I don't think so/but I thought I'd put it up here, anyhow.
I've dealt with completely frozen, seized, stuck valves on equip that has sat for extended periods, especially outside. those engines would not run at all, til fixed.
And I've heard of guys talk about "sticky" valves on running engines before, as long as I can remember. But don't remember in all the years of messing with engines, of having to deal with this issue. Maybe I have, and chased "other" possible causes/ without realizing that this was the real cause, of the issues I chased.
I have a 170402 Briggs 7 hp L head horizontal engine, on an old snow blower that I just got last week. The Briggs "Code" number says this engine was made in Aug of 1980. Story I got with it, was that it has been run once in the last 10 years, (about 5-6 years ago) before they decided to sell it recently.... was in the garage of an elderly woman, hasn't been used, since her kids lived at home. Her son had it on CL, which was where I found it. I never tried to start it, til I got it home.
It has great hot spark, starts really easy, looking in spark plug hole doesn't look like much carbon buildup (I have seen worse)
The engine has a little oily residue, starting-- even with, and below, the crankcase breather (hose that used to be there connected to breather, was MIA/ I replaced it with a brand new, OEM hose) I want to power wash the whole machine when I can, and re evaluate that part of it (power wash won't happen, til I can turn on outside water spigot so I will evaluate the oily residue, later)
Does not smoke at all, while running. whether under load, or not.
I think the oily residue was overblown/ due to sitting and gathering any dust that floated by, as it sat. not concerned with it at this point, yet. Oil might have even been something spilled while sitting, for all I know.
I cleaned the carb, (was surprisingly clean before I started on it, float was good-- no holes--- and float level was OK, when I checked. Plug was burning nice and tan from when it last was run, so I didn't want to mess with too much.
When I started playing with it, it would fire on gumout, or gas, or whatever I'd dribble into the spark plug hole/ until that flammable substance was spent. but wouldn't take off and run on its own. Only real problem I found, was the gasket between carb and elbow (2 pc Flo jet) was installed wrong, only 1 mount screw was thru the hole and other hole in gasket was "off" by the thickness of the gasket, was bolted on with outside of gasket laying against mounting screw.... so, it was able to suck air via one side of carb mount flange.
Strangely, no other evidence besides that out of place gasket/ and VERY clean oil in the crankcase, that this machine has ever been worked on, in the last 40 years.... no paint missing around bolts, etc.
BUT... as easy as this thing starts, while trying to set the carb, I can get it to run smooth at speed, until I go to use it/ then have to richen the adjustment, under load... then it's too rich, and surges, while running/not being worked...the surge reminds me more of a Tecumseh Snow King, than the Briggs that it is.... try to split the difference between good running while working/ and while not working, (carb definitely responds to carb adjustment, as expected) and it bogs down hard, under a load.... though I was trying to move snow that was nearly as tall as the bucket/ that had a couple days to set up, and start gettin hard.... but with the bogginess, and not really being able to make it "happy" under both conditions with carb adjustments, I was thinking maybe the valves are sticky? But I would not think it would start so easy, if they were? this is my 1st ever Briggs "Sno-Gard" series of engine. Have had many Tecumseh's over the years thru here.
the throttle is such that it's "on" or "off... no way to idle it down. its full speed, or nothing, that is how the linkage/throttle control is designed.
When I dunked the carb, both because of the fact this thing isn't able to run idled down, and because of the clean, tan, and not fouled plug that had been in this machine for eons, I left the idle speed mixture screw alone in the ultrasonic. Didn't remove it, before the dunk.
and there is no hole for screwdriver access to it anyways, with the snow-engine specific metal cover over the carb. I was gonna drill a ~3/8" hole in line with it, so I could monkey with that adjustment point. Figured that it apparently ran OK with the settings as were when it was last being run regularly, probably was pretty close to where it needed to be anyway. (judging by reading the spark plug that was originally in it)
In my experience, the idle setting doesn't effect hi speed operation much, anyway/ except on engines that have a regular throttle control, that can be idled/ when transitioning from idle to hi speed/ if the idle mix is off, there can be a hesitation when idling up towards hi speed.
Again, on engines that can be idled down, that low speed mixture adjustment would definitely have an effect on how the engine would run while idled down of course..... but I don't believe that applies here/ since this one can't....
I never did a compression test (I usually don't on these engines, because of the compression release built into the cam) but as many small engines as I have had thru here over the years, the effort needed to pull the rope and turn it over, seemed quite normal.....and that, plus how easy as this engine does start and get up to full speed, makes me not suspect burnt valves or valves not sealing while closed..... but with no real way to test for sluggish/sticky valves while the engine is actually running, I thought I'd see what you guys thought.....
I have run about a tank of gas out of it, (1 gallon) since I rebuilt the carb. I doubt I will have to use it enough the rest of the season remaining, to burn another tank thru it. so unlikely the valves will have enough opportunity to unstick themselves just from being run, the rest of this season. (if in fact that's what is going on in the 1st place)
I've dealt with completely frozen, seized, stuck valves on equip that has sat for extended periods, especially outside. those engines would not run at all, til fixed.
