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TommyLud

TommyLud
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Hi I'm Tommy. I live in the Lehigh Valley in PA. I recently acquired a 1978 CB750F with 30K miles on the engine. The bike hasn't been registered since 1984 and the engine turns over with the kick start without a problem. My friend was saying "just do a compression test and if it's good then go with it..." I'd rather tear the engine down, do a "full rebuild." "Full rebuild" is in quotes because it'll the a rebuild done by me...the typical amateur try-hard.

I've found a few youtube rebuilders, Hackaweek and Peter Anderson and others I'm sure, but these are my main inspiration, and I've acquired a very in depth manual. I'll be using those youtubers and forums like this as a guide and try to verify with the manual.


1)The first question I have is related to where I can get hardware from. Vintagecb750.com has a kit, Part #: 73-0146, which seems like a good start.

..Background..
I've been slowly moving forward with tearing down the engine down. I'm finding that a lot of the screws(allan and phillips head) have been stripped. I"m thinking most likely due to the last guy wanting to tear down the engine himself and then giving up. I've zipped a few out with a "speed out" and hence destroyed the screws. A couple of other screws I've really laid into, to avoid stripping them, and STILL destroyed the heads as if I was sticking the driver into clay. SO...I'm expecting ALL of the rest of the screws involved with holding the engine together to follow suit. I would like to find a new screw/bolt kit.

2) I'm thinking I'll need to change out the crank shaft bearings and connecting rod bearings as well as connecting rods and stretch bolts.

..Background..
I've been "researching" on youtube and google how to go about a rebuild. One of the rebuilders whose inspired me is Dino on Hackaweek(youtube). He went as far as to order new connecting rods, stretch bolts and bearings. I think I'd like to do the same. I can scroll through his videos and website to find out where to get them. But I'm curious what other builders have used.

3) Brake calipers are seized.

..Background..
The cylinders aren't budging. I've been soaking one in WD40 and the another in PB Blaster(penatrating oil). Hoping one of them will help to unseize them. No luck whatsoever. Any suggestions?


I know this is a lot that I might sound like I'm demanding..but I really am clueless and sites like vintagecb750.com and partsnmore.com seem to have products with NOOOO amplifying info, like for the engine hardware. It says that there's 60 pieces...but doesn't tell you what they're for!!

I'm sure I'll have a million more questions as time goes on. I also have a youtube channel where I'll be going through my build as well as my house. I just bought a house and it needs a few things done to it haha. I"m not sure if I'm allowed to post my channel here..but here it goes.
https://www.youtube.com/channel/UC7Vs2LKrkmbueRGZESnrLWw?view_as=subscriber

(I'd attach pics but this site doesn't like .jpeg for some reason)

TommyLud
 
So you say its a 78F is this a true supersport motor? Verified with motor vin? The F's will be harder to find engine parts and have some issues that need to be upgraded while doing the rebuild which makes these the most expensive of the 750's to rebuild the correct way. Also you need to determine if you are going for absolute stock rebuild or if you want to go for some more power. Some parts need to be upgraded no matter which way you go.

The original screws are soft, always first try a hammer driver, then if they strip I use a dremel and cut a slot for straight blade and use the hammer driver 9 times out of 10 I get them out. Check ebay also for bolts and many other parts, it is my go to place for good used and obsolete items for these bikes.

You wont know what you need for bearings until you get it apart to inspect and measure...dont loose the positions of where the bearings come from, they are select fit bearings...from the factory they are color coded on the bearing shells but over time the color fades and you wont know what color they are...if the bearings check out good and clearance is correct no reason to replace them, if you remove them and lose position you can use plastigage and do alot of swapping. I suggest you get a OEM honda manual and read up on how the bearings are selected, they with that information with the amount of miles you should get a micrometer to measure the crank journals and determine the wear and adjust your bearing selection from there.

I'll let you use the youtube videos and hackaweek as you will, I am not impressed and stopped after two videos on his 750 rebuild, I found several misleading and inaccurate bits of information in the videos. So take that as you will.

