Forums Archive Index > Outdoor Power Equipment > Needle adjustment not having an effect.....
Date: 8 Dec 2006 7:53 pm
Trying to get my Snow King 8HP to idle correctly. I was able to get it to idle nicely by adjusting the low speed screw. After that I figured Id try to dial in the high speed (when I engage the auger, I get a drop in RPMs, so I figured high speed was too lean). Doing the recommended procedure (turn out until it stutters rich, then in until it stutters lean, and then split the diff), I notice that the high speed needle is having no effect. I can turn it all the way out and it never stutters rich, and all the way in and it never stutters lean.
What does this mean? I pulled the bowl off quickly, and there is no varnish or anything. Fuel seems good. Clean out the high speed needle passages (even the ultra-tiny one) but nothing came out.
Im this --><-- close to just buying a new carb. My wife says I should just buy a new snowblower Smile but they dont build em like they used to (not affordably anyway). This is a 1987 Bolens 8HP/24" cut, tough little snowblower!
Date: 8 Dec 2006 10:01 pm
Hey Chris, can you post your model #'s for those that really know.
http://www.cpdonline.com/692509.pdf
This is a big pdf that is a sort of complete service manual. There are some updates and changes to it but it is pretty helpful.
Are you trying to set the high speed jet at idle?
Date: 8 Dec 2006 10:15 pm
Engine is an HM80 155282J
Carb is a 632334A
Trying to set the high speed jet at high speed/no load. I had set the idle by dropping the throttle down to idle and turning the needle in and out from lean to rich, then splitting the difference. Once that was done, I tried the same with the high speed (after raising to 100% throttle) but I never got it to run lean/rich, it just stayed a constant RPM from the needle fully closed to the needle almost falling out of the threads in the nut.
Ive been thru that service manual several times....if you look at the carb troubleshooting charts, my issue can be one of many things. For instance, is it a "hunt at high speed"? "erratic idle"? or is it a "engine runs with needle closed". The chart doesnt really narrow it down that well, suggesting anything from clogged fuel passage to damaged needles to a stuck ball check valve which the manual doesnt make very clear if its supposed to move or not, or how to clean/test it. Ive already cleaned the carb 4x last year, including replacing every part I could (all gaskets, o-rings, fuel lines, etc). and this issue still exists.
Funny thing is the engine fires right up on the first pull once its primed. Runs OK at idle for a little bit, then goes back to the hunting idle (which I corrected with the low speed needle adjustment, but then discovered the high speed needle issue).
Date: 9 Dec 2006 10:54 am
Quote:
to a stuck ball check valve which the manual doesnt make very clear if its supposed to move or not, or how to clean/test it.
Yes, the check valve is supposed too move. You should be able too shake the carb and hear it rattle.
What happens a lot of times is when guys rebuild the carbs, they install the low speed needle and seat it for the initial adjustment with the carb being held upside down. The problem is when the carb is upside down, the check valve slides down its passage and when the low speed needle is turned in "to seat it", it stabs and distorts the check valve so it doesnt move freely anymore. (Trashes it.)
Where is your low speed needle set at right now?
Did you clean the main nozzle with a wire or small drill bit?
Any air leaks on the way too the cylinder. (Gaskets, worn throttle shaft bore?)
There is a passage that sits on the bottom of the carb throat (venturi?) that vents the main nozzle, is that clean ?
Is the governor set correctly?
Can you get any pictures so that we can "take a look" and see if we can see anything that might be out of place?
Date: 9 Dec 2006 1:38 pm
I assembled the carb to the service manual specs (which says specifically to not insert the low speed needle with the carb upside down, and I didnt). The way the manual puts it, only carbs with a metering valve will have something moving up and down. My carb does not (I believe) have a metering valve. I can see the check ball at the end of the idle/intermediate fuel xfer passage, but Im not sure if thats supposed to move up and down either.
I actually removed the carb from the engine (again). The needles were at factory settings (1 out on the low speed and 1.5 out on the high speed). Engine would start fine, but the high speed was still having zero effect on how it ran (again, all the way in to all the way out, it ran the same). Still getting a drop in RPM when engaging the auger. I assume the high speed needle not affecting anything will create problems when Im engaging the auger and actually trying to throw snow.
