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Kohler rebuild question


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#1 jojagard OFFLINE  

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Posted August 29, 2011 - 05:36 PM

I have a question about the rebuild of a Kohler K321 engine (for my John Deere 140) that I hope you might be able to answer. After cleaning-up the block and looking at it more closely, I noticed some damage that I am concerned about.

I have attached a few photos that show the damage. Do you think that I can go ahead with the rebuild using this block as is, or would it be unwise to do so? If this damage is unacceptable, is there anything that can be done to repair it, or do I simply need to look for a new block?

I would greatly appreciate your careful evaluation and advice. :worshippy1:

Thanks!

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#2 maddhorse OFFLINE  

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Posted August 29, 2011 - 06:08 PM

I would say that you should replace the block, if it where me I would. The cylinder wall does not look right either. It should be scourn in a cross hatch pattern. I am sure that a few of the guys with more time on the wrench will have some good advice for you. Good luck and welcome to GT Talk.

#3 ncb OFFLINE  

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Posted August 29, 2011 - 06:20 PM

I see just enough damage that i would constantly worry about the next failure,i,d change the block

#4 olcowhand ONLINE  

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Posted August 29, 2011 - 06:25 PM

If the bore is good, I would use that block for myself. If that remaining pin is tight, I would leave as-is. If loose, it must be removed, and any cast that might be nearly breaking the rest of the way off. I would take a small round file & slightly chamfer the edge of the chip in the cylinder bottom. The cross-hatch is a bit narrow. Hone needs to be ran slower, and up & down in the cylinder faster. You want the angles to run 40 t0 45 degrees to the block head face, making the opposing hatch marks cross each other at 90 degrees.
So did a rod toss itself & do this, or the counterbalance gears cause it. I read in another thread that John Deere did not use balance gears in their engines? Maybe someone can give more info on this. Or possible it's not the original engine?
I've used blocks where they were cracked, & even with large "windows" punched through them. Weld them with Ni rod slow & careful with a slow cool. This block wouldn't scare me off. But them I'm cheap! LOL

#5 JDBrian OFFLINE  

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Posted August 29, 2011 - 06:52 PM

So did a rod toss itself & do this, or the counterbalance gears cause it. I read in another thread that John Deere did not use balance gears in their engines? Maybe someone can give more info on this. Or possible it's not the original engine?


Daniel
The only one of the early 300 series to have the balance gears was the 300 with the K341. The later 316 which was pretty much identical to the 300 did not use them. I'm not sure about the 140's. Surely someone here has rebuilt a 140 motor. I was surprised that Deere did not use them, as these tractors shake a lot at low rpm's. Perhaps it was the tendency for the gears to cause problems that was the issue.

#6 JDBrian OFFLINE  

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Posted August 29, 2011 - 06:59 PM

Daniel
I just went to jdparts and the balance gears show up on the parts list for both early and late (30000+ ser no)production 140's. The 140 mounted the engine directly to the frame and the 300 series used rubber mounts. That may have something to do with the balance gear change as well.

#7 jojagard OFFLINE  

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Posted August 30, 2011 - 01:41 AM

Daniel,
The cause of the most recent failure was a broken rod, but this engine was rebuilt at least once prior to my owning it. The balance gears were previously removed. This is a later model 140 H3 (42720).

Is the pattern on the cylinder wall a real concern? I had it bored by a local shop that specializes in marine engines having aluminum blocks...he had no experience working with single cylinder, cast iron engines. I suppose that nothing can be done about it at this point anyway, as the cylinder has already been bored to the (.030) limit.

Thanks all for your input and welcome.

John

#8 maddhorse OFFLINE  

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Posted August 30, 2011 - 04:13 AM

As far as the cylinder all you need to do is hone it, it's easy and you don't remove much material. I would take the advice of JD and Daniel I am still a grasshopper in the ranks of tractor ninjery.
Cylinder bore refinishing is extremely important in the engine rebuild process. There are some basic rules and facts that will prevent common problems incurred when deglazing or refinishing cylinders.
CROSS HATCH ANGLES

The correct angle for cross hatch lines to intersect is approximately 45 degrees. Too steep an angle promotes oil migration down the cylinder resulting in a thin oil film which can cause ring and cylinder scufflng.
Too flat a cross hatch angle can hold excess oil which conversely causes thicker oil films which the piston rings will ride up on or hydroplane. Excessive oil consumption will result.
The diagrams will illustrate cross hatch angles.

Posted Image
Quick Video on How to Use A Flex-Hone via YOUTUBE





What diameter size should I order?
<FONT size=2>A hone tool's diameter is determined by the nominal bore size in which the tool is to be operate. A cylinder hone is always produced and used in an oversize condition. The degree of oversize creates pressure and a soft cutting action on cylinder walls. For example a 1" Flex-Hone® tool is ordered if a 1" bore (I.D.) is to be finished, the built in oversize provides the proper cut. Remember that all tools are provided in over-sized, so do not add inches or mm's to the ID that you are machining. If the bore size is between standard Flex-Hone® sizes, the next larger standard Flex-Hone should be selected.

