Nik's Poulan Thread

[challenger]

I'm pretty sure the solid state ignition mount holes aren't compatible with this saw.
I got the seals done today and got it all back together. It would not fire off. I put some gas in the carb and it fired up. It wasn't getting fuel obviously but the reason is a first for me. It turned out that the fuel filter I had installed was too restrictive. The carb couldn't pull fuel through the dense material. I replaced it with a small mesh style and it runs great. Prior to the seals being fixed I had a lot of trouble getting it to four cycle and still stay running. Now it adjusts great and has a slight four cycle out of the wood that disappears in a cut. Runs better than ever for sure.

I would dump the points and put in a solid state ignition module.

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[Ginger15]

Hey guys, I'm back with my Craftsman 3.7/Poulan 3700. Finally got a mityvac pump/vac to test out why it wont run well. I cant get it past 5 vac and then it leaks back to 0, same with pressure, wont go past 5, then down to 0. Where should I start? Anyway I can narrow down the leak location? I had the muffler and carb ports sealed off with an innertube piece.

 

[3000 FPS]

Put some soapy water around the seals and then pump up the crankcase. Also there is a small hole for the oiler you need to block off when testing.

 

[heimannm]

Hey Roger - it's been a while...I've added a few Poulans to my collection as well.


This 4900 is more recent. I got it from Mark (tickbitn) last October at the Mastermind GTG and he was able to run it this year.



Mark

 

[Ginger15]

Put some soapy water around the seals and then pump up the crankcase. Also there is a small hole for the oiler you need to block off when testing.

Where is this oiler hole you speak of? That might be my problem...

And thanks for the soap idea, I was drawing a blank, doh!

 

[Todd Loosli]

It's by the bar bolts

 

[redunshee]

It's by the bar bolts

He may be referring to the impulse hole under the oil pump. If he meant the discharge hole that would be easier to block off, though I've never had an issue with not blocking it.

 

[hotshot]

It is the impulse hole leaking test air.

You can cut a “dummy” oiler diaphragm in the same outer shape as the oiler diaphragm from your inner tube material, but only punch the 4 screw holes in it.

Install it while P&V testing to block off the impulse hole, then swap it back out.

Or you can pull the pump all the way off & find a small rubber or silicone plug to block the impulse hole off from the crankcase.

 

[3000 FPS]

Hey Roger - it's been a while...I've added a few Poulans to my collection as well.

View attachment 681309
This 4900 is more recent. I got it from Mark (tickbitn) last October at the Mastermind GTG and he was able to run it this year.

View attachment 681311

Mark

Hey Mark how you doing. If I know you all your Poulans are great runners too. Some nice saws.

 

[3000 FPS]

It is the impulse hole leaking test air.

You can cut a “dummy” oiler diaphragm in the same outer shape as the oiler diaphragm from your inner tube material, but only punch the 4 screw holes in it.

Install it while P&V testing to block off the impulse hole, then swap it back out.

Or you can pull the pump all the way off & find a small rubber or silicone plug to block the impulse hole off from the crankcase.

Yep Hotshot has it. +1

 

[3000 FPS]

Frankensaw! Nice.

Yep a Fankensaw. It is a Poulan 505 with a Stihl MS660 piston the cylinder was finger ported and the gas tank and handle are from a Jonsered 2083. It is a runner.

 

[Ginger15]

It is the impulse hole leaking test air.

You can cut a “dummy” oiler diaphragm in the same outer shape as the oiler diaphragm from your inner tube material, but only punch the 4 screw holes in it.

Install it while P&V testing to block off the impulse hole, then swap it back out.

Or you can pull the pump all the way off & find a small rubber or silicone plug to block the impulse hole off from the crankcase.

It goes just under the silver oiler cover? On top of the plastic? Or it needs to go against the crankcase? Thanks for the help gents. About to start working on it.

 

[hotshot]

Yes, under the silver cover, on top of the plastic. It either replaces the diaphragm or could be in addition to it. The 3 case screws are plenty long enough. But just snug them down.

Pulling the whole pump & pickup tube to get to the crankcase usually ruins the gasket, so you’re trying to avoid that.

