Quote:
Originally Posted by Lakeside53
Originally Posted by Jack Russell
... For some reason I had the feeling I may not be using good judgment running the shorter bar. ...
reply by:Lakeside53
JACK RUSSEL:
Yes I do this (16 inch) also, and love it... just have to be careful that the WOT isn't exceeded - if you primarily use a short bar, set the max RPM with that bar. It will then be lower for longer bars, but it's better to err on the side of caution. if you have an MS260-pro without an adjustable H, then check it, but they are very conservative anyhow.
Jack Russell said:
You have told me something I did not know. Could you post more information on this. As saying goes Man have I got egg on my face
This came up in a thread last week, where if you tune a saw with a short bar (i.e. 16 inch) to say 14,000, and put on a long bar (28) and the WOT drops to (example) 12,500, do you then re-adjust the carb leaner to get back to the 14,000. You can see the problem - now you have a longer bar but a leaner saw. Which is correct? I bounced this off my Stihl technical contact yesterday. They use the example in the Silver certification class out here of a guy tuning his 064 with a 32 inch bar, then putting on a 16 and blowing up the motor due to over speed. While these are two different things, they are related. Firstly, the MAX RPM is just that - MAX. You don't have to set WOT to MAX, you can set it slightly richer and be below that. Secondly, you need the correct mixture to keep engine temperature low enough. It turns out that running it as lean as you can before exceeding maximum temperatures give the best power, but at the expense of life expectancy, AND more importantly, you'll have no buffer for changing conditions (fuel, weather, bar length etc). While it's popular on AS to wring the last drop out of a saw, it' may not be the wisest thing to do for a work saws that you aren't watching continuously.
What would I do? 1) always adjust the carb for a bar length you use most often, preferably the shorter one. 2) stay a tad bit richer than "perfect WOT". Timed cuts are the only real way to see if the richer setting materially alters your throughput.
o.k. everyone - jump in and disagree...