thanks. in the cbfarmall link, Modified Mark was able to fix his by plugging the hole in the top of the nozzle and using the H needle as in a normal carb. will mess with the 2 nozzles I ordered when they get here before I try that.
Homelite Chainsaws
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wasted a couple of hours this morning trying to make the nozzle into a check valve. punched a check valve disc out of a left-over diaphragm, pulled out the split ring. was a ***** to get it out and worse to get it back in. tried it with the H needle all the way in, 1/2 turn out and 1-1/4 turns out. did not work. still revs on prime and dies immediately unless I keep it running.
compression on this thing is insane. if I prime it and it fires right away it's not bad but if it doesn't fire, really hard to pull. seems odd that if it's flooding thru the nozzle, why does it start right away when I prime the carb with a shot of mix?
Is it acting like this? (Crappy video that I made a couple years ago when I was having issues)
exactly what mine is doing. did you ever get it fixed?
Nope. Swapped it for a different carb and never looked back
Nope. Swapped it for a different carb and never looked back
I went back and you said you used a carb from a 700. was that a Tillotson HS26A?
HS26A I believe. The needles are different so you would need to swap the appropriate grommet. The choke rod should be interchangeable but possibly the hole on the lever is smaller. You could easily swap the choke lever from one carb to the other through.
found this bulletin where Homelite switched from the Tillotson to the Walbro WJ27 for the 925. googled around and don't see any for sale.
so, a number of big Homelites, and some other saws used a variety of carbs that were different in 2 ways to add more fuel at high rpm to keep people who don't know how to tune a saw from seizing them up. these carbs had a nozzle and a governor. have discussed the nozzle above. the nozzle is located where a normal Tillotson HS carb has a small welch plug with a screen and a small neoprene disc that acts as a check valve. the nozzle hangs down into the throat of the carb and is connected to the passage that the Hi speed needle screws into.
the nozzle does not appear to come with a check valve in it.
the governor is a large brass plug that screws into the side of the carb.
the nozzle does not appear to come with a check valve in it.
the governor is a large brass plug that screws into the side of the carb.
when the plug is removed, there are 2 small passages in the threaded hole. the smaller passage goes to the fuel pump and appears to supply fuel to the governor. the other passage goes directly into the throat of the carb right underneath the nozzle, which is where the fuel is sprayed into the engine I assume.
the brass governor itself has a recess machined into it which has 2 holes in it and a hole in the end. there is a steel ball and spring inside. my assumption is that under high RPM pressure, the ball allows fuel from the float bowl into the 2 passages in the recessed groove that then goes to the throat of the carb.
it must take a lot of pressure to move the check ball as I put a hose on it and could not get it to move as hard as I could blow.
This is great information! Thanks very much! Max.
The high speed governors likely saved thousands of saws from burning up. Homelite started to add those setups to help folks from running them too lean on the top. The governor is not like a typical ball/spring check found in the oiler system and does not activate through typical vacuum. It operates on an inherent threshold resonance frequency. Once the saw vibrates at the resonance of that “check”, it opens and dumps fuel. This works to moderate the RPM independent of the H needle. If it is malfunctioning and/or stuck open it could dump fuel regardless of rpm. This could explain some tuning symptoms. I tend to block them off with a disc from a soda can or 2-3 layers of spent diaphragm. Easy to eliminate the governor and eliminate that source of fuel. The saw tunes fine without them. If you run them with a heathy burble, they clean up in the cut and you’ve got fresh plumbing/seals/gaskets they are somewhat redundant.
Tilly had variations of the setup on the 151 in other carbs. With those carbs, there are two means to eliminate excessive RPM. Ones I run that have the additional high speed check, are happy at 1/8 - 3/16 open on the H and a blocked off governor. They still run fat enough to keep them in the happily safe zone. And it helps to keep the fuel from boiling like crazy on those hotter days.
Pioneer had similar setups on some of their 3xxx muscle saws where the H needle could be seated or just cracked depending on load/bar length. Same idea…keep saws from burning up.
Tilly had variations of the setup on the 151 in other carbs. With those carbs, there are two means to eliminate excessive RPM. Ones I run that have the additional high speed check, are happy at 1/8 - 3/16 open on the H and a blocked off governor. They still run fat enough to keep them in the happily safe zone. And it helps to keep the fuel from boiling like crazy on those hotter days.
Pioneer had similar setups on some of their 3xxx muscle saws where the H needle could be seated or just cracked depending on load/bar length. Same idea…keep saws from burning up.
altatim
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Picked up a SXL-922 in sort of rough shape recently. I'll get to it one of these days but here it is with the two smaller brethren. I read something about some of these being 77cc and some being 82cc, I'll have to see what this one turns out to be but I don't think it really matters lol
great information, had no idea it was resonance. that would explain a lot. mine looks and feels fine when I push on the ball, but even wear on the ball or brass could affect it I suppose, or spring tension over time. do you know what the function of the nozzle is? most HS series carbs just have a small passage in that location with a neoprene disk for a check valve and a screen to hold it in place. thanks.
Given the good information regarding the Tilly Carb I've been reading here I took a moment today and brought out my Homelite SXL-925. Yes, it's got the challenging carb and I remember the difficulty I had with this one years ago. I bought this from the original owner in Rock Hill, South Carolina and added the full wrap. I have the original 24-inch bar it came with and it's in good shape too. It's very strong, and one of my favorite saws minus the carb! Max.
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Well....sometimes it eventually becomes apparent why I end up with free chainsaws. It would appear my 240 has a dying ignition module. I have a replacement on order. Has anyone installed a new module without pulling the engine out of the housing? It seems....possible. the challenge is routing the stupid cap and wire behind the engine.
The saw was running great until it wasn't, got hot and seemed to lose spark. Started again once it cooled down, and then spark went bye-bye. Now it will only fire intermittently, and acts like someone is flipping the kill switch. Tried a new spark plug but no improvement, I'm losing spark.
The saw was running great until it wasn't, got hot and seemed to lose spark. Started again once it cooled down, and then spark went bye-bye. Now it will only fire intermittently, and acts like someone is flipping the kill switch. Tried a new spark plug but no improvement, I'm losing spark.
You may be able to pull the boot off the plug wire and remove the spring connector, that would allow you to pass the wire through much more easily.
Mark
Mark
