[JSB Case]

Hello all,

When I purchased a 646 project tractor (S/N 9698903), the engine turned freely but it definately had some water issues from sitting over the years. The valves were stuck and not working properly and the cylinders had light surface rust on them.

I brought it to a trusted small engine mechanic, who then took it to a machine shop to be thouroughly checked out. I haven't heard any results yet, but I have committed to do what is right and have a professional repair/rebuild the motor.

One thing that may or may not be a problem is a missing engine shroud. Obviously, I will need this later for proper cooling/air flow, but it is also the piece that holds the engine ID tag (C20580). How important is this information for the engine builder? I know that the engine is a CCKA, but that is the limit of my knowledge.

After looking at an Onan parts website, it doesn't look like the different versions of this motor have different internal components. Pistons, rings, gasket sets, etc. look like they are the same across the board, so I'm hoping that the missing ID info won't be a problem. I am trying to educate myself a little bit so I can give the mechanic as much info as possible. Any advice or instructions on the subject are appreciated.

 

[Hydriv]

You need to talk with Boomer, our resident Onan expert. He can advise you on what the spec should be for the OEM engine and he may also have the tin you need to keep the engine properly cooled.

I'm sure that he will be along some time today and reply to this thread.

 

[boomers_influence]

jeff.
your side tin was on my to/do list today anyway.
i have/ can get the # 1 side tin that you need.
i also have a CCKB for sale.
same c.i. as yours BUT rated at 20 H.P.
call 651 437 2826
M/F 5 to 8 pm
sat /sun 1200 to 800 pm.
please measure the dia. and length of your crankshaft
1 1/8 or 1 7/16 dia.
thank you. boomer

 

[JSB Case]

Thanks Boomer.

The engine is still at the machine shop for inspection and an estimate. It should be back in the next couple of days, so I will wait until I have more info and give you a call.

 

[robynrj]

Jeff
The answer to your orginal question...yes piston/ring/bearings are same. The clearances are same. Bob M

 

[robynrj]

Boomer
Is your CCKB complete...intake manifold and hi po cyl heads? If so, Jeff this is way to consider going.
Bob M

 

[boomers_influence]

bob
he will have to use his intake, (mine is side draft)
the other issue is the crank shaft DIA.
mine is 1 1/8 .
i have been told that CCKA in case is 1 7/16 dia. ???
the S.N. on the tag matches the one on the block.
it states CCKB
thank you. boomer

 

[robynrj]

Boomer
No reason he can't use side draft....he has room. And if you want full CCKB HP its needed. He'll have to adapt air cleaner.
CCKB used oil bath alot with rubber tube from carb to cleaner. Crank dia just means different lovejoy, correct? Bob M

 

[JSB Case]

Engine Update:

The Machine shop checked out the entire engine top to bottom. Everything is well within factory specs. The machine shop and the small engine mechanic recommended the cylinders be properly honed, a valve job, new rings and gasket/seals kit. That is the GOOD news...

After the cylinders were honed, one small spot has some pitting that honing couldn't clean up. The area is smaller than the size of a dime and not deep. Both the machine shop and the mechanic agree that the mimimum boring would be necessary to remove the pitting. But, they also agree that the pitting should not affect the performance of the engine. They make the arguement that the pitting is isolated to one small area and does not run the entire length or circumference of the cylinder. They claim that compression would not be able to "get by" the area and the engine would not smoke or burn excessive oil.

The final desicion was left in my hands. My thoughts are to give the engine a try as it is. I am about $300-$400 (parts and labor) into the engine repair right now and boring would essentially put me back to the beginning. I am not against investing the time and money to make the engine right, but I just don't know what I should do. Any thoughts are appreciated.

 

[Hydriv]

I would listen to their advice because both are experienced and both are there to see the problem. Why carve away the next oversize NOW, for the sake of a small issue on one cylinder. That won't shorten the engine life and since these engines often last for 20 years between rebuilds, how old will you be 20 years from now?

Yes... perfection is always desirable but you have to weigh the cost of perfection against practicality.

I would just put it back together.

 

[JSB Case]

I would listen to their advice because both are experienced and both are there to see the problem. Why carve away the next oversize NOW, for the sake of a small issue on one cylinder. That won't shorten the engine life and since these engines often last for 20 years between rebuilds, how old will you be 20 years from now?

Yes... perfection is always desirable but you have to weigh the cost of perfection against practicality.

I would just put it back together.

That is music to my ears.

These guys are true professionals but niether of them claim Onan to be of thier expertise. I figured it wouldn't hurt to get a second opinion about their theory. The small engine mechanic told me these engines are very well built and nice to work on. (Labor discount?)

I was born two years after this tractor was built, so I am really hoping to outlive it!

Thanks for the 411.

 

[Hydriv]

You do not have to be an ONAN guru to make that judgment call. Anyone who is well-experienced on rebuilding small engines can advise you as to how important that flaw in the bore is. As time rolls on, that flawed area will likely get smaller due to wear. Therefore, you might say that it is "self-healing".

 

[boomers_influence]

jeff
i agree with tom, put it back together.
boomer

 

[Nutcase446]

Are the machine shop and the mechanic both telling you that it will be alright or that it will probably be alright? If they are using words like probably it means that if it isn't alright, it's on you. Did the machine shop hone the block then tell you that it was still in factory specs or did the mechanic? I know that with a cylinder with pits or scratches the tendancy is sometimes to run the hone through a few more times to try to clean them up. You can hone a cylinder to where it's no longer in spec. I know of few more dissapointing things than to rering and hone an engine and get that little piston knock. I've seen engines go for a long time with the knock but it's still iritating. If it is a reputable shop and they are willing to stand behind it you will probably be fine. Gregg

 

[JSB Case]

The engine is back together. I have around $200 in parts and the same in labor. Valves and points were set to factory specs and new rings, seals and gaskets installed. The machine shop really didn't do much work that could be warranteed, and the small engine mechanic promised to stand behind the labor costs if I have problems.

I have high hopes, but I am keeping my fingers crossed. I will report back when the tractor is back together and the engine is running.

For what it is worth, I couldn't be more impressed with onanparts.com. They had everything that I needed in stock and the shipping was incredibly fast. I'm not sure if they are a common supplier, but top notch in my book.

 

[Hydriv]

Onan Parts dot com is a member here.

 

[JSB Case]

One thing that may or may not be a problem is a missing engine shroud. Obviously, I will need this later for proper cooling/air flow, but it is also the piece that holds the engine ID tag (C20580).

I have a little problem with this engine shroud. The parts manual shows that the heads changed after engine number 292517. Since I am missing the shroud that had the engine ID, I am assumining that my engine is the earlier one. The problem is that the mounting bolts for the shroud/tin on the LH head are not the same as the newer engines. My LH head has two threaded holes on the top and bottom to bolt the tin to. The newer head has two bolts near the center of the head that the tin attaches to with nuts. The parts book accounts for the different heads, but there is only 1 engine tin listed for the LH head. (C20580)

Is anyone familiar with this or am I going crazy? Possibly another part number for this shroud? Any help or advice is appreciated.

 

[boomers_influence]

jeff
my parts book (spec A thru J) only shows one tin.
the one i have has the two holes for the side of the head.
poss. that you can drill two new holes?
boomer

 

[robynrj]

Jeff
NEVER saw head as you discribed new head...picture maybe? CCKA used a stighly higher comp head over CCK and not as high as CCKB did usually......are both combustion area the same? Bob M

 

[JSB Case]

Here is the normal right side.

Here is the oddball left side.

I spoke to the small engine mechanic who worked on the rebuild and he said that the heads would only fit on one way and that they were the same internally.