OuiBJammin

Corkster,CFD designed for engines is pretty pricy and there's really not enough money in the ATV game to justify buying it.A lot of time to set up a run too as there are a lot of parameters necessary for accurate simulation,more than the runtime on a decent home machine likely. There are free CFD programs not specifically designed to be used on engines that may be useful if you are up to the task http://www.openfoam.org/features/ There are free programs for some of the aspects of porting and stuff like EngMod2T http://vannik.co.za/EngMod2T.htmthat's $400 but they don't address radial or axial angles, interior radii etc just exit area and chordal widths. The best thing about ENGMOD is that it is updated regularly as more info is shared back from users and as newer technology becomes available,most of the rest are legacy programs based almost entirely on Jennings,Blair and Bell stuff that is either years or decades out of date.

Bought TZ cylinders that were junked cheap,read up the best I could pre-internet. Went in the Navy,spent years in engineering schools and built turbines,gas motors and diesels for money after that. Built two strokes for me. I learned where useful information is to be found and that I now know half as much as most of the people posting on the internet. Still don't know what I was doing wrong,I learned what doesn't work.

Unless your flow bench has the capability to interrupt the flow of all transfer and inlet ports in the manner and timing a moving piston would over the range of RPM you plan to run the motor at it seems pretty pointless,Not to mention vary the pressure ratio on both sides of the equation,pipe and crankcase at the same time and RPM. Software can simulate this with a fair amount of accuracy without the need for grinding up usable cylinders and making lots of aluminum dust in hopes of outsmarting the laws of physics by chance,I tried that as a teen(1970's - 80's) with RDs and RZs along with some other older 2 stroke motocross bikes my brothers had.Rarely got any faster,almost always got less dependable.

Ram air and cold air intakes are not rocket science or new. Getting them to work on a two stroke isn't that hard. Fabbing the box and plumbing it is far cheaper HP than some other mods. Remember this is a streetbike that will be used on a track a lot where higher speeds mean more pressure at the intake as speed go up.

The airbox will give more HP and allows some ram effect at speed if ducted properly.

Re:reverse cylinder.As you can see in the above pics the exhaust would be far to long to fit in a road bike. Reverse would work maybe up to 200cc per cylinder in my frame. Also plan on having a very big airbox to keep intake air as cool and clean as possible.

I hadn't thought of having them only partially machine the upper,awesome. I was planning on using a crank made for the cases in any final configuration,then find a piston with the right wristpin diameter and pin height.We used to mix and match TR,TD,TZ and RD parts to get up to 423cc RDs.So I'm used to piecing together frankenbikes. Worst case would be to have an adapter machined to take up any excess transfer area and to match narrower cylinders.Some guys have done this to match 4 cub cylinders to a v4 RZ500 at up to nearly 800cc. But thats 2 cranks,4 cylinders,4 pipes,carbs etc on top of an already expensive build(of rapidly dwindling parts).I'd have to buy a lot of shoes,pocketbooks and probly jewelry to get the wife onboard.

I'd seen the wider bores in the Mattoons.Where I got the idea of dropping other cylinders.I really do have clearance issues with pipes as the displacement gets bigger than 600 or so I wanted as much as possible out of as little as possible. Better to stay with readily available stuff where I can.Thanks for suggesting the call to CP If it's only a matter of stud alignment then it would depend on if the billet cases have enough meat in the right places to drill them in the right place.Match the upper to the cylinders and go with it. It is going to need a crank,cylinders,pistons and heads anyway no matter how it goes. I agree that custom one off cases are out.The CAD time and and labor would be as much as Mattoons alone.

Dozer,thanks I will look a the supers again.And thanks for not being a dick. I got 120 now and the motor can get up to 140.But I don't like red bikes or 4 strokes,this bike was nearly a gift pricewise. so I run it.

ru,bust my balls all you want it's how ideas get fleshed out.I have a thick skin after being an engineer in the USN. I was in hopes of hearing something I hadn't heard or thought of.I did learn that you can get 120+ on stock cases on gas. I will probly end up taking base gaskets from various modern 250 to 300cc bikes or snomos(like the old crankensteins) that do have better transfers/geometry and overlaying them on stock,dm and the wider Mattoon gaskets to see what may work.The main issues so far are mechanically driven PVs in the cylinder,rotary valves or case reeds. As far as a good tuner,not me.I am just a garage hack who likes smoky bikes better than sewing machines.

The kart and roadrace guys who raced anything but square lost mostly.They get 90+ out of 250 twins(how big does a cub need to be on gas to get that?).65+ out of a CR250 based single.FPE and BRC motors may make even more. The 500 4 cylinders made 180+ when they stopped racing them 15 years ago.On racegas not alky.Granted they had frequent maintenance cycles If I could find one those 500cc GP motors for less than what my truck cost I wouldn't be dicking around on an old ATV motor based on an old street motor that I had nearly a dozen of in the 70's and 80s. I'd looked at RZ500 and even RG500 street motors but they would cost nearly as much as the GP motors to get going that well and barely weigh less than the H@nd@ 600 motor on my current racebike.The banshee stuff seems the best compromise of reliability,availability and cost and I am a big Yamaha fan. I think the cramped transfers from narrow bore centers or just crappy transfer design period may be the culprit in your experience seeing them perform poorly.There may be more to it because i looked at the Sphynx and Puma HP#s and they don't really seem impressive either even square.The other big cylinders(Athena,ESR,ProX etc) look even worse. I just don't see a reason the country who made the Space Shuttle and Ohio class subs can't get the performance out of motors that Aprilia,KTM and Japanese did already 10 to 15 years ago knowing exactly what they did to get it.Then again,we(2 strokes) are a small market. I really do appreciate all y'alls help ,the bike sites and at least one other ATV site really discouraged any out of the box ideas.

Awesome,thanks. I may still want the billet cases just for durability but those are in the ballpark.

Cool,I'd seem most of that lurking for years. I am stuck with gas as the bike will be 1.Street ridden occasionally 2.Alky needs almost double the volume,cutting track range I am stuck with lower CC to get an exhaust to clear,10.4 inches of clearance with no pipe and simulated load currently.No way a bigger motor will be happy on pipes too skinny to breath. I had looked at the Super series Cub/Servals but it looks as if 120 is out of reach on gas and that the intake chokes them too.If a 14 to 18mil Super Cub/Serval was available and could work that would be cool as it would save a few $ and pounds.

Thanks, Square motors make more power per CC.Even in cases with transfers flattened out by narrow bore centers. It is my understanding Servals/Cubs/Wampus are intake limited HP wise. Yes 72x72 = 2 x 293cc=586cc Street legal trackday bike with modern frame and suspension. I'd seen a 72mm DM cylinder but it was 4mil on the CP site but I had heard there were other options not on there. I'd considered an RZ500 motor but it would need a lot of work and would weigh quite a bit more,even than the billet cased Banshee based motors. Looking for 120+rwhp on pumpgas or 110 with a decently wide spread.

Looking to build a 600cc twin for a hybrid bike.I would rather use a CP cylinder and Mattoon cases. I have looked and saw that Sphynx cylinders are available 72x72 but I assumed it would take a wider bore center to fit them as well as different stud pattern. I am limited by pipe diameter to 300cc ish to get them under the case and clear the swingarm. My background is building and racing 2 stroke bikes(dirt and track) since 1975 and working on turbine engines in the Navy.I am familiar with a lot of bikes but always like my RDs and RZs best. Thanks for any help and suggestions.