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General Category >> Rubber Side Down! >> Head case
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Message started by Armen on 06/28/16 at 13:53:39

Title: Head case
Post by Armen on 06/28/16 at 13:53:39

Someone once told me that if you are working on something that is hard to see, buy one and cut it up. In the long run it'll be a cheap investment.
So, I got a junk head and pushed it through the band saw. Really can see how sucky the exhaust port is. Oh boy...

Title: Re: Head case
Post by Armen on 06/28/16 at 13:54:19

Another view

Title: Re: Head case
Post by Armen on 06/28/16 at 13:54:53

more fun...

Title: Re: Head case
Post by Armen on 06/28/16 at 13:58:18

So, methinks the gag will be to raise the roof of the port a little. And build up some JB Weld between the spring seats. Try to straighten things out without making to thin a port wall between the ex port and the oil.
Then open up the restriction at the exit (donut).
Then taper the valve guide and guide boss on the port side.
And fill up some of the valleys in the ex port to lose the speed bumps.
Have this high temp epoxy from Manley that is designed to be used in exactly this application.
One way to find out ::)

Title: Re: Head case
Post by Ruttly on 06/29/16 at 10:02:33

That was no casting flaw that was put there on purpose to keep it from breathing , thanks Suzuki!

Title: Re: Head case
Post by Armen on 06/29/16 at 13:32:55

I think the GiveAShit levels were pretty low when they were designing the head on this one ;)

Title: Re: Head case
Post by Ruttly on 06/30/16 at 11:58:19

No Armen I think they wanted it to be that way, lots of torque and limited HP. When you open it up it looses low end torque and gains some power. I've seen bad castings before that was done on purpose and it really shows it the way you cut up that head. That was very cool to see it in such a different way,Thanks

Title: Re: Head case
Post by Armen on 06/30/16 at 13:17:35

Ruttly,
Not sure if I see the connection between bad exhaust ports and low end power.
How's this for a thought line:
Most people opening up the ports are doing other things to their bikes. Larger carbs and longer duration cams move the power band up.
Haven't dynoed or flow tested these engines, so I can't say for sure, but that's what makes sense to me.
Kinda fun cutting up that head in a sick sadistic way. Wouldn't have done it to a good head. That one ate an exhaust valve.
-A

Title: Re: Head case
Post by Ruttly on 06/30/16 at 15:15:24

If you have a dirt bike with a supertrapp on it you can tune your exhaust by changing amount of discs,create more back pressure use 4 discs ton of low end torque bike is good for the woods, same bike 12 ok 15 discs looses low end but now hauls ass in upper rpms now the bike loves wide open spaces and not so woods friendly, back pressure = torque low back pressure = HP

Title: Re: Head case
Post by Armen on 06/30/16 at 18:07:46

Been there, done that.
Had an XL250 Honda with a 4" Trapp in the late 70's/early 80's. A restriction that far downstream has a much different effect on back pressure and the pressure waves returning to the exhaust port than does a simple crappy port that restricts the exhaust flow out of the combustion chamber.

Title: Re: Head case
Post by Ruttly on 07/01/16 at 17:12:07

No not really,same effect just more dramatic. A stock savage you feel when piston fires due to restricted port & exhaust cause it is building rpms slower. On my bike firing of piston less pronounced , smoother , builds rpms faster due to less restriction. Back pressure has everything to do with low end torque just different effects where & how you create it !