312 Carb Adjustments??

[Jsieao 10]

My 312 starts right up when I get ready to plow snow. But it seems to be running rich. I have three paved driveways that I plow. Two of which have a bit of an increase in grade.

When I start up the grade the motor seems to bog down and I'll see a bit of black smoke from the exhaust. By the time I get to the highest point of the driveway, the tractor is moving considerably slower and the RPMs are down. I turn around and head back down, it seems to be running better, unless I have a load of snow on the blade. I'm guessing it is an adjustment that I haven't figured out yet. Running on my flat driveway, it seems to clear up and run fairly smoothly, unless of course I have a heavy load of snow on the blade.

Can you point me in the right direction?

Thanks!!

[Ed Kennell 41,931]

If you can't get improvement by slowly  adjusting  (turning in CW) the High Speed jet,   I would look at the float adjustment.    The float could be grade related.

[kpinnc 14,630]

Almost sounds like your govenor is out of adjustment- or you've got a little slop in the throttle link. 

 

Magnum engines have tiny holes drilled in the top of the governor arm and the tab on the throttle shaft at the carb for adding a small spring just for that purpose. I will never understand why they made the holes but didn't use a spring from the factory. Anyway, most hardware stores sell light springs that you can use. It won't affect anything except it eliminates the slop between governor action and carb reaction. 

 

Might be worth a try. 

 

 

[8ntruck 7,831]

I'll agree with @Ed Kennell.  Sounds like it is a tad rich.  Try 1/8 turn CW on the high speed jet needle as a start.

[oldlineman 1,537]

Check your plug color, that can give you information on fuel amount. Bob

[tunahead72 2,543]

17 hours ago, kpinnc said:

Almost sounds like your govenor is out of adjustment- or you've got a little slop in the throttle link. 

 

Magnum engines have tiny holes drilled in the top of the governor arm and the tab on the throttle shaft at the carb for adding a small spring just for that purpose. I will never understand why they made the holes but didn't use a spring from the factory. Anyway, most hardware stores sell light springs that you can use. It won't affect anything except it eliminates the slop between governor action and carb reaction...

 

I just picked up my first Magnum tractor this past fall, I did not know that.  Thanks for posting!

 

[peter lena 9,255]

  @Jsieao referring to @kpinnc  spring picture , use delicate  top spring , pete

[kpinnc 14,630]

2 minutes ago, peter lena said:

referring to @kpinnc  spring picture , use delicate  top spring , pete

 

For clarification- I mean you should place the spring between the governor arm and the tab on the carb. I do not suggest attaching it anywhere else. To do so will affect the throttle response. 

 

My spring placement merely eliminates play between the governor and throttle shaft, which equates to a more precise governor response. It in no way changes anything otherwise.

 

 

[peter lena 9,255]

@kpinnc referring to your carb spring picture , used a very delicate spring in that , was just enough , another thing, your straight vertical fuel line from the fuel pump to carb is a perfect spot for a 5/16"  check valve , evil energy has them , when installed there  it looks like it was made for it ,  vertical fit , consistently gives quick starts , have it on my 3 magnums  , pete

[kpinnc 14,630]

Just now, peter lena said:

another thing, your straight vertical fuel line from the fuel pump to carb is a perfect spot for a 5/16"  check valve , evil energy has them , when installed there  it looks like it was made for it ,  vertical fit , consistently gives quick starts , have it on my 3 magnums  , pete

 

Thanks Pete. I will have to check one of those out.