562xp Hot start?

[Andyshine77]

First off I want to be clear I have absolutely no brand preference whatsoever, and at this time I own 7 Husqvarna saws, more than any other brand. This thread and the fallowing video is not intended to bash this model, Husqvarna, those who sell them, or use them.

With that being said, my new 562xp will not restart after use in hot humid 90° weather, even when only sitting a minute or two. The primer would not pull fuel, and the saw was obviously not getting enough fuel from the carb. The saw would often fire rev for a second and die, if you touched the throttle the saw would die. Vapor lock is likely the problem, but what is actually causing the ongoing issues with these saws I really do not know at this point. When the saw is running, it is a pleasure to use and could very well be the nicest running stock saw I've ever had my hands on.

So what are your thoughts?

Here is the video, I apologize for the video quality, it was taken with my phone.

 

[CoreyB]

That was painful to watch. How frustrating. Hopefully someone can come up with a solution.
Is this with trying the special starting procedure that is supposed to be in the manual? I have seen many refer to that.

 

[Andyshine77]

Is this with trying the special starting procedure that is supposed to be in the manual? I have seen many refer to that.

That made me laugh out loud.[emoji1]

 

[wde_1978]

My PS-7900 has restarting-after-sitting-hot issues, but Your 562XP is extreme!

I wonder whether deleting the primer bulb would mediate the issue Your saw has as my PS-7900 does not feature one and actually can be revived with 10-20 pulls.

My PS-7900 is also starving for fuel!
I pulled the plug numerous times to check for flooding AND to help cooling and venting the cylinder.
The plug was never wet nor did it ever made any difference leaving the cylinder "open" for a while, it would still require over a dozen pulls to sound off.

Do not engage choke, but if possible engage half/full throttle lock - that seems to work for my PS-7900 when she refuses to restart.
Also, after running Your saw hard let her idle for a minute on the ground preferably in the shade.
Restarting and bliping my PS-7900 a couple times within the next 1-2 minutes after running her hard also seems to mediate, even counteract, the vapor lock phenomenon.

I noticed hard restarts after shutting off while hot before on my PS-7900, but I used to think it was a freak coincidence.
This year though I bucked my neighbors and my uncles firewood logs, fuel tank after fuel tank, and I can confirm that my PS-7900 has an issue regarding this phenomenon.

I hope You can at least mediate the issue Your saw has.
It is a nice looking saw!

P.S.:
Modern saw design flaw, the saws are becoming too compact - they are unable to expel the heat they generate.

 

[7sleeper]

I remember a member mention here that letting the saw idle for ~30 sec was enough that the problem went away without any further procedure.

Good luck!

7

 

[Chris-PA]

What you showed there was classic vapor lock, and while that's maybe more extreme it has become routine for me over the last few years. I'm not 100% sure it has happened with all of my saws, but I think so, and only a couple of those are strato and none are AT. Sometimes it's mild and sometimes it's been as bad as you showed, and I just couldn't get them going again. I've had hot saws fire and continue to idle on full choke.

Mostly I've just learned to work around it, which means never setting the saw in the sun, trying not to leave it off too long, preferring saws with separate controls and carbs that don't have an automatic choke shut off. And I always bring a backup saw if I'll be cutting in the heat.

Is your fuel E10?

I'm convinced the fuel is boiling in the carb, although it could be in the lines. The carbs are basically the same on all saws, and the characteristics of a given fuel can will be the same too. So if one saw is worse than another then it must be due to a hotter engine, or some effect where the carb is more enclosed or the engine heat travels to the carb more easily. It could be a hotter cylinder from a leaner mixture, but my saws are not AT - although I don't set them fat either. Then again I run E10 which makes it worse.

Husqvarna has recently modified the top cover for that saw with extra vents, so that's probably a clue.

 

[J.Walker]

I've had some restart problems too! So in hot weather I take a old school saw like a 372.

 

[c5rulz]

I WAS a big fan of the auto tunes when they first came out, (I am on my 2nd 562 and one 550,) now not so much.

 

[Chris-PA]

I WAS a big fan of the auto tunes when they first came out, (I am on my 2nd 562 and one 550,) now not so much.

I'm not sure vapor lock has anything to do with AT. I've dealt with it for years and made threads about it and talked about it quite a bit - I have no AT saws. I think it is more of a consequence of how the saws are constructed and how the fuel system is enclosed.

 

[Jeffkrib]

Often wondered if a few pumps with a little hand held spray mister through the cooling vents onto the outer surfaces/side of the carb will suck out enough heat to solve the problem quick and easy and yor off again.
May be worth a go!

