Pioneer P-50 rebuild?

[ross01]

I am going to try putting a new piston and rings in my p-50. The compression seems pretty low and am having a hard time getting it to run. Someone told me that low compression can give you fits when trying to get something to run. I had the carb rebuilt but still can't get it to run very well. I don't have a compression tester but an older guy told me that I should be able to pick the saw up off the ground by the rope pull.

The saw will start but runs rough and you have to keep chokeing it to keep it running. When it starts to get hot it is really hard to keep running.

Where could I get a new piston and rings from? I'm sure that it's hard to find genuine pioneer parts but I should still be able to find a piston and rings that would work right? I looked on e-bay but haven't found anything. If someone has a number to call or a part number to get me started in the right direction that would be great. Thanks for the help.

 

[PES+]

You may have a stuck compression release valve (if it has one...I am pretty sure it should) carefully remove the recoil and see if it has a wire actuator that engages the compression release valve when you pull the recoil rope

 

[ross01]

I don't think that it has a compression release valve. The only wires under the recoil are the ones for the ignition and the kill switch. I could be wrong but that is all I see. Any other ideas?

 

[PES+]

Can you post a pic? It would help as I have all those models jumbled in my head

 

[ross01]

sorry can't post a pic. It is yellow with a green handle with a sticker that says p 50 on the air filter cover. I think my dad bought it in the mid to late 70's. Hope that helps.

 

[PES+]

Does it look like this?

http://www.acresinternet.com/cscc.n...0281287a8efd708f88256b00001f006c?OpenDocument

 

[ross01]

Nope, it is the model before that one.

 

[PES+]

Found it

http://www.acresinternet.com/cscc.n...06d054537105f1d288256b00001e38bb?OpenDocument

Remove the muffler and see if the piston is scored. You may just have stuck rings with any luck

 

[lesorubcheek]

You may have a stuck compression release valve (if it has one...I am pretty sure it should) carefully remove the recoil and see if it has a wire actuator that engages the compression release valve when you pull the recoil rope

The bigger p series saws didn't use the easy-arc method for compression release. They had a push button. I don't have an IPL for the P-50, but P-51, 61, 62 use a push button mounted on the cylinder.

Dan

 

[PES+]

Yah....I got them all confused. It doesn't help that most that I get ahold of have blended parts from various models.

 

[ross01]

The piston is a little scored, enough that I can feel small grooves with my finger. The cylinder doesn't have as much scoreing as the piston.

 

[PES+]

If you are up for it...tear it down and see what you have...be very careful not to lose any parts and we can help you along the way. If you have never taken one apart it is a great learning experience but time consuming so be prepared

 

[ross01]

I have it tore down now. Wasn't too bad but the pin that holds the piston to the rod broke when I was trying to get it out, I hope that I can find another one. I am worried about being able to find a new piston and rings for it, any ideas where I should call or start looking? Thanks for all the help.

 

[PES+]

I know I have pins that will fit...the piston can be harder but I can get rings for it. How bad is the piston?

 

[pioneerman]

The piston that you are looking for is #475398 (new part #) or 474529(old original #). The P51 used the same piston and you might find one of those around. The piston pin # is 428367 and is used in the P50, P51, P60, P52, P62, so you have a large selection to work with. How does the nickel coating look on the cylinder? If it is wore out or has deep scratches you are wasting your time putting in a new piston. Sometimes you can find a good used piston and cylinder from a broken saw. When you put the piston together, heat the piston around the pin area lightly so that the pin slides in easier. Otherwise you are going to bend your connecting rod if you haven't already done so.

 

[troutfisher]

You may have a stuck compression release valve (if it has one...I am pretty sure it should) carefully remove the recoil and see if it has a wire actuator that engages the compression release valve when you pull the recoil rope

I have 4 P-26 pioneers that have similar problems, and they do have the easy arc starting. How does that set up work? I suspect the problem is compression, I thought they were just worn out.

 

[pioneerman]

The original P50's did not come with a decompression valve. The P60's and P61's along with the P51 had a decompressor valve on the cylinder that was pushed in by hand and would close from back pressure when the saw fired. Only the small series saws P20's to P28's and the farmsaws used the recoil activated decompressor valve.

 

[troutfisher]

The original P50's did not come with a decompression valve. The P60's and P61's along with the P51 had a decompressor valve on the cylinder that was pushed in by hand and would close from back pressure when the saw fired. Only the small series saws P20's to P28's and the farmsaws used the recoil activated decompressor valve.

Was there any history of problems with that valve? maybe that's what's wrong with mine.

 

[pioneerman]

If you are referring to the P26's, first pull off the recoil and check the decompressor. There is a spring on it that keeps the valve closed for normal operating conditions. With the recoil off you should be able to push the valve open with your finger and it should spring back closed when you release it. There should also be a washer on the end that's about 3/4 inch in diameter that holds the spring. Sometimes that washer comes off and the spring comes off or can't keep the valve closed without that washer. New valves are no longer available, so your only choice is to fix it yourself or find a used one. The recoil has a little lever inside that is attached to a gear. When you pull on the rope the gear is pushed inward to engage the flywheel, at the same time the lever pushes open the decompressor valve. When you release the starter rope everything goes back, and the decompressor valve closes.

 

[pioneerman]

Forgot to mention that the farmsaws and farmsaw ll's use the same setup and the same decompressor valve if you are looking for donor saws for parts.