Working on a Miller Bobcat, mid 2000s with an "Onan P220IGOHV" engine which is really a Subaru/Robin EH65. Both exhaust valves burned/bad, have not torn heads off yet to see. Otherwise good engine. Complete heads may be available but expensive. Owner came up with this https://www.surpluscenter.com/Brands/Robin-Subaru/22-HP-Robin-EH65-Engine-28-1872.axd But I don't think it is right because the crankshaft looks like a keyed straight shaft for a pulley drive and I suspect the welder has a tapered shaft. Plus all the accessories, fuel pump, valve covers, oil fill, carburetor look to be wrong/different. I am wondering if any of you guys have done an engine swap on one of these welders and how it turned out.
Most of the welders I've gone through were running Onan twin flatheads, Briggs or Kohler. I'd suggest just a quick repower with a Briggs or Kohler, but there's still possible issues with exhaust routing, and not sure if welders are subject to any EPA rules or regulations in California. IIRC, the welders do use tapered shaft like the gensets. Depending on the hours, I'd personally pull the heads, lap and prussian blue the exhaust valves and see what you come up with before tossing another engine in.
My welder guy tells me that my Trailblazer 302's with the Subaru have threaded cranks, both are 2014 and 2015 models. He said "Don't break a crank or you will never get it uncoupled". Not sure about the older stuff.
The info I am getting says it is a threaded crank also. Uncommon engine on the used market. I believe we have changed directions and are now going to attempt to repair the heads, hopefully we can get all the parts. This appears to be a very early production engine, have not seen one quite like it.
If you have the serial number you can look up the manual online but I'm not sure if it will show if it's tapered or threaded. Miller has really good tech. support if you call them though. https://www.millerwelds.com/support
Is this one a pushrod or overhead cam engine? I was told (Miller Certified Service guy) to change oil and filter at 100 hours using only the recommended oils to prevent problems with the overhead cam engines. Mine are at 1800 hours and 850 hours with no problems yet. My TB 325 only has 350 ish hours but it has the fuel injected Kohler.
Pushrod engine. I can't think of any with OHC. The older ones had a flathead though. Maybe that was the difference the Miller guy was citing. I think this problem came about because of zero lash burning the exhaust valves. I see this engine in a lot of generators. It has its fair share of problems. Subaru/Robin gave up in this country a couple years back. I wonder why.
RZ, how to you like your TB325? Is it as good as they claim?
Love it so far. still learning to play with the arc force control. But I do think it welds 6010 nearly as well as an old SA200, and it really runs my 12VS feeder nicely with both dual shield or fluxcore. My favorite part is running grinders and a chop saw with out revving the engine up. Plus it will burn 1/8' rod and only come off idle every now and then. The weld at idle is hard to get used to... after years of hearing the engine respond to the arc and using that as a gauge of how deep you are digging.