Homelite 925 Tillotson HS151B Governor Problem

capperja

capperja

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Merry Christmas Eve everyone, I've searched around this forum many times in the past and have always found helpful information here from the members. After doing some research I've found a partial answer for my problem but I still need assistance.

I recently picked up a beautiful Super XL925 with tons of compression, advertised as needing some carb work. After checking fuel lines and overall condition, I threw some fresh fuel in it and got it to fire and run after 7 pulls or so. The saw was not happy idling, as it would want to die, so I made my adjustment to the L screw and got it to stay generally happy. When making my H screw adjustments, I could get the saw to 4 stroke but it would then want to die a couple seconds after releasing the throttle from WOT, at very best it would bog down for a second or 2 and then resume normal idle speed. I tried balancing my adjustments but never found a happy medium for everything. Later on I pulled the carb and checked the condition of everything, all gaskets and the diaphragm were in great shape, metering lever was set correctly, this leads me to my overall question. Would these governors, if they were faulty, make it so the saw dies or idle imporperly after WOT? I'm assuming it would create an overly rich condition.

I noticed this carb has a governor for the high end need, I'm understanding this can be bypassed with a bb or some tin cut to fit, however, I believe there is also a high end governor on the metering side of the carb. Please see the following pics, the carb kit I picked up has two welch plugs and I assume the smaller of the two is to replace the piece of brass with a hole in it on the metering side? (http://www.vepetersen.com/images/hspartslist.pdf, part no. 19) Wondering what experience you all have or what recommendations you can offer whether I should or should not bypass both or if i only need to bypass the governor on the side of the carb body. I'll try and get pictures to upload as well.
 
Old2stroke

Old2stroke

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The brass plug that screws out is indeed the governor (called a rattle ball governor) and it's one of the things that should be disabled as it can leak and produce an over rich condition. Sometimes they are hard to remove so I just find the drilled hole in the carb body that supplies fuel to the governor and plug it there. The brass plug with the hole in it looks suspiciously like a check valve, if it is, there will be a rubbery disc inside it that must be operating properly. They are often destroyed by blowing them out with high pressure air, fortunately depending on the carb, the engine often runs fine without it. They are there to stop air from being sucked back into the carb from the main jet and upsetting the mixture at idle, with the fine screen in the main nozzle acting as a sort of check valve your carb is probably one that can get away without it.
 
capperja

capperja

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Thank you for the reply, so I’ll bypass the governor on the side of the carb body and then punch the check valve on the metering side of the carb out through the Venturi and verify the rubber ring you speak of. At that point my options would be to replace it with a new check valve or can I put a screen or Welch plug in its place? I appreciate your assistance
 
Old2stroke

Old2stroke

Never too many toys
Joined
Jan 24, 2016
Messages
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Location
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Hard to tell from the parts diagram but it looks like the carb could come with either a welch plug and screen covering the main nozzle well or the brass thing that looks like a check valve but not both. If it is a check valve there will be a flat black rubbery disc contained in a cage inside the brass body, not an o-ring. There is another possibility that the brass thing is not a check valve but just a fixed orifice for delivering a safe minimum amount of fuel to the main jet, in which case the H adjustment screw just lets extra juel to the main jet in addition to what is supplied by the fixed orifice. If it looks like you can punch it right through into the throat of the carb then it is probably a check valve but you really have to be sure of what that damn thing is before knowing what to do with it. Hopefully someone that is familiar with that carb will join in.
 
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