Topic: Tore into one of my engines today; tell me what you think of these parts

[JBMorse]

Tonight I took apart the top end of my CB500k engine.  This is the engine that hauled me and my fiance 10k miles this past summer.  First gear broke in it, and for the moment I am abandoning the lower end of the engine and saving what's good from the top end. 
What do you think of these cam bearing surfaces?  Can you even tell in the picture?  And if they're bad, what do you do?  Can they be reground at all?




Here's a shot of the head.  That one cylinder, #2 I think, looks like it was pretty lean.  Are those valves toast?


Here's what the pistons look like:


And finally, is this what a worn cam chain tensioner looks like?  Should it have those grooves?


My plan right now is to measure the cylinder bores and the piston diameters.  If they're within spec I want to get a ball hone and rehone and install new rings.  If they're out I'll try and locate a piston kit.  There's been a couple of 1.00 over kits for not too much money, but I'd rather save the cost of the kits and the bore job and put that money elsewhere on the bike.
I talked to MReick a while back about doing some minor head work and a possible valve job.  I'll get back in touch soon about that part after I get a look at the other head I have and see which one looks better.

I should add that I'm simply rebuilding this bike as a strong and reliable runner.  I plan to use it for everyday use and the occasional tour. 
Finally, my idea was to use the bottom of a CB550 to take advantage of the better gearbox and clutch.  My first gear broke on my trip and I want to try and limit the likelihood of that kind of problem in the future. 
A generous member in Brattleboro gave me this bottom end and I'm not sure what to do with it.  The con rods are a little rusty and there's a little rust on one of the visible bearings.  Would it be stupid to try and clean this thing up and use it?  I was planning on getting a new clutch kit anyway.



Thanks for any advice.  I can't wait to get the old girl back on the road.  Our short NH riding season is well under way.


 

[DarcyCB400F]

Are you calling your fiancé an old girl?

[KingCustomCycles.com]

Short, concise, questions are easier to answer. 

[dave500]

if you cant feel the marks in the head or tappet cover where the cam rides itll be ok,so,,?first gear broke?the only advantage to the 550 bottom end is better gear selection,and clutch action,it aint no stronger,whats with your first gear?sheared all the dogs off?or just jumping out,,ill bet its got a damaged fork, the bottom end you got might be ok,,id strip it down though,,thats just me,you take pot luck on running unknown assemblies,if your keeping the bike and got it apart this far replace the cam tentioner and guide and chain and primary chain as a matter of course,along with all the seals.

[Retro Rocket]

Short, concise, questions are easier to answer.

We have rules on questions now.....

[JBMorse]

if you cant feel the marks in the head or tappet cover where the cam rides itll be ok,so,,?first gear broke?the only advantage to the 550 bottom end is better gear selection,and clutch action,it aint no stronger,whats with your first gear?sheared all the dogs off?or just jumping out,,ill bet its got a damaged fork, the bottom end you got might be ok,,id strip it down though,,thats just me,you take pot luck on running unknown assemblies,if your keeping the bike and got it apart this far replace the cam tentioner and guide and chain and primary chain as a matter of course,along with all the seals.

So I have to be able to feel imperfections in the cam bearings?  They feel pretty smooth but look worn, as if some of the finish has worn unevenly.
As for my 1st gear problem, it was half way through my trip and started by jumping out of gear and getting stuck somewhere between 1s and Neutral.  Then it got so 1st wouldn't work at all.  I suspected bad shift forks but I have a couple of good bottom ends so I'm going to wait on tearing into it since I don't know much about that lower end business.
The reason I wanted to use a 550 lower end is due to the better gear selector and upgraded clutch engagement mechanism, both of which are more robust and designed for the bike.  I have read somewhere that the CB500k gear selector is adapted from the 350 twin, which is smaller and less powerful.   
As for that bottom half I showed, it was supposed to have been good but sat outside (though upside down) this past winter, so that's why it's all rusty.  I don't know whether I can clean it up without taking apart or not.  What am I getting myself into if I split the cases?  Is everything as straight forward as what's on the top end? 

[Oddjob]

TBH the cam surfaces look not too bad, ok some wearing but it look consistent and doesn't appear to be grooved. Do the finger nail test, if you can feel any parts of the cam journals with your fingernail then you have to think about what you want from the bike, it however your fingernail glides over the surface with minimal snagging then your ok. Pics aren't great in detail but I'd use that setup if it was my bike.

Cam tensioner blade is shot I'm afraid. I'd also replace the guide, as said change the primary chain and also check the primary chain cush drive rubbers whilst you've got it apart.

The 550 engine needs to come apart, you have no idea what grit and dust has blown into those open areas. You can clean all the surface rust off once you've got it apart and checked to see how much wear it's showing inside. Crankcase split is easier than topend split IMO, only tricky part is making sure you locate the gear shaft dowels into the roller bearing cages holes, or you can reassemble it into the upper crankcase and refit the primary shaft once you've got the cases back together, I prefer to assemble it into the bottom casing and locate the selector forks and dowels as the upper case is dropped in place but that's just me.

[JBMorse]

Thanks for the tips oddjob.  I looked further into the case splitting and I now think I can do that task just fine.  I've never been that deep into one of these engines.
Why should I replace the primary chain?  Do they have a tendency to stretch out or is it just a good idea while I'm in there? I didn't even know about that cush drive but it looks like the rubbers are still available so I'll probably do those too.
Thanks again, looking forward to a weekend of learning!

[Oddjob]

TBH you'd think the primary chain which runs permenantly soaked in oil would last a lot longer than they do. However in practice they tend to have had it around 30-50k. Although they still look ok they sag and that means that they start to lash around a lot and also hit the bottom of the crankcase. As right under the chain is the main oil gallery going from the oil pump to the crank journals it's this the chain hits, I've seen this gallery worn through or almost so.
It's usual to change the chain when the cases are split just because it's a #$%* to change and you may as well whilst your in there. Cush rubbers go brittle with age, this allows the chain the move more than it should and will wear a new chain out quicker than good cush rubbers.
Also a new primary chain will stop that bloody annoying rattle from the bottom end as it's the chain lashing around which causes this.

[turboguzzi]

definitely go with the 550 bottom end, it's better, period.

would take it apart and clean first, an open motor can collect lots of dust if its hasnt been hermetically sealed in a nylon bag.

[bryanj]

OK
Nothing wrong with head that a good clean and new stem seals won't cure.

Can chain tensioner blade will have grooves in it within 1,000 miles from new!!! Inspect carefully and if the rubber in the middle of the grooves is level with the rubber outside the grooves(or damn close) it's fine to use, plus look at the ends and see if the rubber is coming off the steel backing, If so its NOT fine to use.

Remember with the tensioner the side plates of the chain will "cut" into the rubber till the rollers hit the rubber. Cushion only needs changing if damaged or rubber falling off.

Finally READ THE MANUAL CAREFULL on cam cover replacemant OR bend the valves