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Discussion Starter #1
I figured I would leave the "Performance Cam" thread and start one dedicated to opening the exhaust passage on the TW head.

Having gone as far as I could on the first head because the studs on the exhaust port got in the way of my die grinder I decided to move on and violate my other spare head. (Actually when I first got it I cleaned it and lapped the valves and got it ready for the day I needed it. At that time I opened the exhaust port a little bit and it is evident in the pictures. Technically started the modification a long time ago.)

In the first picture you see the exhaust gasket sitting a kilter on the end of the exhaust pipe.

In the second picture I placed the gasket squarely on the end of the exhaust pipe and you can see the inside diameter of the gasket matches the inside diameter of the end of the pipe.

In the third picture I placed the gasket in the exhaust port of the head and you can easily see the inside diameter of the gasket is much larger than the diameter of the hole the exhaust gases exit through. It seems to me that this can be improved upon! So with no studs in the way and lessons learned on porting the first head I will charge forward and see what I can do on the second and last spare cylinder head I have.

PA280049 (2).JPG
 

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Discussion Starter #4
. Dyno before and after would be really informative, but probably not practical.
No money in the budget for dyno tests.

Are you going to put bigger valves in it?
I am sticking with the stock valve. Hopefully this will become a project anyone can do at home for very little $$$$$ and get an improvement in performance.
 

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I've always believed that letting an engine breathe full always helps. Head porting both in and out can only improve things, imo
 

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my mentor and buddy back in the day spent countless hours porting and polishing go kart motors but it really helped besides he was 6'6" tall and 80 lbs heavier than the other drivers and he won when the motor didn't grenade lol
 

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Looking good Tony!
 

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I always think about building "The Worlds fastest TW200". Lighten it up as much as possible, slam it to the ground, cafe bars, mod the engine to the max, gear it to the moon, 203/204s inflated to 100 psi. Sounds to fast for anywhere in Canada... road trip to Bonneville :) I'll never get to sleep now.
 

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Don't forget the Jimbo screen...

I always think about building "The Worlds fastest TW200". Lighten it up as much as possible, slam it to the ground, cafe bars, mod the engine to the max, gear it to the moon, 203/204s inflated to 100 psi. Sounds to fast for anywhere in Canada... road trip to Bonneville 🙂 I'll never get to sleep now.
 

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Discussion Starter #14
The finishing touches and a blast with the power washer and the head is ready to reassemble. I am starting with the stock cam that came with it to establish a baseline. The hi-perf camshaft will come later.

Higher lift and longer duration camshafts let the engine breath better. If the intake and/or the exhaust is restricting the flow the performance camshaft will never meet its expectations. With that in mind I think the exhaust side of the TW head is very restricted.

Final views:

Left side of the port:
left wall.jpg

Right wall:
Right wall.jpg

Ceiling:
ceiling.jpg

Floor:
floor.jpg
The floor has been lowered and the short side radius rounded to hopefully prevent turbulence.
Look in the exhaust port of the TW head and see how much of the back side of the valve you can see.
This seems like it will be a straighter more open path for the exhaust gases to flow.

Head on:
Head on view.jpg
No depth perception. Hard to see what has been done.

This is where it now stands. More reports to follow -- someday. Tony
 

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Looking good Tony, nice that you didn't smooth the surface overly much. Your not supposed to. You did a great job contouring it. :)
 

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Watching with amazement at another members innovation. :icon_thumright::icon_thumright:
 

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I always though fine smoothing and polishing was an integral part of a proper port and polish job. View attachment 174897

Flow benches generally show a 60 grit finish is where a difference falls off to an unnoticeable affect on performance.
Some subscribe to" "Textured" intakes tend to keep the air/fuel rolling and mixed up (and it also keeps fuel on the ready hanging on the walls for a 0 to open throttle change) and "and some think " A Mirror" finish for the exhaust is considered best (but it really doesn't improve that much after 60 grit) according to flow benches, so they say. Some people go nuts, trying to make an actual mirror, it's a waste of time IMHO.

Now how about that oil, what kind to use on the chain, jeeze should that be an o-ring chain? This is that type of discussion.

Back in my day working at a Kawasaki shop that raced the pro circuit I got cut apart for over polishing ports. I argued, the Japanese head mechanic proved me wrong on the flow bench. I had to clean his messes for the whole summer.. :(
 

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You can even see in this pic it's not actually: "polished", there are plenty of machining marks etc..

I always though fine smoothing and polishing was an integral part of a proper port and polish job. View attachment 174897
 
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