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Rocket, Cpi, Shear, Which Ones Do You Prefer?

9K views 50 replies 12 participants last post by  Atombomb 187 
#1 ·
Im Think Of Going With One Of These Name For A New Exhaust. What Experiences Have You Had With These Pipes?
 
#2 ·
check in the exhaust forum, I think this has been discussed before
 
#4 ·
ive run rockets and shearer pipes and know alot of peeps who run CPI adn it really depnds o nthe porting between the shearer and the cpi ,the orckets are not being made anymore ot muy knowledge and arent as good as the other 2 IMO,if it was me id always go wit h shearer pipes hands down no questions asked .they wil lrev higher hold the powerband longer and make more peak horspower over an ypipe ,the cpi will give you more torque down low and have a more rider friendly powerband ,try a search -lots of info on this matter



 
#5 ·
On a stock cylinder motor I would choose CPI's most of the time. Shearer only when the Exhaust duration is over 196, even then I would consider CPI unless its over 198 then shearer for sure. Basically if its a supposed drag port then the shearer equate to the max hp but the CPI are a bit more usable.
 
#6 ·
i ahve shearers on my stroker banshee.. and this thing make power everywhere.... also....... odaens dynos with his ported421 cub had sheares and he still made soem impressive low end considering the engine he is running... i say go with the shearers.... oh and rockets well....... i wouldn't even bother.... there is a dyno floating around of an engien EXACTLY liek mine (in fact i bought the cylinders from the guy and built the exact engine) it shows a 8 gain by ditching the rockets and going with a shearer...
 
#8 ·
370banshee said:
i ahve shearers on my stroker banshee.. and this thing make power everywhere.... also....... odaens dynos with his ported421 cub had sheares and he still made soem impressive low end considering the engine he is running... i say go with the shearers.... oh and rockets well....... i wouldn't even bother.... there is a dyno floating around of an engien EXACTLY liek mine (in fact i bought the cylinders from the guy and built the exact engine) it shows a 8 gain by ditching the rockets and going with a shearer...
Those are both 4mm motors, a stock stroke isnt going to make the torque a stroker does. Personally I prefer CPI's for a dune ported stock stroke motor.
 
#9 ·
i have not tried cpi yet but on my stock stroke dune cylinder shearers definityl outperformed the rocket pipes and was not lacking in t he low rpms considering the durations i was running. it had surprisingly good midrange and a violent hit and the thing i liked best was its over rev it could hit a rpm and hold it and stil lpull . i would think the cpi would make a good dune motor for the sand because the torque and linear powerspread is lower and would be more linear for traction ,i jus treally liek the way the shearers perform on a she and a blaster and the price is right ,now thats not saying cpi are shit btw ,most every builder recommends shearer for cubs and there port timing is usually only i n the mid 190's for exhaust . i thin k between the 2 pipes it comes dow n to preference of power delivery characteristics moreso than the cylinders port timing .my 2 cents



 
#10 ·
The power delivery between shearer and CPI is very similar. People have this perception that CPI are much less drag oriented since the shearers came out when they aren't. The shearer is just shifted up a slight amount, which in my opinion does relate it to port timing a bit. Its not critical but a lower duration motor will normally like CPI's better than Shearers. I mean its all about making the motor work in conjunction. I personally dont think mid 190's are low durations, they are a bit low for a all out drag on stock cylinders just because of their lacking efficiency compared to the cubs. I just see, and have been told by builders that Shearer like about a 2 degree longer duration on stock cylinder motors than CPI's. And that if your running lower than 196 EX the CPI's are more suited to the motor. The CPI's also come with much better chrome than the shearers, unless you spend a bunch more money on the show chrome ones.

Of course I agree that rockets are shit.
 
#11 ·
fiveOnick said:
The CPI's also come with much better chrome than the shearers, unless you spend a bunch more money on the show chrome ones.

yeah the cpi have nice show chrome. i have no experiance wit h cpi but all the internet dyno plotts comparing them seem to make shearers look like a better option for extensivly ported engines ,again not saying they suck by an ymeans



 
#12 ·
cpi's are junk unless the bike is ported, and have zero bottom end and torque.
 
#14 ·
on a 350 the cpi would pull better than the shearers.

what ive seen the cpi get off the line better compared to shearers. heard if you gear the shearers down a bit then they will take off better.

both are good pipes.


rockets were ok, probably better on a cub but for my setup they were lacking. also they burn the shit out of your legs. try to shut the gas off good luck with that.

i would like to try some cpi and compared them to the shearers. who knows
 
#15 ·
hey, wesw, I went and bought an ipod just because of your sig..........I still cant figure out what she is saying.......oh, thats probably because I am staring at her ipods the whole time...
 
#16 ·
the only thing i didn't like about my shearer was it colored a little too fast for what riding i've done. . . and the fitment wasn't the best at the exhaust port of the cyl. . . it leaked a tiny bit of exhaust and got a little gooey around that end of the pipe. . .
is that why they aren't the best off the line? i dunno just a wild guess. . . .
 
