Topic: 1978 CB750F rebuild: The Long and Slow Road: And now, on to the pistons!

[filipo]

Hey fellas,

First-time poster but some-time lurker, mostly of the inspiring work of both Tweakin' and brandEn -- all 40-something pages of their builds.

Somewhere around 1992 or '93 I picked up a CL 360 from a girl I knew; "fixed" it up by cleaning out the carbs and spray painting the tank what I would call "sewage brown"; and used it to get myself to and from the college bars and to impress various other girls I knew. If only I had seen some of the mods possible with those little bikes, I would never have gotten rid of it, but when I saw an ad in the classifieds for a 750 -- yep, in the newspaper, that's how it was in those easy days -- I traded the little brown tooter +$300 cash for a 1978 CB 750 SuperSport F3, complete with junkyard tank. Upon hearing the Kerker header roar, my roommate christened it the God of Thunder. By now it was 1996.

The GoT shut down on me about a week later. I was motoring along on my way to work when it just … blanked out, turned off and rolled to a stop. Knowing nothing about bikes, I took out the carbs -- pure gum. I took a look in the tank -- pure rust. So I cleaned out the carbs and cleaned out the tank (pea gravel, shake for hours, rinse with water, wet-vac, rinse with alcohol, repeat), got a fuel filter and was pretty decent for a while. By no means was this a performance bike. But I knew it was badass, with a lot of potential.

Moved East in 1997, left the GoT in my parents' garage, moved back West in 2002 and hauled the bike to my new place. Without ever once starting it up, I (stupidly, yes) decided to pull the whole thing apart, so I removed the carbs, the oil tank, the seat, the gas tank, and the engine. Got a gasket set. Got an allen bolt set. And promptly left it all sitting in my garage for a year, then moved the bike and all its pieces to our next rental house, then to our next house. This is 2004, and not a lick of work has been done to the bike since deconstruction.

The GoT rests, for many months. Months turn into years. So-called friends offer to take it off my hands; I resist. So-called friends offer to rebuild it for me; I take them up on it; they do nothing. I find a guy parting out his '78 on craigslist -- he's turning his into a cafe racer -- and pick up a new tank, seat & cowl, front fender, gauges, side covers, indicator lights, some other stuff. For $400. Though I feel like a champ for getting what I consider a deal, none of this stuff goes on the bike. This is now 2008.

Maybe somewhere around June 2011, I decide enough is enough -- coincidentally this happens around the same time I have less work and more time to pipe-dream -- the time has come to resurrect the God of Thunder. My goals this time are basic: I just want to get it cleaned out, cleaned up, find my way around the engine, and see if she starts up after 15 years of hang time. Prettiness, style and true performance can come later.

That's where the forum comes in. I want this to serve both as a record and as motivation, as well as a source of help. I'll try and post anytime I do something, and to put pics up with it. All my pictures of the bike as a whole are analog; I'll have to find them and get them on the scanner to post those.

That's it for the long and slow intro. The rebuild begins with the next post. Thanks for reading.

[filipo]

So, as I said, the engine's been out of the frame since 2002. (All that's really left on there are electrics, shocks and brakes. I'll put a pic of that up soon.) And I've had a "new" gasket kit in its box since 2002 as well, and the set of new Allen bolts. I started in on replacing the bolts back in 2002 and got pretty well all the way through that task; of course, I did not do any work on what lay *behind* those bolts -- didn't even look at the clutch, or the gear box, none of it. This was out of fear; didn't want to screw anything up.

I bought a shop manual off eBay; I think they're more widely (and freely) available now, but whatever. (I also have the mostly useless Clymer manual from back in the day.) The more I look at the shop manual, the more it makes sense -- except for the electrics, which is like ancient Sumerian to me.

Since June or so, I've been working on replacing all the gaskets. Again, that's without much work on the actual engine. The GoT ran OK before I took it apart, and I'm banking on that fact to get it running anew. Again, at this point I just want to get it back together and started up, see what my problems are and go from there.

