Top End Reconditionaing

[cbx6ss]

Symptoms:
Significant smoking at startup/cold; smoke at idle, cold or at temp. Plugs are fouled at every check. Number 3 worst; number 4 cleanest.

I recently did a compression test resulting in the following:

Cyl initial w/oil
1 135 150
2 145 140?
3 85 90
4 115 115
5 140 150
6 115 145

Valve clearances (MM) :
baseline:
Cyl exh a exh b int a int b comment
1 .10 .10 .10 .10 loose
2 .10 .10 .10 .10 loose
3 .10 .10 .09 .10 loose
4 .09 .10 .08 .08 loose/ok
5 .10 .10 .10 .10 loose
6 .10 .10 .10 .10 loose

My assessment is:
1. worn rings; valves (seat) marginal
2. leaking valves, marginal rings
3. leaking valves, worn rings
4. leaking valves, marginal rings
5. worn rings, marginal valves
6. worn rings, marginal valves

Ok, so the head is off, disassembled. Chemical warfare was unsat, so I bench-grinder-wire-brushed the valves clean. I used rubbing compound to clean the very-hard glaze off the exhaust valve heads. I removed the old seals for replacement.

What is the best way to remove the pesky washers from on top of the valve guides?

I am dremal-brass-wire-brushing the chambers and ports. Then, I am planning to lightly port and polish the exhaust and intake ports using my dremal arsenal. Thoughts on this appreciated.

Cylinder Honing
I found what seemed to be a pretty good article on honing cylinders.

http://www.babcox.com/editorial/ar/eb110242.htm

I bought a 3-stone unit from the local auto parts store.

1. What is the best honing lube; engine oil?
2. How tight should I set the hone?
3. Any thoughts on "plateau finishing" as described in the article?

After honing I plan to mic bores and ring gap to ID replacement rings. Thoughts?

Valve Clearance Target:
1 .07 .07 .07 .07
2 .07 .07 .07 .07
3 .07 .07 .07 .07
4 .07 .07 .07 .07
5 .07 .07 .07 .07
6 .07 .07 .07 .07

Thoughts?
Thank you.
/r
Brad

[cbxtacy]

magnet to get the pesky washers out.

[EMS]

After a top end overhaul you should set your valve clearance on the loose site initially. They will get tighter relatively quick. One of the most common causes of burned valves are (too) tight valve clearances.

[alimey4u2]

If you're goin through the trouble of pulling the head, may as well do it all.
Go through the procedure in the shop manual & you wont go far wrong.

Pop a good ring down each bore ( squarely) tapping it down with a ringless piston. Check the gap in the ring at several different positions down the bore to check it's parallel. May need more than deglazing depending on use & milage.. IE rebore. Check valve guide/valve stem clearance too.
Head work... Hmm lots of heads have been screwed up by die grinder enthusiasts. If you're not sure what you are doing, just clean up the obvious sharp edges & transitions & leave the finish as a flat finish, not highly polished.
Finally, hand the head to a professional shop for a 3 angle valve seat job..

[cbx6ss]

I measured the cylinders per the service manual. This is what I came up with. Seems the cylinders may need to be rebored. I would have a shop do this but I was wondering;
Are there specs somewhere for setting up for a rebore?
Is there a point of reference on the cylinder assembly for set up?
What's the exact distance between cylinder centers?
Do the piston rods float to accommodate an off-center bore?

"Dr, Dr, what's the prognosis? Will I ever be able to ride again?"
Advice gratefully appreciated.
/r
Brad

BTW, 45K on the bike...

SERVICE MANUAL
Cyl ID 2.5394 - 2.5398
Service Limit 2.5430

Cylinder Assembly
X Y
1 Top 2.5392 2.5395
Mid 2.5410 2.5399
Bot 2.5401 2.5400

2 Top 2.5394 2.5395
Mid 2.5398 2.5391
Bot 2.5420 2.5400

3 Top 2.5394 2.5420
Mid 2.5406 2.5420
Bot 2.5410 2.5410

4 Top 2.5380 2.5395
Mid 2.5410 2.5395
Bot 2.5410 2.5395

5 Top 2.5410 2.5393
Mid 2.5420 2/5405
Bot 2.5390 2.5403

6 Top 2.5410 2.5410
Mid 2.5415 2.5405
Bot 2.5410 2.5395

[alimey4u2]

Superb data, well done.....

Looks like you have a great excuse for a big bore kit which I highly recommend...Spose it's all about the amount of money you want to spend but a big bore kit is quite attractive. Yes, you can punch the stock sleeves out to 1168 but I wouldn't go more as they become quite thin at the base. The Wiseco kit is well within those limits..... Stock rods ?? In good condition shouldn't be a problem...
Be very careful on disassembly, do not allow the rods to hit against the crank case mouths. Tape them up with rubber tape or protect them in some way. A little ding can progress into a fracture quite easily....
If you want "insurance" get the rods shot peened. As I said... it's all about money....
A "good" machine shop should be more then capable in the setting up....

Just one mans opinion here, not gospel....

[alimey4u2]

Oh, there are aftermarket rings which are spiral wound. Specifically designed for bores that are above spec. A friend of mine installed them in his CBX to good effect....Maybe worth a try if cost is an issue....

[cbx6ss]

with a rebore in mind, does anyone have an over-size piston set, rings they would like to sell?
Thank you.
/r
Brad

[piit]

alimey4u2, do you have a link on aftermarket rings which are spiral wound or do you know recommended manufacturer?

[Dave Hansen]

Good advice on the porting work, Larry. I worked for a shop where I did port work using a flow bench. A very small amount of grinding was the difference between good flow and no better than what you started with. A good three angle valve job and a LITTLE bit of cleanup in the runners is all you should endeavor in your garage.