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carb adjustment


cgar's Avatar
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Join Date: Nov 2002
Posts: 170
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12-09-03, 06:52 PM   #1  
carb adjustment

Hey guys. Please correct me if my thought process is wrong. On my parents snowblower (8 HP Tucumsen), I was able to bring it back to life (varnished up and dirty carb). I have one small issue which I am not sure how to correct.

I have read the Tucumsen manual on how to preset the mixture screws (main and idle). I set everything last spring. During this last storm, I swung by to help clear the driveway but it was already done. I pulled the snowblower out and it started right up. It was dark, so when I put the engine into "fast" I noticed a small blue flame coming out of the exhaust every so often. I was under the impression that this means the engine is running lean. I unscrewed the main mixture screw until the blue color vanished (about 1/2 turn). I figured everything was OK so started to put it away. I also noticed then that the muffler (right were the exhaust gases exit out of hte engine and into the muffler) is red hot. The entire muffler is not hot just were the exhaust gases hit it as they exit out of the engine. I alos am not sure if I noticed this just because it was dark out or not.

I guess my question is, is this normal. If not is it running too lean or rich. Is my logic that some blue flame out the muffler indicates engine is running lean.

Thanks for any replies


was red hot right where the exhaust portis out of hte engine

 
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cheese's Avatar
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Join Date: Jul 2001
Posts: 16,575
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12-10-03, 12:17 AM   #2  
Hello cjar!

Don't worry...it's normal. The muffler is normally red hot like that, but not visibly so during the daytime. The blue flame could be normal...depending on how much and when, but it sounds like you got it to stop, so it may have been running a little lean...maybe.

Hope that helps!


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
cgar's Avatar
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Join Date: Nov 2002
Posts: 170
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12-10-03, 05:57 AM   #3  
Hi cheese. Thanks for the reply. Prior to the final adjustment, it did not feel that it ran with the power it should have. After the adjustment it was much better.

It sounds like some (minor) blue flame out the muffler is not an indicator of a lean mixture? Is that true?

 
cheese's Avatar
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12-10-03, 08:32 PM   #4  
Depends. Generally, yes, blue flame is an indication of running lean, but just because it is running lean it doesn't mean you'll see a blue flame, and just because you see a blue flame doesn't mean you're running lean. It depends on engine temperature, when it shoots the flame (all the time, when accelerating, when decellerating, etc...), what type exhaust system is on it, etc...

Sounds to me like your case was that it was running lean. Glad you got it fixed!


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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