Jump to content
homegrownusa

520H Onan Surging and Puffing Blue Smoke

Recommended Posts

My trusty 520H starts surging and between surges puffs a little blue smoke.  It still mows but the surging is annoying and seems to make the engine weaker and rattly (if that is a term).  I have cleaned carb, new fuel pump, new air filter,  fuel lines, fuel filter, spark plugs, spark plug wires and coil.  My next step is to clean out tank and make sure no junk is between tank and fuel pump.

 

Am I getting warm?  Does anyone have the same experience and/or know a solution?  

 

 

Share this post


Link to post
Share on other sites

Is it that way at start up or only after it has been working for a while? Have you removed the engine tins to clear the cooling fins? Have you considered doing a compression check?

Share this post


Link to post
Share on other sites

Did you  clean the carb after installing the new filter, pump and lines or before?  You could have dislodged dirt during the installation.                                                            

 I had to clean mine 3 times to stop the surging.      Another possibility is a bad gasket on the two piece intake.

  • Like 1

Share this post


Link to post
Share on other sites

My 520HC got puffing blue smoke and it turned out to be a loose welch plug allowing air to be sucked into the crankcase.

 

This made the breather blow too much air into the air cleaner and it passed oil with it which the engine then burned.

 

Also, it made the air filter get oil soaked.

 

When you clean the carb, is there any oil in the air cleaner ?

 

  • Excellent 1
  • Thanks 2

Share this post


Link to post
Share on other sites

Try adding a good dose of Seafoam to your gas tank. It cured about 85% of my 520's surging issues.

  • Excellent 2

Share this post


Link to post
Share on other sites

The surging starts after about 10 to 15 minutes of mowing.  I can cut throttle back to 75% and the engine calms down but lacks good power to mow...

Share this post


Link to post
Share on other sites

Does it sound like it's over revving or do you see the RPMs reg over 3600? 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Recently Browsing   0 members

    No registered users viewing this page.

×