Topic: '78 750K first project by a car guy...

[RandyBMC]

Hello all!

I have had bikes in the past, but this is my first CB, and I'm very excited about it.  It is a basket case, but the price was right.  The engine turns, and with the kick start, it seems to have good compression, so that's a start.

I've been a car guy my whole life, and have auto-crossed and road raced for most of that time.  I even owned my own MINI/Lotus shop for 8 years back in my heyday.  I've built cars from scratch (a Lotus Seven style home built was the most adventurous), but I am certainly happy to have the resources of a forum like this to get expert opinions on all things Honda bike!  I'm a newbie to building/working on motorcycles (though I faintly remember working on YZ80's when I was all of 13-14, but to say that's hazy would be an understatement).

I'm already a huge fan of these forums.  I've been pouring over the project threads, and have already gotten help from several members.  I have even met Steve-o and bought a new (to me) tank from him for a good deal (thanks!).  Besides the resources, there is a ton of inspiration in the photos of other folks' ideas.

When I got the bike, it was a roller with the engine and gearbox mounted.  I have since pulled the rear swing arm and managed to get the engine out using ideas from the C-arm engine hoist thread (and the bracket idea from madmtnmotors).  The whole bike needs to be cleaned up.

So my plan is to make a nice riding, good looking resto-mod of sorts.  I like some of the cafe elements, but I don't need it to be as bare boned.  I was leaning toward more of a full figured (read normal oil tank and electrics) brat look, but I want it to ride not just be a looker.

So the first question - how to make a decent 2-up but still ditch the stock seat?  I want to be able to take my wife or my kids for a ride every once in a while.  I know off the bat that will mean a compromise suspension, but I am thinking I will gear it to be tuned more for a single rider.  Some progressive front springs and a decent (but not $$$$) set of rear shocks/springs, a decent rear set, Cognito Moto style rear set mounts with a passenger foot peg mount like these http://cognitomoto.com/collections/rearsets/products/cb750k-rearset-brackets-with-passenger-peg-mount?variant=791902389 and some clip ons.  The seat then becomes the issue, because I don't want to slide off the back when I'm solo!

Anyway, here are a few of the photos I snapped with a phone.  That's about as artistic as I get with photography.

How I got it:




Starting the process













Feel free to critique as needed at any point.  I will be the first to admit my lack of knowledge.  Thanks in advance for the help!

I'm in Texas, just north of Houston.

Randy

[Stev-o]

Hey Randy.........looks like your off to a good start.  First off, are you planing any mods to the frame and do you plan to paint? Be sure to change the swing arm bushings while you have it off.

I had a 550 cafe, the hump on the seat was padded and upholstered, not the best looking but was able to do two-up.

[calj737]

I think you might consider upping the HP on the motor and dropping it in that little red beauty in the background! 

Instead of clip-ons, consider Superbike bars using the stock top clamp. With a passenger, clip-on bars can be quite uncomfortable. And SB bars are still very sporty, yet forgiving.

As for seats, a gunfighter model from Corbin is a decent option. Or a Guilari style has vintage bones, but modern foam.

[Stev-o]

I think you might consider upping the HP on the motor and dropping it in that little red beauty in the background! 

Hey Cal - I saw that little red beauty last weekend, it is the real deal and Randy did a great job restoring it!

[calj737]

Yeah, no doubt. Anyone who has the God given patience to endure restoring Lotuses must be a pretty good guy. Anxious to see his bike come together-

[RandyBMC]

Thanks for the suggestions.  There are kits to put bike engines in the classic Minis - makes them screamers!  I prefer the A-series lump just to keep it real 

I have been toying with different bar options, as well as the seat.  I do plan on removing tabs and such as needed to make the frame a little cleaner.  I like the Tuffside seats, but they are definitely not bargains.  Wish I knew how to upholster!  I've been watching YouTube videos and such on it.  Maybe down the line when I'm ready for the seat I can go that way.  The problem is, before I mod the frame, I need the seat!  I still have a little time to sort that though.

