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broken camshaft holder, leaking tachometer oil seal cb750 dohc

Honda, like all OEMs would have had more than one parts vendor on assembly line parts, they have them to quickly switch to if the one being used right then begins to have problems. They then jump to the other and keep that line going.

All of those may well be fine, just the name does not detail the bearing construction and like I said the better ones were dropped long ago to use up the other stock on shelves. That bearing size gets used in more than one Honda engine type.

Just the fact we still have new bearings to buy is pretty unusual in itself.
 
Hello all. Back after a long time and I have some updated to share. I plastigauged my main bearings yesterday. My OG bearings were Black for journal 1 and rest all Brown. As per the general sentiment, I went for a looser fit, opting for all green bearings but I was surprised to find how high the clearance was. Here are my readings: 0.076mm, 0.076mm, 0.068.m, 0.05mm, 0.076mm. I am really surprised as was expecting the clearance to be in the 0.03 to 0.05mm range. Here are some images:

https://drive.google.com/file/d/1Rjpj7hahwdXPiXmPA84o94pVtEaXbxBK/view?usp=sharing
https://drive.google.com/file/d/1RrQn7qsK8k0-75xX9vL5EPfTRjCnxBJX/view?usp=sharing
https://drive.google.com/file/d/1RswknWoBplhED4lvS-JKFNWreKvEM8lb/view?usp=sharing
https://drive.google.com/file/d/1Ru-w7sMLZssAUjC7CA7CqbtQg-Vyq3KL/view?usp=sharing
https://drive.google.com/file/d/1Ru-w7sMLZssAUjC7CA7CqbtQg-Vyq3KL/view?usp=sharing

What do you think/suggest?
 
Part of that work is heavily skills based. Why you measure the big metal journals too, to add emphasis on which way you are going. With spaces that small even dust on bearings or oil can foul the numbers up. look at how tight you tightened the cases up.
 
Part of that work is heavily skills based. Why you measure the big metal journals too, to add emphasis on which way you are going. With spaces that small even dust on bearings or oil can foul the numbers up. look at how tight you tightened the cases up.

I fully agree with you on that. I will admit it is my first time doing this level of engine work. That said, I have been very careful and slow about doing things right. I tried plastigauge twice on the mains with 18 lb.ft torque at the bolts and the results were the same. Have not done the conrods yet but will do that and then check clearance with the OG bearings just to get an idea of what it was before. Other than tightness anything else I may be overlooking?
 
The numbers may be real. Getting the same twice reinforces that.

Common to be off either way easily .0125 mm. or a half thou. it's often there for the finding when you button things up to check.
 
Okay... Measured the con rod clearance too. All 4 are are slightly above 0.038mm, which is exactly what I was expecting. Will do the mains one last time and give you an update.
 
So I finally got down to measuring the clearances on the OG bearings for the mains. The plastigauge indicates the clearance to be very much identical to the new ones. So it leads me to believe that the bolts are not tight enough although I did set them to 18 ft lbs or there is some other systematic/technique error. The only thing I noticed was that I had not oiled the threads on the crank bolts. Could that be it? Could that account for the looseness?
 
Hello to all! I have been doing some reading on honing cylinders and why it is necessary for the piston rings. I took the cylinders off (about 10 months to a year ago), and they have been oiled and stored all this while. As for the rings, I had taken them off the pistons to check end gaps etc. All were within spec and were then stored (without oil). A few months back when I checked on the rings, I saw some surface rust and so bagged them and soaked them in oil (the rust came off when I smeared them with oil but there has been some discoloring on them). Now, after sitting all this while, I see some discoloration and marks on the cylinders too (these were power washed recently). Here are some images:

https://drive.google.com/file/d/1gehPiNSaABb02KFjDW9_hX4mtWZRI9T9/view?usp=sharing
https://drive.google.com/file/d/1gn529B0iiyYK_5f0W-y6r1vz6JzGynnM/view?usp=sharing
https://drive.google.com/file/d/1gbZzMgLgEbEaRc9DawADH4qY7w1qgK8g/view?usp=sharing
https://drive.google.com/file/d/1gXOhuQzleDiLQEBzq0zodmAe55dwVLQH/view?usp=sharing (UNDERSIDE OF CYL)
https://drive.google.com/file/d/1giIm3sBfZWdFtQAsWzzCa39lhIiP441K/view?usp=sharing


My question is, given the background story and these images, should I be reusing the rings and the cylinders as is or would it be better to hone the cylinders and get new rings? Note: Nothing that you see in the images is deep enough to be felt with the fingers or fingernails and the cross-hatch pattern is still visible on all walls.

Thanks
 
You need to have the cylinders measured, then honed if they are in spec. If the rust or any scratches are too deep you need to bore to next size or find a better cylinder. Never reuse rings when they are removed from the bore. Always hone and use new rings if they are removed from the bore or you will more than likely have sealing issues/blowby and oil consumption.
 
That is basically how I have always done a breakin. I get them warmed up, look for any leaks, then run the engine hard. I fully believe in breaking in hard, if its going to break i want it to do it right away.
 
Alright. Thanks dirtdigger. Btw, would you happen to know what's up with amc49? He has helped me a lot on this build but seems to be quiet these days. Hope all is well with amc49
 
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