Governor should be set correctly, I never touched it. Throttle shaft bore seems intact (no play on the throttle shaft itself), gaskets were all replaced last year (Ill replace them again when I reinstall the carb). Main nozzle was cleaned again, and nothing was plugged. All passages should be clean, I might try to boil the whole carb just to make sure.
-Chris
Date: 9 Dec 2006 2:37 pm
If your carb is 20 years old I am pretty sure you will have the metering valve. One way too tell is by the shape of the low speed needle. If it comes too a sharp point it has the metering valve. If it has a stepped, blunt, square tip it doesnt.
Quote:
I can see the check ball at the end of the idle/intermediate fuel xfer passage, but Im not sure if thats supposed to move up and down either.
I believe what you are describing is just a beebee and not a check valve that is pressed in too block off the passage after installing the metering valve at the factory. That should not move.
You may want too check your valve clearences too. (While you have the carb off.) .008 is a good setting on those.
Date: 9 Dec 2006 6:59 pm
The low speed needle thats installed doesnt come to a point. Im wondering, however, if somewhere along the rebuild line the kit I received had an incorrect screw. It shouldnt, I used the kit recommended by T-man on the Yahoo! group, but I guess anything is possible.
Thanks for the info on the BB. I didnt think it was supposed to move, so technically Im back to square one.......unless there really should be a metering rod moving and a different low speed needle.
I think Im just going to break down for a new carb, Im tired of fighting this one. Maybe there is a problem, but at this point I dont know what else to try (short of "boiling" it overnight and praying).
-Chris
Date: 9 Dec 2006 7:14 pm
Chris.
The carb could have been switched at one time in it's life.
There are numbers punched into the carb casting that can confirm if the correct kit was installed on the correct carb.
What is the shape of the high speed needle.....pointed or flat nosed?
Date: 9 Dec 2006 7:19 pm
Its flat nosed, which actually had me worried a bit (wondered if it was supposed to be pointed, but it doesnt look like there was a point that was broken off, its a nice flat nose).
-Chris
Date: 9 Dec 2006 8:31 pm
Chris.
Quote:
Its flat nosed, which actually had me worried a bit (wondered if it was supposed to be pointed, but it doesnt look like there was a point that was broken off, its a nice flat nose).
For a carb that is supposidly that old (1987 bolens) that doesnt seem right.
The old carbs used a 38140 kit. (Pointed low and high speed needles.)
I cant look up Tecumseh parts at home....but if you want too shoot me the engine numbers and carb casting numbers I can do some homework and see whats up when I go back too work Monday when I have access too Tecumseh lookup.
Either you have the wrong kit in the right carb or the right kit in the wrong carb.
Feel free too drop me a PM or an email with the numbers and perhaps we can get things straightend out. :)
Date: 9 Dec 2006 8:52 pm
I sent you a PM.
Just for others that might be reading along....
Engine is HM80, date/mfg code is 155282J
Carb casting is 903 4F21. Ive been told the correct rebuild kit is 632347, and thats the one Ive bought (been buying). If you see a pic of the kit contents (good pic here: http://tinyurl.com/yhbtr3), the needles are *not* pointed. However, I dont know if the 903 series carb is expecting the pointed needles or the ones with the flat-nosed ends.
-Chris
Date: 10 Dec 2006 12:57 am
Also - check to make sure the atmospheric vent (the tiny hole on the side near the top of the carb body) is clear...
Marty
Date: 12 Dec 2006 2:49 pm
Rebuilt and reinstalled yesterday. Runs a little better, at least the high speed needle has an effect on the engine now. Still cant get it to purr.....seems to have a miss/sputter at high speed, with or without the auger engaged.
I did note, however, that there was no washer between the idle needle spring and the o-ring. Would this make a difference? I might try to track down the correct size washer today (didnt have one lying around).
Aside from the washer, the only thing left I have is to try a new sparkplug, then I have to wait for snow to see how it handles an actual load on the engine. Hopefully it works OK.
-Chris