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S3/KH400 Porting with H2 Carbs
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Author:  Phil46 [ Fri May 17, 2013 10:20 am ]
Post subject:  S3/KH400 Porting with H2 Carbs
I have posted about my triple having the VIN being S2, but as the brain-trust for triples here pointed out, my old race bike is actually a 400cc S3/KH. Anyway, am getting ready to rebuild the carburetors and find it has H2's on it! So I am wondering if it is so highly ported to race, that it will be unpractical on the street, which is my intention. So, I read up and pulled the cylinder and did my 1st mapping. I have not been able to find a stock map of the 400's, so I need some help. I'll follow this post with my 1st try on photo of the cylinder and my cylinder port map, to see if anyone can tell if this looks to be a stage 1-2, or if it looks like a full blown stage 4, pain in the @$$ on the street.

Thanks, Phil
Author:  Phil46 [ Fri May 17, 2013 10:36 am ]
Post subject:  Re: S3/KH400 Porting with H2 Carbs
Image

Image

Image
Author:  Phil46 [ Fri May 17, 2013 10:38 am ]
Post subject:  Re: S3/KH400 Porting with H2 Carbs
:clap: Hey, I think I got it 1st try! :e12
Author:  ThreePipesSmokin [ Fri May 17, 2013 10:51 am ]
Post subject:  Re: S3/KH400 Porting with H2 Carbs
Looks like the transfers (timing) are untouched (a little "shaping" at the "knife edge") but the intake and exhaust have been cleaned up, exhaust may have been raised too. Can you see if the piston skirts have been cut on the intake side? I ran that exact setup (w/H2 carbs,K&N pods, Denco H1 stingers) on my '77 KH400, even with stock (S3) pipes it ran good on the street! :thumbup: Can you post pic of the carb adapters? If they're a real hack job you may have my old motor! :lol:
Author:  III [ Fri May 17, 2013 11:23 am ]
Post subject:  Re: S3/KH400 Porting with H2 Carbs
ThreePipesSmokin wrote:
Can you post pic of the carb adapters? If they're a real hack job you may have my old motor! :lol:


:lol: :lol: :lol:
Author:  Ja-Moo [ Fri May 17, 2013 1:48 pm ]
Post subject:  Re: S3/KH400 Porting with H2 Carbs
There wouldn't be casting flash in the transfer windows if they were raised. I don't see the exhaust height, that measeurment is the tell.
Author:  usernameandpassword [ Sat May 18, 2013 8:19 am ]
Post subject:  Re: S3/KH400 Porting with H2 Carbs
I have a stock cylinder as I'm sure others do as well. If you can post the port height of the exhaust, someone can tell ya for sure. I'd think the exhaust would likely be one of the first ports raised if any porting was done. It could be someone just adapted 30s to it, which make the 400s run very well. :thumbup:

The intake and exhaust ports looks awful smooth. Maybe a port widening or just cleanup?
Author:  Phil46 [ Mon May 20, 2013 9:34 pm ]
Post subject:  Re: S3/KH400 Porting with H2 Carbs
I can't believe I missed the exhaust port! :roll: Hello, Mr. Learning Curve! :lol:

I did the cylinder exhaust port and it measured 30 mm along the cylinder bore. So, taking into account the angle, it would be called 27mm or something? I measured the port in the piston skirt at 15 mm parallel to the cylinder/piston. Is that enough info?

Thanks, Phil
Author:  Phil46 [ Mon May 20, 2013 10:37 pm ]
Post subject:  Re: S3/KH400 Porting with H2 Carbs
Here is the exhaust port - 30 mm high at the center:

Image

Image


Oh, yeah, and here is a shot of an adapter plate:

Image
Author:  usernameandpassword [ Wed May 22, 2013 4:22 pm ]
Post subject:  Re: S3/KH400 Porting with H2 Carbs
Is that 30mm measurement from the top of the cylinder? If it is, I hate to be the bearer of bad news, I guess its all in how you take it, but the stock exhaust port is 33mm. This means someone milled your exhaust up 3mm. :shock: You might have to reed those to bring back the low end grunt. If youre going to throw them out, dont forget about me. ;) :lol: I have another 400 motor I might can use them on.

You check the deck yet?
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