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Burchie70

Burchie70

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I have a Homelite XL2 Auto that I’m having issues with. The saw was given to me because the guy couldn’t get it to fire at all. I rebuilt the carburetor, checked and cleaned the reed, put in a new gas line and filter, spark plug, duck bill in fuel tank and also cleaned the points, adjusted the points gap(which was way off) and checked the air gap. I also checked the compression before doing all this which was 135 psi. I got the saw to start and rev up but then quits. I have to use the choke to restart but then it does the same thing. I started with the low speed at 1 turn out and it got a little better as I backed the low speed out all the way to 3 turns but still quits. I pulled the plug and it’s dry and a grayish color. Where should the low speed be to start with before tuning ? Anyone have any ideas for me to try ?
thanks for any help
 
Old2stroke

Old2stroke

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It sounds like you still have a carb issue. There are many reasons why a carb won't deliver fuel except when being choked, one of the most common ones after a rebuild is the inlet valve control lever is set too low. Is the fuel control diaphragm in the right way so that it's button will operate the control lever? Fuel pump diaphragm in right with the gasket on the cover side? Not sure how that saw gets the impulse from the crankcase to the carb to operate the fuel pump, if it gets it through the carb mount gasket, make sure the gasket is in right and not blocking the passage. If it gets the impulse from a separate line from the crankcase, verify the line is good and working. If the carb is working and the saw is healthy, 1.5 turns out on both the L and the H screws should get it to run well enough to be tuned from there.
 

Okie

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Does that one have the primer bulb?

Sounds like maybe a fuel delivery issue.
Did you replace the fuel lines and clean the in tank filter?
I've seen them carbs act like that. (even after being kitted.
 
Burchie70

Burchie70

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farmguy It’s a walbro HDC15.
Old2stroke I didn’t adjust the metering lever height and the diaphragm is in the right way so the button hits the lever. The diagram I have for the hdc15 shows the diaphragm goes on the cover plate and the gasket between that and the carb body ? Is it supposed to be the other way around ? It gets the impulse through the reed plate and then through the carb. I checked that gasket and the reed plate and both ports are open. And this saw only has the low speed jet, no high speed adjustment.
okie no primer bulb and gas line and filter are are new
thanks for the help guys D1EFAB5E-783A-4B00-8A68-C41E179DE203.jpeg
 
farmguywithasaw

farmguywithasaw

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Ok # 12 could be your problem as well it is a check valve for the high speed circuit. It can be clogged under that screen causing it not to run right. Also if the check valve won’t seal it causes the idle to lean way out I believe. Something about it back feeding air into the idle circuit
 

Okie

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Here is a link to Walbro HDC carb service manual from the Horses mouth (walbro)


Here is another link from the Walbro site for several of their other small carbs: (for possible future reference if needed)

What is the UT number on your saw?
(the reason I ask this is sometimes you can find a clone carb over on flea bay for around $15 but you have to use your UT number and look at the pic's of the carb carefully to make sure it bolts up and the linkages are the same.

Don't mean to discourage you but I've seen couple of them XL2 carbs that were bad internally (probably due to non-serviceable check valve bad)and would not operate a saw. Most user friendly way to determine such is by subbing a donor carb for a test run. Sometimes as a last resort after knowing for sure that it's a bad carb and my own equipment I would strip the carb down to it's body, heat up some water, mix 50/50 white vinegar and warm water, soak the carb for about hour then gently blow out the passages making sure the screen is clean then mix up some baking soda (spoonful in water and soak the carb for 15 min's.
The baking soda mix stops the vinegar acid from further working on the carb body. (the vinegar is a weak acid. Wear rubber gloves to keep the aluminum from turning your fingers black. (due to the vinegar reaction to the aluminum sometimes.
I also use this 50/50 vinegar mix in a UltraSonic tank for small carbs with good results. Do not use high pressure air when cleaning the carb passages or you will ruin the internals and blow out welch plugs. A spray can of carb cleaner (and eye protection is ok for blowing through the passages during final cleaning after the soak in vinegar/water.
 
Old2stroke

Old2stroke

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farmguy It’s a walbro HDC15.
Old2stroke I didn’t adjust the metering lever height and the diaphragm is in the right way so the button hits the lever. The diagram I have for the hdc15 shows the diaphragm goes on the cover plate and the gasket between that and the carb body ? Is it supposed to be the other way around ? It gets the impulse through the reed plate and then through the carb. I checked that gasket and the reed plate and both ports are open. And this saw only has the low speed jet, no high speed adjustment.
okie no primer bulb and gas line and filter are are new
thanks for the help guys View attachment 810495
The diagram shows the correct assembly. With the fuel control diaphragm the gasket is between the diaphragm and the body. With the pump diaphragm it is opposite, the diaphragm goes flat on the body and the gasket goes between it and the cover. The check valve can certainly screw up the function of the carb, it contains a small rubbery disc that is subject to deformity if alcohol is in the fuel and can stick open, closed or just be intermittent. They can be replaced but dealers never stock them and they aren't part of a kit so they have to be ordered but they are cheap in the USA. When you clean a carb it is important to use a spray can of carb cleaner and make sure that it is blowing freely through the idle port at the throttle plate and the transfer port(s) behind the plate as well as the main jet in the venturi. May have to remove welch plugs to confirm this.
 
