Nik's Poulan Thread

[leecopland]

120-130 seems pretty standard for these.

 

[RedneckChainsawRepair]

This one was 1.812 just in the one place checked.

 

[redunshee]

This one was 1.812 just in the one place checked.

Seems fine. Bet rest of cylinder is similar.

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[Acornhill]

I did mic the bore and the piston from the 3400 last night. Someone reported the bore should be 1.810", I got 1.814" very consistently top to bottom (o.k. maybe +0.0005 at the top) and very round. The piston is only 1.807" so I guess 0.007" clearance is a bit much. Decisions, decisions...NOS 3400 top end, find a better used one, or look for a 3700??? Of course if I could find a reasonable 3700 piston and cylinder the choice would be obvious.

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I also put this one on the bench, was supposed to be a runner and in 8 pulls it was. I tried adjusting the carburetor but this one is not exactly...snappy...I assume it should be a bit quicker on the pick up than it is. I did not check the compression but it is not stellar. Reminds me of a worn out 10-10 with the bullfrog carburetor.

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Mark

Mark, you can get a 3700 or 3800 top end for $183.82 plus tax & shipping from Poulan still.

 

[Boomer 87]

Ok gentleman, just got a really nice poulan farm pro 375. Thing looks perfect except the crank bearings are loose, loose enough to cause crank seal leaks as you can see the lip of the seal moving. Question is, are the bearings nominal size, or am i gonna have to track down some NOS parts. Thanks cody

 

[fossil]

Bearings a n seals all the same in that series.

Bearings are BH-108 both sides. Make sure you ask for full compliment.

Seals are SKF cr 6119 or timken 253747.

Keep in mind that those needle bearings are quite sloppy even when new. Radial play is around 0.005". I haven't seen any that were worse than that so you may not need new ones.. Cheap if you want to replace them. If you do, remember that the bearing position sets the lateral play so they can be a pain to set correctly if you don't have the Poulan tool.

 

[Boomer 87]

i dont have the poulan tool, i know with the recoil off and bar and chain off. You can rock it back and forth and hear an audible clunk from inside. It sure seems like too much to me.

 

[Boomer 87]

I just looked up your part number for the bearings, they show to be flat needle bearings which are what i thought was in there. However looking at ebay i found a listing for a NOS crank assembly for 3400-4000 and it has what appears to be ball bearings on it. So are the needle bearings i found the right style? Thanks cody

 

[Boomer 87]

So i found these bearings all over the internet, full comp bearings, but they say 6200 Rpm max?

 

[fossil]

Yep. The original bearings were manufactured by Torrington.

https://www.amazon.ca/Koyo-BH-108-Bearing-Complement-Rotational/dp/B007EDX030

There are lots of bearings and seals used in chainsaws that are run at over spec speed.

The lateral play should be somewhere between .008" and .015" I guess as I don't have the tool and the Poulan spec isn't anywhere I can find it.

I have seen pics of a few 4000's that had excessive lateral play and grooves were cut into the piston from hitting the saw case.

 

[Boomer 87]

Mines not nearly that loose, i need to put a dial indicator on it, it just seems looser than normal. I found koyos for $3.75 from Johnson bearing.

 

[fossil]

Koyos are amongst the best bearings in my experience.

 

[Boomer 87]

Well i was concerned about the speed rating, but if you guys have ran them with luck ill just use em. Now i just gotta do some measuring to see if i really need them or not

 

[Just a Guy that cuts wood]

Well i was concerned about the speed rating, but if you guys have ran them with luck ill just use em. Now i just gotta do some measuring to see if i really need them or not

I can help you spend your $ .......Buy them now with all your toys someday you will want to install them
Than you can tell me if they hold up. I don't have that model yet but someday I may. lol

 

[redunshee]

Seems to me if there is radial play the bearings need replacing. Axial play is generally acceptable. The Torrington bearings are fine. I've used them for years. When replacing them just look at the depth of the old bearings and use that as a guide. Naturally you will need to split the case. Also check your thrust washers.

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[Boomer 87]

Im gettin ready to put the dial indicator on it ill post what i find.

 

[Boomer 87]

Ok .... so best i can tell my dial insicator tells me theres .006" play. Flywheel side is less i can tell by the feel. So would you guys do a tear down or just do crank seals and see how it goes. I dont want to tear it down if not necessary

 

[fossil]

All the 3400 -> series of mine I've checked have a radial play of .005" to .006. I put new bearings in one and guess what? Same amount of play. You won't find that in ball bearings which have very little radial play. Bearings that have an inner ring are easy to control but drawn cup needle bearings don't have one as they sit on the crankshaft (in this case) so that fit and radial play depends upon the clearance Poulan set on the crank surface.
Unless you're into welding up and regrinding the crankshaft, it's not going to change, and...it doesn't need to.

Make sense?

 

[Boomer 87]

And that .006" is not from crank centerline thats total endplay so really its about .003" each direction from crankshaft centerline i cant help but think a good pliable seal will keep .003" of crank deflection sealed up. I was horsing on it pretty hard to get the .006" total, more torque against it than there would be with it running. I may just have an air leak.

 

[Boomer 87]

Yup i get it, the bearing deaign lends itself to being alittle more " sloppy". I think now the bearings are fine. Im gonna bonk new seals in just bc i have em.