I spent the day after getting back from work (I was gone 6 days doing some off-site training) making brackets to mount the engine to my stand.  A few pieces of angle iron, 1" tubing, washers and a welder did the trick.  Photos below:









So that worked out pretty well.  Then today I got started taking parts off the engine to see what I have (and to learn how it all works).  Good news and bad news as I started disassembly.

It looks like it has been gone through not too long ago.  The clutch looks pretty new, and turning the motor over, it seems each cylinder has decent compression.

Bad news, the alternator cover has been hit.  It is bent and from the inside, looks cracked as well.  See below:







I'm not sure if this is bad, but I can't make sense of why it should be this way, some I'm leaning toward yes - it isn't a good thing.  When I pulled the alternator cover, there was oil in it.  That isn't normal, is it?  See below:

Looks oily...


Yep, it is.


If that isn't normal, any idea what the "normal" cause of this issue is?

Other not good news, my clutch actuator was bent all up, which is weird since it is behind a cover.


Then a second question.  After removing the cam cover, I found what looked like gouge marks from the chain itself on the inside of the cover.  The chain looked fine all the way around (as I rotated the engine with the kickstarter to feel compression).  It also did t seem to have any chunks in the oil that came out as I rotated the engine.  What's this all about?




The whole chain looks like this:


So any input is appreciated.  If anyone has a decent alternator cover, I could use one of those too.

On a side note totally unrelated, calj737, what's the meaning behind your user name?  I'm a Boeing 737 guy here in Houston.  Just wondering if it was related to flying.

Thanks in advance for any and all help!

[calj737]

My friends call me 737, but my stage name is Calj. Keeps people from confusing me with Brad Pitt I guess. 

Oil behind alternator cover is normal. Yep, cover has been hit, replacements are available through a number of members, Bill Benton in GA most notably (he has a mother lode hoard of spares, unless Stev-o has one stashed).

Cam chain looks to have taken a bite out of the head, not unusual, definitely needs a tensioner and chain likely.

I've got no input on the clutch adjuster...

Name is Cal Jeffrey. 737 is a combo of meaningful things to me. 

[RandyBMC]

Oops - I put the wrong photo for oil in the alternator cover.  It looks like what I saw after pulling the stator and rotor, but here is a clear shot of the oil:

[madmtnmotors]

Yep, oil in the alternator is normal.

[RandyBMC]

Is it possible that the tensioner was just not tightened?  Wondering if the damage to the cam cover requires a new timing chain, or if I can just snug up the adjustment on the tensioner and call it good.  Seems the proper way to do a chain is to split the case, and I was trying to avoid that.

Thanks!

[HondaMan]

The gouged-up cam cover is normal for an engine with a real loose cam chain and a worn roller tensioner. If the bike is downshifted at high RPM (making it even higher RPM) and used for compression braking, the chain can momentarily "pile up" the slack and ride up on the cam sprocket, hitting the cover like that. The rubber roller-tensioner wheel is probably chewed up, and the cam chain slipper tensioner probably has grooves in it. Under racing-like conditions, these parts are not "hard" enough to prevent chain slack on the top sprocket during these events. Honda (Yoshimura, actually) solved it by making a steel roller for the tensioner, but that can be hard (and noisy) for daily-rider type use.

[Stev-o]

Looks like the bike went down on the stator cover, luckily only minor damage. 
I do have a spare but is being held for forum member ChrisP in Conroe, will let you know if he no longer needs it.

[RandyBMC]

Is there a measurement for allowable slack on the cam chain? 

So the head comes off to change the tensioner bits, from what it sounds like.  If that's the case, then I may as well take the cylinders off and check the bore, then re-ring the pistons (at least that's what I'm thinking would be prudent but still economical)?

Steve-o, that would be great.  Let me know if ChrisP doesn't need it and I'll take it.

