The Saga of my First CBX

[erik]

All,
I finally was able to split the cases and I was relieved at what I found. The mains are good, and so are the cases! The only bottom end damage are the two rods that spun. The crank seems decent, however I will be replacing it anyway. I found sealant between the mains, and in the main bolt threads, and upon closer inspection of the oil screen, I found a fibrous material in it. I'm thinking somebody left a paper towel in it! How the hell that happens I have no clue. I will disassemble the oil pump in the next few days to see it there is any more trash in it. I will also note the oil pickup screen is "sucked in" Like the pump was pulling a vacuum on it. Hopefully that was the answer to my problems.

[RJ CB650]

Well, with junk and gunk inside, a blocked siphon screen would kill your oil flow but good! Keep up the feedback hope you can get it on the road soon! I would say would like to help with info in any way I can, but still learning the details of this engine, so until then, for me it is...

[NobleHops]

Goodish new Erik, as much as that can be the case with spun bearings. Hope you're up and running again soon.

[daves79x]

Finding fibrous material in the sump screen is not unusual after a rebuild if the builder was not meticulous in his work. I had to re-rebuild a lower end for the exact reason you found here. I think you've identified the reason for the spun bearings. Clean everything up and take the oil pump apart to inspect. Blow every oil galley thoroughly and be as very clean as you can. Clearly this bike has been apart and sloppily put together. Don't take anything for granted and check everything.

A new crank will bring it's own set of puzzles - study the manual for main and rod bearing selection VERY carefully and be aware that a bearing part number is for ONE HALF shell and you need 2 for each journal, obviously. You will find some crank codes that will be the same as yours and it's your call to reuse bearings. It's OK if you Plastigauge everything. Leave nothing to chance and gauge and record all main and rod oil clearances. .040 - .050 mm is normal for most engines with some wear on the crank journals.

Now, despite your best efforts, you will still have some lint/paper towel litter/other contaminates left in the engine. No way I know to avoid it. How you nullify this is to run the engine no more than 100 easy miles, then drop the oil/filter and the sump. You will find some debris in the sump and screen. There will also be very fine flecks of babbitt if many new bearings were used. Don't be alarmed at that, they're just wearing in.

After everything is clean, with new oil and filter, run another 300 or so miles and do the same thing again. The sump and screen should be completely clean this time if all is well. Then you're good to go. I can't emphasize enough the need to drop the oil and sump after any rebuild at 100 miles to check things. That would have avoided (likely) what happened to your bike.

You should check and gauge every journal on any used crank you get, as well as have it checked for run-out. You never know how it might have gotten thrown around.

Keep us posted.

Dave

[Kool_Biker]

Eric, in your quest to build a meticulously clean engine as advised by our resident guru, Dave, PLEASE also do not forget to look / clean / blow / whatever, into the top crank cover holes, THEY ARE NOT BLIND and in my case have proven fatal traps of various debris ..

Check an old thread of mine and beware: viewtopic.php?f=25&t=7088&start=225

In my case, it was glass beads hiding there (another story), munching my big end bearings within few Km. I sure hope nothing nasty hides there for you, but with an engine of unknown history few things can.

Good luck with your endeavour, we are all looking forward to seeing you back on the road!

[erik]

All,
Sorry for my 4 month absence from updates, my job has kept me on the road and away from the bike. I'm preparing to purchase the necessary parts to begin rebuilding my X. I do have a question for y'all, as far as matching main bearings, I read in the manual that there are several different thicknesses that must match the crank, what are the odds of me purchasing a crank online and finding the correct bearings to go with it? How forgiving is this clearance? I have the opportunity to buy a very nice crankshaft on Ebay at the moment and want to be led in the right direction. Also, what is the best quality gasket set to buy? I'm looking at a Forsetti on Ebay and was curious what y'all thought.

Thanks

[daves79x]

You need to buy new bearings for your new crank, identified in the shop manual as you saw. They are all still available from Honda and yes, you need to use he exact ones prescribed on the charts. Same goes for the rod bearings. Some, with luck, can be re-used. Also note you need two bearing halves per throw, price is for one half. And be prepared to Plastigauge everything just to be sure. You will have several hundred dollars in bearings alone.

You might check out TIMS CBX for gaskets. They are mostly aftermarket as well, but proven to be suitable.

Dave