Flush tank, drain lines, clean carb bowl

[Forrest Carver 52]

Thanks lynnmor. Luckily the bolts attaching the exhaust to the engine came off easily (maybe a little too easily?!). Those gaskets appear to be in good shape. The muffler clamps are basically welded and I don't have much hope in loosening those, but I circumvented the issue by removing the front part of the frame, allowing me to remove both muffler/exhaust pipes. With the exhaust out of the way I was able to remove the intake manifold and confirm that both intake manifold gaskets were no good. I have replacement gaskets and will use the proper torque of 8-14Nm when reinstalling. Exhaust will be 12-15Nm and I will reuse the gaskets...good thing they're still good because I don't have extras of those. While I have it disassembled to this level, I'm willing to do a bit more.

 

I attached some pictures below, not sure if they will help or indicate any other preventative maintenance. It certainly looks like it needs a good cleaning, and there's an alarming amount of oil/gunk buildup.

 

I'm intimidated by a compression test and don't have the tools.

What's involved with adjusting the valves?

I don't think I'll go to the trouble/expense of media blasting the exhaust...could I simply hit them with a wire brush on the angle grinder and then spray paint them? Anywhere I shouldn't hit with the paint?

 

Once I get the machine running reliably I will be selling it to a good friend, who is very interested in going the extra mile to maintain, recondition, restore, and give it the care it really needs. While I've grown to love this Horse, the kubota I inherited is meeting all my needs (log splitter, powerful loader, etc) and is more practical for my acreage and needs.

[lynnmor 6,794]

Completely cleaning the exhaust will give the best results, wire brushing is better than nothing.  I use Rust-oleum High Heat spray paint.

 

To do a compression test you simply remove the spark plugs then insert the tester in a spark plug hole and crank the engine.  Test both holes and the results should be over 100 psi in each, the repair limit is probably 75 but I don't like to go that low.  A tester can be bought or rented at many auto parts stores, a cheap one can be found at the usual online stores.  If you find a low reading then there is a lot more work to do.

 

 

Carefully clean the valve covers and then remove them, a shop vac can be your friend. Work clean and don't allow debris to fall into the engine.  Turn the engine by hand till a valve reaches maximum opening, mark a pulley or flywheel then turn it one more time.  At that point, adjust that valve to specification using two wrenches and feeler gauges.  Repeat three more times.  Your service manual will have the information and specifications, it will also tell you to use timing marks and have you do more than one valve at a time, but to avoid confusion just do it the way I explained.  The intake and exhaust will have different settings so be sure which you are adjusting.

 

 

[Forrest Carver 52]

The compression test now seems like a cinch although it appears I need to put everything back together before doing that, so I will do it after adjusting the valves, or attempting to.

 

Unfortunately I removed a valve cover before reading the section on valve adjustment and realizing this job is well beyond my skill level; the valve cover gasket came apart upon removal and I don't have spares, so I will need to obtain at least one of those now regardless of whether I can adjust the valves properly or not. Anyway I am committed at this point so might as well stay the course. I think I understand how to adjust the valves but what I haven't figured out is where the clearance I'm trying to measure is. The manual says "between the valve stem and tappet" but I don't really have a good grasp on the anatomy of the system. The EV in the manual indicates it's the gap circled in blue? Also another dumb question (if you're not used to them now, you will be soon), on my image below, is the valve on the right or the left "maximum open"?

 

Does anything look visibly amiss in the image? I'm headed to the hardware store now to get a feeler gauge set and a compression test kit.

[lynnmor 6,794]

You can check compression with parts removed, just be sure that no moving parts are in harms way and you aren’t pumping gas out of the open fuel line.

 

Maximum valve opening is when the spring is compressed the maximum.  Your blue circle is at the adjustment place but there is no opening due to the tapper pushing it, one full turn and that one can be adjusted.  To adjust, hold the tappet by its flats with one wrench while turning the hex with another wrench.  It usually takes very small movements to get it right.  Use feeler gauges on size smaller and one size larger as go and no go gauges.  A light drag with the correct size is perfect.
 

you might need three valve cover gaskets depending on how your covers are made.

[Forrest Carver 52]

All right, feeling a little better about this now. Took a while to realize I need to physically push the tappet in to reveal the gap. I measured all four gaps; one was spot on, two were slightly too large, one was slightly too small. They are now all adjusted such that the .006" feeler gauge will not fit through. However, after going back to double check the manual I realize that I read the chart wrong and was mixing up my X and Y coordinates. Turns out the exhaust gap needed to be .013". No matter, I can go back and readjust them now.

