Anybody that thinks longer bars means a crooked cut is absolutly and utterly wrong. I use long bars on stihl saws and they cut perfectly staright. The problem is that the larger the diameter of the wood you get into the more noticible any crooked cutting is.
For example a certain 20 inch bar and chain may cut up wood 8 inches and less just fine, but cut in a curve on a 2 foot diamenter tree. If you were to look closely at your 8 inch blocks you'd notice that they were cut in a curve too but the diameter wasn't great enough so that it presented any noticable problems with cutting.
When you get into the size of tree that requires a 28" bar even the slightest imperfection in your bar or chain can make it impossible to make a straight cut (a problem you wouldn't notice on a small tree).
netree's advice was right on the money:
Check your bar:
Worn bar rails (chain rides sloppy in groove)
Burr on edge of rail
Bar bent (look down the length of both rails)
Check your chain:
Are the rakers at the same height?
Are all the cutters at the same PROPER angle (and sharp)?
Are the cutters all the same length (or pretty close)?
Does the chain gauge match the bar?
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And I'm talking about a very slight imperfection in those area's. It takes a true expert to sharpen chains of that legth that perfectly over the long term, because every time you hand sharpen there may be tiny diffeances in how you sharpened each tooth. It may be time to buy a new chain, or to have the chain(s) proffesionally sharpned or to measure each tooth with a guage and make sure that they are equal in length down to 0.010 of an ich or better.
I'm betting it's the chain and not the bar. You'd have had to have used that bar a hell of a lot to get burrs on it and I doubt you've used that length of bar for
that much cutting as to cause burrs.
And I don't think switching brands is going to help you either. All the reptutable bar and chain brands (Stihl, Husquvarna, GB, Laser, Oragon, Widser, Carlton, cannon, etc) should cut straigh when they are new.
If this were not the case then how do you think anyone logs 5 foot trees with a stihl?
