Hi,
Pardon to weigh in here, but as the "self appointed" expert on these engines (the air cooled yanmar clones), I feel the need to chime in. I also sell these engines, so I get a little annoyed when they get generalized. I've offered them for sale here several times, and I get more "3600RPM crying" than phone calls, so I still sell them, but dont expect a marketing campaign. I have "United Power" engines, 4.7, 6.7 & 10HP. Mounting diagram for the crankshaft is an email away if you want it. I'll simplify the brand breakdown of these engines:
Real Yanmar: Very Nice
Some Chinese Brands: Pretty Darn Good
Many Chinese Brands: Runnable, but not so hot.
Some Chinese Brands: DONT EVEN START THEM!
As with all chinese engine products, there are somethings that money CAN'T always buy in China. I have tried many different manufacturers of these engines, and I have only 4 unsolved issues that no amount of discussion/money seems to be able to fix:
1) It may leak fuel or oil around a hose, or ring, or gasket surface. Not sure what it is about the seals they use, how they handle them, or the difference in the chemicals. Usually very easy to fix this problem. Sometimes fuel valve bolts need to be tightened. Just dont "fill" anything the first time!
2) Paint not always pretty. Looks good from far, but not necessarily "show room" finish up close. Most engines pretty good, some worse than others.
3) Crankcase needs to be filled with clean oil, run engine for 5 minutes, then drained, oil strainer cleaned, and refilled. Removing metal shavings is best done in North America according to the chinese!
4) Engine must be run with a substantial load and clean dry fuel for the first 10 minutes. This purges any air out of the injection system, cleans gum out of the pump and injector, and insures the injector seats properly. Timing is very critical on these engines, and gum/varnish/air can put the timing off so bad you will think the internals are about to become externals. 99% of engine isssues (hard starting / knocking / smoke / backfiring / excess vibration) seem to go away after the engine is loaded up and run up to temperature.
I hope some of these tips can help you fix your engine, or help you make purchasing decisions. They are a nice little engine, but they aren't quiet. The right brand will run 2000+ hours pretty easily. The wrong brand will fail in less than 20 hours. The governor response is excellent, and very tight. Most 10HP engines will fall from 60.5Hz to 60Hz when loaded down with a 5kW load. The only thing you will notice is a slight change in exhaust note. My suggestion for power generation is to cut the engine back to 1800RPM, and use it to drive an alternator. Noise falls off dramatically as the RPM decreases. Generally, these engines start well in the cold, because they have very high compression. The rope starter is really more of a backup, I wouldn't plan on using it at all below 5C or 40F, unless you are really engergetic. Ether and a the rope starter WILL cause injury to the untrained person.
Very tired now, if you want more details, just ask, and I'll ramble on some more tommorow, with a little bit more form and clarity.
Steve