 

While I wait for the gaskets and compression test kit (hardware store didn't have one) to arrive, I might as well give the engine a good cleaning. Can/should I soak the valve covers in degreaser? After covering the intake, exhaust, and valve cover holes can I spray it down with engine degreaser and pressure wash it? Or should I wait until it's reassembled?

 

Any other things I should do while the engine is disassembled to this point?

 

 

[lynnmor 6,794]

As long as you were sure that the oblong holes went to the intake valves you did good.

 

I wouldn't use a pressure washer, not even if it were completely assembled.  Use parts cleaner and a considerable quantity of paper towels.  The bolt holes should be cleaned out, you can use compressed air or stick the straw of the parts cleaner in and blast them out, be sure to use face protection.

 

The valve covers often rust, so clean them with parts cleaner and paint the exterior side.  All that oil sludge may be coming from the breather, check the rubber in that area.

 

The intake manifold is probably the two piece design that is riveted together, inspect that seam closely to check for leaks.  I clamp a flat plate with a homemade gasket where the carburetor mounts and then fill it with gas, diesel or whatever to test it.  Also, look for notches cut into the edges where the heat shields might touch, I cut back the shields to make sure they can't touch.  Your engine may not have that issue.

[Forrest Carver 52]

Thanks again for all the help so far, this has been above and beyond. Good trick on checking the intake manifold, I did what you suggested and fortunately it does appear to be leak-free. The valve cover gaskets arrived and I properly adjusted the exhaust valves. I forgot to bring my torque wrench home from work today to properly reinstall the valve covers, intake and exhaust bolts, but tomorrow I will be putting it all back together. Before I do, though, could you clarify what you meant by "the oblong holes went to the intake valves"?

 

At this point the only thing I can think of that may have caused the original problems was the poor condition of the intake manifold gaskets. I guess time will tell, tomorrow is the big day!

 

P.S. I gave it an oil change tonight. It was critically low on oil, and the oil was pitch black!

[lynnmor 6,794]

11 hours ago, Forrest Carver said:

Thanks again for all the help so far, this has been above and beyond. Good trick on checking the intake manifold, I did what you suggested and fortunately it does appear to be leak-free. The valve cover gaskets arrived and I properly adjusted the exhaust valves. I forgot to bring my torque wrench home from work today to properly reinstall the valve covers, intake and exhaust bolts, but tomorrow I will be putting it all back together. Before I do, though, could you clarify what you meant by "the oblong holes went to the intake valves"?

 

At this point the only thing I can think of that may have caused the original problems was the poor condition of the intake manifold gaskets. I guess time will tell, tomorrow is the big day!

 

P.S. I gave it an oil change tonight. It was critically low on oil, and the oil was pitch black!

The exhaust pipes go in the round holes, the intake goes in the ones that are not round.

 

You need a 1/4" torque wrench since the specification is a very small number.  Resist the temptation to tighten more, it is easy to strip the threads or distort the parts.

 

Aftermarket gaskets often fail, I have had some turn to mush in one season.  Never reuse gaskets, they are made to crush one time.

 

If the oil was that black, I would change it again after just a couple of hours.  Always drain the oil hot and immediately after shutting the engine off.

[Forrest Carver 52]

I used my 1/4" torque driver which goes from 3-15Nm so everything is tightened to spec. I reassembled everything, cranked it up, and.... *drum roll*

 

*sad trombone sound* Same issue! The engine seems to run well when almost fully choked. I'd like to think it sounds better and more consistent than it did before, but that might just be wishful thinking. When fully choked it stays running but doesn't sound good. Anything less than almost-completely-choked and it runs like crap, backfires a lot, and eventually dies. The "window" is extremely small; even a microadjustment in either direction of the choke from the sweet spot will cause a noticeable change in performance.

 

I assume at this point it comes down to a carb adjustment. Just follow the instructions in the manual? Any caveats or tips?

 

Will be borrowing a compression test kit from a friend today so that's on the list too.

[lynnmor 6,794]

I didn't see where you had the carburetor completely apart when you had it off.  You still have a closed off passage.  Did you remove the mixture screw(s) and blast carburetor cleaner thru there?  Did you adjust the mixture screw(s) by the manual?  The problem is that we can't see it from here, photos would help.

[Forrest Carver 52]

On 2/19/2023 at 9:06 PM, Forrest Carver said:

 

Let me know what other angles/pics you need. I removed the idle and main mixture needles and shot carb cleaner through the holes. The carb cleaner came out of the center right hole when going into the idle mixture hole so it appears to be clear. I replaced the needles and set them to the recommended setting (1 turn out on idle, 1.25 turns out on main.) Won't be able to check my work until the AM, but I'm hopeful that did it.

 

Regarding the compression test, what am I doing wrong? Everything is installed properly but pressure is not building as I manually crank the engine. Air is coming out of the crankcase breather tube once per rotation.

