Topic: 19yrs old, first build - CB750K5 cafe

[Lammers000]

Hello everyone,

So I have been scouring the interwebs and such trying to gather all information and knowledge regarding CB750s over the past year or so. Even after a year I've only scratched the surface  Anyways, I'm only 19 years old and fell in love with vintage bikes about a year ago. Its funny how taste changes as you mature. Im originally from Connecticut but live in Indianapolis as I am studying both Mechanical Engineering and Motorsports Engineering at IUPUI (minors in Math and Physics). So a few weeks ago I hauled my ass 4 hours north up to Michigan to pick up a running cb750k5 for a cheap 450 bucks. No complaints there.

I have been an avid reader on this forum as well as dotheton.com and have decided to finally post my project build. Considering Im in college and take school quite seriously this will be a fairly slow and steady build (and im the typical broke college student  )!!! Currently the bike is half torn down in my living room which I've made into a work space of my own (previously empty room, literally). I do not have pictures as of now but will be uploading a few soon.

Considering I am very new to this and very enthusiastic about this build, I will appreciate any pointers or suggestions that come my way. Thanks everyone and take it easy. Stay warm

[Bill/BentON Racing]

K, good luck. I bought my first one @ 19....... and then put on a supercharger, lol, Bill
You came to the right place.

[MCRider]

Lots of Indy members here, and surrounding area. Help is not too far away.   

[mystic_1]

I will appreciate any pointers or suggestions that come my way.

- Take your time
- Ask lots of questions, we're here to help!
- Take lots of pictures, this will help you when it comes time to reassemble
- As you remove fasteners during disassembly, either place them in well-marked ziplock bags, or screw them back into the part you removed.
- Measure twice, cut once
- Listen to advice from others, but stay true to your own vision
- Few things require massive force, apply judiciously

Not sure if you'll be cracking open the motor, but if you do:

- Make everything clean, clean, clean before reassembly.
- It's worth it to replace all the bearings while you're in there
- Honda doesn't call for RTV or other gasket sealants, except between the crankcase halves
- Don't re-use questionable parts, this can be a false economy

and above all else:

Have Fun!

mystic_1

[Lammers000]

Here are a few pics to show you guys where I am currently. Feel free to judge  haters gonna hate hahaha

[Lammers000]

Hold on...does anyone know how the hell to post pictures on here. Ive tried to add attachments...but clearly im a noob 

[goldarrow]

Hold on...does anyone know how the hell to post pictures on here. Ive tried to add attachments...but clearly im a noob 

Hang around some more, I think one more post and you'll be able to....

[mystic_1]

Personally I upload my pics to Flickr and then use the BBcode IMG tags to post images

For uploading pics via the Attachments options, I may be remembering this wrong but I think you need to have 5 posts before this is allowed.  I may be mis-remembering this or thinking of a different site though. 

mystic_1

[dusterdude]

Welcome young fella

[Lammers000]

For anyone curious as to what my plans are, they are as follows:

Cosmetics:
- Replace current 1978 hondamatic tank with a 75 supersport tank (love the more boxy look)
- GSXR front end swap (including new front / rear wheels)
- Chop the frame and weld in my own homemade frame hoop (have access to a pipe bender at a motorsports lab via school)
- Powder coat the frame and other misc parts in satin black (have access to a powder coating gun and ovens)
- Paint the throttle bodies black
- Velocity stacks with appropriate re-jetting
- I will fab my own electronics tray and locate it under the seat
- I may cnc machine my own top triple tree and install LED indicators for oil pressure, neutral, etc... motogadget products are out of my price range 

"Performance mods"
- GSXR front end swap as mentioned above
- Disc brake in the rear as standard with gsxr rear conversions
- I will design and machine my own rear sets
- Newer rear dampers (either progressive or fox) havent decided yet. May go with adjustables such as Ohlins
- Stainless oil lines (i need to cut my own lengths for the relocated oil reservoir so mine as well do it right)
- I will make my own new wiring harness (my roomate is very good with making looms for formula cars so Ill get him to assist me as I HATE electrical)