What GRIT should I order?
Hone grit is one of those topics that will vary vastly from OEM manufacturer, ring designer to professional engine builder and will depend on how bad the cylinder wear is and whether a deglaze will do the job . If you have a poor condition bore with rust or deep grooves you will need to use a 120 grit hone to remove the rust and remove the deep grooves. Then follow up with the appropriate grit depending on ring application. For a basic deglaze to refresh the engine just use the grit depending on ring type. EngineHones.com has built several engine mules (our guys race too!) to investigate the grit question with on-track results. The table below which was derived from our engines, ring manufactures and technical literature. Our best seller to commercial engine rebuilders and power-sports shops is the 240 grit hone. Our guidelines are as follows:

Iron Cylinder Ring Type:
OEM Iron rings: 180 or 240 grit

Chrome rings: 240 or 320 grit

Moly Rings: 320 or 400 grit

Plasma Rings: 320 or 400 grit

not sure ring type: 240 grit



<FONT size=4>Manufacturers Recommendation:

Hastings: 240 grit

Akerly & Childs (Ductile Iron): 240-280 grit

Akerly & Childs (Moly): 400 grit

Perfect Circle (Ductile Iron): 240-280 grit

Perfect Circle (Moly): 400 grit

Speed Pro Hellfire (Ductile Iron): 240-280 grit

Total Seal (Ductile Iron): 240-280 grit

Total Seal (Moly): 400 grit

Harley Davidson(stock): 320 grit

Wiseco (chrome top): 320 grit


<FONT size=2>If the Ra (surface finish) of the part being machined needs to change more than 20 to 30 points, you may need to use steps to achieve the proper final Ra. As an example, if you were trying to change a 80 Ra to a 20 Ra, you may need to start with a 120 or 180 grit hone and then finish with a 240 or 320 grit.


To assist in selection of proper hone, this information is a good starting point. Actual measurements must be made after honing, as numbers will vary depending on the material being honed and the media used.

Grit Finish Range600 gritRa 8-12.2 - .3 Micrometer400 gritRa 10-20.3 - .6 Micrometer320 gritRa 18-26.5 - .7 Micrometer240 gritRa 24-32.6 - .8 Micrometer180 gritRa 30-40.7 - 1.0 Micrometer120 gritRa 35-50.9 -1.4 Micrometer80 gritRa 45-641.2 - 1.6 Micrometer60 gritRa 60-801.5 - 2 Micrometer

How do I refinish my bore <FONT size=2>
</B>There are several steps in refinishing your cylinders in preparation for new rings. The first of course is to remove all bearings leaving a bare block. The metal from the honing or deglazing process with go everywhere. Note that the worst thing about honing is the block cleanup. You can never spend to much time cleaning your block. With the engine bare and cylinder ridged reamed (if necessary) place the Flex-Hone® (registered trademark of Brush Research Manufacturing) in a hand drill or drill press. Lubricate the cylinder with 10-30wt oil or Flex-Hone® hone oil (recommended). Spread the lubricant in the bore with a brush or your fingers. Make sure the cylinder is completely covered. For the first use of a new hone lubricate the bore several times as the hone itself will absorb some of the oil. Future cylinder honing will not require as much oil as the first was with a dry hone. Insert the hone with the drill rotating slowly while inserting in to the bore. With the hone in the lubricated bore, run the drill at 600-800 rpms with a vigorous motion up and down in the bore for 60-80 strokes. How vigorous a motion? basically as fast as you can move your arms. You are seeking a 45 degree crosshatch in the bore. If you are not achieving a good crosshatch (see tech section below) then you will need to slow the drill speed down to achieve a MUST HAVE 45 degree crosshatch. Run the drill for 60-80 rotations and wipe the bore with a clean cloth. Inspect the bore. If a dull grey is visible (it will stand out from the freshly honed surface) continue until the bore is completely resurfaced. While honing continue to squirt oil in to bore as a medium to wash away the cylinder material. Once the bore dull grey color is not visible STOP honing. The most important step is the cylinder wall cleanup. Use a nylon cylinder wash brush or a clean cloth soaked in warm soapy water and run up and down the bore. Continue this process while flushing the bore with warm soapy water. The goal is to remove every microscopic particle that is embedded in the cylinder wall grooves. After extensive scrubbing take a clean white lint free cloth with warm water and wipe up and down the cylinder bore with force. Inspect the cloth, if you see grey on the cloth, and most likely you will, you need to go back and clean the bore again. Repeat until you see no grey on the white cloth. Once each and every bore is perfectly clean then coat each cylinder with oil to preserve until piston placement. Once again the bores must be clean or you just left lapping compound in your high dollar engine.

