[Bob DiGiacomo]

Hi,
I have a mower that ran perfect a month ago, but now when blades are engaged it runs erractically. The mower surges idleing or at full throttle. When the air cleaner if off, it slightly backfires (out the air cleaner opening). I cleaned the bowl of the carb, but it did not help. It is 14 Degrees out today would that effect the engine? Even after the engine was warmed up I still have the same problem. I'm thinking I need to clean the entire carb rather than just the bowl. Thanks for any help.
Update: I cleaned the carb completely (was not dirty at all), I changed the spark plug, (the old one had cracked porcelin) I set the gap to 30, but then read in the manual it should be 24-28. So, tomorrow I will change the gap. I noticed that if I hold the throttle (to stop it from surging the engine runs fine) There is one adjustment screw on the back of the carb, I have it turned out about 1.5 turns from the closed position. Anyone know where that should be set. Please help... Geo -- 30yr. Thanks

 

[30yearTech]

Disconnect any kill switch leads to the engine and or coil assembly and check to see if this makes any difference in the way the engine runs.

 

[Bob DiGiacomo]

I turned my attention to an electrical problem and found a short between the blade saftey switch wire and the metal handle. I also regapped the plug and it ran perfect. What any easy fix.

New Question

The mower is still hard to start because it seems as if there is so much compression that I can't get it cranking fast enough to start. How does the compression release work and how can I test to see if it is working?

 

[30yearTech]

I turned my attention to an electrical problem and found a short between the blade saftey switch wire and the metal handle. I also regapped the plug and it ran perfect. What any easy fix.

New Question

The mower is still hard to start because it seems as if there is so much compression that I can't get it cranking fast enough to start. How does the compression release work and how can I test to see if it is working?

That's where I was going with my previous suggestion. I figured if it ran alright with the kill lead disconnected, then you would need to look for a possible issue with one of the switches or leads.

The only way I can think of to check for operation of the compression release, is to visually inspect the valve operation, either with the breather cover removed or the head off. Slowly rotate the engine and near the beginning of the compression stroke one of the valves (usually the exhaust) should crack slightly open to relieve some of the compression. It's a good idea to verify valve lash before you do this. Excess valve lash will render the compression release inoperative.

If it's cold out, then the oil in the crankcase can make an engine very hard to pull over and difficult to start, especially if using a single grade oil.

 

[Bob DiGiacomo]

Thanks for the advice about the compression release. I was searching some of the other postings on the web and found the the FB460V is notorious for not starting if the choke is opened a little bit. Although the spring loaded set screw that adjusts the choke was all the way seated the choke was still open a little bit. By wedging a screw driver at the bottom of the choke set screw, I was able to shut the choke all the way. It took 3 pulls from a cold start (and my garage temp is about 34 degrees.) Now all I have to do is figure out how to extend the choke set screw, hopefully by adjusting the cable I can close the choke a little more. Thanks for your help.

 

[30yearTech]

hopefully by adjusting the cable I can close the choke a little more.

That's usually all it takes. :thumbsup: