520H running rich, Cleaned up first.

[Duramax7man7 505]

Hey Gang I have a 520h that was smoking a bit especially at startup and moving to WOT. 

 Pulled the Engine as it stopped charging. Replaced the needed parts, pulled the heads, cleaned all carbon from them and the valves and seats as well as readjusted the valves. After a thorough cleaning of the engine and tractor and I put the unit back together and she fired up. BUT, I'm still getting smoke and when I try moving the throttle to WO the carb will gasp and die unless I feather it up. The carb spits quit a bit fuel out with the lair filter off as well. I can hear the engine fouling out while at idle or WOT and the plugs are all carbon'd up as well as the exhaust. 

 

 The carb is a Nikki 6100 #146-0479 There is only the low idle speed stop screw and another screw at the base of the carb which was set to about 2 1/2 turns out. Ive tried everything from 1 1/4 to 1 1/2 down to 1/2 and 2+ turns out and nothing affects the "missing/ fouling" sound... 

 

 Do I need a new carb being that the unit has 2360hrs on it? The engine doesn't knock and seems to have good compression when cranking by hand. Thanks.

[Duramax7man7 505]

I take it that it's something simple and I should know better? ha ha. I guess I'll pull the carb and take a look at it. Maybe something is wrong with the float or float needle. Don't really think so as it runs mostly good other than the what's happening. 

[lynnmor 6,847]

Do an actual compression test and report the pressures.  Oil smoke comes from oil going past worn rings or valve guides.

[Duramax7man7 505]

When I removed the intake last night there was carbon in the exhaust valve ports of the block and a wet layer of gasoline in the intake valves ports.  

 

So this isn't oily its carbon build up. How many hours will a fixed jet carburetor like the Nikki 6100 #146-0479 [238] last until it starts running rich from warn jets? Because this carb has 2360hrs on it. 

Edited November 2, 2016 by Mastiffman

[lynnmor 6,847]

Jets don't wear out.  A worn carb would have too much clearance at the throttle shaft making it run lean.  Too much gas might come from a faulty float or float valve.

[Duramax7man7 505]

Gotcha. I was under the impression that with extensive use they did wear out being that some rebuild kits have new OEM stock jets in them to replace old ones. 

 

Well any way. I did play with the mixture screw a bit more and settle at 1.75- 2 turns out from lightly seated based off of no smoke production at idle or when switching to WOT. 

 

 BUT, I'm still getting a choke out when I do try and give it full throttle or even half throttle. Not sure if that has something to do with the throttle linkage or what. |
 Here's a video from this afternoon of what's going on... 

 

 

 

[WHX?? 46,994]

Watching this with interest as mine does the same thing when throttling up. Didn't worry about it too much as it lessens & goes away after it warms up. Never could figure out why & also why it seems to run on one cylinder when it is cold out. After 30 seconds or so smooths right out but can return  when throttling up if I don't let it warm up more. Can be aggravating as my 520 is my winter worker.

 

Yours looks pretty clean for those kind of hours so somebody has been taken care of it!

[Duramax7man7 505]

Thanks. This machine stopped charging the week after I purchased it. It also had a bad flywheel and starter pinion combo. So I Pulled the engine, removed the manifolds, flywheel, heads, starter, shrouds, stator and valve covers.  Decarboned the heads, pistons and valves, set the valve lash and cleaned up the block. Got a new (used) stator, stater pinion, manifold gaskets and one head from Boomer (thanks Boomer!) and a new (used) flywheel and new rectifier and cleaned up the wiring harness and slapped it all back together... 

[WHX?? 46,994]

Does it do it or lessen as it warms up and is at temp???

 

BTW nice battery clamps!

 

Its gotta be either not getting a enough gas or too much (flooding out). Closing the choke a little would indicate not getting enough gas at idle but it sure looks like yer getting a good spurt at throttle up. Seems to run smooth otherwise for that many hours ... I couldn't catch that miss you mentioned. What's it like under a load? Same, better worse??

[lynnmor 6,847]

Please, check the compression.  Your doctor always checks the blood pressure first thing.  That engine seems rough like the two cylinders aren't doing an equal share. 

 

While the later models were more cold blooded, but not as bad as your video.  If you check the compression, then check for vacuum leaks, the next move is to clean the carb properly.  Check for a missing welch plug right above the mixture screw.

 

If we do this one step at a time, success should come.  Step one is to be sure the engine is sound, did I mention compression?

[WHX?? 46,994]

33 minutes ago, lynnmor said:

Your doctor always checks the blood pressure first thing

Good way of putting that lynn , I'll double that suggestion, even though I hate doing compression checks on Onans...must be fear of the dreaded .....never mind I don't want to jinx him.

