10324 Duraforce runs fast but then slows down when warm. what to do?

[lawnboywillneverdie]

ok so when i start it cold it runs quite fast i prime it only once and start on slow. but when it gets warm it slows down substantialy. what is going on?

 

[lawnboywillneverdie]

ok so when i start it cold it runs quite fast i prime it only once and start on slow. but when it gets warm it slows down substantialy. what is going on?

i have to go so i typed bit fast and dint have enough time will add more later

 

[bt3]

Lots of threads on this.

Some possibilities.

-Check the Governor and make sure it is freely moving. If you have a Governor Vane (most are plastic wind vanes) that protrudes up to the fan area of the shroud, make sure this Vane is freely moving. If not, spray Carb Cleaner and some Penetrating Oil onto the pivot point to get the gunk out and to make sure it is freely pivoting. Do not break the spring nor work it so hard you break the Vane or the pivot point. Easy does it.

-Check the spark after it gets hot and slows down. Pull plug, ground it against the motor and with lights low or off in the garage and pull the starter and see if you have a good spark when the motor is hot. If not, your magneto is failing when hot.

- Make sure your linkages are moving all carb adjustments correctly. Clean with Carb Cleaner if not. I also lightly spray Penetrating Oil on NON RUBBER OR NON PLASTIC Carb parts - Metal Parts ONLY - to make sure they are clean, then wipe off excess with rag.

- When was the Carb last cleaned? If you have a screen filter at Carb gas input remove it and spray it with carb cleaner to make sure it is passing all fuel efficiently. Is the choke vane moving freely? Is the Air Filter clean as a whistle? I put a little Marvel Mystery Oil in my sponge filter. Not sure if your model has a sponge or paper filter. Spray a little carb cleaner into the carb and fuel line input. I also run a little SEA FOAM in my fuel. EASY DOES IT. Four Cap fulls per tank if I am experiencing problems, 2 cap fulls for maintenance. I believe you stated your mower was serviced and rebuilt. Was the Carb cleaned when this was done? I have been able to solve issues by spraying Carb Cleaner into the fuel input after removing the filter screen, and by spraying into the carb air port.... when the engine is off of course. If you can remove the air filter, run the machine when hot with the air filter off and see if it runs normally. If it does, there may be an issue with the filter not being clean enough or possibly an issue with the Governor, or the mixture setting or jets. I am assuming you or whomever rebuilt the machine set the adjustment screws properly.

- Is your Spark Plug clean and properly gaped? Is there a good spark when cold and hot? There are threads where operators complain that even new plugs cause issues and they end up replacing the plugs and upon replacement all is well with the mower.

- Are your exhaust ports dirty or clogged? Worth a peek IMO. Even partial carbon build-up in or around the ports can cause issues.


Just some ideas from years of fiddling with my LawnBoy. Some others here may have other ideas.

Good luck. Keep us posted. You may help somebody else out in the future.

 

[lawnboywillneverdie]

Lots of threads on this.

Some possibilities.

-Check the Governor and make sure it is freely moving. If you have a Governor Vane (most are plastic wind vanes) that protrudes up to the fan area of the shroud, make sure this Vane is freely moving. If not, spray Carb Cleaner and some Penetrating Oil onto the pivot point to get the gunk out and to make sure it is freely pivoting. Do not break the spring nor work it so hard you break the Vane or the pivot point. Easy does it.

-Check the spark after it gets hot and slows down. Pull plug, ground it against the motor and with lights low or off in the garage and pull the starter and see if you have a good spark when the motor is hot. If not, your magneto is failing when hot.

- Make sure your linkages are moving all carb adjustments correctly. Clean with Carb Cleaner if not. I also lightly spray Penetrating Oil on NON RUBBER OR NON PLASTIC Carb parts - Metal Parts ONLY - to make sure they are clean, then wipe off excess with rag.

- When was the Carb last cleaned? If you have a screen filter at Carb gas input remove it and spray it with carb cleaner to make sure it is passing all fuel efficiently. Is the choke vane moving freely? Is the Air Filter clean as a whistle? I put a little Marvel Mystery Oil in my sponge filter. Not sure if your model has a sponge or paper filter. Spray a little carb cleaner into the carb and fuel line input. I also run a little SEA FOAM in my fuel. EASY DOES IT. Four Cap fulls per tank if I am experiencing problems, 2 cap fulls for maintenance. I believe you stated your mower was serviced and rebuilt. Was the Carb cleaned when this was done? I have been able to solve issues by spraying Carb Cleaner into the fuel input after removing the filter screen, and by spraying into the carb air port.... when the engine is off of course. If you can remove the air filter, run the machine when hot with the air filter off and see if it runs normally. If it does, there may be an issue with the filter not being clean enough or possibly an issue with the Governor, or the mixture setting or jets. I am assuming you or whomever rebuilt the machine set the adjustment screws properly.

