Poulan Exhaust Port Advice Needed

[Hedgerow]

Did you ever get a measurement of the squish?
Just curious what it was...

 

[Chris-PA]

Did you ever get a measurement of the squish?
Just curious what it was...

Nah, I didn't bother, partly because it's a clamshell engine and changing it would have required adding material to the piston. I don't have any way to do that. It would have been interesting to know though.

 

[Chris-PA]

Well, kinda disappointing so far. It will run hard if I keep the revs up, but it has little torque if I bog it. If I push it a little the revs drop and it "4-strokes" like crazy. Now I know I don't have the tuning right yet, but I think the problem is low compression.

This was not a great P&C, rather a crappy one I was trying to clean up. After trying it for most of a tank I checked the compression (as best I could with my lousy gauge) and pulled the muffler and plug to look in. I only got 115psi. Things don't really look too awful in there - there are a couple of shiny section forming on the ring edge, and corresponding polished stripes on the cylinder wall over the exhaust port. They're not grooves, just polished, but it indicates the ring is not seated everywhere yet and must be riding on those high spots.

Just for grins I tried the other flywheel with less spark advance, and that didn't help at all.

I'm going to run it for a while until the ring seats (which may take longer if it's not that regular a surface), play with the tuning and see what happens. It actually runs pretty well if the revs stay up.

 

[Hedgerow]

Well, kinda disappointing so far. It will run hard if I keep the revs up, but it has little torque if I bog it. If I push it a little the revs drop and it "4-strokes" like crazy. Now I know I don't have the tuning right yet, but I think the problem is low compression.

This was not a great P&C, rather a crappy one I was trying to clean up. After trying it for most of a tank I checked the compression (as best I could with my lousy gauge) and pulled the muffler and plug to look in. I only got 115psi. Things don't really look too awful in there - there are a couple of shiny section forming on the ring edge, and corresponding polished stripes on the cylinder wall over the exhaust port. They're not grooves, just polished, but it indicates the ring is not seated everywhere yet and must be riding on those high spots.

Just for grins I tried the other flywheel with less spark advance, and that didn't help at all.

I'm going to run it for a while until the ring seats (which may take longer if it's not that regular a surface), play with the tuning and see what happens. It actually runs pretty well if the revs stay up.

Can you video it at full throttle in and out of the cut?

 

[Chris-PA]

Can you video it at full throttle in and out of the cut?

That would take some time to put together. I tried tuning it in the cut, and it wanted the H much leaner than I had it set no load. Ran much better that way, and that's consistent with it being too rich. But it didn't sound too rich!

I didn't have enough time to work with it any more and I know it's not right yet. I have to put the other flywheel back on and try again. It may be that tuning is really the main problem.

 

[Hedgerow]

That would take some time to put together. I tried tuning it in the cut, and it wanted the H much leaner than I had it set no load. Ran much better that way, and that's consistent with it being too rich. But it didn't sound too rich!

I didn't have enough time to work with it any more and I know it's not right yet. I have to put the other flywheel back on and try again. It may be that tuning is really the main problem.

Is the coil rev limited? I know very little about that model saw... I do know, however, tuning can make a huge difference. Tuning in the wood can present its own challenges... Ideally, the saw should burble when you pull it up, and clean up when you get in the cut... Of course I've seen ported saws that are constantly wanting to bounce off their rev limiter, even when they aren't running lean...

 

[Chris-PA]

The coil isn't rev limited, it's a pretty simple saw. I did the initial tune so it sounded like it was 4 stroking no load. Tried it a couple of times wide open, enriched the H until I just got a bit of that blat sound. But that seems way too rich in the cut. I wasn't comfortable leaning it too much though. I need more time and was rushed because we had somewhere to go. Of course there is only an L and H adjustment, and it seemed like it would pull well at revs but if it got down in revs it would get stuck and sounded very rich. When I tuned it in the cut I was able to get it to pull better by leaning it.

Too many beers tonight and I'm not being clear - what I felt was appropriate no-load seemed way too rich in the cut when the revs dropped, but what pulled better in the cut didn't sound like it was 4-stroking no load.