Of course, you can't replace the head and base gaskets without *some* wrench work, and that's where I find myself today. Took the valve cover off, took the camshaft and rockers off, took the head off -- after much effort with trying to wedge it off using cedar shims, we found we had forgotten a screw, d'oh! Removed that last one and head popped right off, no damage, thankfully. Took the cylinders off, even. Some pics are below. Not the most illustrative, but in future I'll try to capture more detail. (Also, please note that this is NOT my shop -- but even I'm embarrassed at how sloppy it is.)

Removing the head for the first time ever.


We dropped a washer where no washer should go.


Camshaft, rockers, and all appendages waiting in orderly fashion for the rebuild.


Head removed, pistons waiting for a scrubdown.


I managed to get the piston head cleaned of carbon with a citrus-based solvent; I'm wary of the petroleum-based ones, being a bit of an enviro. That said, I had no luck cleaning the carbon off the valves, nor in getting the old head gasket gunk off the block using the citrus stuff. Which leads me to my first questions...

1. There seems to be a lot of differing opinion floating around the 'nets on the best way to remove head gasket gunk. Anyone have a CB750 specific way they prefer? I've read use razor blades, use acetone, use automotive gasket removal cream, have it soda blasted... Any guidance here? Mike Nixon's guide is awesome, but doesn't really address removal aside from "apply aerosol gasket remover" and "scrape using a window scraper". Maybe that's it, that's the best way, and I just need to nut up with the toxic chemicals.

2. Carbon on the valves. They are BLACK and crusty. Again, I've heard: oven cleaner, soda blast, angle grinder, brake cleaner... I don't want to pull the valves out, necessarily (don't want to buy the spring compressor tool), but if that's the way it's gotta go, that's what I'll do.

Thanks in advice for any help. This weekend I'm hoping to get the old gasket off and the new gasket on and get everything back together, at least so I can take the engine back to my shop!

[Trav-i]

To answer your Q's here's what I did on my engine...

When it came to head gasket gunk I carefully used a razor blade scraper to get the really nasty stuff off, then I went with the 3M brissle wheels for small compressed die grinders.  I used the brissle discs because unlike abrisive discs the brissle discs don't remove base material, I think they're a bit more expensive then "rol loc" discs but they just safer on soft material.

When it comes to crusty valves nothing is better then a wire wheel on a bench grinder.  Trust me spend the money and get a GOOD compressor.  Remember those valve guide seals are 32 years old, and probably hard as a rock.  Plus with the later F engines they were know for valve guide wear and this the perfect time to check that too.  Once all that is done then you can lap the valves, install new valve guide seals, and know that you won't have to pull the engine anytime soon because you skipped sometihng you should have done now.

Hope you find some of this info helpful.

Good luck

Travis

[MikeKato]

  Plus with the later F engines they were know for valve guide wear .......

The later F's? I was reading that the first year F's were the ones with the problem guides and that problem disappeared by late 77 early 78.

[filipo]

When it came to head gasket gunk I carefully used a razor blade scraper to get the really nasty stuff off, then I went with the 3M brissle wheels for small compressed die grinders.  I used the brissle discs because unlike abrisive discs the brissle discs don't remove base material, I think they're a bit more expensive then "rol loc" discs but they just safer on soft material.

Thanks for this, Travis. Do you know if those discs come as a drill bit? Or is that not a good idea re spin speed?

When it comes to crusty valves nothing is better then a wire wheel on a bench grinder.  Trust me spend the money and get a GOOD compressor.  Remember those valve guide seals are 32 years old, and probably hard as a rock.  Plus with the later F engines they were know for valve guide wear and this the perfect time to check that too.  Once all that is done then you can lap the valves, install new valve guide seals, and know that you won't have to pull the engine anytime soon because you skipped sometihng you should have done now.

Hope you find some of this info helpful.

