Topic: 1978 CB750F3 rebuild start

[majorzozo]

I think Vapor blasting will be the way to go.  Problem where I am at is it is a 4 hour round trip ride to get it done.  Didn't realize how much time and effort go into cleaning and polishing all the corroded parts...Hahahah.  Frame, swingarm, and center stand are back from powder coat and I just finished cleaning and painting the triple trees so once I get the new bearings and bushings I can stary assembling.  Just wish I had more time.  Good luck with vapor blast and thanks for the compliment.     

[BenelliSEI]

I used paint stir sticks, banded together, copying you photo, to hold up pistons. Worked great!

[RAFster122s]

I've got Com Stars on my 78 CX500 ( Plastic Maggot) and the bike lived on an island in Rhode Island for several years. Most annoying thing about the wheels was the rust that was started between the spokes of the 5 stars... Impossible to get to short of blast media.
You cannot disassemble the wheels to redo the steel spikes as the rivets holding them all together use a monster press and one shot for the rivet function... Not a user assembly process without access to some special equipment.
I still will take the STD ComStar over the Reverse ComStar every day of the week. The later are ugly.

[majorzozo]

Glad the sticks worked out.  Almost the perfect size.  By the way your sandcast is awesome.  Agree with you RAFster on the Com starts but just hated to paint.  Should have had more patience and aqua blasted as i bet that would have came out better. 

[majorzozo]

My wife and I were able to stab the engine in about fifteen minutes.  Luckily no damage.  This site is awesome with all the experts and ideas.  Just used alot of towels under the RH side of the engine.  Next is the swing arm and forks.  Both ready just need to find the time.

[Gamma]

Looking great

[majorzozo]

Thanks Gamma.  A few things for the first  timers like myself.  The fork inner tubes that came with the bike measured 23 inches but everything I read is 23 7/8.  Purchased new 23 7/8 tubes and used 2 1/8 1 inch OD washers sandwiching a 5/8 piece of schedule 40 3/4 inch ID PVC.  Had to sand the OD of the PVC to get it to go down under the fork tube threads.  My thinking is the spring preload should now be the same as it was and if I dont like the look I can slip the tubes up above the triple trees to get my desired height.  I used all balls tapered bearings for the triple trees and getting the lower bearing on was a little tough.  I first used a thin washer then a dust seal and then the bearing.  For the upper I used a washer only without the dust seal as I am hoping I will not need to shim the headlight ears that much.  The swing arm bushings went in easy using a long bolt and nut as a press.  Before installing the swing arm I need to get my act together as alot of other crap occupies the same bolt as the swing arm.  Thanks again to all that post as the information is so valuable.   

[majorzozo]

A few more lessons learned.  Stupidly I thought the ID of the new swingarm bushings would provide just enough clearance so I could slide the steel insert through.  No Joy so now I will need to get the bushings reamed to approximately .3MM wider than the OD of the insert.  Also finding out that the rear wheel bearing retainer removal tool I purchased will only work on the Disc side not the sprocket side.  They are two different spacings between the 4 holes.  Wow.  41231-283-000 for the sprocket and 41231-286-000 for the disc.   

[majorzozo]

HI all,  Throwing this out to the experts if anyone knows.  After installing my swingarm it is a little stiff to move up and down.  Without the rear shocks it will just not drop down it needs a little help.  Not much but was wondering if it should move with zero resistance.  I have new hat bushings installed and honed to fit the sleeve.  Thanks in advance.

[newday777]

HI all,  Throwing this out to the experts if anyone knows.  After installing my swingarm it is a little stiff to move up and down.  Without the rear shocks it will just not drop down it needs a little help.  Not much but was wondering if it should move with zero resistance.  I have new hat bushings installed and honed to fit the sleeve.  Thanks in advance.

Is it torqued?

[majorzozo]

Yes.  I think it be because I had the swingarm powder coated and installed the hat bushings without sanding down the powder coat where the hat of the bushing mates.  Too wide now so it creates too much of a clamp up??  Thanks for the help

[newday777]

Yes.  I think it be because I had the swingarm powder coated and installed the hat bushings without sanding down the powder coat where the hat of the bushing mates.  Too wide now so it creates too much of a clamp up??  Thanks for the help

That will do it. Too tight with powder coat on the ends of the swingarm.  The Devil's in the details.....

[majorzozo]

Free as a bird now.  Thanks Newday....

[majorzozo]

Would anyone know what the 3 tabs are for on the forward LH upper side of the swingarm?

[newday777]

Would anyone know what the 3 tabs are for on the forward LH upper side of the swingarm?

To hold the chain guard in place

[majorzozo]

Got it thanks...

[HondaMan]

Sorry to be late to the party...
The engine, and leaks: by chance, did you mill down the cylinder deck (0.010") and/or install thicker O-rings in those 2 oil ports between the cylinders and head (the 2 at the middle back, nearest the camchain tunnel)? If not, the engine WILL leak oil.

The reason: all modern head gaskets are thicker than Honda's were when asbestos was their major material: in the 1990s they all became something other than asbestos, and thicker. Honda's head gaskets were 0.80-0.82mm thick. The modern ones are at LEAST 1.00mm thick, some more than that (especially the MLS gaskets), so this port loses its O-ring seal, and the high-pressure oil leaks out. It then moves forward, coming out of the engine between the head and cylinders, in the front, at the middle.

Again, sorry to be late to the engine's installation...

[PeWe]

If the thinner stock o-rings (2.5mm thick) and thick gasket 1-1.2mm thick.
 
Not too late to take engine out, remove head and replace o-rings to thicker version.
Just add a little bit more torque when reinstalling same head gasket. Stock studs can cope with 20 ft lbs.

I tightened mine 20.6 ft lbs when using stock studs and 836. I used good torque wrench from my job. The tools were checked rather often.

[majorzozo]

Hey guys.  First off thank you.  I did not deck the head as the bike ran great before disassembly and I checked for flatness as best I could with a steel rule.  For the 4 holes with the cap nuts and brass washers I believe I used Oring 91301-410-000 from NPN and for the 2 holes between the cylinders I used Oring 91310-300-000 from NPN as well.  I cannot remember how thick.  The head gasket is Vesrah.  Boy I hate to take apart now even though I know it would be easier so I might just roll the dice and if it leaks then out it comes.  Thanks again guys and just wish I had more time. 

[RAFster122s]

If you wait until it leaks then a retorque reuse with a bit more torque likely won't be enough to prevent a leak.

Order new set of orings and check their thickness. Then you know if you need to take it apart.

[majorzozo]

Thanks Rafster.  A smart man would remove the engine and head now to be sure the thicker Orings were used.  I have never been accused of being smart. Hahahahaha.  I think at this point I am willing to accept the risk of the leak and when done with everything and the engine leaks then I will remove and fix for a winter project.  Wheels go on next.  Thanks again all...   

[RAFster122s]

I think reorder of orings used would tell you with less effort if you need to consider the steps backwards.

[MauiK3]

That would keep me up nights.
Pulling the engine is tough but thinking about the problem all the time is tougher
Just me

[majorzozo]

I think I will reorder and measure like your suggestion.  Good idea and thanks.  Still inclined to finish bike to get all tuned and running good and if it does indeed leak then pull the engine at that time.  I agree it will be a pain in the ass but for me it is worth the small chance it may be bearable. Thanks again...Great site. 

[HondaMan]

I can send you 2 of the correct O-rings: PM me your address? I have 150 of them, for days just like this.