Topic: CB750 Motor rebuild... for dummies

[Terry in Australia]

Hey all the best to you and your wife mate, I hope she gets well soon! We'll continue to keep this thread alive for you, in the meantime. Cheers, Terry.

[jevfro]

All the best to you and your wife Smack
Here's a question that may help some others and keep the thread rolling too.

Is there any consensious about which gasket set is best? shouldn't be used?
Honda oem: Most ppl say are tops. Looks like ~$150 if I'm lucky enough to find both sets & the $ on the same day 
Vesrah: Seems ok, a little cheaper too. ~$80 (I see a few being used by ppl here)
Athena set: ? ~$70 Partsnmore
Z1 has a set, I couldn't obtain the maker from the site, for only $63!
Cyclex is probably the cheapest. couldn't get the price because page is down. ~$60?  Some of the kit is made by Emgo?

I need to order these so I'll get going on my LONG overdue rebuild!  Thanks for any advice!

[Jerry Rxman Griffin aka MuthaF'er]

Whoever may have Z1's handle on here could perhaps pm the question of which brand he sells.

[harald]

There is another way of removing cylinder studs without heating. When you have taken the upper engine case off put one of the studs ( start from the most left) on to your clamp. The clamp must grip very near the bottom of the stud. Now the upper engine case will be 90 degrees compared to the stud. Now turn the engine case counter clockwise till the stud loosens, then you can easily remove the stud with a vise or pliers. The stud might get some marks from the clamp but it can be remove. The clamp must be bolted of course to a table.
Try it and you will be suprised how easy that is.

[Terry in Australia]

Back to TC's question, I don't think any gasket set is bad, the only problem I had was using the EMGO/Cyclex head gasket on a late model (K6) top end, the holes for the dowels are too small and just won't fit. I laid it over a K2 head though, and it was perfect.

The head gasket is a metal/fibre sandwich, and looks really good. I use similar head gaskets on my Suzuki GS1000 engines, and they work very well, and I'll even re-use them with no issues, something I'd never do with a fibre Honda head gasket.

The Emgo kit also contains the rubber pucks for under the cam towers, another thoughtful touch. The Honda kit has the exhaust gasket rings as does the Emgo, and the Emgo kit has both types of cylinder stud "O" rings.

All in all, the Emgo kit is good value, particularly if you're rebuilding a K0-K3. If you're rebuilding a later engine, you'll need to modify the head gasket (enlarge the two outer dowel holes) or get another one.

As far as stud removal goes, if I'm taking them out I'm not putting the OEM ones back in, so no problem  butchering them. I just bend the suckers at right angles to "crack" them, then bend them up to some semblance of straightness to wind them out. No heat, no penetrating fluid, no double-nutting, no vice-grips. Down and dirty, but effective. Cheers, Terry.      

[Kevin D]

Z1 has the Vesrah kit, which was pretty good IMHO. I modified the head gasket to use orings at the oil return studs. No pucks included for cam towers.

[SandwichEnthusiast]

Arg.

I've destroyed the mesh screen on the oil pump. I'm not sure if it was because the rubber was so hard or what, but I mangled it up proper. Any words of wisdom on that and also on ordering parts from inside the oil pump assembly? (it isn't exploded in any of the diagrams except the service manual, not in clymers or any online fiche I've seen)

To get a stuck ring off a piston, I froze the piston then poured hot water (and repeated) then took a small punch and tapped the ring (I don't think I did any damage to the piston doing that), but I got lazy and left it in a pickle strainer I was using to dunk it, and some moisture condensed on it, I still have to give it a good look, but when I pulled it out the ring had already got a little rusty.

Any wisdom about the importance of replacing the wrist pin clips, and transmission circlips (the general service manual stresses it)

Season's a wasting, time to pick up the pace.

