Crank needle bearings
- Thread starter dave76
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I'm sure someone will chime in soon with truly good info... But until then I can tell you than when I had a Poulan 3400 with needle bearings, I thought they were a little losse because they had some up and down play. I read that that was normal and they tighthen up when hot. As far as I know that saw is still running good, another member has it now. Ball bearings, on the other hand I think they should have no play or virtually none.
no up and down play and should turn smoothly.
Fish
Tree Freak
I would go by noise and air leaks/running problems more than a little slop.
Otherwise, I would run it!!!
But since you are asking, I would guess you have some problem......
redunshee
Addicted to ArboristSite
Not sure what kind of saw he has, but not sure they can be replaced on the old POulan Countervibe saws.
Doesn't matter, take it to a bearing company and they'll probably have it on the shelf. There's nothing special about a needle bearing. Take the crank and the case if you can. They can take any measurements they need off of it. May as well replace the bearing race as well, if you can get them out.
See if you have a Motion Industries near you.
Hey Buddha maybe I don't get it or maybe you don't. There are usually three crank shaft bearings. On most of the saws I have taken apart the end ones are ball bearings and the center or rod bearing is the needle bearing. If you can change that bearing in most saws you are better than 99.99% of the people that use this forum. the outside race is the rod and the inside race is the crank shaft. Some old saws (090 stihl, mcs, etc.) have the split rod but not many new ones that I am aware of. Mike
Sorry, not a chainsaw mechanic, just a plain old vanilla wrapped mechanical engineer. I didn't know he was talking about the rod bearing. He said crank bearings. I took that to mean he was talking about the crank and not the rod. The fact that he also said bearing's' threw me off track. Either way, if you have the case apart and the crank out, why not split it and put in a new bearing?
redunshee
Addicted to ArboristSite
OK. Now we're on the same page. When he said needle bearings I assumed he meant rod bearings. Some saws you can replace them like on the Stihl 011 but I know that the old Poulans there is no way to replace them. Crank and rod are forever joined together.
They can be replaced by pressing out and balancing the crank when finished but I am not so sure you can buy the bearing separate.If there is no up and down play but side to side it is good.
Yes you can. It is not impossible to take the crank apart and put it back together and get it in alignment again. It is beyond the scope of most folks here. Both in equipment and knowledge. But the real problem with doing this is ( was previously stated very accurately), the bearing is the easy part, the crankpin is the inner race for the bearings and the big end of the rod itself is the outer race. These items are not sold separately by any saw company that i know of. They are also heat treated to specific hardness so that the actual bearings and both races wear at the same rate. The other thing to keep in mind is that parts that are pressed together with an interference fit (only) to hold it all together is never quite as tight a fit the second time around and may not stay in alignment when run. Main bearings are easy to replace but if your big end con rod bearing has any up and down play, either buy a new crank assembly or a good used one.
That's my take on it any way!!:agree2:Yes you can. It is not impossible to take the crank apart and put it back together and get it in alignment again. It is beyond the scope of most folks here. Both in equipment and knowledge. But the real problem with doing this is ( was previously stated very accurately), the bearing is the easy part, the crankpin is the inner race for the bearings and the big end of the rod itself is the outer race. These items are not sold separately by any saw company that i know of. They are also heat treated to specific hardness so that the actual bearings and both races wear at the same rate. The other thing to keep in mind is that parts that are pressed together with an interference fit (only) to hold it all together is never quite as tight a fit the second time around and may not stay in alignment when run. Main bearings are easy to replace but if your big end con rod bearing has any up and down play, either buy a new crank assembly or a good used one.
Crank nee-noo?
redunshee
Addicted to ArboristSite
See what you all are saying after looking at a spare 3400 crank I have. You'd be better off getting a used one than trying to fix it. Too much effort and too little economic benefit .
