Onan 5500 Longevity? Valve Adj?

I see your original post couple years old. have a shop that works on these gennys. replacing cyl heads is relatively expensive.
I suggest checking valve lash @ 900 or so hrs. have literally hundreds of these sets in customer base, many in commercial use. Most common problem with engine is valve guides come loose in heads, but usually not before 2000-3000 hrs. Drive belt & tensioner typically lasts about same amount of hours. make sure you check field brushes & rotor slip rings at 1000 hrs or so. Probably should replace @ 1000 hrs, probably will not last for 2000 hrs, and if brushes wear to point where they arc and burn slip rings, then you have a $1000+ repair instead of $75.00 brush replacement. Have had customer get 7000hrs with nothing but basic maintenance, and have seen complete engine failure at less than 1000 hr.
All function of usage, maintainance, and some luck factor, I guess..

Just did the lash check on my Onan Micro 4K that has 511 hours.

The intake was .003 and the exhaust was a slight snug .002 (Spec range is 0.0008 to 0.0032)

Reset both to .002

Installed a new valve cover gasket as well. Anyone who has this generator (Micro 4K 1 cylinder) can look for my instruction here: https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29631579.cfm

Pirate wrote:
1800 hours just oil/filters. runs perfect. oh, new fuel pump and choke pull off.

Yes Sir.....Should last to 10,000 hour's. :)

Having experience working on aircooled engines (VW's) these gererators use the same principal of cooling. Even when under load the load is not close to what a load is on a vehicle with an air-cooled engine. As long as the maintenence is kept up such as oil, filter, plug and spark arrestor cleaning one should not need a valve lash check after 450 hours.

Part of ones maintenance should be carefully checking the generator for cooling blockages of any kind such as nests or any type of potential blockages that will impede cooling.

A friend with a 7kw Onan just had a bent rocker arm at around 450 hours- did not have to pull the unit for the repair. The rocker arm was discovered when he took it for the valve adjustment. This unit is in commercial use, run at full load if it is run at all, still I was disappointed in the failure.

Generator Jim wrote:
Most people don't run their generators at full load and they carbon up around the valves, cylinder head pockets, muffler and exhaust piping. ONAN has set up their maintenance suggestions based on AVERAGE use of the units. IF the unit is pinging or knocking, then a "carbon job" is necessary. If it is running smoothly, try some Sea Foam in the fuel and the oil. This might help clean out inside and outside of the engine.

Is it necessary to clean carbon at 450 hours -- no. But you should start thinking about keeping the exhaust passages fairly clean.

Jel

Thanks. This is good to know.

My only concern about the maintenance requirement to "Clean or Replace Cylinder Heads" every 450 hours is for warranty purposes. Onan warrantees all parts and labor for the first 2 years and, for lack of a better description, a basic "power-train" warranty for the 3rd year.

At the rate we're going I can see us easily passing the 450 hour mark before the 2-3 year warranty is up. At some point gonna have to weigh the benefits of paying big $$ to a certified Onan dealer to do a valve adjustment and head cleaning job vs. losing warranty coverage.

To clarify, not debating whether the maintenance should be done, but whether to do it DIY, or pay the big $$ to an Onan dealer for the valve/head maintenance to keep the warranty valid.

Most people don't run their generators at full load and they carbon up around the valves, cylinder head pockets, muffler and exhaust piping. ONAN has set up their maintenance suggestions based on AVERAGE use of the units. IF the unit is pinging or knocking, then a "carbon job" is necessary. If it is running smoothly, try some Sea Foam in the fuel and the oil. This might help clean out inside and outside of the engine.

Is it necessary to clean carbon at 450 hours -- no. But you should start thinking about keeping the exhaust passages fairly clean.

Jel

otrfun wrote:

Crazy Ray wrote:
ON old RV had 6200 hours on 5500, ran like clock. call onan for valve work. JMO

That's a lot of hours. Good to know they can potentially last that long :)

The Onan 5500 manual says it's necessary to "Adjust Valve Lash" and "Clean or Replace Cylinder Heads" every 450 hours. Adjusting the valves seems reasonable . . . however, not sure what to make of the requirement to pull/clean both heads (and potentially replace them) every 450 hours :?

I put sea foam in the tank and then run the genny. I once took my RV to a cummins place to have them work on the generator. They made it worse.

1800 hours just oil/filters. runs perfect. oh, new fuel pump and choke pull off.

Crazy Ray wrote:
ON old RV had 6200 hours on 5500, ran like clock. call onan for valve work. JMO

That's a lot of hours. Good to know they can potentially last that long :)

The Onan 5500 manual says it's necessary to "Adjust Valve Lash" and "Clean or Replace Cylinder Heads" every 450 hours. Adjusting the valves seems reasonable . . . however, not sure what to make of the requirement to pull/clean both heads (and potentially replace them) every 450 hours :?