Lincoln SAE 300 idle issues

[milomilo]

A good friend of mine has a Lincoln SAE 300 that the idle down is not working as it should. The symptoms are:

1. Starts fine goes to high idle and after a minute goes down to low idle but will not go back up to high idle when an arc is struck.

2. If manually put on high idle and you start welding it will stay up without the manual over ride of the throttle linkage.

3. After welding stops it will idle down and again not go back up to high idle when an arc is struck.

I have used this welder before and everything worked as it should, and I have not worked on these welders before. Do I have a bad idle down unit? Or is it something in the generator function? Or is it just a matter of disassembling the idle down and cleaning it up?

Serial number of the welder is 4452315, Code 4824. Seems like it is a 1962 or 1963 vintage when looking at Lincolns chart.

Almost forgot. What is the correct idle rpm and high idle rpm supposed to be?

[milomilo]

Any info from the experts?

[123weld]

not sure, but if its the same as a 200, and i was having that problem, i would try striking an ac at the same time w/ your other hand barely pushing on the linkage to barely increase the idle. if it then tachs up by itself, it means your low idle was set to low, so thread in the little bolt against the stop on side of carb to keep your idle increased a lil. in other words, idle is to low to give the exciter the juice it needs to tach up. it should say on the faceplate somewhere what your calling high idle. it should say real small like, maybe faded.

[milomilo]

I'll give that a try. Thanks.

[123weld]

someone gave me a 300 w/ a shorted armature bar, i looked at it and its 1400 rpm

[milomilo]

someone gave me a 300 w/ a shorted armature bar, i looked at it and its 1400 rpm

Do you know the low idle RPM?

[123weld]

no, but if you try what i described, and it works, that will put you real close

[duaneb55]

Below is the Operators Manual for your unit based on the Code# 4824 and per manual IM179-G that covers timing, carburetor governor and idler adjustments, your low idle speed is 1000rpm, full load is 1450rpm and no load high idle is 1550rpm.

http://www.lincolnelectric.com/asset...oln3/im203.pdf

[milomilo]

Thanks Duane. Very helpful.

[milomilo]

Below is the Operators Manual for your unit based on the Code# 4824 and per manual IM179-G that covers timing, carburetor governor and idler adjustments, your low idle speed is 1000rpm, full load is 1450rpm and no load high idle is 1550rpm.

http://www.lincolnelectric.com/asset...oln3/im203.pdf

I looked through the manual you attached and I could not find anything regarding idler adjustments. Did I miss where to look in the manual?

[duaneb55]

I posted the link to the machines operators manual (IM-203-E) and only referenced the speed information from the IM-179-G manual.

Here's what you're looking for:
http://www.lincolnelectric.com/asset...oln3/im179.pdf
Page 8.

[milomilo]

That is what I needed. Thanks much.

[milomilo]

I adjusted the idle speed screw to up the idle to see if it was too low and not activating the idler. I upped the idle speed to 600, 700 and 800 and struck an arc and the idler did not ramp up as it should. If I held the carb throttle linkage to high idle and welded it would hold at high idle, but right after you quit welding it would idle down and not idle back up when an arc was struck. I checked the vacuum line and it was clear with n damage to the line.

Any other checks I can do to find the problem? Or is it time to get a idler upgrade kit? I see Weldtron has a couple different versions of upgrade kits.

[duaneb55]

800rpm should be fast enough to develop sufficient current thru the idler coil when first striking an arc BUT 1000rpm is the low idle spec.

If the idler won't release at 1000rpm the two things that come to mind are the needle valve is sticking or the time delay petcock adjustment is too lose allowing too much vacuum into the diaphragm chamber for the needle valve to evacuate under low idle high vacuum conditions.

[milomilo]

Am I correct that if it holds at fast idle while welding it means there is enough vacuum to the idler? Maybe I should try adjusting the vacuum petcock at the back of the idler?