Thanks for that, also. I'm not sure how to check for wear on the valve guides, but I'm about to order Hondaman's book, hoping that will help with issues such as these. I know I need to clear them out of gunk/carbon/other obstructions, but not sure how to ream them out. As you can tell about now, I'm new to all this! So I appreciate any and all help you can give. Much obliged!

Today was dedicated to house chores, so not much more than daydreaming got done on the bike, but I'm hoping tomorrow brings more progress. I'm also at the mercy of my (kinda fickle) buddy, in whose garage the bike currently awaits my attention!

[Trav-i]

@Mike Kato.  I was actually the F2 and F3 engines that had the valve guide problem (77-78).  Honda used a steeper angle on them thus the accelerated wear, the earlier engines were K engines fitted with slighly higher comp pistons and slightly different cam shaft.

@Flippo.  You probably could use them in a drill as the adapter they require had a 1/4" shank on it.  The only thing I can think of is that the drill may not have enough RPM for max effect.  And +1 on Hondamans book it def gives tons of great info.

[AbbyRider]

Filipo: I'm currently rebuilding the engine on my '78 750F. I was hesitant about removing the valves, as I didn't want to purchase a spring compressor either. So I cut a piece of 5/8" pipe that I had laying around, cut a 'v' shaped slot in it, and then used an 8" c-clamp to compress the spring. Removal of the keepers was easy with a telescoping magnet tool. I'm just at the point of cleaning the valves as well -  currently have them sitting in a bath of Simple Green. But it makes it a whole lot easier to clean them when they're out of the head.

[filipo]

Ohh, nice. Don't suppose you have a pic of this homebrew tool, do you?
Thanks!

PS Bike is still at my buddy's house. I don't know what his deal is -- I think I'm going to have to break into his garage and steal my damn bike back!

[AbbyRider]

Make sure you put some sort of padding on the underside where the clamps sits against the edge of the combustion chamber. This version has a hole in the pipe, but I found that a "v" cut in it makes it a bit easier to access the keepers if they're being stubborn.

[filipo]

Thanks for this. Don't suppose you have a photo for the V-cut, do you? That's where you're losing me.
Thanks

[AbbyRider]

Instead of where the hole is, picture an upside down V. Or just drill a hole like the one in the pic.

[filipo]

Man, time passes. Apologies to my massive audience. Anyway.

After much haranguing and whatnot, I finally got the engine back from my buddy's house a couple of weeks ago. Poor guy -- he decided to go back to school and finish his PhD. Great for him, not so great for me trying to get into his garage and work on my bike. I had to leave the rest of the bike -- frame, wheels, tank, etc. -- but I thought at least I could work on the good part.

In the meantime I tried to set myself up a little better. Built a work stand with some nice casters...



Bought an engine stand of Craiglist and set it up with the angle iron mods I found on this forum...







Also bought the $15 worth of parts to build the homebrew soda blaster I found through the forum...



I figured since I had the engine and had the head off I would work on what I could -- check the valves, clean the pistons, etc. I got as far the Hondaman-recommended valve leak test: valves held pretty well, after 30 minutes there was still oil in the chamber! I bought a micrometer and a digital caliper, but before I could really dig into the engine, my PhD buddy called again a couple days ago: he wanted me to come get the rest of the bike. So here she is, back in her homeland.

Oh lovely clean tank! This will be the 3rd tank I've bought for this bike -- only one has actually run on it; the rest went back to ebay...



The gauges I bought back in 2008; also my 3rd set of gauges. (Got a mismatched set if anybody's interested...)



4-to-1, Kerker header, beautiful but loud...



Seat intact! Also from 2008 mass-purchase...



The bike, engine-less, as she looked after I took out the engine in 2003...



Blargh. Headlight electrical barf. Half fascinated, half terrified of the impending rewire...



I found what looked like a couple of homebrew mods on here. One was the use of what looked like ordinary metal strapping to attach the horn to the front brake manifold to the, uh, what's it called -- fork brace?