And I've heard of guys talk about "sticky" valves on running engines before, as long as I can remember. But don't remember in all the years of messing with engines, of having to deal with this issue. Maybe I have, and chased "other" possible causes/ without realizing that this was the real cause, of the issues I chased.
I have a 170402 Briggs 7 hp L head horizontal engine, on an old snow blower that I just got last week. The Briggs "Code" number says this engine was made in Aug of 1980. Story I got with it, was that it has been run once in the last 10 years, (about 5-6 years ago) before they decided to sell it recently.... was in the garage of an elderly woman, hasn't been used, since her kids lived at home. Her son had it on CL, which was where I found it. I never tried to start it, til I got it home.
It has great hot spark, starts really easy, looking in spark plug hole doesn't look like much carbon buildup (I have seen worse)
The engine has a little oily residue, starting-- even with, and below, the crankcase breather (hose that used to be there connected to breather, was MIA/ I replaced it with a brand new, OEM hose) I want to power wash the whole machine when I can, and re evaluate that part of it (power wash won't happen, til I can turn on outside water spigot so I will evaluate the oily residue, later)
Does not smoke at all, while running. whether under load, or not.
I think the oily residue was overblown/ due to sitting and gathering any dust that floated by, as it sat. not concerned with it at this point, yet. Oil might have even been something spilled while sitting, for all I know.
I cleaned the carb, (was surprisingly clean before I started on it, float was good-- no holes--- and float level was OK, when I checked. Plug was burning nice and tan from when it last was run, so I didn't want to mess with too much.
When I started playing with it, it would fire on gumout, or gas, or whatever I'd dribble into the spark plug hole/ until that flammable substance was spent. but wouldn't take off and run on its own. Only real problem I found, was the gasket between carb and elbow (2 pc Flo jet) was installed wrong, only 1 mount screw was thru the hole and other hole in gasket was "off" by the thickness of the gasket, was bolted on with outside of gasket laying against mounting screw.... so, it was able to suck air via one side of carb mount flange.
Strangely, no other evidence besides that out of place gasket/ and VERY clean oil in the crankcase, that this machine has ever been worked on, in the last 40 years.... no paint missing around bolts, etc.
BUT... as easy as this thing starts, while trying to set the carb, I can get it to run smooth at speed, until I go to use it/ then have to richen the adjustment, under load... then it's too rich, and surges, while running/not being worked...the surge reminds me more of a Tecumseh Snow King, than the Briggs that it is.... try to split the difference between good running while working/ and while not working, (carb definitely responds to carb adjustment, as expected) and it bogs down hard, under a load.... though I was trying to move snow that was nearly as tall as the bucket/ that had a couple days to set up, and start gettin hard.... but with the bogginess, and not really being able to make it "happy" under both conditions with carb adjustments, I was thinking maybe the valves are sticky? But I would not think it would start so easy, if they were? this is my 1st ever Briggs "Sno-Gard" series of engine. Have had many Tecumseh's over the years thru here.
the throttle is such that it's "on" or "off... no way to idle it down. its full speed, or nothing, that is how the linkage/throttle control is designed.
When I dunked the carb, both because of the fact this thing isn't able to run idled down, and because of the clean, tan, and not fouled plug that had been in this machine for eons, I left the idle speed mixture screw alone in the ultrasonic. Didn't remove it, before the dunk.
and there is no hole for screwdriver access to it anyways, with the snow-engine specific metal cover over the carb. I was gonna drill a ~3/8" hole in line with it, so I could monkey with that adjustment point. Figured that it apparently ran OK with the settings as were when it was last being run regularly, probably was pretty close to where it needed to be anyway. (judging by reading the spark plug that was originally in it)
In my experience, the idle setting doesn't effect hi speed operation much, anyway/ except on engines that have a regular throttle control, that can be idled/ when transitioning from idle to hi speed/ if the idle mix is off, there can be a hesitation when idling up towards hi speed.
Again, on engines that can be idled down, that low speed mixture adjustment would definitely have an effect on how the engine would run while idled down of course..... but I don't believe that applies here/ since this one can't....
I never did a compression test (I usually don't on these engines, because of the compression release built into the cam) but as many small engines as I have had thru here over the years, the effort needed to pull the rope and turn it over, seemed quite normal.....and that, plus how easy as this engine does start and get up to full speed, makes me not suspect burnt valves or valves not sealing while closed..... but with no real way to test for sluggish/sticky valves while the engine is actually running, I thought I'd see what you guys thought.....
I have run about a tank of gas out of it, (1 gallon) since I rebuilt the carb. I doubt I will have to use it enough the rest of the season remaining, to burn another tank thru it. so unlikely the valves will have enough opportunity to unstick themselves just from being run, the rest of this season. (if in fact that's what is going on in the 1st place)