 

I think I just saw a comp. tester coupon for a hobbyist at HF if you don't have one.

[Duramax7man7 505]

I will end up testing the compression but I did find a definite problem... 

 

I believe one of the wire to be bad. I tested the short wire (both are 7mm P220 wires) and it was producing about 10.5 ohms of resistance. 

The longer wire was producing anywhere from 18.75- 34.26 ohms DEPENDING on how I bent it... 

 

 So I will be getting a new set of wires first and then testing the compression for sure as like suggested... That's very important. If it needs rings, it will get them. 

[lynnmor 6,847]

Compression is not just rings, I had a front cylinder down to 72 PSI and it needed a valve job.  If by chance you didn't adjust the valves correctly, that too can cause low compression.  Then there is the unmentionable, that I won't bring up just yet.

 

Finding the 7mm wires is a pain, I've used 8mm and was able to force them to fit.  The Onan wires are priced so high that you can get a set for a V8 and save money.

[Duramax7man7 505]

Right, valves. Check! I will eventually rebuild the engine. But for now I will do the simple stuff and if that doesn't clear things up a bit I will do a rebuild. here is a video after shortening and re attaching both of the spark plug ends. 
 

 

Edited November 3, 2016 by Mastiffman

[Duramax7man7 505]

Can anyone do me a favor and test the ohms of their wires on their Onan engine? I'm curious what the normal resistance is of a good set...

 

Thanks. Looking for resistance of electronic ignition wires as well. I think that there's a difference. At least onanpart.com and other sites state there is.

 

 Thanks! 

[1995 520H+96+97 935]

Plug the vacuum leak (hose, line). You had it your hand in the first video.

Post a new video.

[Duramax7man7 505]

6 minutes ago, 1995 520H+96+97 said:

Plug the vacuum leak (hose, line). You had it your hand in the first video.

Post a new video.

 

 That was just the air cleaner sensor tube. I don't think that would affect the engine if it's open and has air flow. The vacuum tube from the intake to the vacuum gauge is connected and working fine. 

 

 

[1995 520H+96+97 935]

Take the crankcase breather apart. Make sure the steel wool is not touching the three balls.

The balls should move freely.

[lynnmor 6,847]

The ohms can vary greatly on plug wires.  There are different types of cores and attachment to the terminals vary.  Your best bet is to take an old spark plug and make the gap twice what it should be, then attach a wire, lay it against a metal engine part and check for spark while cranking.

[boomers_influence 106]

1995

there are FOUR balls in the top of the breather

there should be a screen

to protect the balls from the stainless breather mesh.

thank you. boomer ( the used onan engine parts guy, also NOS and new )

[Duramax7man7 505]

8 hours ago, 1995 520H+96+97 said:

Take the crankcase breather apart. Make sure the steel wool is not touching the three balls.

The balls should move freely.

 There's actually four and that thing is sparkley clean. 

 

 

4 hours ago, lynnmor said:

The ohms can vary greatly on plug wires.  There are different types of cores and attachment to the terminals vary.  Your best bet is to take an old spark plug and make the gap twice what it should be, then attach a wire, lay it against a metal engine part and check for spark while cranking.

 

 To late, Went to the local Cummins/ Bridgeway facility and picked up some brand new wires.  Check out the video. 

 

3 hours ago, boomers_influence said:

1995

there are FOUR balls in the top of the breather

there should be a screen

to protect the balls from the stainless breather mesh.

thank you. boomer ( the used onan engine parts guy, also NOS and new )

 

100% as always Boomer! Thanks for the help as always. Sorry I got impatient.. I ended up picking up a new set of wires for about $17.

 

The old wires were testing at 10.59ohms (9" lead) and 18+ohms (18" lead)

The new ones were 1.5ohm (9") and 5.5ohms (18")... I slapped them on gave it a test to warm the engine and then changed the oil again and here's the outcome video... I'm feeling a lot better about this 520h. And I was right about the oil seepage. 

 the 2 bearing plate bolts on that side were a bit loose. Not moveable by hand by I was able to snug them up for the night. 
 

After the oil change and new wires. All buttoned up... Is the idle to high? My tach is not working for some reason... 

 

 

Edited November 5, 2016 by Mastiffman

[woodchuckfarmer 333]

Check the 9 pin block for the tack connection .     Wayne

[Duramax7man7 505]

I removed the 9 pin molex and used male to female individual connectors that are all heat shrunk. For each of the nine circuits. Is there a way to actually test it? Maybe a voltage application that will show that it's working. It an SW Gauge.