The second was this strange horn-like device, wired through the fork covers/headlight bracket along with the turn indicator. Anyone seen this before?



Got that all off, though, and pulled the main wiring harness. I felt like I had just disemboweled the Alien Queen...



Noticed these guys were numbered. Is that a factory standard, or did someone at some point mod this bike and add those numbers? Kinda handy...



Wheels look in decent shape -- though the new Chin Shin (?) tires I put on in 1996 are probably done for...



One of the last things to come off were the two stands. And if it weren't for this genius tip from the forums, I never would have gotten the side-stand spring off (thanks, mystic_1!). You can use coins OR bottle caps you've smashed with a hammer...



I also was highly paranoid about disassembling the front and rear brake assemblies, probably from reading some of the F-series brake discussions here. So I just took them off whole hog, that way I can research the #$%* out of them and hopefully avoid any massive foul-ups...



And voila!



The frame is very very very almost close to being ready for blasting and powder -- I just have to get the triple tree off! Don't have a socket big enough for the steer tube. Actually, I don't know how you're supposed to pull it off -- got this far after about three beers and thought I'd better quit before I #$%*ed something up.



Looks like I've moved way beyond my original goal of just getting her running. I blame Tweakin and his stupid beautiful build. I'm planning to work on the engine as I have time, while collecting a pile of stuff to be prepped and painted, then sending it off when I have a few extra dollars. (Should be sometime around 2016...) So, next up: digging in to the top end, and a session of deep thinking over whether I want to crack the cases. At the very least I want to check all the valve & piston clearances, probably replace valve guide seals and piston rings, unless something is super heinous and I need a more thorough overhaul. A note to AbbyRider: for the C-clamp valve spring tool, I'm using the cut-off from a mountain bike fork steer tube. Haven't notched it yet, but I'll keep you posted on the surely amazing details...

Thanks for reading.

[brandEn]

Looks like I found this thread just in time, thanks for the honorable mention! I will be following along for sure. I think you can go to AutoZone or the like and rent a valve spring compressor for next to nothing. I definately would change the valve guides since your in there. As for cracking the cases I had the same questions as you and ended up just doing it for the experience. Glad I did because it eliminated any wonder about the condition of things. I also found the primary chain tensioner rubber was hard and brittle.

[knowsnothing]

That strange "horn like device" is the turn signal beeper.  Shoud beep when you have your turn signals on to help you remember they are on.  It makes a very very very annoying sound. 

I cant wait to see The God of Thunder in its glory once again.  Keep up the good work.

[filipo]

Looks like I found this thread just in time, thanks for the honorable mention! I will be following along for sure. I think you can go to AutoZone or the like and rent a valve spring compressor for next to nothing. I definately would change the valve guides since your in there. As for cracking the cases I had the same questions as you and ended up just doing it for the experience. Glad I did because it eliminated any wonder about the condition of things. I also found the primary chain tensioner rubber was hard and brittle.

Hey man, thanks for the inspiration! As for cracking the cases, yeah, I'll more than likely end up doing it. But the cracking part seems the easy half -- it's getting it all back together in working order that gets me!

[filipo]

That strange "horn like device" is the turn signal beeper.  Shoud beep when you have your turn signals on to help you remember they are on.  It makes a very very very annoying sound. 

I cant wait to see The God of Thunder in its glory once again.  Keep up the good work.

Ha! I guess the reason I never heard it was because I never had the indicators hooked up, even way back when it was rideable. Thanks for the insight, and for following along!

[Roach Carver]

Dont mind me. I'm just lookin.

[filipo]

Oof. Holidays, man. Holidays.