- Is your Spark Plug clean and properly gaped? Is there a good spark when cold and hot? There are threads where operators complain that even new plugs cause issues and they end up replacing the plugs and upon replacement all is well with the mower.

- Are your exhaust ports dirty or clogged? Worth a peek IMO. Even partial carbon build-up in or around the ports can cause issues.


Just some ideas from years of fiddling with my LawnBoy. Some others here may have other ideas.

Good luck. Keep us posted. You may help somebody else out in the future.

why thank you i will try this and get back tomorrow thx bt3
:smile:

 

[lawnboywillneverdie]

why thank you i will try this and get back tomorrow thx bt3
:smile:

btw my mower is not rejetted so could that be one of the possiblities on it? it doesnt surge at all when nice and hot so i havent rejetted it. has brand new governer vand is set properly, air filter was clean good spark but the jeting is the only thing not done to it lol.

 

[bt3]

It could be the jets. I'd squirt carb cleaner in the air intake and in the fuel line inlet (after removing the screen if you have a screen - tiny little tube screen).
But suspect jets are usually not "only when hot" issues. On motorcycles, high speed jets can be suspect from hot motor issues, but I have not seen that on a lawnmower, since the jets are set up differently. But you never know. Make sure the carb is clean and set up properly. Set screws need to be right.

One more thing, just make SURE your air inlet on the fuel cap is not clogged and that you are not creating a fuel tank vacuum when running. Since the time it would take to create this vacuum would coincide with a motor finally becoming hot, it is another possibility. So do check that as well.

 

[lawnboywillneverdie]

It could be the jets. I'd squirt carb cleaner in the air intake and in the fuel line inlet (after removing the screen if you have a screen - tiny little tube screen).
But suspect jets are usually not "only when hot" issues. On motorcycles, high speed jets can be suspect from hot motor issues, but I have not seen that on a lawnmower, since the jets are set up differently. But you never know. Make sure the carb is clean and set up properly. Set screws need to be right.

One more thing, just make SURE your air inlet on the fuel cap is not clogged and that you are not creating a fuel tank vacuum when running. Since the time it would take to create this vacuum would coincide with a motor finally becoming hot, it is another possibility. So do check that as well.

thank you and i hope this ominous problem will be figured out. Hard to say if it really is a problem but i am kinda just worried but thx for the help. the fuel cap is probably the issue. last week i was mowing and it was under no load and it suddenly stalled, i opened the fuel cap and had a half tank. started right up and was fine for rest of the lawn which was over half finished. this seems to hint at that clogged fuel cap vent. thx for suggesting it. i will definitly check that out.:thumbsup:

 

[lawnboywillneverdie]

thank you and i hope this ominous problem will be figured out. Hard to say if it really is a problem but i am kinda just worried but thx for the help. the fuel cap is probably the issue. last week i was mowing and it was under no load and it suddenly stalled, i opened the fuel cap and had a half tank. started right up and was fine for rest of the lawn which was over half finished. this seems to hint at that clogged fuel cap vent. thx for suggesting it. i will definitly check that out.:thumbsup:

update. its being a stubborn little child now lol. i have been noticing a weird occurance if you want a vid i will take it. i am gonna get a pic of this odd thing. runs amazing at low speed but when i reach about 1/4 to 1/3 it slows and then goes up and says "no i refuse to go faster" to me in my head. ill get a pic in a sec. definitly need all lawn boy fanatics to help here i am stuck on this.:confused2::smiley_aafz:

 

[lawnboywillneverdie]

update. its being a stubborn little child now lol. i have been noticing a weird occurance if you want a vid i will take it. i am gonna get a pic of this odd thing. runs amazing at low speed but when i reach about 1/4 to 1/3 it slows and then goes up and says "no i refuse to go faster" to me in my head. ill get a pic in a sec. definitly need all lawn boy fanatics to help here i am stuck on this.:confused2::smiley_aafz:

Heres the pics i promised i dont like the sign the oil is indicating what could it be?

 

[bt3]

LBWND;

What mixture are you running in that LB? I have gone synthetic to about 40:1 -maybe a tad leaner but that's the ballpark I aim for now. Made a big difference in oil residue and crap in the carb. Is your motor skipping or mis-firing? I'm thinking you are passing 32:1 rich fuel through the compression chamber. It's either that or a fuel leak somewhere, and I'd investigate your carb mix setting. After that checking, we are back to looking at Spark plug and Ignition coil. You'll get it! These machines are like Swiss watches. They need a bit of TLC, but when they are wound correctly, man, they hum!

Keep us posted.

BTW, I bought a replacement coil on Amazon for $19.95 DELIVERED! It works fantastic. No issues at all, and 1/5th the price of the OEM coil at $100. If you do replace the coil, check Amazon before you spend big bucks.... unless you are the kind of guy that absolutely has to have OEM and won't do Chinese coils. Me? I like saving the money AS LONG AS the part works well. Sometimes a new coil, with new spark plug can work wonders.