Burchie70

Burchie70

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Ok thanks I’ll take a look at this later today and post results. I cleaned the carb with carb cleaner with all the gaskets and needle valve out but didn’t look at the check valve that closely
 
Burchie70

Burchie70

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I tore the carburetor back apart and checked the metering lever which was quit a bit higher than the carb body using a straight edge. Also I removed the clip and small screen where the check valve is according to the walbro parts diagram. There is nothing in the orifice where the check valve goes(as in no check valve at all). Would I be able to see the check valve ? I have never pulled this screen off on the carburetor so maybe whoever rebuilt it before me lost the check valve. Also on the end of the carb there is another small screen held in with a clip. It’s on the end that mounts to the reed block. Is this just a screen or is there something behind it ? I can’t get the clip out to remove the screen. I’ll attach photos. Thanks for the help 3E9315F6-143A-4BE9-A3C3-E4DE04D24269.png 5AC3B90E-A85A-4AC1-A023-3CD93D828F88.png
 
farmguywithasaw

farmguywithasaw

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There should be a little disk in that hole rubber or fiber if you shine a light in the the hole and can see through it it’s gone. You can get a replacement on eBay you will have to pop out that brass seat to put check valve in. Kit comes with new one I believe. Not sure on the other one though
 

Okie

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There should be a little disk in that hole rubber or fiber if you shine a light in the the hole and can see through it it’s gone. You can get a replacement on eBay you will have to pop out that brass seat to put check valve in. Kit comes with new one I believe. Not sure on the other one though
Farmguy: or anyone?

Can you post up a picture of a HDC15 kit from ebay that has the check valve? (or from anywhere)
Reason I ask is the kit's I've been buying from flea bay only had the screens, gaskets, diaphragms, pump needle valve, but no check valve.

Walbro at the link I provided above for a Walbro HDC15 indicates that a valve is available in the REPAIR KIT, not the gasket kit.

I do see some valves for a HDC15 listed at this link
as part number 86-520 and a 140-69-8

I've never dug that deep into the check valve removing the screens area of the HDC's due to pg 6 of Walbro's Service recommendations for the HDC carb.
 
Old2stroke

Old2stroke

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Hard to tell from the diagram what's going on with that check valve. In the diagram it looks like a regular check valve but in fact you may not have one. Many carbs have that fine screen in the main jet instead of a check valve. The screen is so fine that the surface tension of the fuel is enough to block air from being sucked back through it at idle. I have never seen a carb with both the fine screen and a regular check valve. Are you sure you have the right parts diagram for your carb?
The other screen is just an input fuel filter, fuel from the pump section should go through a small passage to the front of the screen and then through to the inlet valve. The carb mount gasket blocks the open end. Make sure the screen is clean or it will restrict fuel flow.
 

Okie

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At this link on Pg 6 (last pg at bottom) Walbro under maintenance instructions talks about the screens, etc. mentions 3 fine screens and no good reason to remove them)


Some of these screens are so fine that I examine them with a magnifying glass while they are still in place

I suspect oldstroke is correct , that some of the HDC carbs probably did not even use the check valve. Seems it;s mainly used for just initial starting, maybe.
 
farmguywithasaw

farmguywithasaw

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Hmmm interesting that could be a problem that I am having with my super mini. I have a carb with the check valve and I remove the screen to clean and damaged it and I used the one that came in the kit. Wonder if it’s two fine
 
Burchie70

Burchie70

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The diagram I have says it’s for a HDC 15 carb and that’s what’s stamped on the side of the carb, but I’m not positive about anything. Not sure what I should do now. I can definitely see the pinhole outlet where the supposed check valve goes so there’s nothing in there. I guess I’ll have to do some more research. Thanks for the help
 
farmguywithasaw

farmguywithasaw

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Well I replaced one of those cheaply valves in a carb that had one that went bad it had like a cross pattern machined into it so the fuel could go around the disc and out the hole. Has yours got the same
 
a. palmer jr.

a. palmer jr.

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Not a bad idea to pressure test the carb after you put it back together. Also you didn't mention but it's also a good idea to replace the duckbill valve in the oil tank up near the cap.
 

KASH

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Go to the second page and see the post on homelite xl12 the fifth post down posted by Okie will give you a link to Leons chainsaws he has a video of him repairing a Walbro HDC .It is very informative and shows you every thing you want to know about the check valve and which gaskets and diaphrams to use from the kit also where to buy the check valve disk.I rebuild my xl2 HDC15 carb yesterday afternoon and found the video last night.I tore the carb apart and double checked it.The saw runs good now setting the metering lever is a pain but is very important make sure you set it level with the carb flat edge with no gasket on.The only thing I can critisise is he stretched the tiny spring these are pre set for the correct pop off pressure.
Kash
 
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