nekovt 0 #1 Posted June 10, 2011 Hi everyone, I am about to start a de-carbon on my ONAN 18. I wanted to check out why the new spark plugs were getting carboned up. It sounds like it may be due to higher octain fuel shouldn't be run and I should switch to 87. The other thing I noticed is that the bottom air flap in the carburetor is staying mostly closed when it's running. It seems to run fine, but I thought that should be open? I was also thinking that it could be running rich and I'll have to adjust the hi and low jets after I get everything going and swith to 87 octane. Does anyone know about the air intake flap? Thanks! Brad Share this post Link to post Share on other sites
Kelly 1,033 #2 Posted June 10, 2011 The top plate is for the choke, the bottom one is the throttle, it opens as you move the throttle control, with the engine off set the throttle to full open, then it will or should be very close to open fully Share this post Link to post Share on other sites
shorts 182 #3 Posted June 11, 2011 proper float level is critical in keeping any engine from running rich even when you have adjustable high speed fuel mixture needles. make sure that the float isn't deformed or sinking and set the highfloat level correctly, check with your friendly dealer to see if their any service updates that apply, the printed manuals are good but the electronic or microfitch updates will be most accurate to deal with the chemical changes in modern fuel blends. :hide: Share this post Link to post Share on other sites
nekovt 0 #4 Posted June 11, 2011 I was able to shut it off and move the bottom throttle flap freely. I was just worried that it was mostly closed when it was running. If I give it some throttle, the flap opens just a little bit and then goes back to mostly closed. I was thinking it might be running rich. I'll check the float to, I've got the service manuals - I didn't know the floats were adjustable! Thanks! Brad Share this post Link to post Share on other sites