 

One thing to note: the throttle has been on "fast" throughout this whole procedure. In fact I can't remember the last time I had it set anywhere else.

Edited April 13, 2023 by Forrest Carver

[Forrest Carver 52]

SUCCESS! Kind of. I cranked it up this morning and it fired right up. I backed the choke off and it started purring. What a wonderful sound!

Unfortunately, after 15 or so seconds, thin black/brown oil started spraying out of the breather tube, soaking everything and getting all over and into the carburetor. What gives? I put the proper amount of oil in during the change.

[lynnmor 6,794]

Did you rebuild the fuel pump portion of the carburetor?  Looking at the photo, I see signs that the carburetor was not given a thorough cleaning.

 

All too often mixture screws are screwed in too tight causing damage that can't be repaired, they only need to be run in till a bit of resistance is felt.

 

I would flush the fuel tank and replace all fuel hose, if there is blockage or leakage the fuel pump will not work correctly.

 

I have no idea what sort of compression tester you are using.  You should be using the starter to crank the engine while doing the compression test.  Crankcase pressure varies as the pistons move, some breathing can be expected.

 

I just saw your latest post.  If the breather is installed correctly there should only be a small amount of mist.  We need to complete the compression test correctly to see if the engine is healthy.

 

 

[Forrest Carver 52]

Thanks. Using the starter, I get 75psi on the right cylinder and 85psi on the left (when viewed from driver's seat.)

 

This oil spray is a brand new development. Could I have overfilled? I did not change the oil when the engine was hot, so maybe a fair amount of oil was still in the system due to higher viscosity? I did let the oil drain until every last drop came out, although it was a very slow trickle and took probably 15 minutes to drain completely.

Edited April 13, 2023 by Forrest Carver

[lynnmor 6,794]

The compression is at the low end of the tolerance, but it should run good enough.

 

The reason to change hot is more about getting the sludge out before it settles.

 

With all that choking, maybe you now have gasoline in the oil, it might need an immediate oil change.  Check to see if the level came up or the dipstick smells of gas.

Edited April 13, 2023 by lynnmor

[Forrest Carver 52]

Good to know. I will check tonight. I suppose I'll need to clean the carburetor again, seeing as how it got splashed with quite a bit of oil? Anything else to be concerned about from the incident?

[lynnmor 6,794]

1 hour ago, Forrest Carver said:

Good to know. I will check tonight. I suppose I'll need to clean the carburetor again, seeing as how it got splashed with quite a bit of oil? Anything else to be concerned about from the incident?

 

One concern that I have is the possibility that you got the valve adjustments wrong based on the lower than normal compression.  Maybe you can explain how you arrived at the adjustment point and your method of marking the full valve open point.

 

Splashing the carburetor is not a problem unless you washed dirt down the throat.

[Forrest Carver 52]

I waited until the spring was fully compressed and then went one full revolution further (based on the clock position of the ratchet that I was using to manually crank the engine) so that both springs were uncompressed. At that point I adjusted the gap based on the manual's specifications (.005" intake and .013" exhaust) 

[lynnmor 6,794]

3 hours ago, Forrest Carver said:

I waited until the spring was fully compressed and then went one full revolution further (based on the clock position of the ratchet that I was using to manually crank the engine) so that both springs were uncompressed. At that point I adjusted the gap based on the manual's specifications (.005" intake and .013" exhaust) 

Using that method you do ONE at a time.  A ratchet can move a few clicks so I would use a breaker bar.  Better yet, put a chalk mark on a fixed part and a pulley or flywheel then rotate one turn till the marks again align.  The idea is to get a cam lobe peak opposite the tappet, doing two at a time might have one starting onto a lobe ramp.  Yes, Onan does show using timing marks and doing two at a time, I just want to be sure that I am opposite the lobe.  I do think you have them adjusted OK, I just wanted to take any error out of the procedure.

[Forrest Carver 52]

Well, I think it's time to close this case!

I came home and checked the oil level, it's right in the middle of the "OK" section. I cranked it up with a little tarp to protect from a possible spray from the breather tube, and lo and behold, no spray! I messed around with the throttle and let it run for several minutes, but did not get a repeat of the oil geyser. It's running great now, just like when I first got it.

 

Please accept my heartfelt thanks for your patience and counsel. I couldn't, and wouldn't, have done this without your help and I will never forget this terrific learning experience.

 

The only problem is that I don't want to get rid of it anymore, even though it's completely impractical for my needs! Oh well, at least it will go to a good friend and I can visit it occasionally. He will be taking great care of it and is looking forward to tackling the other little issues. I'm certain he will be taking my place on this forum shortly after he comes to pick it up in May. He will certainly be in great hands!