Thanks for all the help!

[RandyBMC]

So I did some more disassembly, and had more good news and more bad news.

The good news is that my primary chain measurement was 65.61mm, which is just about new.  That's great.

The bad news is that when I pulled off the sump, there was a surprise on the mesh - see below.  At first I thought it may just be sealant, which would actually bode well in that it may have just been redone not long before it had been pulled apart.  Then I sifted through it, and there are definitely bits of metal.  Hard to tell if it is bearing material, or maybe just aluminum from the damage I found on the inside of the cam cover (from the chain tensioner not being adjusted).  Either way, it went through the motor, which can't be good.  Any thoughts?  Still trying to avoid pulling apart the bottom end, but that is looking harder and harder to avoid.





Good times.

[AintNoEasyWay]

I'm in. Love these k7 & k8 rebuilds. I'm doing one too at the moment. Have you already got a k8 specific guide? If not, here's a link to one thanks to Ron (Restoration Fan): https://drive.google.com/folderview?id=0B4nqeBb662mZZjZjTWdGRk9Qd0E&usp=sharing

Highly recommend checking out his & his son Logan's k8 build thread if you haven't seen it yet!

[RandyBMC]

Thanks for the link.  I've made a three ring binder of the workshop manual.

Today I got the head off.  Not bad.  One thing I'd like to ask - with the cam "slot" facing up, number four can be adjusted with the timing wheel mark on T for 1-4.  With the slot down, number 1 is loose (the rocker arms for adjustment).  I thought that with the slot up, number 1 should be adjusted?  I've taken a shot of it below:




This set up has number 1, on the left side of the bike sitting on it, ready for valve adjustment.

Got the cam out:




Then the head came off.  The number 1 combustion chamber has a little corrosion at the edges.  The rest look good.  Is this acceptable?




Then some disturbing signs on the piston.  This is only on number 3.


But I also found this mark on all of them:

It is at the very edge of the piston top where I am trying to point.  Is this another concern?  It's weird because the valves all look pretty decent.

So this is how it sits now.  I have not cleaned anything up at all - this was what it looked like when I pulled it apart.  The rollers for the cam chain actually look really good, so maybe they were already replaced?  I figure I will clean up all the gasket surfaces.  I plan to pull the cylinders off to look at the pistons.  The cylinders look nice too.  No visible scoring.  The camshaft and rockers look ok as well.  Maybe just hone it, new rings, smooth out that dent on the top - or is that #3 piston unusable?  Then gaskets and back together.

[madmtnmotors]

So I did some more disassembly, and had more good news and more bad news.

The good news is that my primary chain measurement was 65.61mm, which is just about new.  That's great.

The bad news is that when I pulled off the sump, there was a surprise on the mesh - see below.  At first I thought it may just be sealant, which would actually bode well in that it may have just been redone not long before it had been pulled apart.  Then I sifted through it, and there are definitely bits of metal.  Hard to tell if it is bearing material, or maybe just aluminum from the damage I found on the inside of the cam cover (from the chain tensioner not being adjusted).  Either way, it went through the motor, which can't be good.  Any thoughts?  Still trying to avoid pulling apart the bottom end, but that is looking harder and harder to avoid.



Good times.

HA! Looks like the screen is doing what it's supposed to do by intercepting flotsam and jetsam in the oil flow outside the path of the filter. I had one that would go about two miles and the oil light would come on. I cut it off immediately and pushed it home. Checking the oil tank revealed no oil! Damn! I knew it was leaking oil, but holy cow. So I topped it off with oil, went ONE MILE, turned around and came back, and the oil light came on again as I rolled into the driveway. Checked the oil level and the tank was bone dry! Alright, I knew the damn thing wasn't leaking that bad, and the seven plus quarts of oil had to be somewhere....


