Topic: Things to remember when putting together a top-end...

[jessezm]

Just wanted to share these two big mistakes I made, and thankfully, fixed, before calling my engine "complete"....

Mistake #1:  
So I just finished painting my freshly rebuilt CB400f engine (will start a build thread soon with pics) and was getting ready to adjust the valve clearances when I remembered something I read in a thread a few weeks ago that had me worried...

Somebody had written about their cam sprocket bolts coming loose inside the rocker cover and doing major engine damage, and there was this whole discussion about how tightly to install them...   I couldn't stop thinking about how I couldn't remember how much I torqued the bolts on mine or whether or not I used loctite, so I opted to take the cover back off and check it out.  Sure enough, they came loose with just a bit of pressure--not nearly tight enough, which could have spelled disaster...

So I took them out, cleaned the threads, applied red loctite, and torqued them to 15ft-lbs (or whatever the high-end of the spec manual was).

Mistake #2:
Back on goes the valve cover and I go to check my valve clearances and something is totally off.  At T 1,4, there should be some lash in either 1 or 4 on both intake and exhaust.  Well, both 1 and 4 had at least one valve with no lash, even though I had backed the tappets all the way out to avoid bending valves when reinstalling the cover (another common mistake...).

After racking my brain, I finally decided that it was possible that when I installed my new cam and cam chain, I may have had the crank set at T 2,3, rather than T 1,4, meaning that the cam was out 90 degrees.

So off comes the cover again, and much to my dismay, I had indeed used the wrong timing mark when lining up the cam.  Back out came the re-torqued cam sprocket bolts, out came the cam tensioner blade, off came the chain, and voila!  I got the cam back in the right position, and buttoned the motor back up.  Then I set the clearances to .004 (per Webcam specs), rechecked each setting afterward, and now I am finally ready to call the motor complete!  Still have to set the static timing but the bike is not wired up yet so that will have to wait...

Just didn't want someone else to make the same mistakes I did...  All in a night's work!

[sangyo soichiro]

Wow.  Some close ones.  Good thing you caught it.  Thanks for sharing.  I'll take extra care when putting mine back together.

[ealanm]

Let me add a few:

* Ensure you have all six oil seals -- two under each rocker tower, and two between the head and the cylinder barrel.  (I think some older engines may only have one under each rocker tower, but be sure!)

* Ensure the oil ports are completely clear.  Compressed air should flow through in a strong blast.  They're very small, and can clog easily.

* Check the rocker shafts for straightness.  I found one of mine was slightly bent.

* Don't forget the four head bolts under the rocker towers.  While you're at it, don't forget the rubber nickels under the rocker towers.

[mycb750k6]

Remind me again why you can't adjust the tappets with the valve cover off?

[jessezm]

On the 350 and  400, the rockers and tappets are attached to the valve cover, rather than the cam towers like the other models.

[greasy j]

my buddy is doing his 400f at the same time as my 750k. we're taking an engine overhaul class. I noticed the diff in the valve cover and the rocker arms being attached.

this is good info. I'm gonna refer him to it.