#20 ·
wesw said:
you might have to ask nick i dont know much about anything.
Looks like the dick head right here.

First off, you guys are bull shit for jumping into a thread with your little passion groupy action that had nothing to do with Jim in the first place. Nothing at all. I do agree that Curt gives Jim the shorter end of the stick than he deserves, the guy bought the motor back which is very decent of him. I wont say that it wasnt upstanding and I agree that Curt is talking too much shit, Jim screwed up Ok. But if he was willing to buy the motor back then he was obviously willing to fix the problem, so dont get all touted up thinking I'm trying to knock Jim. I will say he screwed up cause he did, but it happens and as long as he's willing to make it right thats good. I can also see why he has a poor taste for Jims stuff in his mouth, he got many promises and ended up with a motor running below where it should have and way below the claims. He takes it too far though, is that what you guys want to hear. It doesnt change the fact you guys jumped into a thread pointing finger that did not need to be pointed at either builder. You wes were the first one to start being a smart ass so dont act so F'n high and mighty. It may appear that I was sticking up for Curt and Jeff, thats fine they needed some sticking up for after all you guys started your BS. That doesnt mean I agree with everything on either side. So fill in that chip on your shoulder and quit being the dick, I didnt single you out on anything there. Hey once again your the one making smart ass statements on here first.
 
#21 · (Edited)
nope, first off there wasnt anything smart ass being said.
he had problems with his first motor cause of domes.which jim didnt cut he tell the guy what spec exactly, now if the guy doesnt follow them then it guess that would be a problem.

then he started bashing jim,

now he had problem with his new domes. but he was willing to take all advice to fix it.


meaning he wasnt in any hurry to try to solve jim motor, but now its what ever it takes. i know for a fact those jugs ran. bud put them on his bike.

i didnt get into the pissing match i was calling out what i thought was ironic.
ive seen jim work and jeff work both ran very well.


i will say i didnt enjoy or deserve curt and jeff bashing me for like a hr in hq chat one nite cause i ran a passion motor. and blah blah but thats ok i can deal with it.
they got somewhat personnal and i havent said personnal stuff about either.

used to talk to curt all the time. even when he got his new motor. then things started to change. barely said hi at the oct hq ride. i guess.

what i said wasnt a smartass comment. you seem to know more about the situation than i did cause i stopped posting.

"thats fine they needed some sticking up for after all you guys started your BS"

please there are like 3 guys from penn that love to give shit or get stuff agoing. there are many other factors to why guys bring shit up, when your bragging on your stuff and have mineons helping your stuff, when some dont even run your stuff. it gets old.

its fine to pimp people out. but after the 100th post of how great a guy is, WE GET IT. OK.


i am not bias towards one builder and shun a person cause you have blah blah build your stuff. many are. i just was calling out shit that beyond fucking ironic.
 
#22 ·
my opinion is weather yo u prefer jim over jeff or billy over bobby or vise versa its pretty fair to say this curt guy has asked for alot of his trouble and sarcasim . only reason i posted in it is becasue i see these guyS who run jeffs stuff go over to ps. and secretly ask about there engine trouble instead of addressing it on hQ where they al lhang out so as to not let anyone know theres any trouble wit h jeffs engines.i think we al lknow how things can creep up when you start highly modify your stuff regardless who built it ,i hope this thread doesnt turn into a pisisng match and we can get back on topic on these drag pipes.my 2 pennys



 
#23 ·
fiveOnick said:
First off, you guys are bull shit for jumping into a thread with your little passion groupy action

does this include me??? because i didn't say a fucking thing about jeff or F.A.S.T. at all... i got a PM from somebody whos not a "passion groupie" that told me to check that thread out.... if your comment doesn't include me nick then please say so... if it does then i would liek to know exactly what i said?? did i bash anybody??.............................. NO!!! do i like jims work... SURE DO MY QUAD RIPS!!! is it the fastest quad on the planet... nope dont's want it to be... it;s a hell of alot of fun right now.... is jim a great guy that wil help you out even if it;s nt an engine he built or a part he sells.. damn straight.. the guy is about the nicest guy you'd ever talk to...... i know that you and i have had our disagreements before... about this that or the other thing... (mostly that tecates are badd ass machines and lt250r's suck the sweat from a paralyziled black tranny midget hookers greasy sweaty nuts) but thats water under the bridge as far as i'm concerned.... anyway back to the passion VS FAST thing... seems to me it was all brought about on the HQ by a certain pair of brothers....... then people started taking sides... and why?? because tyler clark couldnt; make it run right... i ahve sen in past posts he claimed he's not good at jetting... seems to me that coudl be the problem... 12 port engine like fuel... lots of fuel.... nick i'm not sure how you got into this rivalry.... you hate banshees.... what i'm saying is i didn't bash anybody.... and after a year and a half of me and you beign on this site.... i think you can honestly say that i don't bash things i haven't had experiance with..... but i did say that maybe curt doesn't know what he's doing... i heard that though the grapevine....
 
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