HP Loss Due to Pipe Dent

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Jim Crenca

LIFETIME SPONSOR

Mar 18, 2001

509

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• Sep 18, 2002

• #1

You ever climb a long, steep, rock laced hill only to fall near the top on your left side on a giant boulder?

I hate it when that happens and you get a 1" diameter dent, approx. 3/8" deep, just below the radiator tank.

As always, the bike started on the first kick and drove off without complaint. I'm starting to think that the engine doesn't wind up as tight although it's probably my imagination (or perhaps guilt).
None the less, anybody have any experience with the potential HP loss. Dan must have dyno charts on this somewhere.

Come to think of it, how come we haven't heard any great technical posts from Dan on his attempts to build the first 70 horsepower, naturaly aspirated, KDX enduro bike on gasoline?

 

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fatty_k

~SPONSOR~

Jul 3, 2001

1,274

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• Sep 18, 2002

• #2

I heard somewhere that if the dent is more than 6" (6" of pipe, not distance) from the header, than the dent will mean nothing for power loss. But Ive had a huge dent repaired on my pipe that was like 9" from the header and I thought I could feel a difference for the better.

 

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canyncarvr

~SPONSOR~

Oct 14, 1999

4,005

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• Sep 19, 2002

• #3

Hhhmmm....maybe dan is spending all his time on his HARLEY!

There's a local outfit that will have your pipe in and out in a day. Advertises on the web. I need to get my pipe in to take out a couple of dents.

Jim: ..???..fall on the LEFT side. I moved MY pipe to the RIGHT side!! ;)

(don't hate me forever..K?):)

 

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mprest4

Member

Nov 14, 2001

90

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• Sep 19, 2002

• #4

i read an extensive article by one of the big mags that said if its in the first 6-10" of the header pipe it will degrade horsepower.

if it is anywhere else it really didn't matter - it some cases it increased peak horsepower and took a fraction off top end.

if i can find it i'll post it

found it - http://www.motocrossactionmag.com/readtopten.asp?id=37

 

Last edited: Sep 19, 2002

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Battered Sav

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Nov 16, 2000

273

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• Sep 19, 2002

• #5

Well done mprest4, I remembered the article, didn't have a clue where I read it though.

 

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Jim Crenca

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Mar 18, 2001

509

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• Sep 19, 2002

• Thread starter
• #6

CC,

I never had a Harley, but I always thought that they were overweight, underpowered, foo foo bikes that sounded like the choke was on. Dan is way smarter than to be thinking that a useless antique like that is cool ;)

 

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munich

Member

Jul 29, 2002

22

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• Sep 19, 2002

• #7

Heres a pipe repair link. I never used them but there website looks good
http://www.piperepair.com/
FOG

 

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lpracing77

~SPONSOR~

May 28, 2002

58

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• Sep 20, 2002

• #8

www.piperepair.com is a pretty good outfit. I have used them before. I crushed a pipe in an enduro. When I got it back it looked great, fit well and had all that great power again. I have to give the a two thumbs up on the work.

 

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Jim Crenca

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Mar 18, 2001

509

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• Sep 22, 2002

• Thread starter
• #9

In regards to the MX Action article. do you read the distance from the header as linear inches of pipe as opposed to distance from the head pipe? If it is linear inches I'm a good 12" out so I guess all is well other than cosmetics. :yeehaw:

 

acutemp

LIFETIME SPONSOR

Sep 4, 1999

197

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• Sep 29, 2002

• #10

Jim, CC,
Come on now guy's it could be worse, my other bike could be a KTM :confused: I have put on many road miles this summer though and the weather has been great for streetbike riding. I'm more into the flatrack style HD's myself, the big crusiers I can live without.
The rain's are finally here so the woods can reopen everywhere. It seems like half of the state has been on fire at one point or another. It will be good to get some dirt riding in soon. I do have a some new parts to try along with a fresh set of 756's and a new top end. :)
--Dan

 

J

Jim Crenca

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Mar 18, 2001

509

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• Sep 30, 2002

• Thread starter
• #11

Sorry Dan,

When I hear Harley I immediately get the impression of a poorly tuned reclining chair whith wheels. When you say flat track, well that's a different bike entirely. Do they still make that 750 cc flat track bike & what would it take to make it a "Street Tracker".

 

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BRush

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Jun 5, 2000

1,100

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• Sep 30, 2002

• #12

Must be something going around. I too fell this weekend and put a 4” fold in my pipe just forward of the footpeg. It pulled the cyl head end far enough out that there wasn’t a good seal. I rode the rest of the event and strangely, I did not notice much power loss (it was louder!). Of course that could be because I was too busy bouncing from one rock to the next… :confused: