Rob257 1 #1 Posted August 13, 2015 I have a 1994 520-H with P-220 Engine with about 700 hours of running time. Over the years I followed the recommended schedule for lube, oil changes, air and gas filters, etc.Never gave any thought to actually tuning the engine and if I understand correctly timing is not adjustable and carburator, while adjustable, is recommended only for authorized dealers with special equipment.Sounds like there's not much I can do other than throwing in a new set of spark plugs. Is the carburator really that hard to work on? Share this post Link to post Share on other sites
rmaynard 14,932 #2 Posted August 14, 2015 It's not tuning as such, but removing the engine covers, cleaning all debris from the cooling fins and pulling the heads to de-carbon seems like a reasonable thing to do at 700 hours. The rear cylinder is prone to overheating and damaging the valve seats. It may be a good time to be proactive. 1 Share this post Link to post Share on other sites
motox25 36 #3 Posted August 14, 2015 How's it running? If it's running well all that is probably needed is a valve adjustment and maybe decarbon the heads. Share this post Link to post Share on other sites
Rob257 1 #4 Posted August 14, 2015 Running well enough but my wife says it sounds "rougher" than it used to. May have to crank it a few more times than in earlier years but I wouldn't swear to it. I keep the fins and all other areas blown free of debris with a regular visit from the air compressor. Sounds like pulling the heads will be a good idea. Thanks, guys!Rob Share this post Link to post Share on other sites
bmsgaffer 2,043 #5 Posted August 14, 2015 Remove the tins, you will be surprised what you cant see that you miss with compressed air, I was.Based on what I have heard from others, you will need to adjust your valves and that will get it purring again. Good luck! Share this post Link to post Share on other sites
rmaynard 14,932 #6 Posted August 14, 2015 There are several folks selling "de-carboning/valve adjustment" kits which include head gasket, exhaust gaskets, intake manifold gaskets, and valve cover gaskets. RedSquare member @boomers_influence is one.OnanParts.comGary's Place Share this post Link to post Share on other sites
boovuc 1,090 #7 Posted August 16, 2015 Your carb is the non-adjustable fixed-jet type. All electronic ignition, etc.Basically what everyone stated above for a tune-up. Fliters, (gas especially), maybe new fuel line while your at it. At 700 hours, the heads should be taken off and decarboned. This is when you would also adjust the valves which can make a huge difference on performance if they are out of adjustment.Short of taking just the top off your carb and giving it a good cleaning with seafoam or carb cleaner, these are your options but it needs a decarbon and valve adjustment regardless of how it is running. Share this post Link to post Share on other sites
