Craftsman 3.7/Poulan 3700 Cylinder and Ring Replacement

[fossil]

I am the one that bought it. Although it might not be used too much, I purchased the wrist pin removal kit, from Saw Salvage Co. https://www.sawsalvage.co/products/...ch-press-fit-wrist-pin-extractor-removal-tool

I may be getting ahead of myself, but does anyone know where I can get a complete oil pump assembly for the 3.7. It hasn't worked for the last 20 years or so. The part # is 530010639. I have been having to squirt my oil can on the chain periodically to get by. I am getting rather tired of doing this, and while I have the saw torn apart, now would be a good time to address this issue.

Check your inbox

 

[GBertolet]

Thanks, I just bought it.

 

[GBertolet]

I have another question. Being now, I have a piston, cylinder, oil pump, and wrist pin installation/removal tool coming, I might as well look at the bearings and seals also. Before I tore down the saw, I pressure tested the crankcase. I made plates, with gaskets for the inlet and exhaust ports, and I made up a dummy spark plug with an air fitting on it. I have a lathe and a mill to play with, so making these things are easy. With the piston at BDC, I put 8 lbs of air, from my MityVac 8500, and it held for several hours. Tried vacuum also, and it held. Still, I have some moderate wiggle on the crank bearings. Is it worth bothering with this, since there are no air or oil leaks? How much wiggle is too much?

Fossil listed some aftermarket replacement oil seals on a previous post, but what about the bearings. They are discontinued, NLA, with no sub listed. Is there an alternate aftermarket part number, that will work? There is a ball bearing supply store near me, with sales to the general public, I might try them, if I can get some numbers. Even if I don't do the bearings and seals right now, it would be great to have the part numbers written down on my owners manual. Thanks again to all for the great help.

This is going to be a great saw, when completed. I have now a little over $100 tied up in it. The saw listed for $400 back in 1984. Who knows what it would cost now in 2020 dollars. I was fortunate to buy it when the 1985 model came out. Sears knocked $150 off, because it was a 1984, a last years model, and the salesman said, the only difference between the 1984 and 1985 models are the color, the 1984 (mine) is orange, and the 1985 is grey.

 

[Lightning Performance]

I am the one that bought it. Although it might not be used too much, I purchased the wrist pin removal kit, from Saw Salvage Co. https://www.sawsalvage.co/products/...ch-press-fit-wrist-pin-extractor-removal-tool

I may be getting ahead of myself, but does anyone know where I can get a complete oil pump assembly for the 3.7. It hasn't worked for the last 20 years or so. The part # is 530010639. I have been having to squirt my oil can on the chain periodically to get by. I am getting rather tired of doing this, and while I have the saw torn apart, now would be a good time to address this issue.

You could have had a whole saw from here.
GL

 

[GBertolet]

Fossil, For the archives, I just measured the diameters of my old 3.7 piston and cylinder. Piston=1.870, cylinder=1.883.

 

[fossil]

I have another question. Being now, I have a piston, cylinder, oil pump, and wrist pin installation/removal tool coming, I might as well look at the bearings and seals also. Before I tore down the saw, I pressure tested the crankcase. I made plates, with gaskets for the inlet and exhaust ports, and I made up a dummy spark plug with an air fitting on it. I have a lathe and a mill to play with, so making these things are easy. With the piston at BDC, I put 8 lbs of air, from my MityVac 8500, and it held for several hours. Tried vacuum also, and it held. Still, I have some moderate wiggle on the crank bearings. Is it worth bothering with this, since there are no air or oil leaks? How much wiggle is too much?

Fossil listed some aftermarket replacement oil seals on a previous post, but what about the bearings. They are discontinued, NLA, with no sub listed. Is there an alternate aftermarket part number, that will work? There is a ball bearing supply store near me, with sales to the general public, I might try them, if I can get some numbers. Even if I don't do the bearings and seals right now, it would be great to have the part numbers written down on my owners manual. Thanks again to all for the great help.

This is going to be a great saw, when completed. I have now a little over $100 tied up in it. The saw listed for $400 back in 1984. Who knows what it would cost now in 2020 dollars. I was fortunate to buy it when the 1985 model came out. Sears knocked $150 off, because it was a 1984, a last years model, and the salesman said, the only difference between the 1984 and 1985 models are the color, the 1984 (mine) is orange, and the 1985 is grey.

The bearings are drawn cup needle bearings and are readily available.
BH-108 bearings. Many bearing companies make them. Make sure you specify full compliment.

I doubt your bearings are shot. Typical radial play is .005" to .006". Very easy to feel without measuring. Certainly not like the typical ball or roller bearings.

