smokeing xl

[junkyarddoggie]

Hello guys

I have a little xl trimming saw that I'm having trouble tuning. It smokes like a freight train and I'm all out of adjustment, and do not want to run it lean for obvious reasons. It's spiting fuel and flames out of the muffler. It's got the walbro HDC carb. That may or may not be the original carb. I have several of these saws and trying to build one good one. I have a tilly carb that came off of one of the parts saws but the high mixture screw is broke off so I can't use that one. Is it possible that the walbro HDC carb is to big for the saw? What else besides the carb could make them smoke like that?

Thanks Mike

[MCS]

Junky,
The HDC 65 is the correct Walbro carburetor for this saw. It has both a high and low mixture adjustment.
1. Will the saw idle?
2. If so, does closing the low speed screw make it stop? It should. Open the idle about 3/4 turn.
3. Next, will it run with the high speed screw closed down? If it does then the high speed seat could be damaged. If it will not run with the high speed closed down then the carb would appear to be OK for the most part.

Other possibility for smoke and fire could be ignition. If the saw is missing at high RPMs fuel could build up in the muffler and then light off the next time there is spark. These saws use the solid state module, no points.

Steps 1,2, and 3 will help eliminate the carb as the problem.

BTW, I don't see Tillotson listed for the XL in the IPLs I have. Some had Zama carbs.

[junkyarddoggie]

I got the saw to idle and will stay running. I tried closing the low screw down briefly and it does shut it down. Haven't tried closing the high all the way down. Will try that. I do have another NOS HDC carb to try, but will have to change over the choke lever. That is an option. That toiletson carb was on one of XL my parts saws. According to the Acres site they came with walbro, tilly, and zama carbs. I would rather stick with good old walbro. I've not had much luck fixing the toiletsons when they act up.

I just came up with something else, by looking the specs closer. Seems as if I'm running to heavy of a mixture. All my other older homies I run a 16:1 mix including a little super 2. The little xl calls for a 32:1 mix will try the lighter mix and see if some of that smoke clears up. I just assumed that the xl ran on the same as the super 2.

I grew tired of having to mix a bunch of different mixes for things. So now days it's 16:1 or 40:1. Eliminated the 20:1,32:1,50:1 Some people would have a cow but it works for me, never had a problem.

[junkyarddoggie]

Ok Fuel mix didn't change anything. I got it tuned to where I believe it would cut. It sounds good with lots of power. At high speed it doesn't smoke, but as soon as you let it idle down it smokes so bad that you can't hardly see the saw in your hand. It will smoke up the entire yard.

Closing down the high mixture screw will shut her down MCS. I guess I could try changing carbs again and see what happens. Any other ideas? before I do that.

[MCS]

Sure sounds like the idle circuit is hose up
Here is the link to the Walbro service document for the HDC. Maybe some theory will help understand what's going on
Walbro HDC
Any chance that the idle mixture screw and the high speed screw are swapped Not sure if that's possible on the HDC but I know on some carburetors it can be done.

[polardoo]

I have a craftsman(electrolux) that had a bad check valve in the crankcase to the oiler. On occasion it woulkd smoke like mad on bar oil. Im not familiar with the oiler on the xls but a possibility?

[MCS]

Yes this is a possibility and the symptom seem to fit. At high RPM the saw is able to digest a little extra oil but at idle it gets more than it can handle.
It could be the check ball or a leaking diaphragm.

[junkyarddoggie]

Great carb cut away picture by the way. Yes it is possible to switch the mixture screws on the HDC carb. They will thread into either hole.

Yep I found that bar oil is a big part of the problem. There was just to much oil all over the saw. I tore the saw down earlier this evening and I could see bar oil in the cylinder through the muffler hole. Then decided to look at the oiling system. There is a rubber diaphragm which seems to pump the oil. Also a hole in the crankcase for vacuum, so I can see how the oil is getting in there. Any way, the diaphragm was dried up and very hard. Took one out of my parts saw and installed it, put the saw all back together. It made quite a bit of difference cut down on the smoke to where I think It's usable now. It seems to oil the bar better now as well. However it still seems like it's leaking some bar oil into the crank case. Had something come up and couldn't finish testing it, will have to run the saw some more this week and see what it does.
Thanks guys

[junkyarddoggie]

Took some time to get back to it, but ran the saw again yesterday. Replacing the oil diaphragm makes a big difference. It seems to only smoke when you tilt the saw to side with the recoil down towards the ground ? I have it loaded up on the trailer, and ready to put her to use. Hopefully it will start earning it's keep. Had the saw for two years now and it's had more bench time that run time.

Still confused with the goofy oiling system on this saw. Is there any one that knows the ins and outs of the system? I've had it apart so many times, that I'm good and familiar with how everything looks. I could put one of these saws together in my sleep now.
www.cmasalvage.com/xlmini.jpg

[woodplayer]

junkyarddoggie if you have a look at this thread I started and review it in it's entirety should help you understand how they work.
www.arboristsite.com/showthread.php?t=63415


good luck

[junkyarddoggie]

Yes I have been hearing a lot about this duck bill. All the fuel and oil lines were rotted off when I got this saw. I replaced them with new, never found any duck bills. It sure wouldn't hurt to get a duck bills on that vent line. I Know I have my lines hooked up correct. It smokes like mad when you reverse them, tried that last night just to make sure.

[MCS]

Two scans that may help: