View Full Version : lawn boy problem looking for some help

casey humphrey
06-07-2011, 03:09 PM
I have a 2 cycle commercial 6.5 HP 21'' lawn mower

problem, the idle goes up, than down goes up ,than down consistanly I have to push lever all the way to choke and the idle smooths out but it smokes alot and if it dies good luck getting it started again.

what I have done so far, new carb last season ran great with this but later that year it started doing this. This year pulled carb off cleaned,installed new plug. thoughts?

My thoughts I was thinking stater since it is so hard to start I don't use machine alot only about an hour a week. So it doesnt get used that much and the machine is kinda cool looking so I just can't let it go it has some sentimental value to me I started with this machine 6 years ago.

06-07-2011, 03:59 PM
Casey- I use LB's but mine are 2002 or so model's 6.5 Dura-Forces. The 'surging' at idle is a common complaint. I cured all of mine by drilling out the main jet and also the Pilot jet. This cures the lean condition. One of my mowers seem's to smoke a bit for short while then clears up..others don't smoke- but none go up-and-down now. To do it right..you could drill out the main and try it- then do pilot if still surging. I just did both as I had carb on bench and bit of hassle removing and re-installing. You can get the tiny drill bits at a hobby store/model store. They are VERY tiny so be careful and do it by hand (not drill)..I put them in a tiny vise grip. And if doing pilot only go thru the outer jet hole..don't go all way thru to other chamber. Ideal size bits are as such: Main-#68 Pilot#78 ( I ended up buying #67 for main as they didn't have#68) Geno

06-07-2011, 04:45 PM
to fix mine i just turned the engine up a few clicks to the left and it works fine and i mow a little faster too. i havent had any problems when i turned up a little.

casey humphrey
06-07-2011, 05:17 PM
could I just go to the dealer and get the next size UP in jets?

Diddy what do you mean by turning it up a few clicks? Is there an air screw or something on the carb I can just turn?

06-07-2011, 06:09 PM
the air fan right behind the carborator. its the big white thing that controls how much gas gets into the engine

casey humphrey
06-07-2011, 06:24 PM
oh I see now!! That must be the tall white plastic piece that governs the motor I did know that was adjustable this is good intel!

06-07-2011, 06:49 PM
I also turned mine two or three clicks. I forgot about that. But maybe re-jetting wasn't nessesary- I did all three same time. I sure would just do the air vane first..take it from that point but maybe that will do it..Did for Diddy.

06-07-2011, 07:47 PM
just dont go crazy over adjusting it. i have a silver series that is supposed to have the self propell speed at 2.6mph i turned mine up so i was going around 4.2. and then i little while after i blew the bottom seals. as long as you dont double the rpm on the engine youll be fine and your surge problem is gone

06-08-2011, 01:37 AM
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06-08-2011, 01:42 AM
Yeah, throttles and governors and chokes are things of the past, everything's automatic nowadays
so throw that thing in the garbage, run to Home Depot and buy yourself a Honda HRR for $400'ish, gtg.

06-08-2011, 01:47 AM
EPA crap for the surge. Too lean. There's a larger jet you can buy to replace your smaller stock one.Search here or gardenweb forums for the jet part number.
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