[Superbiker_uk]

I've destroyed the mesh screen on the oil pump. I'm not sure if it was because the rubber was so hard or what, but I mangled it up proper. Any words of wisdom on that and also on ordering parts from inside the oil pump assembly? (it isn't exploded in any of the diagrams except the service manual, not in clymers or any online fiche I've seen)

I damaged the same part when I was re-assembling my motor. Don't worry though - they are available from DSS and CMSNL part number 15150 300 000. According to CMSNL "Suits all Honda SOHC four cylinder engines of 500cc,550cc and 750cc including F1 and F2"

[Jerry Rxman Griffin aka MuthaF'er]

I believe you might be able to get the screen from Honda. Other oil pump parts, probably not.

I'd replace the wrist pin clips.

As far as reusing the "stuck" ring, I believe I'd at least hone the cylinders if you can get by with that little of work and go with new rings considering it was stuck. Clean the grooves and visually inspect for damage.

[SandwichEnthusiast]

I'm definitely sending the cylinders out for a hone, and I've got new rings... and now that I have to get a new strainer, I will probably add some wrist pin clips to the shopping list (never ending).

I'm worried about the (#12 11x15x3 Oil seal) that fits on the oil pump gear shaft all the rest of the seals came off easy, but this one is stuck and I
A) don't want to mangle it if I'm going to have to go to lengths replacing it
B) melt it when I pour the horrible chemicals on it to clean it.

[SandwichEnthusiast]

Speaking of which, the cleaning:

the plan is, now that its all disassembled (save the one bearing in the case, and the shift drum) to pour in some releaseall (in the jug) in there, do some light scrubbing with a plastic brush, wash it out with water, blow it out with the Kompressor, and coat the inside with some fresh oil. The flanges don't look messy, they don't feel like they have any permetex on it at all, but I'll clean them up nice.

but I'm wondering about keeping the outside (factory finish, whatever it is) corrosion free,
what I should put on the bearing (the transmission one in the case, not the crank bearings).

and whether or not I should remove the crank bearings (From what i gather from the general service manual i should take them out, clean them put them back and put some moly 60 on the inside surfaces (touching the crankshaft)

[rugger81]

As far as stud removal goes, if I'm taking them out I'm not putting the OEM ones back in, so no problem  butchering them. I just bend the suckers at right angles to "crack" them, then bend them up to some semblance of straightness to wind them out. No heat, no penetrating fluid, no double-nutting, no vice-grips. Down and dirty, but effective. Cheers, Terry.      

I followed this advice last monday when I removed my cylinder studs.  Shot a blast of penetrating oil at the bottom of each stud everyday for 3 days prior.  Once I was ready to remove them, I bent them down with a rubber mallet, then twisted them out by hand.  Didn't take me more than an hour of my time, and I didn't have a single stud snap.  Just make sure you hammer them down to at least a 60 degree angle.  If you don't they tend to just bend around the base rather than twist out.

Oh and thanks big time for this piece of advice Terry, I was a bit afraid of removing my studs with all the horror stories, but found this method very easy.

[Terry in Australia]

No worries mate, it's mechanical butchery, but bloody effective! 

[gregimotis]

I am just about to pull the engine for the third time and attempt to staunch my oil arterial bleed.  I hate posting that in public - except for replacing the studs, I really tried to do everything right... except this:


After I reassembled the first time, I had worse leakage than I had had before.  I assumed the problem was my valve cover gasket or rubber pucks, not the head gasket and so only replaced those items.  That assumption is why I'll be doing this a third time instead of riding.

Today, I sprayed athletes foot powder around the head (a technique I read here) and then ran the engine until oil stained the white powder.  It is 100 percent obvious that the leak is all along the left side and rear of the head gasket.

Further: 
I assumed the valve cover gasket was the problem because when I put it on, it didn't fit (EMGO from Cycle-X).  I had to cut about an eighth of an inch from the sides to get it on and then sealed the cuts with Hondabond.

[mustangcar]

i just got my 750 motor back in the frame today (relief)for the first time,no easy task,hope mine doesn't start to leak,,so what head gasket brand are you going with this time?,wish you luck

[paulages]

mine just went out the door! 50 miles on a rebuilt engine and a fresh paint job... i think this guy got a nice deal personally. i'll miss it, but there'll be more...

[Terry in Australia]

Hey nice work Paul, that 750 looks sweet!

