b pipe porting

BruceSki

Formerly Motoman25
Location
Long Island
Okay I just picked up an older b pipe with the small diameter exhaust mani and headpipe. Can I drop this off to a machine shop and have them bore it out? what is the biggest I can go on the older pipe?
 

Shifty

- SuperJet Thursday -
There is some good write ups about this somewhere, try doing a search. I opened mine up a bit with a dremel with a flap disc. It worked well for me although I bought mine new from FPP a few years back so it already had the larger opening.
 

Waternut

Customizing addict
Location
Macon, GA
I opened mine up to 46mm. It was the older style that was originally 42mm (I think). Mine works really well but this was done in conjunction with a bunch of other things so it's hard to know if it really made a difference. I've heard of some going as big as 50mm but that seemed like overkill for my motor.
 
Sent mine to art at jetworks , from 42mm-48mm dont forget to use right size gasket ( jetmaniac has them ) will only notice in conjunction with other performance improvements.



I opened mine up to 46mm. It was the older style that was originally 42mm (I think). Mine works really well but this was done in conjunction with a bunch of other things so it's hard to know if it really made a difference. I've heard of some going as big as 50mm but that seemed like overkill for my motor.
 
Sent mine to art at jetworks , from 42mm-48mm dont forget to use right size gasket ( jetmaniac has them ) will only notice in conjunction with other performance improvements.

What size hole to the gaskets he has have in them.where else can you get them... I have always used the kawi 650 gasket which is the right hole pattern and shape .just not sure if i had to cut the id..
$2 a piece


I have to bore a manifold also I thought it was best bored off center or something..post a link if you find the thread
 

sjetrider

615 Freeriders are addicted to T1 madness.
I opened mine up to 46mm. It was the older style that was originally 42mm (I think). Mine works really well but this was done in conjunction with a bunch of other things so it's hard to know if it really made a difference. I've heard of some going as big as 50mm but that seemed like overkill for my motor.

one of y'all need to change ur avatar, too close to the same, color angle ? I thought dude was answering his own question for a minute.

Just get the dremmel and a hog bit and drum wheel or flapper wheel and open her on up. I went 48mm form 44 on the mani and 48 from 46mm on the headpipe. Its one hole, no need for serious precision.
 

sjetrider

615 Freeriders are addicted to T1 madness.
just lay the gasket on the manifold with bolts in 3 holes once the manifold is opend up and match the gasket to it with the drum wheel then use the gasket to line up hole in the headpipe. An hr. work max for all whith the right hogging pit in a right angle air tool. 2 hrs. with a dremmel only.
 

BruceSki

Formerly Motoman25
Location
Long Island
just lay the gasket on the manifold with bolts in 3 holes once the manifold is opend up and match the gasket to it with the drum wheel then use the gasket to line up hole in the headpipe. An hr. work max for all whith the right hogging pit in a right angle air tool. 2 hrs. with a dremmel only.

this is what i planned on doing, I did this with the new pipe I bought for my SJ two years ago. Just wanted to see if there was a "too big" I could go with the older pipe before I go to town. I had planned on grabbing a jetmaniac gasket for a template too. Thats funny you suggested that.

Thanks for the help. Oh and here's a different avatar for you lol.
 

SUPERJET-113

GASKETS FOR CHAMP BRAP!
Site Supporter
Yes the Kaw 650 head pipe gasket is the same gasket used with a Yamaha B pipe. The only difference like mentioned is the throat hole.
The early Kawi 650's had a 44mm hole. The later 650's had a larger 46.50 measurement. Jetmaniac and I sell both the 46.50mm or the larger 50.50mm for the big engines.

I did my ex manifold and headpipe and opened it up to a true 49mm and its all matched and flowing inside, not just reamed out on each end. I also do like mentioned above to make the perfect fitting 49mm gasket for my set up using a larger drum/barrel sander.

Figuring out what size to open the throat of the manifold/head pipe has a lot to do with the size of your engine and mods done.
Best to consult a professional engine builder.
 
Last edited:

In case anyone needs the part number for the gasket between the Factory Pipe headpipe and the manifold, it's Kawasaki 11009-3723. LOL.

If you need the center hole bored larger than the stock Kawasaki gasket comes, you can simply use a Dremel and make the hole larger.
 
Top Bottom