I did find time to yank off part of the last little bits from my frame: the headlight ears and the top fork brace. I already took off the handlebars, front wheel and fork legs, so I ended up with nothing to brace against when unscrewing the stem cap. Nothing my handy copper breaker bar (now almost broken) couldn't handle:



Clamped her down in the handlebar hole and cranked it almost in half. I had to put my old handlebar over the ratchet arm to get enough extra leverage to pop it. A squirt or 6 of WD-40 helped as well.

Since I already bought a $14 30mm socket for this, I really didn't want to buy a spline tool to pull off steer tube nut. As I was staring off into space wondering what to do, I remembered a tool from my bicycle-fixing days:


Not at all the right size, but a single spline matched up enough to get it loose. Huzzah!




And done -- except for the races, which is a job for tomorrow, when everybody else is back at work. Took a closer look at the ID badge while I was at it -- the bike was built exactly 34 years ago this month!

[filipo]

First off, thanks again to abbyrider for the clamp spring-compressor idea. I first tried the POS tool from AutoZone, didn't work right at all. It grabs the lower coils and pulls them up to the collets, rather than pushing the spring down and releasing the collets. It also doesn't compress the inner coil, just the outer, so it's not useful -- for my F3 coils, anyway. Maybe I'm just stupid. But as a result, I bought a $5 C-clamp from Harbor Freight, cut a bit of bicycle fork tube up, and presto -- valve spring compressor tool!



Got all the springs off and the valves out. All of the intake valves were nice and tight against the guides, but the exhaust valves had a little more play. I'll try to get an actual measurement today. The guide seals were toast. So now I'm wondering the best way to remove them. They seem to have two retaining wires, one up top that looks like a guitar string, and a bigger one lower down that looks more like a thin key ring.



I believe I could carve away at the seals with a blade or X-acto knife, but I'm paranoid about gouging bits of the head. Any suggestions?

I also picked up a 50lb bag of soda from HF. I ddid a little experimenting on one of the chamber heads; came pretty clean with only a little effort (see the right-hand one in pic below). As far as the blasting goes, I need to get a funnel attached to my gun setup, so I'm not constantly having to shake a box of soda around…



Not much progress, but at least it's forward progress. As soon as I get the guide seals off I plan to set the head aside for blasting, then move on to the cylinders and pistons. Got a call for a potential week of work next week, so that will slow progress even further -- but at least I'll have a few bucks to buy some new seals, cam chain, tensioner, roller, headset bearings, engine paint…

[filipo]

Interesting. I went at one of them for a bit with some needle nose pliers, and rather than shatter it mostly just fell apart. Pretty old and raw, but still lubed up -- which is a good sign, no?

At any rate, if I try your approach should I be worried about damaging the guides themselves? Or is the goal to avoid pinching the guides?

Thanks for the tip!

[filipo]

Nice! Thanks again. I'm about to give it a go now; will report back.

[lucky]

Man, time passes. Apologies to my massive audience. Anyway.

After much haranguing and whatnot, I finally got the engine back from my buddy's house a couple of weeks ago. Poor guy -- he decided to go back to school and finish his PhD. Great for him, not so great for me trying to get into his garage and work on my bike. I had to leave the rest of the bike -- frame, wheels, tank, etc. -- but I thought at least I could work on the good part.

In the meantime I tried to set myself up a little better. Built a work stand with some nice casters...



Bought an engine stand of Craiglist and set it up with the angle iron mods I found on this forum...







Also bought the $15 worth of parts to build the homebrew soda blaster I found through the forum...



I figured since I had the engine and had the head off I would work on what I could -- check the valves, clean the pistons, etc. I got as far the Hondaman-recommended valve leak test: valves held pretty well, after 30 minutes there was still oil in the chamber! I bought a micrometer and a digital caliper, but before I could really dig into the engine, my PhD buddy called again a couple days ago: he wanted me to come get the rest of the bike. So here she is, back in her homeland.

Oh lovely clean tank! This will be the 3rd tank I've bought for this bike -- only one has actually run on it; the rest went back to ebay...



The gauges I bought back in 2008; also my 3rd set of gauges. (Got a mismatched set if anybody's interested...)



