mopar1rules

pm sent on cylinders

no problem. glad i could help. :thumbsup:

you can find out the cranking PSI w/a compression gauge. IMO, its not the most accurate thing to go off of for fuel octane determinants. you need to know the total cylinder volume, w/the piston @ BDC. this will include cylinder volume in cc's + head volume + head gasket volume, if using a stock head gasket. then you take that total amount of cc volume and divide it by the trapped volume @ TDC. to find the volume @ TDC accurately, you need to use a burret and then fill the cylinder up (w/piston @ TDC) and see how many ml's/cc's of kerosene are needed to fill up to the top of the spark plug hole. subract 1.8cc for the volume of the spark plug hole and you have your trapped volume. then once you divide out the total cylinder volume by the trapped volume, you will have your comp ratio. from the comp ratio, you can then determine the octane of fuel to run. you can even use a corrected comp ratio, as that is the most useful comp ratio to go off of, as compression doesn't start until the exhaust port closes. for now, i guess, just put a comp gauge on it and just see what it pulls for cranking PSI.

thanks deckheight!! :thumbsup: yeah, i've been pretty busy playing w/the software here. i love the stuff. i still didn't get the chance to run my buddies shee, as we are waiting on a new throttle cable. during reassembly, i noticed that the throttle slides didn't want to return correctly to idle position, when i was syncing the carbs. tracked it down to a piss poor throttle cable. good thing i didn't try to take it out for a spin.....LOL. i'll keep in touch w/you. hey deckheight, do you have any info to help this fellow out? you gotta have some valuable input, as you always do....LOL. take care.

i personally would start out rich @ 330-350 mains, until you can check the plug color and know exactly what the motor wants. i would also run the needles in the middle position and 27.5 pilots and air screws around 1-1/2 turns out. i would suggest finding out the comp ratio and timing advance if any, so you know exactly what octane of fuel to be running. also, there is a topic on peoples jetting in the jetting forum. the topic is called "what is everybody running for main jets?" here is the link to that topic... http://www.bansheehq.com/forums/index.php?showtopic=99361

yeah, that piston drilling is for lubrication on bridged exhaust ports. very common mod on 250R hondas. not needed on a banshee, as there is no bridged exhaust port.

disregard my previous blow down specs, timing specs, and measurement specs. i punched in the wrong data into the software....LOL. $hit in just gives $hit out. here are my corrections..... i would personally use 186*-188* of duration....if using OEM base gaskets, you should have around .017" of deck height, so measurement from exhaust port roof to cylinder deck would be 29.38mm (186* duration) and 28.9mm (188* duration). blow down timing would be 34.56* for 188* exhaust and 35.57* for 188* exhaust. if i was in your place, i would keep the blow down timing around 34* for your beach/dune riding. so, raising of the transfers would be required some. if you are still stuck on having 190* duration, your measurement from cylinder deck to port roof would be....28.4mm=190.07* of duration. hope this helps.

i'm not sure what the pt hi-rev pipes like for durations etc, but i feel that you should be widening your exhaust port first, to get the time/are needed, before raising. that way you'll help the upper mid-range and top (which is what you want), but still hold the current bottom end. if you raise the exhaust (measurement from cylinder deck to port roof will than be 28mm) to have 190.15* of duration, w/o doing any widening, then you will kill the bottom end and have such a long blow down timing....39.22* to be exact. if you want to raise the exhaust that much, which IMO i don't think you need to (IMO 188* should probably suffice), you should IMO raise your transfers too, to help shorten the blow down timing and help hold a decent power delivery, in the bottom and midrange. IMO, I don't think you'll want a blow down time of more than 36*. also, remember that port roof arcs will also dictate the way the power comes on. large radius' which = flatter roofs, will equal a strong pulse and hard hit, versus a smaller arc/radius, which will = a more arced roof will give you a smoother power delivery. maybe someone else can input something? maybe someone else has some port timing specs for your pipes that they would like to share?

can i get pics please?

you need to have the bores matched to the pistons, to have the correct piston/cylinder clearance. you have to have some clearance in there. you can't have a piston that measures 64.75mm for example and a bore that measures 64.75mm. you will have seizure within minutes of running, if you get the piston to fit inside the bore ok, seeing as that would be a "size-on-size" fit. you need to have like .003" clearance, for stock bore and stock cast pistons. larger pistons and forged pistons, require more clearance. the bore will always be a few thousandths larger in diameter, than the piston, to allow room for the piston to "grow/expand", when it gets warm while running. understand? if i'm not mistaken, the pistons should measure the 64.75mm or whatever is stamped on the domes, and the bore is going to be a few thousandths over that. for measuring bore diameters and taper, you take measurements at 3 points thru the bore. you measure at approx 1/2" down from the cylinder deck, straight across where like the wristpin would be and then 90* from that measurement. then do the same in the middle of the cylinder bore and then again at like 1/2" up from the cylinder bottom. compare the measurements throughout to compare and find out the taper and out-of-round. out of round should be no more than .0005" and the taper like no more than .002". hope this helps. maybe someone else can explain it better than me.

IMO yes. what are you planning on doing w/this thing, to want to have 190* of duration on the exhaust?

that sounds sexual....LOL.

you will need to get the cylinders mic'ed up for taper and out-of-round. also, if your cylinders measure up to be 64.8mm and the pistons measure up to be 64.75mm, then you are getting a piston to cylinder clearance of .05mm, which is .002". maybe a little tight, if running wiseco pistons?? and the rings do the sealing, not the pistons, so don't think that the pistons are what causes the blow by.

you need to tell him your current jetting setup, altitude, riding temps, and all engine mods, to get good/accurate jetting ballpark.

ok, cool. :thumbsup:

pm sent for reeds and head.

can i get some pics too? i'm interested as well. please send pics to: [email protected]

what were your findings for OEM port heights? i come up w/30.5mm (from deck to roof) for the exhaust. is that what you got?

what are you using as a deck height and for base gaskets? i keep coming up w/179.967* for .127mm (.005") deck height and 181.258* for .4318mm (.017") deck height. the .017" deck height is what i seen personally, using cometic/wiseco base gaskets. i don't see how your getting 176*-178* stock duration. can you tell me what i'm doing wrong?

*all meaurements are from cylinder deck to port roofs 45mm to boost 44mm to main trans 44mm to sec trans 30.5mm to exhaust 76.5mm to intake this is what i found in my notes, from when i measured up a stock cylinder

i have a program at home on my computer. when i get home from work, i can tell you. stock i if remember, is right around 180*-183*. raising 1.5mm should put you around 186* duration, if i recall. what brand of base gaskets are you using.....OEM, Moose, Wiseco, Cometic?

27.5 pilots 1-1/2 turns on air screws stock needles w/clip in middle position 320-330 mains start there. i can't see you needing to adjust anything more than the mains from what i suggest.

if you make the chamber deeper, than the end of the plug will stick into the chamber, which is something you don't want. you could stack up another spark plug washer or something, to fix that problem. if you have access to solidworks or some other 3-d designing/engineering software, you can draw up the current dome geometry and they change it and the software can tell you the cc volume and then from there you can see how much to shave off where to get down to 22cc volume from 21cc volume. i use solidworks for stuff like this, cause i have access to it thru work.

are those pipes mid-top range or bottom?

i have fatty pipes and have no complaints. also i use the carbon tech reeds.