Bogging under load

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Dale

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Hi guys. Been a while since I posted on the forum. Well I have an issue with my 028 Super. It's bogging in the cut, or "under load" as I call it. Pull it out of the cut, and it revs and responds as expected. Was just wondering if there were some simple things I could/should check prior to taking it to the Doctor. I must add, I already had the carb apart to check the diaphragm/gaskets etc...., but no change. Something has me thinking "H" side carb. adjustment if it bogs in the cut ??? I could be wrong though. Thanks fellers.
 
I would 1st check compression and/or remove the muffler and inspect the side of the piston and cylinder. If all looks well, then check your fuel line and filter. A small split in the fuel line will draw air and cause the lean condition you describe. Also, a soft fuel line may collapse under load and restrict fuel flow. Another fuel restriction can be the fuel tank vent not venting properly.
 
In addition to other suggestions try richening the Hi speed needle a bit(counterclockwise). You want saw to kinda burble(4 stroke) out of the cut at wot then clean up in the cut. Sometimes if the H screw is too lean saw will bog in the cut.
Bob
 
I'm confident on all the upfront and easy checks... fuel line soft (not brittle), clean air cleaner/fuel filter, etc... My HOPES are that the saw is not on it's "last leg" as far as the cylinder/piston. This 028 has been a real gem. I bought it used in 1991, so my guess is that it's an early/mid 80's vintage. Reckon a compression test may be in order.

I've changed impulse line on a couple occasions also.
 
When "under load" you are in the cut, so look at loose/worn out av mounts, which when under load will flex fuel/impulse line/boot etc.
and small tears can become large when flexed, making it only starve while in the cut.
 
Hasn't been mentioned but is easy to check. Make sure the spark screen on the muffler isn't plugged. I once fixed a saw with these symptoms by cleaning the screen. It would run like normal until I put it to the wood.

Most likely not your issue, but worth a look anyway.
 
When "under load" you are in the cut, so look at loose/worn out av mounts, which when under load will flex fuel/impulse line/boot etc.
and small tears can become large when flexed, making it only starve while in the cut.


Interesting theory Fish. It is indeed and Anti-Vib (AV) which I don't think I mentioned, as I didn't think it was pertinent, but I will def. check out.
 
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