So I drained off the seven or so quarts of oil that thought the engine was a wet sump, and dropped the oil pan to reveal this:








 

Holy crap! After cleaning the screen and replacing the o-rings, I put the pump back in and ran the crap out of it. Never had any oil feed related problems after that. 


From that point on I now make it a point to drop the oil pan on every SOHC CB750 that I touch. 

[AintNoEasyWay]

All the 750 Pistons will have that notch point toward the exhaust. Not a cause for concern at all. They're made that way.

[Stev-o]

Hey Wilbur - that motor wins the award for the most crap it it! Unbelievable.

[RandyBMC]

That's good news.  The number 3 piston is not the small indentations like the other 3 have (as well as the number 3) - it is in a different spot and certainly from something smacking it.  I'm just hoping whatever smacked it isn't currently part of the valve train (and happened before a top end rebuild).

How hard is it to compress the rings without splitting the case to get the pistons back in the cylinders?

The cylinders pulled when I grabbed the head, so I think even if I don't touch the rings, I'd like to reseal the cylinder.  Thoughts on that?

Thanks again for all the input!

[flybox1]

That's good news.  The number 3 piston is not the small indentations like the other 3 have (as well as the number 3) - it is in a different spot and certainly from something smacking it.  I'm just hoping whatever smacked it isn't currently part of the valve train (and happened before a top end rebuild).

How hard is it to compress the rings without splitting the case to get the pistons back in the cylinders?

The cylinders pulled when I grabbed the head, so I think even if I don't touch the rings, I'd like to reseal the cylinder.  Thoughts on that?

Thanks again for all the input!

No need to split the cases to get the rings/pistons back in.
Jump on over here....a very informative thread
http://forums.sohc4.net/index.php/topic,107040.0.html

[RandyBMC]

flybox1 thanks for the link.  It's great to have all the resources linked to my own project thread for my personal reference!

Well I went ahead and pulled the cylinders.  The piston skirts look pretty good.

I still have a question about the cam timing - refer to the above photos and description.  Anyone know if that's a normal scene?

Here's where I'm at I think.  Re-ring the pistons, hone the cylinders, check the valve train and guides, maybe deck the head to clean up that corrosion on number 1, then new seals and a Cycle X MLS gasket kit.  I do have a small bit of fin damage on the cylinders, but I didn't even notice it until I pulled the head.  I am probably just going to clean up the edges on that and reuse the cylinders I have if they mic out good.  The cam chain and tensioners look decent, which again leads me to believe that the motor has been apart to fix that problem I saw on the top of the cam cover and the number 3 piston.

I am more than willing to take anyone's advice on what should be done.  I'm on a budget, or I'd love to do an 836 and cam!

[madmtnmotors]

Here's where I'm at I think.  Re-ring the pistons, hone the cylinders, check the valve train and guides, maybe deck the head to clean up that corrosion on number 1, then new seals and a Cycle X MLS gasket kit.

+1

Lightly hone the cylinders.

I did the very thing you describe on my regular ride. Of course, I got a little enthusiastic with the hone and ended up a little large... but my intentions are an 836 kit before piston slap starts to rear its ugly head! 

[AintNoEasyWay]

The thread that flybox linked to has been a big help to me. Also, have you heard about Hondaman's book? http://forums.sohc4.net/index.php?topic=65293.0

[RandyBMC]

Thanks for the tips.  I did see Hondaman's book - hoping to get a deal on one, and there aren't any big coupons right now.

I haven't abandoned the project!  I did some polishing of bits, cleaned the surfaces on the cylinders and head, and took some measurements.  Between my day job and some required work on the Mini (gotta love using a classic British car as a daily drive), I haven't had as much time as I'd like to work on he motorcycle lately.

Now I'm waiting to save up for a good gasket kit, some decent piston rings and a honing tool.  I am also planning on having the head gone through buy the machine shop ($).  Still doing some cleaning on the engine bits and chassis parts.

Anyone have any input on the cam timing question I had earlier (reference above photos)?