big bore/small bore pipe

[kawiking]

is there any way to tell the diffrence between a big/small bore drag pipe by looking at it. i have a set of used cpi's and bike didnt like them on the top end.friends wondered if maybe they were big bore's instead of small ... ??????????

[Snopczynski]

I believe the oultets on the small bore pipes are 1 1/8", small bore is 1".

[kawiking]

outlets.... as in tips?

[bigboybanshee]

Yes.

 

Some pipes have unique identifiers, like GRR's have a straight stinger for the small bores and the big bores have a little tip on the end of the stinger pointing out.

 

I'm not too familiar with CPI's though

[kawiking]

well ,i asked because when i got these pipes from my friend he said they were small bores... but the tips were broken off. he ran them like that and said his bike ran good. i had some pipe welded on for tips,could that cause a problem ??

[kawiking]

this comes from the thread i had a couple of months ago--pipes--dyno ??........ im going twith a 17 dome for my k&t head and was thinking about putting my cpi's back on. id really like to get some in frame but dont want to fork out the cash yet...lol

[bigboybanshee]

I'm no pipe expert by any means but the stingers are important to the tuning of the pipe. It just may have enough impact to effect the way it performs in a certain RPM range. Like I said though, I'm by far no expert on pipe building, this is just based off what I've heard

[dajogejr]

Out of frame pipes still need the stinger tube on the end of the pipe to run properly...

I still say 17cc domes are hurting your top end, do you know how much compression you have?

 

The expansion chamber is larger too...

[Snopczynski]

the size is checked on the outlet of the pipe, not the silencer.

[bigboybanshee]

I still say 17cc domes are hurting your top end

 

I totally agree with you, and have a friend of mine that's wondering why his top end pull is gone w/210psi. His bike launches very hard and pulls hard till about half track and then it just seems to lose it's pull.

 

Too much compression WILL kill your power on the higher RPM's

[kawiking]

well i just got my domes in on tues.. so i havent put the head on yet. i just figured 140lbs with a shaved.30 head(19-20 dome) was low so i got the 17 to try and bump comp.. up to 160 range. u think that will hurt me in a 300 ft drag ??

[Snopczynski]

19cc dome in a cool head at sea level should be about 170 psi compression with a stock bore and mild port job.

[kawiking]

that was 140 with a drag port on a new top end..... im about 330 above sea level

[bigboybanshee]

I thought you were running a stock shaved head? Or am I thinking of someone else? I had 18cc domes in my bike last year with a drag port and had 180psi. I'm at 400' above sea level. 17cc domes will probably put you around 190psi or so, which is quite a bit. I dropped my compression almost 10psi this year to 172psi and could tell a difference in the higher RPM's. :shrug:

[kawiking]

no your right !! i am running a shaved head,that was 140 with shaved head.i got a k&t head and my domes,studs and o-rings just came in tues... hadnt head time to put them on yet. you think i'll go from 140 to 190 ish ?? if it is that high,i will be dropping to 18.. how big of a pain is it to get the stock head bolts out ??