noneyadamnbusiness 2 #1 Posted August 17, 2019 So, my 312-8 no longer idles when the throttle is less than half way down. It used to a year or so ago but no longer. I cleaned the Walbro carb out remounted it. Am running 90 octane ethanol-free gas through it with some added seafom. I read online jackssmallengines . com that it could be a bent choke plate or bent throttle plate. It doesn't have any surges, it does however bog down like it wants to stall out but comes back to full throttle where I keep it. Any suggestions or recommendationson how to fix this? Thanks. Share this post Link to post Share on other sites
richmondred01 2,307 #2 Posted August 17, 2019 When you say “cleaned it” did you completely tear it down, soak it in carb cleaner, intstall a new carb kit, adjust the float, and properly set the high and low needle valves? 1 Share this post Link to post Share on other sites
gwest_ca-(File Mod) 11,489 #3 Posted August 17, 2019 Many believe the mixture screw settings in the service manuals are gospel. They are what the engine manufacturer has determined will allow the engine to start and run. But 99.9% of the time they will not run their best. No two engines breath the same and that is why the mixture screws have threads and are adjustable. You must find the optimum setting after the engine is warmed up by adjusting the screws while it is running. Garry 1 Share this post Link to post Share on other sites
pfrederi 18,689 #4 Posted August 17, 2019 Being a Walbro on a magnum i will guess it is a fixed main jet. (Not one of my favorite carbs). The idle passages are very tiny and easily plugged. Cleaning them is problematic. Over night soaking and a lot of compressed air will usually work. If that fails yo may have to remove the welch plugs and clean it again. 1 Share this post Link to post Share on other sites
noneyadamnbusiness 2 #5 Posted August 17, 2019 Okay, thanks. It does have a fixed main jet. I cleaned out all three jets and soaked. I found this in the float bowl upon removal. I suspect it's from ethanol. Running 90 octane ethanol-free gas with seafoam. Replaced fuel filter about 2 months ago. Share this post Link to post Share on other sites
noneyadamnbusiness 2 #6 Posted August 17, 2019 10 hours ago, pfrederi said: Being a Walbro on a magnum i will guess it is a fixed main jet. (Not one of my favorite carbs). The idle passages are very tiny and easily plugged. Cleaning them is problematic. Over night soaking and a lot of compressed air will usually work. If that fails yo may have to remove the welch plugs and clean it again. Which brand(s) do you prefer? I went to the walbro website and entered the numbers I could find. One was WHG-xxx. I can't remember the last four numbers but the site couldn't find it when I entered it. I'm calling them Monday to see what their rebuild kut is if they still make it for that carb. Thanks, Dan Share this post Link to post Share on other sites
gwest_ca-(File Mod) 11,489 #7 Posted August 17, 2019 Should be in this manual. Click on the picture and read the notes on this file. Garry 1 Share this post Link to post Share on other sites
noneyadamnbusiness 2 #8 Posted August 18, 2019 3 hours ago, gwest_ca said: Should be in this manual. Click on the picture and read the notes on this file. Garry Thank you Share this post Link to post Share on other sites
ebinmaine 72,719 #9 Posted August 18, 2019 11 hours ago, noneyadamnbusiness said: Okay, thanks. It does have a fixed main jet. I cleaned out all three jets and soaked. I found this in the float bowl upon removal. I suspect it's from ethanol. Running 90 octane ethanol-free gas with seafoam. Replaced fuel filter about 2 months ago. That is most likely from ethanol, yes. Often referred to as "ethanol pearls". It'll be right again. I've had carbs I've had to thoroughly clean 3 times to get them running good. Share this post Link to post Share on other sites
AHS 1,546 #10 Posted August 18, 2019 Do you run a fuel filter, and shut off valve? I always shut mine off and let it stall; that way the gas is gone from the carb. 1 Share this post Link to post Share on other sites
noneyadamnbusiness 2 #11 Posted August 18, 2019 4 hours ago, AHS said: Do you run a fuel filter, and shut off valve? I always shut mine off and let it stall; that way the gas is gone from the carb. I run a fuel filter, which I just changed in June or so.i don't have a shut off valve but may pick one up. I just ordered a walbro rebuild kit. It's the same carb and components since '95. I bought the horse off a older woman that got it in her divorce 1 Share this post Link to post Share on other sites
noneyadamnbusiness 2 #12 Posted August 18, 2019 7 hours ago, ebinmaine said: That is most likely from ethanol, yes. Often referred to as "ethanol pearls". It'll be right again. I've had carbs I've had to thoroughly clean 3 times to get them running good. Thanks! I just ordered a walbro rebuild kit. I don't want to buy chinese junk carbs for $20. Thanks for the help. I may get a shut off valve as another member recommended 1 Share this post Link to post Share on other sites
