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How does one tell if the nose sprocket is wearing?

Started by GammaDriver, November 29, 2005, 09:05:17 PM

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GammaDriver

Simple question: (for my Poulan Pro 295) - from reading bar and chain product brochures / ads / web pages, it seems that nose sprocket life is of concern.  How do you guys know when a nose sprocket is going bad?

for that matter...

How does one know when a bar has gone 'bad'?  All these replacement bars and replacement sprockets being offered tells me that sooner or later I may need a replacement (especially with the situations I found my saw in when I was first learning what to do and not to do during hurricane clean-up jobs last year).

The sprocket on the saw itself looks like it has indentations from the chain on both sides of each tooth, but no teeth are chipped, so I guess that's ok for awhile longer.

Thanks!

sawguy21

The sprocket should turn freely and there should not be signs of the bar spreading at the tip. A worn bar will have ridges on the rails where the chain has worn into it and it may be blued. The bar rail should be square to the bar. The chain will also rock in a worn groove causing it to cut crooked.
old age and treachery will always overcome youth and enthusiasm

rickk

If the chain is riding on the nose rails rather than the nose sprocket the nose is bad.
If the nose rails have separated the nose is bad.

If the rails are no longer parallel to the extent that is cutting circles because chain wobbles the bar is bad.

If the bar is not reasonably flat along the rails (they wear a depression eventually, usually near the nose - somtimes closer to the engine... depends on how you use the saw) then there is a chance of loosing the chain because the bar is bad (the bar will probably be blue in this area as well as depressed).

if there are chuncks of the rails missing, or heavily rusted, the bar is bad.

If the bottom edges of the chain do not contact the bar because the drive teeth are touching the bottom of the groove the bar is bad. If the bar is bent the bar is bad.

Did I miss anything? It's getting late... probably. Usually the bad bar will be doing something aggrivating to you, or it will simply look like it belongs in the trash can. If the chain is near end of life you might let is stay a while longer, but such a bar does not need to be allowed to wreck a new chain.

As far as the drive sprocket goes... change it every two chains is what the manufacturers of the saws and sprockets all seem to say. In my experience a worn sprocket makes a chain stretch and get old quicker. If you can use an Oregon clutch/sprocket system with replacable sprocket then the drive sprocket replacement is only going to run about  $5, a whole lot less than a chain.

micky boy

I second what rickk says about the drive sprockets.
I once had a rim sprocket break and smash through the oil pump and damaged a crank seal. I regularly check the rims for wear. As soon as your saw stops cutting perfect and the chain is sharp then it's likely to be the bar needing attention. I can usually tell within a few days that my nose sprocket is going to break by how it sounds. It gets louder and just sounds whizzier. If you want a nose sprocket to last then by my experience ( more than once )  ;D  don't heat it up by pinching,etc !     Assuming that I have maintained the bar as needed I will run a bar until the tip breaks or the chain touches the nose rails thus running hotter. I don't see the need to replace a bar or chain if they are working well as they are.
Three Five Seven............Chainsaw Heaven

Dale Hatfield

If they bar tip sprocket  is still in the  bar keep on keeping on.
When its  hanging  out is the best time to replace.
I have tried both ways grease tip of bar, and not at all.
The end results still same  tip wears out  and needs replaced. knock out the rivit and install new one  if ya can or buy new bar.
Dale
Game Of Logging trainer,  College instructor of logging/Tree Care
Chainsaw Carver

micky boy

I always replace a broken sprocket with a replacement (if the bar allows it) instead of buying a new bar, unless the bar is damaged or the nose splits open bad. I Know it can be fiddly but at half the price of a new bar for me (15"/18") I am happy to put the time to it. When I happen to run a power match bar It will usually have 3 replacement noses before the bar grooves start to wear bad.
I might be wrong but I seem to find that if you grease your tip regularly ( say every hour or so) from new and continue then it will last well, or if you don't grease it at all it lasts well but I have noticed that if after greasing my tips and then maybe not greasing them for a few weeks and then start greasing regularly again they last about 2 weeks and the sprocket breaks. Puzzles me ?
Three Five Seven............Chainsaw Heaven

Rocky_J

Micky-
That is because dirt, grit and grime will stick to the heavy grease. If you grease hourly, you constantly push out the grimy grease and replace it with fresh. If you never grease the tip then the bar lube will keep the tip lubricated and constantly flush out the grit and grime. But bar lube will not flush out old grease with grit and grime.

I would never grease a tip sprocket. I let the bar lube keep it lubricated and I clean it out thoroughly with compressed air and an air nozzle every time I service my saws (once or twice a week). I blow out the tip until it spins freely and all the old oil is removed. After putting the saw back together I fire it up and run it for 15-20 seconds to let the bar lube relubricate the bar and chain.

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