Topic: Complete overhaul of a CB750 engine, what parts are a must?

[Martin Thomassen]

Hi

I got at spare engine that I would like to do a complete overhaul of, but as I haven´t done such a engine before I would like to know what parts are need to have, and what parts are nice to have.
Fortunately if got a friendly connection in the business, so I use to get the original parts pretty cheap, so I really want to replace all the vital parts now that I have the engine completely disassembled 
The plan is to install the 850 piston kit from Cyclex, in combination with a Webcams camshaft, Kibblewhite valve springs and a gentle treatment of the cylinder head.

My initial thoughts are (everything that isn´t branded are original parts):

Complete gasket kit fra Cyclex
Crank shaft bearings
Conrod bearings
All engine oil seal
Primary chain
Primary chain tensioner
Cam chain
Cam chain tensioner
Cham chain guide
APE manual cam chain tensioner
Valve guides

I´m a little unsure whether to order the different ball and needle bearings that are used in the transmission and primary chain/kick starter. For ball bearings they are exorbitantly expensive, even by Honda standard (and in spite of a good discount) 
I know it would be next to impossible to replace the bearings when the engine has been assembled, so I´m very curious to know, if it is recommended that you replace the bearings when the engine is open anyways?

Any other parts that are impossible to do without, or anything else I should consider ordering?
 

[Old Scrambler]

The rubber 'cush' parts in the clutch and the oil-pump rebuild kit. Don't know what ignition your planning on.......but new advance springs would be nice.

[flybox1]

Don't do ANYTHING, until you have HondaMan's Book!
I completed all of what you listed above and more, and successfully popped my rebuild cherry using that book and this forum alone.
Its worth every penny.

[edwardmorris]

+1 Hondaman's book, basically mandatory reading for a rebuild.

I did go the extreme length of  replacing all bearings, including those PITA needle rollers on the clutch basket with SKFs, just want a "new" engine that I won't have to open up for another 40+ years. Depends on what your goal is really, if investing in a long haul, change them all with good ones.

[PeWe]

Sure about conrod bearings?  If open the bolts replace them with F2 version.  Check if the rods have lash before doing anything.
If the engine has plenty of miles it might be time for it. My conrod bearings were usually good. Maybe they are more protected than the crank bearings. I replaced all the other bearings in the entire engine at 65.000 km's.

My valve guides have always been good. I replaced a 2 of the exhaust due to massive overheat making rods top end bluish, melted 2 pistons. K engines have good steel guides. Check the radial lash. I think max play at the has at 10mm lift is about 0,1 mm.

Invest in a ported head. 836. Send head, cyl and crank with rods to a professional that port head, fix valves and seats + springs. Bore cyl, balance crank with new pistons, polish the journals.   New cam
-But you might go for a  std CB750 engine?

[Martin Thomassen]

The rubber 'cush' parts in the clutch and the oil-pump rebuild kit. Don't know what ignition your planning on.......but new advance springs would be nice.

I think I´ll be replacing the clutch with the APE "Extra Disc" kit, but I´m not sure what rubber parts you are mentioning are?

I will also look into the oil-pump rebuild kit as you recommend.
In regards to ignition I plan on using the transistorized ignition for dual points from Hondaman. I haven´t seen the advance springs sold separately, where can I get those?

Don't do ANYTHING, until you have HondaMan's Book!
I completed all of what you listed above and more, and successfully popped my rebuild cherry using that book and this forum alone.
Its worth every penny.

That book should already be underway 

+1 Hondaman's book, basically mandatory reading for a rebuild.

I did go the extreme length of  replacing all bearings, including those PITA needle rollers on the clutch basket with SKFs, just want a "new" engine that I won't have to open up for another 40+ years. Depends on what your goal is really, if investing in a long haul, change them all with good ones.

It is hard say. On one hand I like to do things right, but on the other hand I don´t like to scrap perfectly sound parts. The bike is just my hobby, and I got a newer bike and a car for transportation, so I will only use it occasionally, and mostly for fun 

Sure about conrod bearings?  If open the bolts replace them with F2 version.  Check if the rods have lash before doing anything.
If the engine has plenty of miles it might be time for it. My conrod bearings were usually good. Maybe they are more protected than the crank bearings. I replaced all the other bearings in the entire engine at 65.000 km's.

My valve guides have always been good. I replaced a 2 of the exhaust due to massive overheat making rods top end bluish, melted 2 pistons. K engines have good steel guides. Check the radial lash. I think max play at the has at 10mm lift is about 0,1 mm.

