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HELP! Homelite SXLAO frustration

numnutz6383

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Warning, I'm cross posting from other forums so this is a LONG post.

So I have this SXLAO that I picked up a few months ago. It came to me running, but not well. Previous owner replaced the fuel line, filter, duckbill valve, and if I remember correctly, did a carb refresh. Since then I found the p+c was scored and the flywheel side seal failed a vacuum test (passed pressure interestingly). I swapped the p+c with an aftermarket set from Traverse Creek, changed the seal, and did my own carb kit.

I got it running but it idled erratically. Coming down from WOT it would get stuck at a high idle for a few seconds (enough that the clutch engaged), and then come down. It also raced when tilted to the flywheel side, and shut down tilted forward. After I changed the flywheel seal it passed a pressure and vac test so I was fairly certain it wasn't that, but sprayed some brake cleaner on both sides anyway. It didn't shut down with that. Then I thought maybe the fuel line is too short or leaking and it's sucking air, but both seemed fine. But I did find the carb (Zama C2-20-02) wasn't holding pressure, a really slow leak existed, which is weird since it held when I installed a new carb kit.

I thought maybe the inlet needle was leaking, but when I took the metering side apart the needle looked fine. I took apart the pump side, and found the pump diaphragm looking like this:
1000006874.jpg
This diaphragm came from a brand new OEM carb kit from Zama, and after less than a tank of fuel through it. I run ethanol free VP fuel with Amsoil Saber at 40:1. Regardless, the diaphragm was replaced.

Today I had some cleanup work after a 70 foot piece of pine decided to split from the main trunk. Figured it would be a perfect time to finalize the tune and run this thing. Well, I had the same symptoms as last I described in the original post, but also developed some concerning things on top of that. I still had the erratic idle, idling high coming down from WOT, shutting down when tilted down, racing when tilted sideways, but then today I also developed at WOT it would come to about 9.5-10k RPM, and suddenly race to 11K.

So I figured I must have a vacuum leak. So frustratingly (seriously taking that carb off is huge PITA, curse those engineers), I took it apart AGAIN expecting a leak and tested. Nada. Zilch. Passed with flying colors, and I even kept it pressurized/vacuumed over 30 minutes. Needle didn't budge at 10 or 5 psi pressure or 15 mmHg vacuum. I had it sealed between the reed valve and the carb, so to me it must be the carb.

Could this be a bad check valve (it held vacuum when tested for what it's worth)? What other carb specific issues could cause these symptoms? What am I missing?
 

jacktheripper

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How is the sealing surface on your crankshaft? Maybe attempt a pressure and vacuum test while slowly rotating the crank. I wonder if it is only sucking air when rotating...
 

Partner

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What helped me was reversing the reed valve. No additional costs other than the fuel line, I'm missing the duckbill in the fuel cap and the large tank gasket is leaking slightly
 
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