my custom exhaust build.

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a.graham52

New Member
Nov 22, 2013
232
1
0
island of misfit toys, maine
the time has come for me to throw away my gutted CG muffler and build myself my own creation. i downloaded the 2stroke exhaust wizard and will base my exhaust of their calculations. i wll be updating this as i go.

measurments (that i would like to have you guys critique as nessasary):

skyhawk gt5 66cc.

bore 47mm
stroke 36mm
exhaust port degrees: 183
transer port degrees: 122
exhaust port + gasket lenth 19mm
 
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a.graham52

New Member
Nov 22, 2013
232
1
0
island of misfit toys, maine
i removed the head to measure my bore and stroke. used my head bolts and some sockets as spacers to clamp down the cylinder.


i mesured my bore (diameter of the cylinder) and stoke (distance from bottom dead center to top dead center) with basic caliper. my measurments are in the OP.

after that i pulled the cylinder off the engine for measurments of the port sizes.

next i took cooking foil


and lined the cylinder with it


followed by installing a rubber glove inside the bore and blowing it up with compressed air, this formed the tinfoil to the cylinder wall nicely. i still had to take my finger and imprint the ports a bit more to get a good shape. im only worried about the size of the ports, not their locations in the bore and therefore dont care it things move around a bit.

now iv got this: Transfer, Exhaust, Transfer, Intake



the reason i needed do all this is because i needed to know the shape (not hard to tell anyways) of the exhaust port as well as its height and width. all this info is needed for the exhaust wizard.

next step is needing to measure the port opening degrees, (i strongly recommend doing this first before dissasembling the cylinder. i happend to do all this in the order of the wizard). i found a degree wheel offline and printed it off. cut it out and tapped it to the crank of the engine.
 
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a.graham52

New Member
Nov 22, 2013
232
1
0
island of misfit toys, maine
the reserve post is so i can seperate things like design, building, tuning etc and not have tons of conversation in between. i know i can edit the op but imo this is nicer looking.

so far the exhaust iv come up with is very long and very skinny.
 

AssembleThis

New Member
May 11, 2014
163
0
0
NC United States
Hi a.graham52!

I would love to see your exhaust build. Pictures, many pictures, in stages if you can manage that. It would help me a lot in building my own. Welding I can do easily, it's the ideas I'm mostly looking for to mix with my own. I personally visualize things in 3D and go over them in my mind many times, having your ideas would help.

Dave
AssembleThis
 

a.graham52

New Member
Nov 22, 2013
232
1
0
island of misfit toys, maine
my exhaust is on hold until i get a response back from buildandclick. im not liking the design tool. no matter how i make changes to the settings, the exhaust outcome is practically the same.

now they have a wicked anti piracy policy and if you fail to conform to it, the program will give you an exhaust that will "burn up" your engine. maybe i installed the program wrong, maybe its a dud, but either way until somone gets back to me im on hold.
 

Theon

New Member
Jan 20, 2014
1,440
6
0
FNQ Australia
That pipe does look a little thin, length is probably about right though, where were you after max power?
Normally I'd be wanting a 1" id header, with expansion chamber of around 3x header Dia.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
22
0
memphis Tn
I'd guess there's a problem in the software. That pipe is far too thin to have much tuning effect on your engine.
Recheck your inputs. Something is wrong here.
 

Theon

New Member
Jan 20, 2014
1,440
6
0
FNQ Australia
Target RPM of 5500 may be what's confusing the software? Probably too low?
For those revs I would be studying JAG's torque pipe.
This is fairly loosely what I have based my home made pipe on and it was lifting the front wheel at around 4500 to 5000 with a 44t and 26" wheel ( also boost ports, reeds, high comp, ect.)
I have it on a different motor now and a 39t but is still giving excellent power up to 8500 RPM, at which point it seems to put a rev limiter to the engine, likely the baffle needs to be a little longer for more revs, but the low to mid is a huge improvement and I'd like to build another similar , experimenting a little and getting the chamber to clear the cranks better.
 

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