Besides my new Husqvarna (which I don't like at all), I have an old MTD with a single cylinder Briggs engine. It had been causing me difficulty over the last year or so requiring constant carb cleaning, mostly due to rust in the float bowl, lack of use (so kept gumming up) and failure of the fuel filter. Eventually, it needed a more thorough cleaning and that meant removing the emulsion tube. It wasn't coming out despite the fact i could move it the tiniest bit and kept trying to wiggle it with copious amounts of penetrating oil.
Knowing I would undoubtedly break it and the float bowl was rusted and the fact that it was quite old, I decided to buy a new carburetor. Some of this decision was based on the fact I could purchase an entire carb for less than the cost of a new emulsion tube and float bowl for my old one.
But the old adage of "you get what you pay for" came true. When it arrived I found it to be the Nikki equivalent of the old Walbro.
I installed it without trouble, but it would surge... at all speeds. There's a lot of info on Nikki 6 carb surging and the answer appears to be drilling out the pilot jet for more idle (idle meaning any speed, but no load) fuel flow. I will admit this makes sense as the surging either disappears, or mostly disappears when the lawn tractor is under load, such as going up hill or with the blades engaged and cutting (where it runs mostly on the main jet)
However, when I first start the engine, it runs fine for about 20 seconds or so before it starts to surge or hunt. This indicates to me it's too rich; i.e. cold engine likes more fuel, but as it heats up it doesn't.
At first a little application of the choke merely caused it to die, but if I carefully advanced the choke very slowly (at the carb vs. the lever) it did smooth out immediately before further application over-choked it and it would die. So maybe it is lean at no-load.
I checked the governor and it's adjusted properly.
Removing the intake tube and running it shows a bit of flame coming back out the carb every time it surges. There's also a black puff of smoke from the exhaust at every surge. I havn't checked the valve lash yet, however considering it does run OK when I first start it or when under load, I think they're OK.
Basically, I don't want to go drilling out the pilot jet in case it's already running too rich vs. too lean.
I was thinking of bending a very small piece of wire into a V and inserting it the pilot jet to lean things out and see if that makes it better or worse. That's reversible, but drilling it out isn't.
And this brings up another point. Darn Nikki carb... Every time I take it apart, the multi o-ring bowl gasket has expanded due to the gasoline and I have to boil it back down to size to re-install it. What a pain.
Other than taking a sledgehammer to the carb and then finding another Walbro, is there any other advice on this whole situation?
Thank-you.
John
Knowing I would undoubtedly break it and the float bowl was rusted and the fact that it was quite old, I decided to buy a new carburetor. Some of this decision was based on the fact I could purchase an entire carb for less than the cost of a new emulsion tube and float bowl for my old one.
But the old adage of "you get what you pay for" came true. When it arrived I found it to be the Nikki equivalent of the old Walbro.
I installed it without trouble, but it would surge... at all speeds. There's a lot of info on Nikki 6 carb surging and the answer appears to be drilling out the pilot jet for more idle (idle meaning any speed, but no load) fuel flow. I will admit this makes sense as the surging either disappears, or mostly disappears when the lawn tractor is under load, such as going up hill or with the blades engaged and cutting (where it runs mostly on the main jet)
However, when I first start the engine, it runs fine for about 20 seconds or so before it starts to surge or hunt. This indicates to me it's too rich; i.e. cold engine likes more fuel, but as it heats up it doesn't.
At first a little application of the choke merely caused it to die, but if I carefully advanced the choke very slowly (at the carb vs. the lever) it did smooth out immediately before further application over-choked it and it would die. So maybe it is lean at no-load.
I checked the governor and it's adjusted properly.
Removing the intake tube and running it shows a bit of flame coming back out the carb every time it surges. There's also a black puff of smoke from the exhaust at every surge. I havn't checked the valve lash yet, however considering it does run OK when I first start it or when under load, I think they're OK.
Basically, I don't want to go drilling out the pilot jet in case it's already running too rich vs. too lean.
I was thinking of bending a very small piece of wire into a V and inserting it the pilot jet to lean things out and see if that makes it better or worse. That's reversible, but drilling it out isn't.
And this brings up another point. Darn Nikki carb... Every time I take it apart, the multi o-ring bowl gasket has expanded due to the gasoline and I have to boil it back down to size to re-install it. What a pain.
Other than taking a sledgehammer to the carb and then finding another Walbro, is there any other advice on this whole situation?
Thank-you.
John