I am hoping I can get a little help with an old Homelite XL12. Model 3039706 It is the blueish green one so I would be guessing about 1980. It has a Walbro SDC 8 Carburetor. It starts and seems to run OK and you have time to play around with the mixture, then it quits and won't start again. I believe that when it quits it is flooded and there is usually a puddle of fuel in the housing surrounding the carburetor which I think has come out of the carburetor throat. There are a couple of things which I have done but if anything it is worse.
1) Disassembled the carby and blew it out with compressed air. I may have been guilty of blowing air through the nozzle check valve and screen but I am not sure exactly which parts they are. Upon assembly I noted the position of the fuel metering lever (and with hindsight having found a Walbro service manual) which was much higher then it should be. The saw ran about the same as it had earlier. To start it you need the low mixture very lean (out about a quarter of a turn) and high about 1 turn which is about regulation.
2) I put a carburetor service kit in it which did not include the mixture needles, and I did not remove and replace the welch plugs as I could not see how to get them out. I guess that you just punch a hole in them but as I thought the problem was probably the fuel metering adjustment I was a bit lazy and skipped that part. I adjusted the height of the fuel metering lever (the one in the kit was damaged so I used the old one with the new needle) close to specification but possibly a little higher. I adjusted both mixture screws to 1 turn out. The saw started with choke after about 3 pulls and quit when I shut the choke off. Restarted with choke and opened the choke a little slower. The saw ran and idled quite smooth. (I thought I had it) but coughed when revved. It died while trying to adjust the high mixture and had quite a bit of fuel in the housing surrounding the carburetor. I pulled the plug out and it was soaked. I gave it a couple of minutes and turned the mixture screws in about a quarter and started it again. Pretty much the same result, with the saw running at high revs and getting rougher and slower regardless of how much you squeezed the trigger quitting with fuel in the housing and the plug soaked
As I don't know what I am actually doing I thought it best to get a bit of guidance before taking the carby apart again. I would like to see it running as it was an exceptionally powerful little saw in the short bursts that it ran before I started fiddling with it.
If I can get a large enough hammer it will run for awhile just trying to get away from me
One thing many DIYer make as a mistake is to put the metering diaphragm next to the carb body when the order is gasket and then the diaphragm. As the metering lever height it level with metering chamber floor.
And you're correct that you got to use a sharpen punch to get the welch plugs out. But I seldom ever need to remove them as I use an ultra sonic cleaner to clean these carburetors; although, I do like to remove the mixture screw(s) when I am cleaning the carbs which allows the USC access to the back side of many of the welch plugs.
And here is the service manual link for the Walbro SDC.
AVB is right, gasket first then metering diaphragm. Which kit did you install, K10-SDC? Don't remove the Welch Plug if you don't have the tools to punch a new Welch plug back. Welch plug is mainly used to cover the low jets chamber which you said it idle properly means there is no blockage inside the Welch plug. When revs, then you have the problem. The problem is on the H jet. Remove the H mixture screw and squirt with carby cleaner and observe in the venturi if the cleaner coming through the hi jet and shouldn't coming out to the metering check valve. If the cleaner is coming back through the check valve, the check valve might be damaged due to high compressed air.
Thanks AVB and CM I have a bit on at the moment but hopefully will have a minute to pull it apart again today. Yes it was a K10-SDC kit. A bit lower quality then what came out of it. There is a good possibility (50/50) that I have the gaskets the wrong way around. Let's hope so. I did get the Walbro service manual from an earlier post but never thought to use it when reassembling. If that's not the case I will try CM's diagnosis technique and hopefully post the good news tonight
If I can get a large enough hammer it will run for awhile just trying to get away from me
How is it possible we joined ODK on the same year and month?
Take photos of the internal showing metering, Welch plug, check valve, H/L mixture screws remove, fuel pump chamber and mesh, pulse hole and venturi high jet (nozzle/filter side) and low jets (tiny holes/cylinder side) so we can help you to point the issues.
Thanks AVB and CM, Sorry I have been a little slow getting back on to this. I thought I could service a water pump on an outboard motor in half a day, it took two days just to get the thing off. I figure AVB must have done a few things wrong in the past to diagnose that carburetor with the information that I supplied. I am claiming diminished responsibility however. As I know next to nothing about carburetors I started with a nice clean bench and laid out all of the pieces in the order that I had taken them off. Then substituted the new parts out of the kit when I put it back together. I overlooked the obvious that someone had been there before me and neglected to put the gasket back in. I just assumed that the kit was for multiple carbys and the spare pieces were related to them. Reassembled it and it started and ran very smooth, adjusted the mixture a little but it seemed about spot on as it was. Put the bar and chain back on and started on a large dry tuart block, it died under load but after leaning the high mixture in a little cut it up no trouble at all, surprisingly powerful for a small saw. Once again thanks to both of you for your assistance with this.
While I was checking the site for information I came across a couple of references to the Homelite saw, the first one someone was asking why his saw was cutting sideways, it is not likely that he has sharpened it unevenly (although that may be a small contributing factor) but that the bar is no longer level. I had the same problem that it cut at an angle to the depth of the bar and then pinched the bar so it would not cut any further. You can take your bar to most chainsaw service centers and they will grind it level for you. Mine had a chip out of it so I figured they would not do it. I made up a jig with a bit of sand paper stuck to a board and a right angle. It did not take very long as I get bored easily (probably a bit less then it would have taken to drive to the Stihl shop and back. It seems to have been much more successful then I had hoped with the saw cutting true. You can also turn your bar over.
The second item was about automatic oiling on this saw. I had just assumed from the way it is set up that it was a manual oiler, but my saw looks pretty similar to the one in the earlier article (which was a slightly younger saw). It is probably a moot question as the earlier article said it was not possible to get the parts any more, but I was wondering if any one could tell me from the pictures if this saw was likely to have an automatic oiler hidden away in there somewhere.
Again thanks to both of you.
If I can get a large enough hammer it will run for awhile just trying to get away from me
I can't find anything on the model you gave. Can find and post the UT- number? But if Remember correcly it does have oil pump hidden behind the clutch/drum for driving the chain. It been a few year since I had an old metal blue version in my shop.
It seems like that copper tube/pipe is coming from the chain oil tank and going towards the clutch. There must be an oil pump behind the clutch which is driven by the shaft through a worm gear. Check if might be broken and not pumping the oil. Check with AVB message as well he also mentioned this.
Thanks AVB and CM The saw oils pretty well using the plunger on the handle as a manual oiler, as it is unlikely that I would be able to get parts for it in any case , I don't think I will be pulling it apart to check. If I have need to take it apart later I will have a look. I have posted a photo of the serial number but unfortunately if it ever had a suffix it is impossible to read now.
If I can get a large enough hammer it will run for awhile just trying to get away from me