[paulages]

Hey nice work Paul, that 750 looks sweet!

thanks, terry!

[gregimotis]

i just got my 750 motor back in the frame today (relief)for the first time,no easy task,hope mine doesn't start to leak,,so what head gasket brand are you going with this time?,wish you luck

APE studs, Honda gaskets, check the head to make sure it's flat where it should be.  Enlist an old BMW mechanic (in both senses) acquaitance for advice.


+2 on the nice bike.

[bunghole]

I'm starting to prepare for my own rebuild on my '77 750K and I'm a little confused.  I looked at the fiche on ServiceHonda.com and it lists the primary chain twice with different part numbers.  When I pull up the info on one or the other, it says 2 are required.  I know I need two, but should I order one of each part number or two of one or another?

The two part numbers are 23131-300-315 and 23131-300-015.

Thanks for any help.  This thread has been an amazing resource!

[paulages]

I'm starting to prepare for my own rebuild on my '77 750K and I'm a little confused.  I looked at the fiche on ServiceHonda.com and it lists the primary chain twice with different part numbers.  When I pull up the info on one or the other, it says 2 are required.  I know I need two, but should I order one of each part number or two of one or another?

The two part numbers are 23131-300-315 and 23131-300-015.

Thanks for any help.  This thread has been an amazing resource!

when they list two different numbers for the same part, it's because of different manufacturers which have different product codes. there are two primary chains, but they are sold and packaged as a pair.

[Jerry Rxman Griffin aka MuthaF'er]

Yeah, order ONE of either part number and you will get ONE set of TWO chains with the latest updated superceded part number. All the 750's except the Automatic use the same chains.

[Terry in Australia]

Agreed. I ordered what I thought was 2 chains from Terry Quail and I was shocked at the price ($160.00) until they arrived and I realised there were a total of 4 chains! No biggie, the two engine's I've recently rebuilt have received new primary chains. Cheers, Terry.

[bunghole]

Engine stand mounting bolts. Copied from Gordons design 1/4" thick, 3 " long, 1" wide. Welded to #8 bolts with 1/2 holes drilled near the end. I dropped a drawing and the 4 bolts off at a metal shop and 4 days later.... "Come and get 'em...20 bucks!" how they made any money on that I have no idea.

I went and did the same thing for an engine stand.  Except, I used my stick welder to weld up the new mounts.  I'm a little stressed about it as I am by no means any kind of welding expert.  Right now, I've got an '82 Yamaha XJ550R engine mounted on it and it has been holding up for two days.  Every once in a while I go out there and poke it and then run away, but so far so good.  I've even leaned on the top of the engine to test it's limits.  Feels solid, but I'm still going to wear the steel-toed boots around it.

[OTool]

Wow guys...
I guess there's hope for me yet!
I juswt got through reading 20 pages of this writeup and feel like I may actually be able to do this.
The background?
I got my Uncle's old 750 about 8 years ago.
Before that, it had laid against the side of his old garage for probably about 8 or 10 years.
The bike was pretty rusty in spots, but pretty good in others.
Long story short, when I got it, I wanted to "redo" it, but had no idea how.
So, it has sat at my house now for several years!.
Well, a couple of years ago, I found the site and read a few things and decided to go look at it.
The motor had compression when you tried to kickstart it, but everything was obviously dead.
Well, long story short, I repainted a few things and fixed a bunch of rust, and rewired some stuff, and even went so far as to change the oil and get ready to try it out.
Nothing started... So I pulled the spark plugs to go get new ones and replace those (Bad idea). I got nerw ones, but got sidetracked with some home issues and didn't get back to the bike for a couple of weeks (outside with no plugs). The engine won't kick over now.
I'm assuming stuck rings.
So it has sat now for 2 years and probably needs a rebuild. (I did at the time I found it was stuck put wd40 into the plug holes and screwed the plugs back in)
We also had some ice damage that went through the top of the shelter that I had the bike under, and so my tank is caved in, and the tach is smashed.
I'll need to find replacements for those too.
I feel better about attempting this now though!
I'm just a bit lacking in the common sense department though it seems...
Aaron