Tuning / Limiter Tabs on my PS5100

[kingOFgEEEks]

I have read a couple of older tabs on tuning the sweetheart Dolmar that I own, and it seems that there have been issues with not being able to get them to clearly 4 stroke.

I don't own a tach, although trying to tune this saw is making me wonder if I need to break down and get one.

I last ran her this summer, in 80+ degree heat and high humidity, so I knew right off the bat that a re-tune would be necessary last weekend when I was cleaning up my wood pile.

I was cutting down pieces that were too long for my splitter, so the duty cycle was short - pull start, rev 1-2x to get running well, cut the piece, idle down and shut off. Repeat every few minutes as needed. After the 4th or 5th time of doing this, the saw started up on the first pull, but wouldn't rev up. It seemed boggy, and like it had too much fuel, so I figured it was time to fully warm her up, re-tune, and see how things ran. After making several bucking and noodling cuts in a row to warm things up, my idle was too high, and the chain was spinning. No big deal, I adjusted the L and idle screws to get a good idle, and responsive spool-up. Then I attempted to adjust the high screw.

I opened it all the way to the limiter, and noticed no appreciable difference in engine speed, both under load and unloaded. It cut well, and seemed to not bog any more, which was good, but with no 4-stroking, I'm just worried about smoking my top end. I plan on removing the limiters before I go out again to cut this weekend, but is there anything else I can do? Do I just need to break down and get a tach, since this little beast likes to rev so high? My Jred 2188 is so easy to tune in comparison, that I'm just afraid of getting something very wrong.

Thanks for your help.

 

[hatfield]

Your Dolmar may have a limiting coil, so a tach is really no help. You would need to tune the saw in the cut. There are some great great videos from some members showing you how to tune a saw with a limited coil. Yes, you will have to trim or eliminate the H and L limiter caps in order to get a proper tune.

 

[hatfield]

Here's a great video. Watch it till the end.

 

[Rio95]

You may have a slight air leak that is getting worse with time. If it is getting out of tune like that while your working, normally something is wrong with more than just the carb settings. A pressure and vac test would be ideal, but check your fuel and impulse lines for cracks. If they check out OK, and you don't have the tools for a pressure and vac test, you can spray some WD40 around the base of the cylinder and the intake manifold. If spraying in a particular location makes the saw bog, you've found your leak.

 

[kingOFgEEEks]

You may have a slight air leak that is getting worse with time. If it is getting out of tune like that while your working, normally something is wrong with more than just the carb settings. A pressure and vac test would be ideal, but check your fuel and impulse lines for cracks. If they check out OK, and you don't have the tools for a pressure and vac test, you can spray some WD40 around the base of the cylinder and the intake manifold. If spraying in a particular location makes the saw bog, you've found your leak.

I will check for cracks/leaks when I tear down to remove the limiters, but I don't think that's the cause this time. The tune that I set held all day. It was out of whack because I went from using it in 80+ degree heat and humidity to using it in 45-50 degrees and much lower humidity. I just can't hear it 4 stroke one bit. Hopefully pulling the H limiter and fattening up the top end will help, and if it does, I think I'm in the clear. I just am a bit gun-shy on this one, based on some of the threads I read saying that the 5100 can be a bit tricky to tune.

 

[kingOFgEEEks]

I took the limiters off the carb last night, and visually inspected the intake boot. Nothing appears to be cracked. I'll do the WD40 test when I next go out cutting. Those are the easiest limiters to cut that I've ever seen - I didn't even have to take the rubber screwdriver guide out, I just reached in with a sharp box cutter and snipped them off.

I also checked the two fasteners that hold the jug onto the case with my T-27 scrench, and they were slightly loose. Felt like they were snug but not torqued when I turned them. My scrench can't reach the rear 2 jug fasteners, since the hole is too small, so hopefully I'll get into Harbor freight tonight and pick up a t-handle that will fit. It is possible that there was a slight base gasket leak, based on how the jug bolts felt. What is the torque spec for those bolts?

I pulled the muffler, and there was no scoring whatsoever, and a light coating of oil on the piston, so if there is an air leak, I've caught it in time. I might need to get a vac tester while I'm in HF, just to be sure.

Thanks for the advice guys.