2005 1:49 am

would one of those happen to be my spree?

atomikpunx · Post by **atomikpunx** » Sun Aug 21, 2005 8:18 pm

yep, then i showed the pic of yours, i was gonna pick up to a girl and she told me her mom had one in her garage, so im either going to work on hers too, or take possesion of it also...

so good times.

fbergski · Post by **fbergski** » Mon Aug 22, 2005 12:58 am

I hope you mean .0015" not .015"

Philip

atomikpunx · Post by **atomikpunx** » Mon Aug 22, 2005 12:40 pm

precision template and tooling.

.015, that would be 15 thousandths of an inch.

the most a human eye can see is .010, thus why i have a presion starrett scale, calipers, mic, ect. try cutting any tool by hand more accurate than .005, and your a winner. in catia im giving .003+/- tolerance to engineering.
production gets .045 tolerance from engineering. the more accurate my tools, and parts are that are sent to be cnc'd the more accurate the production are.

im not grinding cam shafts here buddy, just making planes.
precision joe blocks only drop down to .001.

so to reiterate it is not .0015 which is 1.5 thousands of an inch, but 15 thousandths. short of laser cutting or edm wire, you wont be able to cut, near your .0015, even the line thickness on eng is roughly .007-.010 and i have to cut their lines in half when scribeing my tools.

Post by **noiseguy** » Mon Aug 22, 2005 1:06 pm

The definition of high precision is dependant on what you're working on. .015" is pretty accurate for some things (for example several parts with stackup), .0015" for others (i.e. crankshafts). Where are you working?

For port matching: My experience with this has been matching up intake and exhaust runners to meet the engine aka blueprinting. Or balancing flow between cylinders on the head on a multi. What are you refering to exactly?

The big potential in these engines are:

- Getting the intake runner straightened out. Port size doesn't match the carb at inlet.

- Re-porting the cylinder, by enlarging the exhaust and intake ports and possibly retiming them. I'm not an expert on 2-stroke timing. Macdizzy runs a pay forum that would discuss this further, and there are books. I have a copy of an SAE publication of 2-stroke theory.

- Enlarging the exhaust port. I'd estimate that the current 9x25mm exhaust port (225mm^2) should be closer to a 380mm^2 port, matching a 22mm downpipe for your custom exhaust (22mm ID downpipe is a common size on 50cc designs.) You will find that the actual size is limited to the current cylinder design, and that you may have to build up a weld on the top of the exhaust port to file it out larger. The current design has a 19mm ID exhaust downpipe, with around a 13mm diam "choke point" in the exhaust runner. The choke point needs to be there from what I've read, and if you enlarge the outlet it needs to grow as well. This 13mm choke point is where you'll run out of material. I'm currently working on a custom exhaust using OTC parts with the 19mm downtube.

I'm assuming that you are aware that ports enlarged vertically changes the two-stroke port timing, which can either help or hurt you. Exhaust, overlap, and intake timing all work together, but bigger is usually better in most cases.

At some point it simply becomes easier to find a '94 Dio motor (85-87 Aero and 97-93 Elite 50 is second choice) and build this with over the counter parts; this will get you to 55+ MPH. The Spree has no variator, so the trans is single speed. This is becomes the limiting factor at some point. You can alter the current pulley slightly, and of course could turn a custom inner pulley for more front ratio. If you turn a few extra inner pulleys, I'm sure you could sell them here. I believe that 45 MPH is about all a modded Spree motor is good for, but no one here's gotten above 40 yet.

If you wish to discuss this further, let me know. I have more time to guide other than do things myself these days.

atomikpunx · Post by **atomikpunx** » Mon Aug 22, 2005 3:10 pm

Im working at vought aircraft, dallas, tx.

and yes all of the parts that we build have a stack up tolerance of .015.

break just ended, but we can talk on aim, tonight.

-nick

Post by **noiseguy** » Mon Aug 22, 2005 11:50 pm

Best post here or PM. Chances of reaching me via AIM are slim, and I like to keep the work here documented.

MySpree · Post by **MySpree** » Tue Aug 23, 2005 1:47 am

mine me wala i have 40!! im done its been dont flat land 40 and if i dint have a stop sign i bet i could get a 42/43 ou t of it

atomikpunx · Post by **atomikpunx** » Tue Aug 23, 2005 2:22 am

so is the corza port matched to the stock cylender, and the other such kits not port matched at all? or is the corza actually ported farther than the port matching, and for performance?

if its simply matching the ports i might go with a 85cc kit and just port match, and take the suggesions, and port it myself.

it seems like a simpler way to go about things, i would also like to go with the mini stroker crank, that 808 sales that dosent req major machine work with the block. with a big bore, mini stroke, port matched engine, it would go nicely when given a good manifold with boost bottle and intake, proper exhaust ( ceramic dipped or taped ) and tuned to the correct jets.

all in all, i think the spree could keep on its feet with this setup.

anyone see any room for improvements?

vette76 · Post by **vette76** » Tue Aug 23, 2005 2:34 am

the corsa is ported and polished i believe. not just matched. bigger ports. which most other kits dont have. if u do do that to the spree. try a elite front and rear fork/shock. they will handle much better then the spree. u will also have to change gearing to keep the front wheel on the ground, and to get the full speed.

Post by **noiseguy** » Tue Aug 23, 2005 10:48 am

Gotcha, you're working on an Elite engine. Any specific info from above was for the Spree plant. You can get 45 MPH easily out of a stock Elite plant.

The only thing to watch as far as ports go is when you overbore a stock cylinder. The ports have often moved after boring. With an 85cc kit, though, you're into an aftermarket jug anyway.

Any port matching usually has to do with matching the steel liner to the aluminum fins, if the jug is constructed that way. There are usually opportunities for improvement there.

MySpree · Post by **MySpree** » Tue Aug 23, 2005 1:15 pm

ok so i was wondering this. now the shape of and elite is in a airodynamic shape. and if wind hits it hard enof it pushes the front tire down. but on a spree its not airdynamic at all. and if wind hits it fast enof it lifts the fron wheel and iv noticed at 40mph every time i hit a even small bump that the shock absorm the fron ed flis about and inch or 2 up even if i lean bakc on flat land it lifs. i think that would be another bad poing of going fast on a spree.

vette76 · Post by **vette76** » Tue Aug 23, 2005 1:26 pm

u can lower it. the problem with lowering it is you lose the rake. so it tends to steer more like a shopping cart at high speeds. you can easily get this back by heating the frame and bending out a couple degrees.

darat · Post by **darat** » Sun Oct 09, 2005 11:32 pm

noiseguy what is ur aim s/n