Join Date: Mar 2009
Location: San Angelo, Texas, USA
Model: GL1200 Interstate
First why are you concerned that you need a flush? Are the lifters making noise? This is usually the first sign of oil passage build up. I would call this a neglected engine to be that bad off. Most owners take pretty good care of their machines, but some are neglected. Maybe it just set for too many years leading to dried oil deposits.
Typically good motor oils have detergents in them and keep the engine reasonably clean if changed as recommenced. If you suspect the engine was neglected and want to run some cleaner through as a preventative maintenance that is okay. Any number of cleaners will work. Seafoam, Marvel Mystery Oil, Gunk Motor Flush, etc., all have properties to break down dried oil and deposits. They do so by softening the deposits so they can be carried away, filtered, and then drained (oil change).
Both methods the Honda deal suggested will work. All these products are additives or detergents and are not designed to run as motor oils, so you are diluting your engine oil some to clean it. This is a compromise. These products act as thinners in the oil and do not provide the protection that motor oils do. They are added to the oil to be circulated so they can clean. Filling the engine with transmission fluid and letting it set will clean without running the engine, no metal scuffing or compromise. It just takes more time while it sets, soaks and softens deposits. When you drain it the majority of the deposits are drained too.
Whatever you do, after a motor flush, I might add change the oil and filter again in five hundred miles. The new motor oil has detergents that will finish the cleaning job. If any deposits are still softening and breaking free the filter will collect them. Again, examine the filter for excessive deposits. You can remove it for inspection and then put it back every hundred miles or so, if you suspect a very dirty engine.
The main goal is to soften the crud if any and carry it away. Change the oil and filter more frequently the next few changes.
Transmission fluid is very high detergent and cleans well. It was designed to keep your transmission lubricated and clean for many thousands of miles.
If you follow the procedures recommended the risk of clogging your screen is slim under most conditions. Your engine would have to have been severely neglected to bring that on.
Does this help?