2 nearly identical issues with a 575 and 576 (carbed) I wonder if you could help brainstorm

[RIDE-RED 350r]

I am fiddling with a 575xp that I did a complete overhaul on and a carbed 576xp that I did a carb kit on.

Both saws seem "cold blooded" on startup. The usual full choke, pull till it pops, release choke and fast idle startup doesn't really happen with these. They will start briefly on fast idle but then die. They will do this 3 or 4 times before they will stay running. Once they stay running and after warmed up they seem to run fine in the cut and idling. I replaced the carb on the 575 with a 576 carb as I was told the 575 carbs were problematic and the 576 carb would be a good upgrade to address the issues.

Now when I rebuilt the 575 it got new crank bearings and seals. I have not built/bought a leak tester yet, but I really don't think this is an air leak issue because once they get past that initial cold bloodedness on startup, they both cut and idle fine.

I got the 576 handed to me with an acceleration issue, not so much the cold blooded start up issue. I put a carb kit in it, set the metering lever height, and after tuning it seemed good to go. I gave the saw back to the owner and it now does the cold blooded issue the 575 does. This is strange to me and I understand that I missed the cold blooded startup issue with the 576 as once it was warmed up prior to final tuning it started fairly normally cold. Again, I really don't think this is an airleak issue as once they get past that initial cold start hiccup, they idle stable, and cut fine.

Am I missing something here?? I have not experienced this issue with older style saws

 

[beaglebriar]

I've never worked on 575/576. What carb is on them?

 

[RIDE-RED 350r]

I'd have to go out and look... But they are the full on strato type carbs that have the extra clean air butterfly below the main carb. Zama is the brand.

In some ways they are weird saws to work on... mainly in the area of getting the carb mounted. It can be a PITA

 

[Mark71gtx]

I would fiddle with the low adjustment screw. Maybe richen it a bit and see how it acts then. When I have that problem, that is usually the fix. Once it acts right, get it hot and then shut it down. Make sure it will start back easily hot. If it don't start back on the first or second pull, lean it back until it does.

 

[RIDE-RED 350r]

Thanks. I will re-tune with favoring a bit richer setting on the low side in mind.

 

[Mark71gtx]

Let us know how it works out for you.

 

[RIDE-RED 350r]

Will do

 

[RIDE-RED 350r]

Well I fiddled with the 575 today a little bit.

Since the problem seems to be isolated to initial cold start-up, before I did anything I opened both jets a bit more than 1/4 turn each from where they were. Problem still remains. When I rebuilt the saw, I also replaced the fuel line and filter so I don't believe that those are an issue. I then started over at 1.25 turns on each and the problem got slightly worse. I ended up with them both out beyond 2 turns each and while the issue subsided slightly, it remains. It will start on fast idle after the initial pop with the choke on. But it speeds up and acts lean then dies. If I am quick to pull the choke back out I can keep it running. Once I work through this process and the engine starts to warm up it will end up running good in the cut and idling. It's almost like the saw is sluggish to pull fuel on initial startup???

I still have the original 575 carb on my bench. Ill take it apart and check it over and swap it in and see what happens.

This has me scratching my head, I really don't think it has an airleak issue as the crank seals are new OEM and the carb boot was closely inspected and found to be serviceable. Plus, once it gets past this initial cold start issue the darn thing straightens out, runs well, and holds a stable state of tune.

To be continued.........

 

[Boo Boudreaux]

Maybe the pump accelerator inside the carb. Zamas have those buggers in them ~!~!

 

[jacob j.]

Try pulling the diaphragm and fuel pump covers, gaskets, and membranes and soak both carb bodies over night in clean, fresh, straight gas. I've had some luck with that method with carbs exhibiting those symptoms.

 

[old guy]

I soak all my carb bodies in sea foam, they always come clean.

John

 

[RIDE-RED 350r]

I do have a can of Napa carb soak solution. It comes in a 1 gallon can just like a paint can and has a little strainer basket in it. The stuff has the viscosity of 10w-30 motor oil and does work quite well. I have had good results with it cleaning 3-wheeler carb bodies from trikes that sat in a garage for ten years without running and had stopped up idle and pilot circuits in the carb body where they can't be cleaned with any type of physical tools. Just chemicals and compressed air.