4-to-1, Kerker header, beautiful but loud...



Seat intact! Also from 2008 mass-purchase...



The bike, engine-less, as she looked after I took out the engine in 2003...



Blargh. Headlight electrical barf. Half fascinated, half terrified of the impending rewire...



I found what looked like a couple of homebrew mods on here. One was the use of what looked like ordinary metal strapping to attach the horn to the front brake manifold to the, uh, what's it called -- fork brace?



The second was this strange horn-like device, wired through the fork covers/headlight bracket along with the turn indicator. Anyone seen this before?



Got that all off, though, and pulled the main wiring harness. I felt like I had just disemboweled the Alien Queen...



Noticed these guys were numbered. Is that a factory standard, or did someone at some point mod this bike and add those numbers? Kinda handy...



Wheels look in decent shape -- though the new Chin Shin (?) tires I put on in 1996 are probably done for...



One of the last things to come off were the two stands. And if it weren't for this genius tip from the forums, I never would have gotten the side-stand spring off (thanks, mystic_1!). You can use coins OR bottle caps you've smashed with a hammer...



I also was highly paranoid about disassembling the front and rear brake assemblies, probably from reading some of the F-series brake discussions here. So I just took them off whole hog, that way I can research the #$%* out of them and hopefully avoid any massive foul-ups...



And voila!



The frame is very very very almost close to being ready for blasting and powder -- I just have to get the triple tree off! Don't have a socket big enough for the steer tube. Actually, I don't know how you're supposed to pull it off -- got this far after about three beers and thought I'd better quit before I #$%*ed something up.



Looks like I've moved way beyond my original goal of just getting her running. I blame Tweakin and his stupid beautiful build. I'm planning to work on the engine as I have time, while collecting a pile of stuff to be prepped and painted, then sending it off when I have a few extra dollars. (Should be sometime around 2016...) So, next up: digging in to the top end, and a session of deep thinking over whether I want to crack the cases. At the very least I want to check all the valve & piston clearances, probably replace valve guide seals and piston rings, unless something is super heinous and I need a more thorough overhaul. A note to AbbyRider: for the C-clamp valve spring tool, I'm using the cut-off from a mountain bike fork steer tube. Haven't notched it yet, but I'll keep you posted on the surely amazing details...

Thanks for reading.

The strange horn device is a turn signal beeper.
It was put on to remind the operator that their turn signal was still on.
They did not have self canceling turn signals.

[brandEn]

Progress is looking good. Just as an FYI in the last group of pictures you posted. The second one of the head. Make sure you don't lose the 2 oil jets that are are pressed in. I would pull them out and bag them up. They could fall out if they haven't already while your working on the head.

[filipo]

Thanks for the note, Lucky.

Branden: Yep, thanks. I thought they were permanent fixtures -- until I flipped the head over and out one popped. Definitely going in the bag!
(Also have a note to self about the O-rings and discs that go there as well.)

[filipo]

Thanks to all who replied with tips about the guide seals in this and the other thread. They came off nicely -- well, not so nicely. Like peeling century-old chewing gum off the bottom of a chair.



Their removal led to a new question: At the base of the valve guides are some washer-like discs. (See photo below.) These spin freely and do not seem to be attached to the guides themselves. Are they removable/replaceable? Or do they stay where they are?




Anyway, got the seals off, now the only thing left is one of the rods for the exhaust brackets. All the others came out easily -- or so I remember, since this was back in 2002 or 2003. I tried double-nutting this guy, no dice. The two nuts just spun in place, so the threads underneath are certainly hosed.



I sprayed some WD-40 (only lube-like spray I have at the moment) as best I could into the fitting, then cut a slot into the head to try and screwdriver it out -- no dice.



I'm sure there are countless notes on here how to release a stuck nut, but -- without welding a new head to the top -- what's the best way to get one out?

Thanks again, everyone!