I'm a little concerned that the compression is low but that at higher revs it holds cylinder pressure better - but I need to just take a little time and work through the tuning first.

I did learn something very important though - if you get a hole in your jeans just below the crotch on the right leg, your pants leg will fill up with chips. This can be uncomfortable.

 

[Hedgerow]

The coil isn't rev limited, it's a pretty simple saw. I did the initial tune so it sounded like it was 4 stroking no load. Tried it a couple of times wide open, enriched the H until I just got a bit of that blat sound. But that seems way too rich in the cut. I wasn't comfortable leaning it too much though. I need more time and was rushed because we had somewhere to go. Of course there is only an L and H adjustment, and it seemed like it would pull well at revs but if it got down in revs it would get stuck and sounded very rich. When I tuned it in the cut I was able to get it to pull better by leaning it.

Too many beers tonight and I'm not being clear - what I felt was appropriate no-load seemed way too rich in the cut when the revs dropped, but what pulled better in the cut didn't sound like it was 4-stroking no load.

I'm a little concerned that the compression is low but that at higher revs it holds cylinder pressure better - but I need to just take a little time and work through the tuning first.

I did learn something very important though - if you get a hole in your jeans just below the crotch on the right leg, your pants leg will fill up with chips. This can be uncomfortable.

Hahahahahahahaha .... And if ya get a hole at the thigh, it fills your boots...

 

[Chris-PA]

I was thinking about this more today - I used the carb from the 46cc 2775, as it was a known quantity and worked well, and it was the same size as the one that was on the 49cc PP315. The carb I'm using is a WT-285, and the one from the PP315 is a WT-610. They look real similar, but the 610 does show a different metering spring. I think I'll try putting that carb on and see how it runs.

 

[Chris-PA]

Well I don't know where I dreamed those carb numbers up - the 2775 46cc carb is a WT-529 and the PP315 49cc carb is a WT-285. I switched to the carb from the PP315 and it is much better. I tuned it and it's running pretty decent but not really anything special. There is a slight hesitation when I crack the throttle initially and I cannot get rid of it by playing with the L screw. Might play with the metering lever eventually, but it causes no problems once underway.

I pulled the muffler and looked in again after running it and I can see the new ring has what appear to be two slight flat spots on it. There is no visible reason for it that can be seen so whatever caused it must be below the exhaust port. In turn I can see there are two stripes where the ring is not fully contacting the cylinder wall above the port - there is no defect in the wall there, it's just not being polished by the ring. I can't get a good compression reading with my junky gauge, partly because it's pretty hard to pull it - feels like the compression is good actually, but I suspect it isn't wonderful.

It's only got a tank and a half through it, and it's running well enough to use, so I'm just going to run it hard and see what happens to that ring. I never canceled the order for the piston kit - if it ever comes in maybe I'll pull it apart again and consider picking up a ball-hone from Bailey's if the chrome isn't peeling or anything.

Otherwise I still have the stock 46cc motor in great shape, so that may go back in. Of course, I could port that too.......

 

[Chris-PA]

You know, if I paid less time attention to what I know that cylinder looks like and more to how the thing runs, I might actually be impressed! I didn't have lot of time to run it today so I went after some red oak crotches that were down by the road from last October. They were about 28" at the narrowest.

With a 20" bar and 20BPX (love that chain) that thing throws chips half way across the road when it's buried. I don't often wear shorts when cutting, but darn if that chip shower didn't hurt! The carb change really did help a lot. I was bucking and noodling and it can really hold the revs and doesn't bog like it did at first. I have no idea what rpm it is turning in the cut but the sound is not something you'd mistake for a stock saw. If I drop the throttle after running flat out it just drops to a happy idle, no fuss. The very first tip in after idling it can hesitate, but if it's been working there is no hesitation at all.

I don't know how long it will last, but it sure is fun now! Here's some shots - I used the recoil cover from the PP315, so it"s got that green and purple thing going on:

 

[Hedgerow]

That's a good looking saw!!!
It will last just fine as long as its getting plenty of fuel...
Sounds like you got a winner on your hands....!!!

