alec
Gots Tree Cred
Posts: 37
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Post by alec on Feb 4, 2020 20:33:39 GMT -5
Just finished putting in a good used piston and new rings in my 925 and also completed wiring repairs on my 3 piece ignition as suggested in this forum. Started up saw. Seems to run pretty good except for wide open throttle. It seems like it dumps fuel down the carb. I remember hearing about some kind of check valve or nozzle in these old tillotson that would dump fuel over a certain rpm? Anybody know about this? How to check repair or replace ? It seems like this check valve is dumping fuel too early .
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Post by rowdy235 on Feb 4, 2020 22:17:10 GMT -5
I believe your saw probably has the Tillotson HS-151 carbruretor which does have a "governor" of sorts to prevent it from running lean at WOT. I've never messed with one but heres a service manual for the HS series carburetors that may be helpful. tillotson.ie/wp-content/uploads/2015/07/techinfo_hs_us.pdf |
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alec
Gots Tree Cred
Posts: 37
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Post by alec on Feb 5, 2020 10:00:52 GMT -5
Anybody messed with a HS151 governor?
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Post by fossil on Feb 5, 2020 11:57:18 GMT -5
Anybody messed with a HS151 governor? Some guys block them off. I've never come across one that's bad myself. When the saw reaches a certain RPM (vibration) the check ball in the governor will open and dump fuel down a little hole beside the metering needle into the high jet. If you rev the saw full throttle with no load it will definitely open. Before you mess with the governor try cutting with the saw. If it's tuned correctly the governor won't open under load. I'm attaching a bulletin from Homelite that deals with tuning the 151 carb. Let us know how you make out.  |
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alec
Gots Tree Cred
Posts: 37
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Post by alec on Feb 5, 2020 12:44:35 GMT -5
Thanks. Perhaps the hi speed screw is a bit rich since I have it out 1 or 1-1/4 for my initial setting. It was interesting in the bulletin that the best performance can possibly be achieved when the hi speed screw is nearly closed. Thanks for the bulletin. I’ll try it this weekend
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Post by fossil on Feb 5, 2020 15:21:08 GMT -5
Looking forward to hear how it goes.
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alec
Gots Tree Cred
Posts: 37
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Post by alec on Feb 7, 2020 9:18:05 GMT -5
So adjusted carb to that service bulletin and it worked great. I guess thinking about it maybe since I changed out the crank seals, the carb adjustment is just a bit different than I expected. The saw must be about 40 years old so maybe I did have some air getting in. Thanks again.
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Post by fossil on Feb 7, 2020 10:38:53 GMT -5
Good to hear it's running well.
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