Engine Related:
- May end up doing an 820 or 836 big bore depending upon condition of the jugs
- New rings
- All new gaskets
- May remove starter motor if I can kick it over myself (only 160 lbs  )
- Main bearings down below if I decide to split the case which is likely (I want to do this rebuild the right way)
- New clutch discs and basket if theyre worn out
- I may check clearances everywhere with plastigauge (depends on how ambitious im feeling)
- I will rebuild the carbs for reassurance and rejet them for stacks


Im sure there are many more things that I cant think of right now. Im about 1500 miles away from the bike so not everything is coming to mind. Yes I do realize that is a #$%* ton of #$%* but I do live by "if youre gonna do something, better make sure youre doin it damn right" and I have given myself a lengthy timeline considering money isnt a profficient resource in most college students' lives. Id like to have it all set and done by next spring.

Feel free to comment or what have you. Thanks

[mystic_1]

Main bearings down below if I decide to split the case which is likely

I would definitely plan on splitting the cases and replacing the crank, rod, and transmission bearings, given all the other performance mods you're planning to do. 

You'll probably want to go ahead and replace the cam chain and primary chains as well as the tensioners for both.

Sounds like a pretty ambitious plan overall!  Have you done any Photoshop mockups of what you have in mind?  This may prove useful.

mystic_1

[SOHC4 Cafe Racer Fan]

If you end up splitting the cases, replace your primary and cam chains with HD models, and check the tensioners. You will almost certainly replace the cam chain tensioner.

[Lammers000]

Yes, I do indeed plan to change out the cam chain, primary chain, and their respective tensioners as well as the main bearings and what not in the bottom end and trans. To answer Mystic's question, I have not looked into photoshop but i have a very good idea of what i wish to do cosmetically. Thanks for the suggestion though!

[Lammers000]

So im at the point where im ready to remove the swingarm. I have the thru bolt removed no problem but the mounting bolt for the right rear shock is sheared flush with the shock mount bracket. Whoever had the bike previously didnt do a pretty job with the rear, mismatching bolts etc.

So my question is as follows: Is the mounting bracket on the swingarm threaded or is it a double strained bolt? Im not sure if I should take a dremmel and cut a notch and try to back out the bolt or if I can bore it out with a carbide drill bitl. I do not want to risk damaging the threads if they exist.

Thanks

[mystic_1]

For the bolt that connects the bottom of the shock to the swingarm:

The swingarm has a bushing pressed into it there that allows some flex during operation.  The swingarm is not threaded.  The inner side of shock's clevis is threaded to accept the bolt.

So, go ahead and dremel a slot into the bolt and try to turn it out.

In a worst case scenario, if you're not planning to re-use the shock, chop up the clevis and things will come apart.

mystic_1

[Lammers000]

Thanks Mystic! yeah apparently theyre cb350 shocks so they dont even belong on the bike. However I do plan on selling them or trading them in at a local parts recycle shop, so I really dont want to damage them in any way.

In addition, another problem of mine are the header flanges. The screws that secure them to the cylinder head are all rusted and dont want to free up. Im worried about torquing them with a screw driver too hard and stripping them out. Thats when ill be #$%* outta luck.

[70CB750]

Welcome and subscribed 

[calj737]

Couple of things: remove the shock mount at the top to allow swing arm to pivot down. Then, with arm off bike, deal with sheared bolt.

Velocity stacks are not a good option for the street due to the debris that will infiltrate your carbs. That debris will constantly clog up your floats and create overflow and starvation issues.

[Lammers000]

I was planning to put catch screens in for that reason but if you guys don't think they work well then I'll go with pod style filters or nice uni foam filters. Thanks for the lookout.

 Trying to figure out picture uploading on here   

[edwardmorris]

..............
In addition, another problem of mine are the header flanges. The screws that secure them to the cylinder head are all rusted and dont want to free up. Im worried about torquing them with a screw driver too hard and stripping them out. Thats when ill be #$%* outta luck.

