Chainsaw Repair

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There is a sentence in here about 803 Japan being the 750 in US. http://chainsawrepair.createaforum.com/echo/echo-chainsaw-history-1963-1986/

We are able to read an information very close to this above from Mark, a member of this site, and also a member  of CSCF site, he seems to be a good collector of old Echo;s.
John Deere 80EV

My recent comparison on several Echo models including 803 tells that the ratio of
  (venturi size) / (throttle bore size)
 given by the original carburetors to each models are somewhat fun to go deeper, see a chart attached below.


This ratio is sometimes said to provide us of an easy comparison index to see throttle responses between carbs and models, the smaller ratio the faster the response.

A fun thing on this chart is that there are nearly the same size of throttle bore, 19.00mm to 19.03mm, while motor size differs in two ways, 60cc class and 80cc class, from the top to the end except for the last model, CS-803.

Carbs for upper 6 models have nearly the same throttle bore, while some have larger venturi size and some smaller from 15.88mm to 15.08mm. So the ratios in these upper six models are nearly two ways, 79% and 83%.

Only the last one CS-803 has a bit larger carb, both of the sizes are larger than other models, and also this 803 has larger ratio than others.

Now one of presumptions I came to see is that this 803 was perhaps designed for some special use, which was mostly needed in domestic market than that of US. On of the evidences I have been hearing here at a largest Echo dealer in this area Yokohama is that this 803 was sold to gardeners who needed tough root-cutter chainsaws.
To my understanding root-cutter saws seem they rarely need high response carbs, rather they seem to need carbs for bigger torque.

The second evidence to this presumption is a pic below, showing two of my 803 out of three, one in the front has a genuine power filter for root-cutting use. A more fun thing to see is that the one in the back has a modified clutch cover in the other side, for this see a pic added below. This Echo dealer says this modification was done for this user at their place.

All these are my presumptions after all, so if I made some misunderstanding pls feel free to let me know the truth.
And if not so wrong, glad if you could keep this in your mind and remind this when you see the name of 803 somewhere some time.

Chy