What if my cylinder is Nikasil Coated?
<FONT size=2>
Nikasil coated cylinders are more delicate than the iron bores typically used with Flex-Hones®. Nikasil is an electroplated oleophilic nickel matrix silicon carbide coating that allows the use of aluminum cylinder walls without a steel sleeve. This coating reduces friction and wear. Great advantages come with the use of Nikasil on coated aluminum blocks or jugs, one of them is the increased heat removal from the piston, pin and ring assemblies. The other advantage is the tighter tolerances can be achieved. Most Nikasil coatings are 0.0003" to 0.0008". To deglaze and freshen up the bore walls you must use an aluminum oxide material based hone. This softer material works well with the hard walls. Use the hone like described above with the exception of much less rotations. Run the hone for 10-12 rotations in the bore and inspect. If the overall cylinder looks touched then you are done and remove the tool.

Achieving A Cylinder Crosshatch Pattern <FONT size=2>
</B>Another misunderstood and highly discussed topic is the subject of cross hatch angle. The resulting cross hath angle produced by the Flex-Hone or a three spring hone (or a rigid hone for that matter) is strictly a function of stroke rate versus RPM. Most OEMs and ring manufacturers state the angle of the scratches in the crosshatch pattern should be about 27 - 45 degrees with 45 degrees the optimum. This angle is referenced from the top of the deck. The crosshatch angle should be consistent throughout the cylinder walls. If the crosshatch angle is too steep the cylinder walls will not retain sufficient oil to aid in the rings seating process. The problem is that the rings will pump oil and rings will rotate too quickly leading to accelerated ring and ring groove wear. To shallow of a angle can cause a chattering affect as the ring passes over the valley preventing the ring from receiving proper lubrication again leading to excessive ring wear, excessive ring break in time and the possibility of engine smoking with no ring seating. To achieve the desired 45 degree crosshatch run the drill at 600-800 rpm and vigorously run the drill up and down in the bore. This vigorous movement of your arm is exhausting but you only need to run the tool in the bore for 10-15 seconds. Then inspect the cylinder surface. If you see a dull grey surface that indicates the hone was ineffective in that area thus continue to run the hone until the complete bore looks exhibits a fresh cut with a cross hatch pattern.
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#9 KennyP ONLINE  

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Posted August 30, 2011 - 04:58 AM

Wow, maddhorse! That's a lot of info on honing. Thanks for posting it.

#10 JDBrian OFFLINE  

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Posted August 30, 2011 - 05:52 AM

Great information on honing maddhorse. It really makes the case for the importance of crosshatch angle.

#11 maddhorse OFFLINE  

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Posted August 30, 2011 - 06:41 AM

I am a tinkerer and have learned hundreds of ways not to do things. I google alot now!

#12 jojagard OFFLINE  

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Posted August 30, 2011 - 10:17 AM

I will join the chorus: many thanks, maddhorse, for the education!

I reviewed the page in the Kohler service manual on honing and they specify a crosshatch angle of 23 - 33 degrees off the horizontal. Based on this, would you still say I should shoot for 45 degrees, or is the service manual out of sync with the latest thinking on this subject? (the manual was last revised in 11/92)

#13 olcowhand ONLINE  

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Posted August 30, 2011 - 10:27 AM

I will join the chorus: many thanks, maddhorse, for the education!

I reviewed the page in the Kohler service manual on honing and they specify a crosshatch angle of 23 - 33 degrees off the horizontal. Based on this, would you still say I should shoot for 45 degrees, or is the service manual out of sync with the latest thinking on this subject? (the manual was last revised in 11/92)


Going by that manual, it would be within spec. It would likely be ok, but you wear rings down a bit more in breaking in with the flatter cross hatch than with a 45 degree hatch. Likely not that big an issue, as long as the stone was fine enough.

#14 Danofbrown OFFLINE  

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Posted October 27, 2011 - 06:51 PM

Going by that manual, it would be within spec. It would likely be ok, but you wear rings down a bit more in breaking in with the flatter cross hatch than with a 45 degree hatch. Likely not that big an issue, as long as the stone was fine enough.


I have 2-321's with thrown rods, can the cylinders be sleeved? The damage is on the bottom of the cylinders and I "could" actually use it as is because the rings don't come as far down as the damage. Just wondering. I hate to toss out old K series blocks.

Thanks in advance,
Dan

#15 olcowhand ONLINE  

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Posted October 27, 2011 - 06:54 PM

I have 2-321's with thrown rods, can the cylinders be sleeved? The damage is on the bottom of the cylinders and I "could" actually use it as is because the rings don't come as far down as the damage. Just wondering. I hate to toss out old K series blocks.

Thanks in advance,
Dan


Yes, they can be sleeved. I've had a couple K341's sleeved myself. NAPA machine shop did mine.




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