Invest in a ported head. 836. Send head, cyl and crank with rods to a professional that port head, fix valves and seats + springs. Bore cyl, balance crank with new pistons, polish the journals.   New cam
-But you might go for a  std CB750 engine?

I don´t know how many miles are on the spare engine, that it, partly, also why I would like to rebuild it. As the engine is already completely disassembled I will need new crankshaft/conrod bearings no matter what (they can´t be reused as far as I know!?!)
I will try and look into the F2 conrod bearings, if these are a better choice. I will also check the lash on the valves and conrods as you mention.
In regards to engine performance see the last part of my initial question - I´m doing a couple of modifications, but I´m not going "over the top", with the engine

I guess I can boil part of the answers down to "it depends" 
I will try and evaluate the current condition of the parts (ball bearing, valve guide etc.) before replacing them. Are there any hard to reach bearings that are a must to replace (needle bearings by the primary chain maybe) when the engine is already opened?

[RAZZ]

Hej Martin

Jeg har en ny ekstra hondaman bog her i dk hvis du er interesseret.

Mvh Rasmus


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[Martin Thomassen]

Hej Martin

Jeg har en ny ekstra hondaman bog her i dk hvis du er interesseret.

Mvh Rasmus


Sent from my iPhone using Tapatalk

Private message sent 

[PeWe]

F2  conrod bolts with nuts are stronger than older.

[Martin Thomassen]

F2  conrod bolts with nuts are stronger than older.

Now I understand 
The spare engine, or at least most of it, is actually a F2.
Should the bolts and nuts be replaced when the rods have been disaasembled?
Is there anyway to identify the F2 conrod bolts and nuts from the regular parts?

[flybox1]

F2  conrod bolts with nuts are stronger than older.

Now I understand 
The spare engine, or at least most of it, is actually a F2.
Should the bolts and nuts be replaced when the rods have been disaasembled?
Is there anyway to identify the F2 conrod bolts and nuts from the regular parts?

F2/F3 are the same for the most part.
My first rebuild was an F3. The PO decided to disassemble it years prior, so it was a puzzle going back together.
The rubber parts for the oil pump Old Scrambler is referring to are best purchased thru member ELAN. 
He's got a slick kit to refurb it.
Yamiya is the only one I know of who sells those advancer springs. 
Once your advancer unit is cleaned up, you might not need.
find and read brandEns 'leak free top end' thread. 

[Martin Thomassen]

F2  conrod bolts with nuts are stronger than older.

Now I understand 
The spare engine, or at least most of it, is actually a F2.
Should the bolts and nuts be replaced when the rods have been disaasembled?
Is there anyway to identify the F2 conrod bolts and nuts from the regular parts?

F2/F3 are the same for the most part.
My first rebuild was an F3. The PO decided to disassemble it years prior, so it was a puzzle going back together.
The rubber parts for the oil pump Old Scrambler is referring to are best purchased thru member ELAN. 
He's got a slick kit to refurb it.
Yamiya is the only one I know of who sells those advancer springs. 
Once your advancer unit is cleaned up, you might not need.
find and read brandEns 'leak free top end' thread.

Mine is a big mess of different F1 and F2 parts, so every now and then I'm uncertain which of the parts are from what 

[PeWe]

Clutch:
Important you will get correct fiber plates. The later models had 7 disks, 6+1. The outer one with wider ears to match the basket. I got wrong disks back in the days, all looked the same. The outer disk ears had a play of 1-2mm which caused the ear and part of the disk to fall apart. Metal and clutch parts in engine, nice, happened twice when I trusted the part dealers.

[Martin Thomassen]

Clutch:
Important you will get correct fiber plates. The later models had 7 disks, 6+1. The outer one with wider ears to match the basket. I got wrong disks back in the days, all looked the same. The outer disk ears had a play of 1-2mm which caused the ear and part of the disk to fall apart. Metal and clutch parts in engine, nice, happened twice when I trusted the part dealers.

I just inspected both of the 2 spare clutches I have, and one is the double steel plate type, and the other is not. The clutch baskets are also different (see the attachments).


Is any of the designs preferable to use? I intend to replace the fiber discs and the springs with some heavy duty. The steel plates seems to be okay.

Would it be advisable to wash out the engine ball bearings and grease them up, if they aren´t damaged? The disassembled engine has been stored on an attic for >10 years, so I guess all kind of debris could have settled in the old grease?   

[PeWe]

Clean all bearings, then motor oil of same model to be used later.
Make sure to gather all parts needed for each clutch when they are not compatible. Double metal disk has other hub with longer splined area. Different washers too?
http://forums.sohc4.net/index.php?topic=64339.0