 

[pro94lt]

I've had issues with mine, but with mine I came to the realization that on mine I have to put it on fast idle... The next question is and I've noticed that some saws the fast idle is not very fast can you check with a tach how fast your fast idle is? I'm just shooting at the moon but I think it's worth a try

 

[CR888]

You must not have read the owners manual! Haha I just wanted to say that. Vapour lock is a heat induced problem, you can stick heat shields in vulnerable places and possibly fix the issue. Though at the price these saws are it should not be up to a customer to do such mods. I think on hot humid days when it may occur letting the saw idle for a minute or two prioe to shut off is good practice. I've found under vapour lock a restart with the throttle at WOT is the only way they will restart short of waiting until things cool down. Ordering the new vented covers may reduce this issue too. My Solo pole saw does it in summer and it pizzez me right off when you r half way through a job. Its easier to start a trimmer/pole saw holding the throttle at wot than a saw but if your creative it's possible. Slightly dangerous but possible.

 

[GrassGuerilla]

 

[sunfish]

 

[mountainlake]

I'm not sure vapor lock has anything to do with AT. I've dealt with it for years and made threads about it and talked about it quite a bit - I have no AT saws. I think it is more of a consequence of how the saws are constructed and how the fuel system is enclosed.

You can bet auto tune has everything to do with vapor lock, they run lean and hot. Steve

 

[Chris-PA]

You can bet auto tune has everything to do with vapor lock, they run lean and hot. Steve

I can assure you AT has nothing to do with any of the vapor lock problems I've ever had.

 

[sunfish]

You can bet auto tune has everything to do with vapor lock, they run lean and hot. Steve

 

[GrassGuerilla]

I can assure you AT has nothing to do with any of the vapor lock problems I've ever had.

I was told a few years ago that vapor lock had been basically eliminated from modern designs. Dismissed as a fool for thinking it could be vapor lock. Seems to me that while moving the fuel tank, carb etc has greatly reduced it, it's still possible when conditions are right. So if this comes down to boiled fuel in a heat soaked saw, I don't think we can completely dismiss auto tune.

I think it'd be interesting to compare head temps on auto tune saws to non at saws to try to see if they're actually running a bit hotter. Doesn't seem unreasonable at all to think that the husky engineers may not have allowed for enough cooling to compensate for engines running leaner than prior pro saws. Speculation? Sure... But what else ya got?

 

[Chris-PA]

I was told a few years ago that vapor lock had been basically eliminated from modern designs. Dismissed as a fool for thinking it could be vapor lock. Seems to me that while moving the fuel tank, carb etc has greatly reduced it, it's still possible when conditions are right. So if this comes down to boiled fuel in a heat soaked saw, I don't think we can completely dismiss auto tune.

I think it'd be interesting to compare head temps on auto tune saws to non at saws to try to see if they're actually running a bit hotter. Doesn't seem unreasonable at all to think that the husky engineers may not have allowed for enough cooling to compensate for engines running leaner than prior pro saws. Speculation? Sure... But what else ya got?

It got to be a tough design issue, as the saws are so small and you've got a large and very hot chunk of aluminum near a small cool chunk of aluminum with fuel in it. Then you shut it off and all cooling air stops blowing over the cylinder, and stops flowing through the carb. Then the carb starts heating. It doesn't take long to get to the boiling point of the fuel, and anything that either increases the heat, traps more of it under the covers with the carb, or reduces the boiling point of the fuel is going to make it worse.

In my case I've never had an AT saw but have been dealing with vapor lock for years, and that is partially because I use E10 fuel and I don't set my mixtures very rich. Having lots of extra fuel that isn't burned probably helps reduce engine temperatures while running quite a bit, so it the cylinder may start out at a lower temp when it's shut off - but that's just a guess and as you said it could be measured.

So I don't know what the difference is between a saw that has a vapor lock issue vs. one that doesn't. For some reason it's a bit hotter at shut off, or the heat is trapped in with the carb more, etc. Maybe they reduced the fan size to cut weight? I'm sure the engineers at Husqvarna know, and they just cut vents in the top cover - maybe that was just the cheapest quick band-aid they could come up with or maybe it's a real improvement.

 

[blsnelling]

I have a customer, @porsche965 , that has reported the same to me on numerous times. EVERY TIME it's near 90 or higher, this happens. It's not the fuel source or the alcohol content. It will do it with pure canned fuel. He's tried every imaginable method of shutdown and starting to remediate this problem. The ONLY thing that works is to set it in the shade and let it cool off.

John also mentioned that, even after re-fueling, bubbles will be coming up through the fuel as if being blown into with a straw. This is with fresh, cool fuel in the tank. Therefore, the issue doesies not stem from hot/boiling fuel in the tank. It's somewhere in the fuel system.

I as well am not pushing or knocking any brand, but MTronic saws do not exhibit this problem. It's a shame that such a great running saw has such a critical flaw.

I, as well as Andre, am very interested in hearing what others know and have to say about this issue. I'd love to see @spike60 weigh in, as I trust his knowledge as much as any.