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build your own expansion chamber!! plus adjustable header design
#11
Interesting. One guy is cutting, rolling, shaping & welding steel into a functional metal sculpture. The rest of us are pecking on keyboards. I can't wait to quit the rat race and be just like this Unknown Welder.

Richard S: hmmm, let's hope that he remembered to leave room for his clutch!

I'm a huge fan of Gordon Jennings' seminal book, Two Stroke Tuner's Handbook, especially Chap 4 on this exact topic. (That book was probably the best tip ever & came from guys on the old forum!) Forty-five years on, I'm sure not every sentence is perfect but at least now I feel like I more or less understand the principles. It's long out of print but the PDF can be downloaded from the web. (BTW, Jennings makes a few references to sources he had at McCulloch.)

As I recall, Gordon said that the distance from the piston to the midpoint of the converging cone is more important than the header length. (I have no way to know if he was correct.)
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#12
Never mind about room for the clutch.  David and I were pecking at the same time, but he drew first.
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#13
I own that tome on two strokes and here's the truth told right up front !

Another mistake commonly made, sometimes even by those who have enjoyed some success in modifying two-stroke engines, is to believe in a kind of mechanistic magic.  Bigger carburetors, higher compression ratios, altered port timings and expansion chambers often do bring an improvement in power output, but more and bigger is not magically, instantly better.  All must work in concert with the basic engine, directed toward the particular application, before they constitute a genuine improvement.  You cannot treat them as a voodoo incantation, hoping that if you mutter the right phrases and stir the chicken entrails in the prescribed manner, your mild-mannered, all-purpose chuffer will be transformed into a hyper-horsepower fire-breather.  With a lot of luck, you might get that result; the chances heavily are that you won't.

For those that don't want to spend the big bucks to buy this Vintage Handbook .

http://www.2strokeengine.net/gordonjenni...ndbook.php
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#14
randy,

i'm pretty sure i have a copy of that book.
great read always find something new to obsess about when i go through it.

on reading these last few swap meets brought me some great mechanical finds but for the forum i was very lucky.
i got several new piles of old 57-60 hot rod and custom mags.
as soon as i figure out what i'm doing wrong with the scanner i'll be posting some neat old engine hop up articles .
many are extremely dated information wise but the performance improvements were legitimate for the times and will still work today.
an especially good one is by butler improving homelite motor performance.
i'll be doing high resolution scans so anyone so inclined will be able to copy modifications with clear pix.

the whole point of this first article and the ones that follow is to provide how to assistance to newbe's coming into this sport.
anyone else that wants to jump in with a how to is free to do so anytime
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Dave L.
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#15
Dave......for many of us finding this old information is "g0ld" .......and as pointed out to me the header design worked
back in the day and it is era correct......so it would be a fun project to construct your own pipe .

You don't have to have the fastest kart in the Vintage classes to have fun, just enjoying working on these old beauties
is worthy of all the effort .

I love discovering old items unique to our Vintage Kart hobby and either building a copy or restoring a found item is
so much a part of it .


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#16
randy, that mcculloch engine cover was being offered as a repop at tbo i think.
but i missed seeing them .
do you know who , how much and if theres any left?
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Dave L.
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#17
Dave......the one I pictured is the real deal and my friend Jim A. won't let go of...so I'm making a pattern so Deb can repop them to fit Mac's and West Bends and maybe some other Vintage foreign engines .

I might ask should they have Brand graphics like the original or would more folks rather have a generic plain engine cover?
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#18
i'd prefer grafix myself.
Dave L.
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#19
Randy, graphics, but don't put "820" on the ones for West Bends...a few of us still run 610's! Ted
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#20
Randy...on the west bend ones,,,just put a picture of a broken rod,,or the head flying off...we'll know what it is....

gw
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