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Hello, I have a jd 630 that spun a main bearing awhile back and have gotten everything taken apart. I'm looking for a good machinist that has experience in two cylinder tractors. I will most likely need either cylinder honing or boring as the tractor set for a long time and was stuck. I also will need the main bearing replaced. If anyone knows of someone in the kc area or around Salina Ks please let me know. Thanks for any information...
 

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Welcome to GTT!

I'm not sure of any machine shops near you that are well versed in your areas of need and expertise of large bore antique JD tractors. That seems to be falling away year by year. However, the cylinder block is easy for any machine shop that can do larger, longer bores. You'll need to consult with them before buying pistons as you want the final boring/honing to match the new pistons. My bet is the crank will have to be sent out to a shop that specializes in crankshafts. I've had them welded back up using a special "spray weld" and machined/polished back into factory minimum specs. It cost me about $500 for a two cylinder diesel generator engine that last time I had that done.

Good luck and let us know what you come up with. I'm very interested in seeing your product. I have a 60 that will probably have to have the same thing done.
 

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GTT's Pilot in Command (PIC)
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You might also check into an aircraft engine shop. They can machine it and chrome the cylinder back to specs.
 

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I don't believe JD two-cylinder tractors ever used a chromed bore. A chromed cylinder requires a different ring package than a standard iron/steel bore.
 

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GTT's Pilot in Command (PIC)
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I don't believe JD two-cylinder tractors ever used a chromed bore. A chromed cylinder requires a different ring package than a standard iron/steel bore.
The cylinders on my 1941 Avery are now chromed. That's what made me think about having it done here.

But, I've been wrong before.....







(But only one other time!!)
 
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Even if stuck you don't need to machine. Only had two tractors we needed to machine out of a LOT we have gotten unstuck. These are low compression engines and if they have the OEM cast flat top pistons from the all fuel engine they are at a 4:1 compression. Once the pistons are out a hone job and bead blasting the rings that were in there is all that is needed 90% of the time. Sometimes you might need a set of rings but rarely. Have had 1/2 inch rust pits in the engine on a 42 GM we had. One guy said don't worry about it. His reasoning was that you have the Petcocks where a hold already is for the rings and it doesn't hurt it so why worry. He was right. It ran just find and we even plowed with it to reseat the rings after going through it.

As for spinning a main bearing-depending on the damage you are good there too. The bearings are shimmed so if it didn't actually ruin the bearing on the crank you might just need the bearing inserts and reshim correctly. Use feelygauge to get the right measurements. These are slow RPM too so you don't need to treat them like a race car engine. They are very forgiving which is part of the reason JD stayed with that design for so many years.
 
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