Be very careful with those. Is your frame intact or cut? If it is intact, you'll probably need to get them off to get the engine out. Use something like marine jelly to get as much rust out first, then liberally spray some penetrating blaster on them. For the three engine heads I had to do this, what worked best after rust containment and penetrating blaster, a proper heavy duty JIS impact driver and a heat gun. Proper JIS bit is key here, in order to keep the cross point from stripping. Forum member Gordon/ilblikes sells excellent JIS tools, well worth the investment IMO, especially when a full tear down is on the road map.

[Lammers000]

Alright guys, im finally able to post pics. Top pic is what it looked like when I bought it. Second pic is after a bit of tear down. Third pic is how it sits right now in my living room. Thanks

[Lammers000]

So I have a question, I will soon be removing the motor from the frame sometime this upcoming week. As mentioned above I will be doing some considerable work to the motor while its apart. However, there is a quite #$%*ty paint job on it right now that is peeling and cracking all over. What is the best method to remove the paint? Id rather use a chemical means than media blasting simply because thats more costly and Id like to do as much of my own work as possible.

Has anyone here had any experience with paint stripper on motors? Im concerned about the cooling fins and how difficult it might be to scrape off old paint in the tight crevices.

[Restoration Fan]

So I have a question, I will soon be removing the motor from the frame sometime this upcoming week. As mentioned above I will be doing some considerable work to the motor while its apart. However, there is a quite #$%*ty paint job on it right now that is peeling and cracking all over. What is the best method to remove the paint? Id rather use a chemical means than media blasting simply because thats more costly and Id like to do as much of my own work as possible.

Has anyone here had any experience with paint stripper on motors? Im concerned about the cooling fins and how difficult it might be to scrape off old paint in the tight crevices.

You can use chemical stripper on it and then wash it off later.  If you're going to be taking it completely apart, then you can take the pieces to a car wash and use the degreaser option to help get it off.  Be forewarned though...there is no easy way to strip the paint.  It may get most of it but there will still be some left that you'll end up having to scrape off.  If yours turns out like mine, the remaining paint will be in the hardest to reach places. 

If you have an air compressor, then see if a friend has a soda blasting setup.  If not, even the cheap ones like the ones you can get from Harbor Freight work pretty well.  Once you see how much easier it is to soda blast than it is to strip with stripper and a scraper, you'll kick yourself that you didn't just do the soda blasting first.

[Lammers000]

Alright so Im running into a problem with rear damper removal. Mystic_1 informed me that the inner bracket of the shock clevis join is threaded to accept the bolt. I have unthreaded the bolt past the inner clevis bracket, so it should be clear of all threading now. However the bolt does not want to slide out. I have tried tapping it from the other side with a mallet and screw driver in hopes of popping it out but it doesnt want to budge and Ive hit it pretty damn hard. I know Mystic_1 said there was a bushing in the swingarm bracket but that shouldnt keep the bolt from sliding out? This damn bolt is keeping me from progressing and its pissing me off now.

Can anyone help or give suggestions. Thanks

[calj737]

And you have removed the top bolt to release all tension on the lower bolt?

If the lower bolt is no longer threaded, then the only means of extracting it is via pulling since you're no longer turning the bolt through threads.

[mystic_1]

So, guessing that you have the bike up on the center stand, and you've only unbolted the shock on the one side, you'll get some sideways pressure from that which can cause the bolt to hang up.  Basically the weight of the rear wheel is causing the threading to hang up somewhere, probably against the outer face of the clevis.

Take a long board and stick it under the rear wheel, pull upwards to lift the wheel up a bit, then try to remove the bolt.

Wiggling things around a bit can sometimes help when trying to pull one out.*

mystic_1






* See what I did there?   

[Lammers000]

I actually have the front and rear ends removed aside from the swingarm. Last night I went ahead and removed the swingarm along with the rear shocks still attached. Therefore there should be no source of loading on the bolt. Later tonight I may post a quick video to help demonstrate my problem.

[Lammers000]

How does one remove the engine from the frame? I'm attempting the lift frame off method but it seems damn impossible. I've been wrestling with it for a good 2 hours.

[edwardmorris]

Do you have the following off?

  Exhaust spigots
  Front sprocket cover
  Oil filter & cover
  ALL cables & hoses
  ALL mounting bolts & tabs
  Shift & Brake Pedals
  Kickstarter
  Battery negative cable
  Coils & wires
 
I'm probably forgetting a few, do you have Hondaman's book?

