grinchsr 642 #1 Posted August 1, 2016 I have a high speed adjustment screw on a Walbro carb on a 1997 312 which will not respond to any adjustments. I bring the throttle all the way up then start turning the screw in to start the adjustment process and nothing happens. I can close the screw all the way in and the motor keeps running smooth. Any ideas?? Share this post Link to post Share on other sites
tunahead72 2,518 #2 Posted August 1, 2016 Have you checked your throttle shaft? A loose shaft will drive you nuts, carb won't respond to adjustments like you think it should, and sometimes it seems like the carb is adjusting its mixture itself, which it is. How clean is the carb generally? Share this post Link to post Share on other sites
grinchsr 642 #3 Posted August 2, 2016 The shaft is good. That was the item I checked first then I broke the carb open to clean it but found no dirt. I cleaned it any way then put back on the tractor and nothing changed. I may have to look around for another one. Is the K301 carb the same as the M12 ??? Share this post Link to post Share on other sites
tunahead72 2,518 #4 Posted August 2, 2016 Did you replace the gaskets, especially the one between the carb and engine block? Try spraying some WD40 at that area while the engine's running, see if that changes anything. The screw itself could be damaged, or the area it seats into in the carb. I'm kind of guessing here. Did this problem just start recently, or has it been going on for a while? Share this post Link to post Share on other sites
Detector 72 #5 Posted August 2, 2016 (edited) I don't think my 90 model 312-H has the main fuel adjusting screw in the top center of the carb to adjust high speed settings, I think air mixture can be adjusted though but the jet is fixed, I may be wrong, still learning about the different variations of the Walbros. Sounds like a vacuum leak as mentioned if adjustments make no difference Edited August 2, 2016 by Detector Share this post Link to post Share on other sites
Detector 72 #6 Posted August 2, 2016 My carb is this version http://outdoorpowerinfo.com/repairs/kohler_walbro_whg_adjustable_carb.asp 1 Share this post Link to post Share on other sites
grinchsr 642 #7 Posted August 2, 2016 Sounds like I am going to look a bit closer for a vacuum leak. Maybe I missed it. Old guys do that sometimes Anybody have the part number for that spacer/gasket at the base of the carb? My info says WH10274 which is a bad number. Thank you for the help Share this post Link to post Share on other sites
rmaynard 15,916 #8 Posted August 2, 2016 Remove the main jet needle. There are several tiny holes in the shaft. Make sure all the holes are clean. The shaft is hollow. You should be able to pass air from the holes near the tip to the holes at the other end. Share this post Link to post Share on other sites
tunahead72 2,518 #9 Posted August 4, 2016 Just a couple of miscellaneous comments I've been meaning to post... On 8/2/2016 at 7:26 AM, grinchsr said: ... Anybody have the part number for that spacer/gasket at the base of the carb? My info says WH10274 which is a bad number ... You should be looking at Kohler part numbers. I haven't seen a parts manual for your engine, but based on what I've seen from a couple of online parts suppliers, I believe the gasket you're looking for is Kohler #271030. Somebody please correct me if I'm wrong, and definitely check with your parts supplier. NAPA dealers sometimes have these Kohler gaskets in stock, or a NAPA equivalent. On 8/2/2016 at 11:11 AM, rmaynard said: Remove the main jet needle. There are several tiny holes in the shaft. Make sure all the holes are clean. The shaft is hollow. You should be able to pass air from the holes near the tip to the holes at the other end. My Walbro main jet needle doesn't have these holes. I don't know how it controls the fuel/air mixture without them, but it does somehow. In any event, grinchsr's carb may have a fixed main jet, like Detector mentioned -- grinchsr, have you checked that out yet? Share this post Link to post Share on other sites
Detector 72 #10 Posted August 4, 2016 I did a brief search but not through Kohler and come up with this set on eBay http://www.ebay.com/itm/Carburetor-Air-Filter-Gaskets-for-wheel-horse-lawn-tractor-10-12-14-Hp-0571-3-/231551611279 . I have not removed my carb so I can't say if the mounting gaskets are correct but the carb to filter looks familiar. I needed a bowl gasket and my dealer wanted to sell me a kit for $40 but he was busy that day but I'm sure a small engine shop can match it up. Share this post Link to post Share on other sites
grinchsr 642 #11 Posted August 5, 2016 (edited) I have not had a chance to pull the carb off again and try some of ideas you guys had. I will be doing that soon. I am trying to finish up a 1987 416-8 project first and besides that the 312 with the carb issue is still running decent over my sons house. I checked that part number and it seems to be the correct one. THANKS Edited August 5, 2016 by grinchsr Share this post Link to post Share on other sites
