Topic: Another CB750 Engine Rebuild...I hope...

[VTCBike750]

As far as the tool used to remove the clutch hub nut.  At first I used a screw driver and hammer, but I ended up buying this tool:
http://www.ebay.com/itm/270759977366?item=270759977366&viewitem=&sspagename=ADME:L:OC:US:1123&vxp=mtr
It works great!

Heres a thread all about it:
http://forums.sohc4.net/index.php?topic=91468.0

As far as the 4 screws that hold the countershaft oiler on.  They can be a #$%*.
This is a great thread that shows how to remove them:
http://forums.sohc4.net/index.php?topic=78643.0

I though I was SOL but then they finally came loose. YOU HAVE TO USE AN IMPACT DRIVER!

Dont forget when you put the new ones in, use some loctite

the original screws were "staked" with a chisel to stop 'em from turning

Just drill the heads off with a 1/4" or 5/6" drill (you've already "countersunk" them, ha ha!) and pull the plate away, then turn the remains of the crews out with your fingers. Use a little threadlock on the new screws, or re-stake 'em. Cheers, Terry.

[filipo]

Excellent thread, thanks for posting. I was feeling a bit lost on my own rebuild -- to hone or not to hone, that is the question -- and yours got me re-energized. Keep up the good work.

[M.Harrigan]

I recently checked with Terry Quail and he is no longer selling the Primary Chains.

[thomellis]

Geeze, been a while.  Work has been crazy, and I just haven't had a lot of time to get a lot of work donw.  I'm also working on a few of the more unexciting tasks like cleanup and stripping.

I'm set to get the engine soda blasted in about a week.  Found a place to get it done for $100 which seems pretty reasonable as far as I can tell?  Compared to cleaning it up myself, I don't think I can complain about it.  Once everything is cleaned up I can get to patching that crack, and finally get to repainting it.

Some parts are in the mail, still a few others to get.  I'm still baffled at the cost of a new cam chain tensioner, $90? Mine is pretty chewed up, so I'm sure I really need it.

Finally got the gaskets cleaned off pretty well, and got that mucked up knock pin out.  Stole a trick from the forum (mcrider?), just went in with a drill bit 1 size bigger and she popped right out.



Otherwise today was a lot of stripper and naval jelly, getting paint and rust off.  As mentioned several times in the forum, this "aircraft" stripper really is some nasty stuff, but i works great!




A bit more cleanup and then I'll get to spraying those, just getting a rattle-can job here.  Hell of a task to get the shock bushings out of the swing arm.  They were gunked and pretty warn so I decided to replace, had to drill out the center, then hack the outer bushing to get it out, but it worked like a charm.  Another trick from the forums

On a side note, really should have taken the front brakes apart before taking em off the bike because these bolts refuse to budge a bit.  Soaking in some pb right now, so we'll see where that gets me.



Other things goign on:
   * Got my new sidecovers from Frankenstuff
   * Trying to determine what I'm going to do for a paint scheme on the tank/side covers
   * Tracking down some emblems/badges
   * Sending off rotor to Tom this week to get drilled.

Anyways, should have more time to work on things in the coming weeks, so hopefully I won't fall off the face of the earth for a month again

Until next time...

[brandEn]

Where are you located?

Looks like you are making progress. One thing I learned during my last rebuild was to loosen some of the big stuff up before taking it off. I had many problems with stuck or hard to loosen fastners as well.

[KRONUS0100]

one of the experts chime in here........noticed in the close up photos of your cylinder head what appears to be a quench band around the combustion chanber.   curious as to your motor being stock, as none of the cb750's ive seen torn down had this look about them.

[lucky]

You have to measure the pistons ,valve guides etc.,. You cannot just move them and think they are smooth enough.

We are talking thousandths of an inch for these parts clearances.

Throw the piston rings away you cannnot re use those.
You need to get the cylinders measured properly to determine if the pistons need to be replaced because you may need to re bore +.025 over.

Those pistons look like normal wear but considering the condition of the cam chain rollers you WILL need a new cam chain so the bottom end will need to be taken apart
and then you might as well put in new lower end crank bearings and rod bearings.

Remember this engine is over 30 years old!!

Just take your time and do it right.
Start looking for a machine shop to help you with these
machining needs.

BTW...You can get that special tool for the clutch nut for about $22 and then just attach it to your hand impact driver. Also when you use your impact driver you apply force in the direction of loosening, while pushing towards the screw, THEN tap it with a hammer.

[thomellis]

hey brandEn, I'm in a bit south of Portland.

Thanks lucky.  Yeah I realize I have a bit more to do engine wise.  I'm on the fence as to whether I really want to split the case right now.  Someone mentioned just getting a new cam chain (obviously not continuous) with a link and just swapping a new one in.

[lrutt]

You don't have to remove the bottom end on a 14k mile motor. You can get a cam chain and rivet it in place. If it ain't broke, don't fix it! Get the open ended chain and just rivet it in place. Use your old chain to help feed it through. You can use a dremel and break a link on the old chain to facilitate that.

From what I saw the pistons didn't look bad. If they measure ok, why replace. How many miles do you plan on riding this bike.

One thing, don't cheap out on the rings. Get HONDA rings. otherwise you run the risk of crappy rings and a smoking engine.

And while you've done a lot of work cleaning your engine. I hope you took great care as to not force crap down the oil feed ports on the case. You have to make sure those are extremely clean. As well as the corresponding ports on the cylinder and head. You do NOT want any crap of any kind left in there or it will find it's way to either block the oil jets or into the soft cam bearings.

[thomellis]

Well I got derailed for awhile between work and life in general, but finally got things back on track and making progress. just a quick recap of updates:

Got the case and head soda blasted to clean them up and prep for paint.  JB welded crack in the case.  Based on feedback and other posts I think it should hold, plus its not visible once the engine is all back together, so I'm not too worried about it aesthetically.  Got it all painted using Duplicolor engine enamel, really happy with the results.

Cylinders were in good shape, so I just had them honed.  Installed new rings, got some off Ebay based on Hondamans recommendation.  One piston had a small ding in it, looks a lot worse in the previous pics, but I just hit it with some fine emery cloth and cleaned it up.  Lapped the valves, cleaned everything up, and started putting her back together.  New tensioner and gaskets, was able to salvage a new dowel pin to replace the one I mangled during the breakdown, and it's finally starting to look like something again:





Still working on polishing valve cover and side covers, in the second pic you can see there is still some leftover residue.  Haven't put a ton of time into the pieces yet, but already really impressed with how far they've come, from a dingy dull to shiny aluminum again:



Image is a bit fuzzy...I'll get a better one once they're all finished.

Also had the rotor drilled by elCheapo, looks great.  Everything else that needed it has been stripped and repainted.  Still quite a few things to polish and clean up, but it's getting there.  Hopefully will get a chance to get things back on the frame soon.

On a side note, these came with my gasket kit, and I'm not sure what they're for.  I'm guessing their some type of stud packing for a different model? but that's a guess, anyone know:



Lots of other little things along the way, but it's all starting to blur together ;P

Cheers!

[wrenchmuch]

Your right . not all models use those seals . They came in around 74 .