Left to right can vary from .010 to .020" That is set by the bearing depths in the crankcase and without the insertion tool from Poulan is a great big pain in the ass to set. I like the play to be .009 - .015" There is no spec.
If I had a lathe I would make a tool.

Your vac and pressure check sounds like all is well there.

 

[GBertolet]

What is full "compliment", I think you meant compliant. If so, what is then full compliant? What does it mean?

 

[fossil]

No it's full compliment. Some BH-108's have a cage inside with spaced needles. Full compliment means the needles are against each other. The caged units have a higher speed capability while full compliment has a greater load capability. The saw comes stock with full compliment.

(If they are not compliant, I hit them with a big hammer)


Full compliment


Caged

 

[GBertolet]

Thanks, I learned something today. What does the installation tool look like? I may try to make one, in case I ever need it.

 

[fossil]

Thanks, I learned something today. What does the installation tool look like? I may try to make one, in case I ever need it.

A pic of it is on page 22 of the service manual. The dimensions aren't known to me.

You would have to split the saw case to put new bearings in. They rarely wear out. If you have the tools, measure the radial play before you do an unnecessary repair.

 

[GBertolet]

Well, the oil pump and piston tool came today. A shoutout to SawSalvage and Chainsawr, for prompt shipping. Anyhow, I needed some reengineering for the oil feed output line. My original pump, had 1/8 inch hard nylon tubing, with a compression fitting and a ferrule, that screwed into the pump. The replacement pump had a nylon nipple, with a larger piece of fuel line, secured by a tie wrap, plus it was too big to fit through the crankcase oil port. I didn't know if I broke off the nylon nipple of the new pump, it would be threaded like the old underneath. If it was, no problem for this transition. But I wasn't taking the chance, so I cut off the existing ferrules, and pulled the old line out. I found some small fuel line tubing, heated it, in boiling water, and was able to insert a brass tip, to mate up with the crankcase port fitting. I was able to squeeze the other end on the new pump nipple.

I put it back together, put some chain oil in the tank, pushed the manual pump bar, and oil came out. Now to wait and see, when I get this saw running, if it works automatically. I don't quite understand how this pump works. There is no drive gear, or vacuum lines. Maybe the oil tank gets pressurized? What powers it, for automatic oiling?

Sorry for being so long winded, I was just passing along my adventures of this project.

 

[GBertolet]

After much anticipation, the cylinder and piston arrived today. No apparent defects, and for FYI, here are the measurements. Cylinder=1.879 diameter, Piston=1.870 diameter. I took off the piston rings, and put them in the cylinder. The ring gaps on both rings exceeded .075. I don't know how the seller claimed to be able get 150 lbs compression with this setup, but I think the rings should be replaced. I ordered the two #530025933 rings. These are the large piston rings for the 3800 engine.

 

[GBertolet]

The replacement rings arrived. I connected the new piston to the connecting rod. The installation tool really made things nice for this, and I manipulated the piston into the new cylinder, carefully compressing the rings one at a time, while wiggling the piston. All done. I made up the cylinder gasket up myself. Compression was much better. The saw needed a new fuel line, so I made that up.

The saw was cranky to start. The engine was not getting any fuel. Apparently there was air in the line and carb. There is a small hole in the HDB carb's diaphragm cover over the diaphragm's metal button. I got a punch and depressed this button, which opened the fuel inlet valve, letting the air out, and fuel in. That was all I needed. The saw started right up, and finally idles nicely also. I did a few test cuts, with success. The new oil pump works also. I see oil spraying out, when I rev the engine. I think this repair is finished.

I happened to see a video on youtube, where the host claims that cutting immediately, at full speed, with a cold started chainsaw, will often score the cylinder/piston, between the exhaust port and the chainsaw clutch. This is due to that side getting heated up faster, and expanding first, before the rest of the cylinder/piston can catch up. This is exactly the spot where mine went bad at. I have been guilty of this activity. I will have to keep this in mind. The host said to avoid this, let your saw run a few moments before letting her rip full speed.

 

[GBertolet]

With the saw running well, I need some advice. I now have a 18" bar on the saw. I would like to get a 24" bar for occasional use on the saw. This summer due to storms, I have had many large trees uprooted, too large for my 18" bar in single cuts. The cut pieces are too fat in diameter to handle and transport, so I will have to rip or noodle them to get into manageable pieces. I don't plan on leaving the 24" bar on the saw, just using it for these situations. Can I use a rip chain for this, or just a regular chain? What kind is recommended? My saw uses 3/8 pitch, .050 gauge chain. I know I am pushing the limit for this 61cc saw.