Maybe I'll give that a try. And while that carb is soaking I might try the original carb on it. If the problem is exactly the same with a different carb, that would lead me to suspect a problem elsewhere....

 

[RIDE-RED 350r]

A little update:

It's been a VERY busy weekend for me, but I was able to get in a little tinkering time with this 575. I pulled the covers and checked the insides of the original carb and found it to be spotless inside, so I swapped it in.

The saw started properly and maintained the fast idle without stalling out.

However, it doesn't like to take throttle. I suspect that the H jet needs to be opened up more and it's at max already. But, I found the jet stops not seated on the jet heads making adjustments impossible without pushing the stops onto the jet heads the rest of the way. This is the second carb of this type that I have found in this state with the jet stops not seated, You can turn the stops through their full range of motion but you aren't turning the jet...So, I seated the stops so I could make adjustments, but I'm afraid I need more fuel on the high side than the stop will allow at the moment. No biggie, I'll shave the stops or remove them all together. Once I'm done with that it should just be a matter of dialing it in.

I'll finish it up tomorrow, I'm pooped right now and frankly don't feel like fiddling with it any more tonight.

 

[rattler]

Most of the time if it don't take the throttle it,s on the low side needs fattened up a bit.

 

[RIDE-RED 350r]

Well, I pulled the jet limiters and gave er more fuel and all seems well. I did 3 cold starts and it fast-idled without stalling and takes throttle well now. Took a little while to get some cold starts as I had to let it cool completely to make sure the issue is resolved.

Same guy brought me a little 338XPT that "runs like crap". I confirmed the crappy running condition and went to removing the carb for disassembly, cleaning and inspection. Didn't get far into that little job before I found my smoking gun... Pulled the air filter cover and found NO AIR FILTER! LOL! Filter base was covered in debris and wood chips/dust! Pulled the carb and went about the mission and now it runs great... It's funny the stuff you run across working on things for people.... I have no idea if any internal damage was done or how bad the damage might be. But it can't be to bad because the little XPT runs A-OK now... Picking up a new air filter for it tomorrow and will be returning it to the owner.

 

[rattler]

Glad to hear it's fixed.

Sent from my XT1060 using Tapatalk

 

[Chainsaw Jim]

Did you flush the crankcase out? When running with no filter all those chips and dust can start collecting in the bottom of the crank.

 

[RIDE-RED 350r]

As a matter of fact, I didn't. That's a good idea. Think I'll pull the exhaust and carb and do just that before I give it back. By the looks of that air filter base I'd say it had been run that way a fair bit.

 

[smokey7]

I have seen some terribly dirty crankcase before I don't know if from no filter or not. But tons of black crap comes out with chunks. Sometimes it's a wonder they still run. These saws are super tough. I have never blower one up. Pops has done a few tho. Only one crank wore out, and his 350 has well been a 350 with all of its problems have happened to that saw.

 

[Simondo]

Well, I pulled the jet limiters and gave er more fuel and all seems well. I did 3 cold starts and it fast-idled without stalling and takes throttle well now. Took a little while to get some cold starts as I had to let it cool completely to make sure the issue is resolved.

Same guy brought me a little 338XPT that "runs like crap". I confirmed the crappy running condition and went to removing the carb for disassembly, cleaning and inspection. Didn't get far into that little job before I found my smoking gun... Pulled the air filter cover and found NO AIR FILTER! LOL! Filter base was covered in debris and wood chips/dust! Pulled the carb and went about the mission and now it runs great... It's funny the stuff you run across working on things for people.... I have no idea if any internal damage was done or how bad the damage might be. But it can't be to bad because the little XPT runs A-OK now... Picking up a new air filter for it tomorrow and will be returning it to the owner.

This L jet thing can be critical on Stihl 024 026 and the ms 200 ms 260 in particular iv found if you ever have to work on them Joe. They can be real hard to dial in a good tune if there a tinny bit lean. Heads up in case.