Here is a test pattern only on the bottom left, notice one hole is missing (the impulse) & the diaphragm is rough cut to outside dimensions...not rocket surgery, lol.

 

[Ginger15]

Yes, under the silver cover, on top of the plastic. It either replaces the diaphragm or could be in addition to it. The screws are plenty long enough. But just snug them down.

Pulling the whole pump & pickup tube to get to the crankcase usually ruins the gasket, so you’re trying to avoid that.

Here is a test on the left, notice one hole is missing...

Was there supposed to be a photo in that post?

 

[hotshot]

Added the photo

Explore an easier way, you could try to put a smaller piece of inner tube strip over the impulse hole & screw/clamp it all down to block it off. Saves a lot of hole punching.

I make my own oiler diaphragms, so years ago I just made one up less the impulse hole.

When you retest it, note that 5 psig is about equal to -10”Hg, so you need to kick your vac up a bit.

 

[Ginger15]

I have it blocked off now, found one small leak at the spark plug adapter, fixed that, I can get vac up to 10 now, but it still slowly goes back down. Neither crank seals are bubbling, the edges of the oiler gasket aren't bubbling on top, spark plug adapter isn't bubbling, and muffler isn't leaking. I'm stumped. Possibly the carb gasket but I cant get water around it to see if it bubbles. Went around most of the case that I could reach, nothing there as well, cylinder was good too. Here I was hoping this would be easy.

 

[hotshot]

I have it blocked off now, found one small leak at the spark plug adapter, fixed that, I can get vac up to 10 now, but it still slowly goes back down. Neither crank seals are bubbling, the edges of the oiler gasket aren't bubbling on top, spark plug adapter isn't bubbling, and muffler isn't leaking. I'm stumped. Possibly the carb gasket but I cant get water around it to see if it bubbles. Went around most of the case that I could reach, nothing there as well, cylinder was good too. Here I was hoping this would be easy.

You mean pressure test up to 10 psig?

Soap & water gets sucked in at 10”Hg vacuum & you won’t ever see bubbles. It can also rust the bearings in short time, so never use soap or water test under vacuum.

Pressure test first. Use a small paintbrush & soapy water. Look for bubbles. Stay below 8 psig, as that’s all a standard oil seal is rated for.

Lather up the intake area again really well, plus the oil tank vent cotter pin when pressure testing, as an internal case leak to the oil tank from failed case seam sealant will come out there!

If you pass pressure & fail vacuum, then use light grade (like 3-in-1 or sewing machine) oil on the crank seals, one at a time, facing upwards, to see which seal sucks it in.

If neither seal sucks oil in, then you’re good to go if the vac leak is very slow, you’ve done all you can!

I think Stihl vac specs are 0.4 bar ( -5.88 psig or 11.8 “Hg,) & not dropping below 0.3 bar in 20 seconds. Spec should also apply to your 3700 too.

I like to see no drop at all.

 

[Ginger15]

You mean pressure test up to 10 psig?

Soap bubbles get sucked in at 10”Hg & you won’t see any bubbles. It also can rust the bearings, so never use soap or water test under vacuum.

Pressure test first. Look for bubbles.
Stay below 8 psig, as that’s all a standard oil seal is rated for.

If you pass pressure & fail vacuum, then use light grade oil on the seals, one at a time, facing upwards, to see which seal sucks it in.

Im pressure testing with soapy water, not with vac. I vac after checking all the locations for a pressure leak. Pressure only goes up to about 5 or so and then slowly goes back down. Vac went up to 10 and slowly went down. Ill keep it below 8 from now on, thanks. Back to searching for the leak...

 

[hotshot]

Ok, you’ll eventually find it since you can see the gauge drop.

I’ve seen the cylinder bolts leak around the Allen heads from a bad cylinder gasket, & the 2 intake manifold screws are bad about loosening up at the cylinder, but other Poulan 3700 air leaks were easy to find & fix.

 

[Ginger15]

Whats an easy way to get the two manifold bolts off without removing the cyclinder? Found some air bubbles at the bottom of the gasket.