Testing the spark on a disassembled Poulan 4200, etc.

[BigDee]

I just bought a cardboard box full of Poulan 4200 Counter Vibe, serial 429322.

The seller said it is all roses, and complete except for the top ring, which he broke. He said it ran like the proverbial “real beast” (next to his 018 and MS250) and he took it apart because he wanted to paint it up “like new”!!! And also there was “excess smoke.” The carb, a Tillotson HS168A538, is set 7/8 open for the low, 1-3/8 high. Does that sound like smoke? The reeds look ok.

Before I attempt reassembly, I would like to test the spark components. Can anyone suggest how I do this?

If I cannot find 1.845 in. (46.86mm) rings as listed on the Acres site, can I go with just one, moving the unbroken ring to the top? or could I try a 47mm ring and file it for proper gap? Are they 1.5mm thick? The piston and cylinder are not perfect, but perfectly useable I believe.

There was something like hot-melt glue that fell away from the crankcase seam, making me wonder if there was a problem. Are these prone to leaking there? I don't want to split the case unless it is warranted. The crank action feels ok.

It appears that a previous, previous owner attempted to install a compression release. So there is a hole in the top cover and a brass plug in the top of the cylinder near the spark-plug hole. It does not look like it was leaking. I don't think to hole in the cover is an issue but I wonder about the brass plug's affect on ignition?

And the air filter – it is a plastic box with screen top and bottom. Do I need some good flocking or what?

Other than that, everything just looks very well used.

Any comments, advice, suggestions and recommendation are welcome.

Thanks to all.

Don

 

[BigDee]

Poulan 4200

Our Friend Dandrikop from ebay says based on my measurement the rings are 1/16th inch, which sounds right for olde-English dimensioning. The ring I have, one of two, has square-cut ends, not notched. Can someone with experience with these saws state that the ring ends are notched or square? Thanks Don

 

[a. palmer jr.]

Our Friend Dandrikop from ebay says based on my measurement the rings are 1/16th inch, which sounds right for olde-English dimensioning. The ring I have, one of two, has square-cut ends, not notched. Can someone with experience with these saws state that the ring ends are notched or square? Thanks Don

Some of the old Poulans used the square cut rings..you can tell by looking at the piston, it won't have the normal pin in it but will have a square cut across the groove. And yes, you can get a slightly larger ring and file it down if you're careful. Make sure you have a little clearance with the ring installed, like the other ring has.

 

[BigDee]

Ring gap

Thanks for the info, Mr. Palmer, here and in the Poulan sticky. Although the ring is cut square, the groove has a typical round pin toward the bottom of the groove above the wrist pin on the clutch side. Since the ring I removed is cut square, I still don't know what sort of gap I should allow. Does 8 to 10 thousandths sound about right? Don

 

[a. palmer jr.]

Thanks for the info, Mr. Palmer, here and in the Poulan sticky. Although the ring is cut square, the groove has a typical round pin toward the bottom of the groove above the wrist pin on the clutch side. Since the ring I removed is cut square, I still don't know what sort of gap I should allow. Does 8 to 10 thousandths sound about right? Don

There's a formula for figuring ring end gap but I can't remember what it is. It's something like so many thousandths per inch of bore. 8 to 10 may be a bit too much but I'm not sure. It's better to gap it too much than not enough and 8 to 10 would probably work. You'll know for sure when you get it together and check compression.
It sounds like the engine had the wrong ring in it to start with but it probably worked before, can't see why you couldn't use that as long as it has some gap at the ends.
I found it, bore X .005 for most engines. It's a little higher for a supercharged or nitrous engines. Bore has to be converted to inches so a 2 1/2" bore would be around 12 thou.

 

[a. palmer jr.]

Most cylinders in engines are tapered, that's why they require a bit of end gap on rings, that plus when engines heat up the dimensions change a bit.