taper boring


9 replies to this topic
  • cataway

Posted January 04, 2009 - 09:52 AM

#1

i would like to know more about this, how is it done ,what its supposed to look like when its done , what kind of specs are used , can it be done with some thing like a brake hone, is it done on both sides of the carb, in & out ?

if i were to be doing it ,it would be done to a 39 FCR , if that helps any.

  • William1

Posted January 04, 2009 - 10:05 AM

#2

Requires specialized tooling. Not for the do it yourselfer or even the typical machine shop.

  • cataway

Posted January 04, 2009 - 10:41 AM

#3

ya ............well .........maybe , i'm from michigan , show me.

  • William1

Posted January 04, 2009 - 10:50 AM

#4

Well, you could try it yourself and see what happens...... Do you think it is a simple matter to bore a precise hole that tapers? Most places that do this sort of work charge about $200+ to do it.

Call Ron Hamp, he is a local MI person.
http://www.ronhamp.c...y/contacts.aspx

  • cataway

Posted January 04, 2009 - 11:05 AM

#5

yes i know Ron , i just don't like to bother him when he has some thing to do .
(by the way Ron ,how long till its done ?)

  • cataway

Posted January 04, 2009 - 01:57 PM

#6

can some one say were the taper starts were it ends ?

  • Dave Hopkins

Posted January 05, 2009 - 09:42 AM

#7

I bore them but no taper, the issue is in the middle there is a atomizer that can not be taken out, it is one piece with the bottom 1/2 of the carb body. So the taper bore guys bore from either end to match the existing bore in the middle. Does this do anything????
I bore the front straight back to the center piece at 41.5mm concentric to the outside of the spigot (as is Keheins 41, the 35, 37 & 39's are below center as the slide relationship to the bottom is always maintained the same!!!!!!)
Then the carb is flipped over and mounted on a rotory table and a long rotory cutter put into the mill and a series of small cuts made so the center and back are matched to the front without touching the bottom, then inside is polished.
Also I modify the AC pump to hit harder initially and taper off quicker. The jetting and the taper of the needle need to be modifed as well to work with the wider air stream, depending on what needle and jets you have in most cases I reprofile the stock needle,
Cost is a little under that quoted above, plus parts, the bigger bikes like a 525 KTM this brings to life!
and bore the back to

  • Eddie Sisneros

Posted January 05, 2009 - 10:10 AM

#8

Does this do anything????


2-3hp on a crf 450.

  • cataway

Posted January 05, 2009 - 12:40 PM

#9

I bore them but no taper, the issue is in the middle there is a atomizer that can not be taken out, it is one piece with the bottom 1/2 of the carb body. So the taper bore guys bore from either end to match the existing bore in the middle. Does this do anything????
I bore the front straight back to the center piece at 41.5mm concentric to the outside of the spigot (as is Keheins 41, the 35, 37 & 39's are below center as the slide relationship to the bottom is always maintained the same!!!!!!)
Then the carb is flipped over and mounted on a rotory table and a long rotory cutter put into the mill and a series of small cuts made so the center and back are matched to the front without touching the bottom, then inside is polished.
Also I modify the AC pump to hit harder initially and taper off quicker. The jetting and the taper of the needle need to be modifed as well to work with the wider air stream, depending on what needle and jets you have in most cases I reprofile the stock needle,
Cost is a little under that quoted above, plus parts, the bigger bikes like a 525 KTM this brings to life!
and bore the back to


I've come to the conclusion that a taper bore could only be a beneficent if the size of the carb bore was smaller in diameter than the diameter of the port going in to the head , more or less doing/making a port matching of the two body's,
does that sound right ?

  • shawnridin4ever

Posted January 06, 2009 - 08:36 PM

#10

dave i own a 525 in port orchard wa can i contact you about this procedure for my bike




 
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