[mystic_1]

First, remove the exhaust collars or studs, whichever you have.    This'll give you some more wiggle room.  Cover the frame rails with tape/foam/cardboard if you're worried about scratches.

Assuming the frame is upright and firmly supported, the engine needs to come up about an inch in the front, and a few inches in the back.  In other words it needs to get lifted and tilted forward at the same time.

The engine will then slide directly to the right and out of the frame.  Note that the rear of the engine will JUST clear the gusseting at the rear right of the engine, and JUST clear the front rail of the frame.  Any twisting or leaning will get you hung up.

I like to straddle the frame, leaning forward over the backbone, and reach down and grab the motor from both sides, by the alternator cover and under the points cover.  when you lift the motor it'll want to lean forward naturally from the weight of the cylinders and head.  Edge the motor out to the right a little at a time.

When lifting the frame off of the motor, the motor still has to take the same "path" as above in order to exit the frame.

mystic_1

[calj737]

Do you have the following off?

  Exhaust spigots
  Front sprocket cover
  Oil filter & cover
  ALL cables & hoses
  ALL mounting bolts & tabs
  Shift & Brake Pedals
  Kickstarter
  Battery negative cable
  Coils & wires
 
I'm probably forgetting a few, do you have Hondaman's book?

And disconnect the chain...

[Lammers000]

Hey guys so I've made a lot of progress with the tear down here and there. I bought the bike knowing there was an oil pressure problem. Upon teardown I found the oil problem. It seems one of the oil galleries on cylinder 4 up in the valve train was clogged.  As a result the on the far right side was shredded to pieces along with the cam tower. I will post pictures next week.

As a result I will be replacing the cam and tower. I know all moving parts in these engines wear into each other. So with camshaft replacement do you guys suggest replacing the other cam tower and rocker arms?

In addition does anyone have any experience with the cycle x camshafts? I'm thinkin bout dropping in a performance cam to make a bit more power.  Thanks

[Wredas]

Looks good! Would be nice with more pictures.

[Lammers000]

As you can see the cam is terribly shredded to pieces. Its supposed to have the radius as seen towards the bottom near the lobe. When I first saw this I nearly #$%* my pants because I know all that metal needed to go somewhere and figured all the metal chips got into the oil and scratched up the inside of the motor. However the oil didnt show any signs of metallic contaminants and the cylinder walls were all good. There was a build of material on the cam tower that corresponds to the missing material on the camshaft. I dont really know why there was a build up (perhaps thats the missing cam material?)

[MCRider]

If you didn't knnow already, that damage is indicative of a clogged oiling system on that side. Has it been apart before?

REason I ask is this usually happens after a rebuild when some debris from the rebuild, especially hardened silicone gasket material, gets lodged in the oiling orifice between the head and cam tower/bearing. IT will need to be cleared.

[Lammers000]

MCRider, thats exactly what I have figured. The last owner had the engine rebuilt. After the fact he was out riding and saw the oil gauge flicker and what not. He brought it to a mechanic who said it looked like gasket sealant clogged up an oil gallery.

[Lammers000]

Hello everyone, I hope you guys are all starting to get glimpses of bearable weather and the spring season. Anyways, I am at the point to remove the jugs. Is there a technique to getting this chunk of metal loosened up? I have been trying to wiggle it ever so slightly but I dont want to pull straight up in fear of damaging the cooling fins. Thanks

[MCRider]

MCRider, thats exactly what I have figured. The last owner had the engine rebuilt. After the fact he was out riding and saw the oil gauge flicker and what not. He brought it to a mechanic who said it looked like gasket sealant clogged up an oil gallery.

Generally, the top end damage will not be foreshadowed by a poor reading on the oil gauge. The gauge is plugged in to a gallery which is upstream from the oil going to the cam. So it can show full pressure, while the cam is starving. The gauge, plugged in to the side usualy, wiill show the pressure in the lower end, crank, rods, and such.

I suppose it could read higher than normal, if that orifice is plugged. Hence the flicker?