Re: jacobsen Greens mower
Yes, depending on how often you use the machine you will have to de-coke the muffler/exhaust manifold, exhaust ports and the head because the 30 weight non-detergent oil does leave carbon build up.
Modern 2 cycle oil of today is far supperior in many many ways to the old school way of mixing non-detergent oil with the fuel.
The fact though is that these vintage Jac engines are plain bronze bearing, slow speed running motors and need the lubrication that the 30 weight oil provides. You can run the modern two stroke oil all you like in these machines, but be ware that by doing this that it will very potentially cause premature wear and that to me alone is simply not worth the risk to loose some smoke and carbon build up.
Here is brief run down that a friend of mine gave me a while back who has a lot of experience with these engines specifically:
" The modern 2 stroke lubricants do provide superior lubrication to modern engines. Engines with hardened bearing surfaces, rollers, balls and chrome molly rings, along with steel cylenders, and High speed - up to 22,000 RPM. The Jacobsen Lawn Queen, and the 321 series, as well as all those before are definately NOT modern They have soft bronze rods and bearings, cast iron rings and cylenders, plain bronze crank bearings, and for the most part, only turn 3,500 RPM Maximun - LOW SPEED! The 2 cycle lubricants do not stay on the bearing surfaces long enough to provide full protection. If you take apart an engine run with the modern lubricants, you will find a dry crankcase - there will be no oil on the bearing surfaces. for roller and ball baerings, this is not an issue, because the lube just has to be there a split second to do its work. On a plain bearing, this dryness is lethal! Plain bearings need oil on both sides to provide non friction issued. direct contact between metals brings on shearing forces that will tear the bearings up. While a roller-ball bearinged engine will tolerate a leaner oil mixture - 32 to 50 to one mixtures, a plain bearing engine will not tolerate it."
Everybody is entitled to their own opinion and that is one of the neat things that makes up a forum. This is simply a run down of my opinion and an explanation of why I run the 30 non-detergent oil in my vintage Jac engines specifically. Therefore, there will be no need for me to debate any further on the subject in this thread.
1971 Bolens 1886-01 'Resto-Mod'
Kohler CH22 V-Twin
Johnson Workhorse 14 loader
1977 Economy Tractor
Hydraulic lift conversion
48" Belly mower
"Direct my steps by Your word, and let no iniquity have dominion over me.." - Pslams 119:133
Last edited by Austen; 09-18-2010 at 02:36 PM.