Connecting rods depend on the purpose and goals of the motor. If stock power and displacement then there is no reason to replace the connecting rods unless it looks like they are damaged or have been overheated. If you will go bigger bore or bump power then yes I recommend replacing the rods with metal not aluminum rods. Several different options available depending on goals. If staying stock then yes I recommend new rod bolts.

Best sites for 750 motor parts and machine work are CycleXchange, Dynoman, and APE. www.hondapartshouse.com for oem parts CB750supply supports this page and has good inexpensive items.

If you really want to get into the engine rebuild I am happy to help
 
Thank you soooo much for the thorough reply!

I think I've found a good bolt set to start out with. I'd just rather have something that I don't have to worry about destroying when reassembling.

As for the bearings..I'll get to that step when I get there. I think I'd definitely like to NOT have to replace them haha. And for the connecting rods...I don't plan on upgrading the engine pistons and cylinders..If they're not damaged..not going to waste my aggravation on them.


I completely get that there are going to be inaccuracies on YOUTUBE!! haha..that's not the source I go to for the truth haha. Just a guide. I like to see what other people pay a little more attention to and then move forward with my own technical common sense and the shop manual I acquired.

But on the topic of youtube..anything in those first two videos he made that I should be steering away from? If anything, I'd love to not blow myself up haha!!
 
I would just say use the videos for entertainment purposes only, not actual direction on a 750 build.

Keep the rods but replace the bolts...cheap insurance.

If this is indeed a supersport motor you will find it difficult if not impossible to find piston rings...no longer available from Honda. Only hope is new old stock, or have a ring manufacturer make some.

Verify what motor you have before ordering any parts or making any decisions.
 
I can help with engine identification. Sometimes the motor vin isnt 100% accurate. Lot of years have past since these bikes were new, parts have been swapped and cobbled together etc. If it is a true F there will be a 410 cast into the top fin of the cylinder head between cylinders 2 and 3.
 
The frame VIN is CB750F-2205019 and the engine is CB750E-3105061. From what i've been able to find it looks like a '78 F3. And there's definitely a 410 in that location.

Still can't seem to upload images. ya think it's because they're jpeg? Just says they're invalid. It must be..because I can't remove other images I tried out...ughh..
 

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I would message Travis the site owner he should definitely be able to figure out the picture problem. As far as your motor now that know that it is a f motor there are some things to know and things to consider. The F was the performance 750, honda changed some things in this model compared to the K. Like I said earlier piston rings are not available from Honda and will be hard to find elsewhere. If you remove piston assemblies from cylinders you have to replace them. Connecting rod bolts are available. Cylinder head had some issues that have to be addressed. The F had bigger valves and ports for better breathing, they used different springs and retainers...the retainers have been known to pull through causing damage....fix is titanium keepers or cycle x has some different options. They also wear out valve guides prematurely, again go to cycle x for the fix....They do complete head work and can make the head good to go, but its gonna cost you money, but do you want to risk dropping a valve and doing major engine damage? The piston issue is this...if the bores and pistons check good you still have to find unobtainium rings. Cycle X has 836cc piston kits, only boring is needed to fit them, no sleeving required at this size. All the sohc 750 have poor cylinder studs and must be replaced with heavy duty units. Cam chain is also weak...at the very least if you stay with a stock cam get the cryo treated chain from Cycle x, if you go with little bigger cam and stiffer springs upgrade to the heavy duty chain. Primary chains have to be replaced....Stock works fine for most applications but go cryo treated for longevity. Cam chain tensioner wheels will be shot so get new....probably primary chain tensioner as well. Stock style head gaskets work but MLS are best but head and top of cylinder need to be surfaced appropriately. Lots has to go into these motors, a stock motor I build will easily be $2000, my drag motor is currently in the $5000 range with all upgrades etc. These motors are not cheap to build and people tend to cut corners to keep the cost down, they will run with cheap bare bones parts but I dont build stuff and leave things that I know can cause issues when you inevitably decided to run it wide open and see what it can do.
 
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