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jverhaag

Thoughts on cckb engine

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jverhaag

 I tore the engine down tracking an oil leak. Lloyd narrowed it down for me to the oil filter mount. The gasket was as brittle as glass. One of the bolts had backed out as well. It’s a mess. Oil and dirt every where. I Though she was just burning oil. Turns out she has been leaking it :)

since I have it on the bench I decided to pop the cylinders and look at the valves and the bore. The bore looks good to me but the valves seem iffy. This is the furthest into an engine I have been. So I don’t have the experience to make a good assessment. 

I would sure like your thoughts at what I am looking at. 

 

F57D5FDC-44F2-4F63-9CD6-6C589A8D5AE8.jpeg

 

F433C9FA-A9C0-4C82-84F2-4A0546F7EF9C.jpeg

89728B30-591B-4238-8EB3-3E3963BDAB98.jpeg

3B63F065-E4B6-4708-B707-4B395BC7D874.jpeg

 

 

 

 

 

Edited by jverhaag

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SimpleOrange

Remove some carbon fro the piston tops, if the engine has been bored out before the over sized piston will have something like 0.010 / 0.020 0r 0.30 stamped into the top.

I think your CCKB engine has forged steel connecting rods that use shells. if the crankshaft has previously been reground the under size shells will have numbers stamped on the backside.

Reinstall the cylinder heads then do a dry and wet compression test, this will tell you the condition of the piston rings. If you have a vacuum gauge connect it to the engine then run her. The gauge will tell you the condition of the valves plus diagnose a lot of other issues.

Now that you have the heads off turn the engine over by hand bring each valve to its most upper most lift then wiggle the valve side to side in four directions as the guide may have worn more to one side than the other.

If you discover a lot of side play with the valves now would be a good time to have the guides replaced any small engine shop should be capable of doing this job. If it were me I would drill the old guides larger than the valve stem but not all the way out. Then I would push the old ones out.

To install the new guides I would warm the engine block with a hair dryer warm to the touch, the new guides in the freezer.

The new guides will fall right into place in fact you would have to be careful not to install them to deep. Because once they're set and assume the same temperature as the engine block their not coming out all that easy.

When  you reinstall the oil filter housing use new bolts with the blue locktite.

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720nut

Gill pretty much hit the nail on the head as they say, but not everyone has the skills to do this themselves and it becomes quite expensive to have a machine shop  rebuild these engines,

If guides are ok I'ld clean and new rings and a valve job.

Definitely seen much worse, you clean the carbon off and it won't look so bad.

Edited by 720nut

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jverhaag

I’ve started getting them  cleaned up. It doesn’t look nearly as bad. Intimidating but not as bad :)

There are marks on the top of the piston but I don’t understand what they are telling me. Can some one intrept. 

07904BE1-75D1-42A6-9721-724FBCEDE4F0.jpeg

D3F98A6F-4E97-4920-92A7-ECA71D8C10E2.jpeg

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720nut

John

STD = standard bore. If were overbore it would read something like this .010 = ten thousands over and so on.

I see you've removed the valves, how were the guides ?

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GregB

One caution no one has mentioned.  When scraping carbon, use something like hardwood so you do not leave a sharp edge or score anything.

Some of the engine companies suggest that to prevent hot spots that could lead to detonation.

 

None of you pics show anything sharp but check with your fingernail etc.  if sharp you could rub with something to break the edge.

 

 

 

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SimpleOrange

As 720nut said STD indicates piston is standard bore, the other marks would identify the person in quality control who checked the piston coming off the line.

To further explain detonation, carbon on the piston after combustion can glow like a burning ember in a fire, the ember will cause the engine to fire before reaching top dead center causing a reaction termed pre-detonation. Fire before spark with a knocking sound some engines continue running ashort time after ignition is switched off with that horrible knocking sound..

Pre-detonation is very destructive to piston and connecting rod bearings.

The small valve is the exhaust valve the tan residue indicates the engine was running top notch on the other side valve looks darker also looks wet at the bottom of the piston. This looks to be the cylinder giving you some trouble. Could be a broken piston ring or carbon build up in the piston ring grooves.

On the piston I'm calling wet near the bottom of the piston you can see where the oil has been bypassing the rings,  the piston top in this area has the carbon washed off.

Turn the engine by hand, bring that wet piston down to bottom dead center and lets have a closer look at the cylinder wall to see if there is any scoring from a broken piston ring.

A compression check would have solved the mystery and taken the questing out of the equation.

 

 

tan.jpeg

wet.jpeg

Edited by SimpleOrange

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SimpleOrange

A better view of the clean area near the bottom of the piston, this leads me to believe this cylinder has a broken piston ring.

With an air cooled engine it's important to keep the cylinder fins clean, also IMO these cast iron Onan engines are well worth the expense to rebuild.

You'll get 40 plus years of service from a cast iron Onan engine that has had regular maintenance versus 5 years with any brand name aluminum engines.

 

wetcarbon.png

Edited by SimpleOrange

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SimpleOrange

If you choose to rebuild the engine have your machine shop measure the cylinder bore. what they'll be checking for is out of round and taper. What looks good near the top of the cylinder isn't necessarily the same near the bottom.

Once the machine shop has measured the cylinder you'll know which over size piston and rings to purchase. There are two different types of piston rings available for your Onan.

One set is cast iron, this will be the least expensive set the other more expensive set will be chrome or a combination of cast iron with a top chrome ring. Make sure the shop you have commissioned to do the machine work has the tools and knowledge to hone a cylinder to accept chrome rings as the stones uses are slightly different than those used for the cast iron rings.

A cylinder honed wrong for chrome rings will never stop using oil, the rings will not mate to the cylinder wall. When this occures some guys use Bon ami as a break in powder, Finning aka caterpillar actually sells a break in powder for hard to set rings.

The powder is introduced via the air intake or carburetor while the engine is running at a fairly decent rpm.

Purchase good quality name brand connecting rod and main bearings, you can use a product called plasti gauge to measure bearing clearances.

A thin strip of plastic thread is placed onto the crankshaft then the bearing cap is torqued to spec, cap is then removed. As shown in the picture below the mechanic is comparing the amount of crush against a chart on the package the plasti gauge came in.

 

 

plati.png

Edited by SimpleOrange

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