 

[Chris-PA]

My redneck cylinder hone:

It's a 1-1/4" wooden dowel with some thin adhesively backed foam wrapped around it, and some 400grit sandpaper wrapped around that.

I decided that I was not happy with the way the cylinder looked, and I tore it apart again. I definitely could feel some defects, but I was not going to spend the money for a 44mm hone, as it doesn't fit any of my other saws. Also, this engine may not be a sow's ear anymore, but it's never going to be a silk purse either. I've got a good 46cc engine that looks perfect inside - so I'm not spending any more on this thing.

Anyway, this worked pretty well. It's a lot cleaner and smoother now, and the saw does run better. I had to change the carb setting a bit, and I can feel that it has more compression on starting.

 

[rmh3481]

WHW, Good Job! Hope you gutted the muffler to help it breath.

Also, be careful with any hone on a plated cylinder. The plating is really thin, measured in microns, so its too easy to ruin a cylinder. If a cylinder is scored badly above the exhaust port, any acid you apply will get between the plating and the cylinder and render it useless too.

 

[Chris-PA]

WHW, Good Job! Hope you gutted the muffler to help it breath.

Also, be careful with any hone on a plated cylinder. The plating is really thin, measured in microns, so its too easy to ruin a cylinder. If a cylinder is scored badly above the exhaust port, any acid you apply will get between the plating and the cylinder and render it useless too.

Thanks - the muffler was opened up before I started this phase of the project. Also, I realize the plating is thin, which is why I stuck with 400 grit, and it looks like the plating is intact.

Really, this was the last attempt before tossing this engine in the garbage. It came as part of a 49cc PP315 I got that was supposed to be rebuildable but was totally trashed, so I thought I'd try to salvage something from it. The ring was not seating properly and I tore it open again to see if there was anything I could do, and I'm hopeful this will work better. The thing actually ran really well, at least at higher rpm, and now it feels stronger down low too.

I used it to noodle some planks out of an ash log (I want to make axe handles), and it really ran well. We'll see how long it holds up!

 

[Chris-PA]

Well, so much for the PP315 engine. It ate a circlip and it is no more! I was noodling some knotty persimmon, and running it hard, and it was working very well. Then I heard a faint click and it quit, and I could tell that was all she wrote. I pulled it apart and found the lunched circlip, but I'm at a loss as to why. Shame too, as the cylinder was looking really nice and clearly the ring was seating better.

I'm going to start a new thread to try to figure out what happened.

 

[Hedgerow]

Well, so much for the PP315 engine. It ate a circlip and it is no more! I was noodling some knotty persimmon, and running it hard, and it was working very well. Then I heard a faint click and it quit, and I could tell that was all she wrote. I pulled it apart and found the lunched circlip, but I'm at a loss as to why. Shame too, as the cylinder was looking really nice and clearly the ring was seating better.

I'm going to start a new thread to try to figure out what happened.

When you installed the cir clip, did you seat it and then rotate it in the groove 180 degrees or so? Sometimes they don't get in the groove correctly...

 

[Chris-PA]

It was in the groove. Based on discussions in this thread: http://www.arboristsite.com/chainsaw/206965.htm I've come to the conclusion that the clip did not have the proper tension. That left it loose and it simply pounded itself and the groove, until it either broke or got loose enough to pop out.

Now I just have to decide if I'm going to port the 46cc engine before I put it in or not. It ran very well just the way it is, but I'm still deciding.

 

[Hedgerow]

It was in the groove. Based on discussions in this thread: http://www.arboristsite.com/chainsaw/206965.htm I've come to the conclusion that the clip did not have the proper tension. That left it loose and it simply pounded itself and the groove, until it either broke or got loose enough to pop out.

Now I just have to decide if I'm going to port the 46cc engine before I put it in or not. It ran very well just the way it is, but I'm still deciding.

Port it... You know how, and it makes an"ok" saw more of a pleasure to run...
Just use new cir clips this time...
:msp_wink:

 

[Chris-PA]

There's no need to even take them off! I'm leaning toward porting it, just 'cause.