Topic: Good Lord where do I start? CB750... ish

[Killman]

So here's the story. Technically, I guess you could call it a roller, but "basket-case with ambition" might be more accurate. I've identified bits from at least 4 different models of machine so far, (most of them at least Honda) and some Home Depot drunken MacGuyverisms. On the plus side, there's so little in decent shape that I won't feel guilty about doing whatever I want with it, unfortunately there's not a lot to pull and sell to help fund things.

We go to rallies and festivals in the Summer up in the mountains and up-island, some pretty remote areas with awesome scenery and people. Do plenty of camping and like to go crabbing, so a fair bit of dirt and gravel. I've decided that this little abused and franken-biked survivor is going to get spruced up and some dual sporty type treatments. A beer fetcher, when beer is 5 miles of dirt road away.

What I'm especially looking for is some help with light off-roady mods and suspension upgrades. Thinking progressive springs up front, not sure what to do about the rear shocks. I'm 210 lbs. on a good day and I can count on having another 20-50 pounds of assorted gear with me on longer trips. Got some Conti tkc70's on the way, a more street friendly version of their tkc80 knobbies. Reviews were good and they were 37% off. I am not rich.

Exchanged some emails with Hondaman, liked the idea of being able to switch back to stock in case of a failure, so I've got one of his transistorized ignitions on the way as well as his on/off switch saver to save potential headaches with the Emgo ignition that's coming, (to replace the plastic toggle). Looking to upgrade to a blade fuse box, as the current one is bodgered. He was kind enough to give me some advice on coils, wires, caps and plugs as well, so all of that's coming, as well as a new sealed battery and points and condensers. I figured why screw around? Hopefully skip winding up on my knees in the cold rain at night with a lighter, tab off a beer can and no beer. At least I shouldn't have to worry too much about electrical afterwards.

Chatted with Carpy last week and I've got one of his headers and a can coming, (to replace the dented and beat to crap 4-2) along with some nice signals. Every light on the bike is busted, drunk with a pellet gun maybe? Also some retainer tools for the wheel bearings. Super helpful guy and he's got some really nice stuff.

I'll be replacing all of the bearings, filters, seals, etc. during reassembly after I get everything painted and powdered. Have a nice over/under rectangular headlight and fog light rig and a breadbox air filter for it. Both cool period pieces that I've always wanted on a bike, Although I like the idea of the replacement stocker headlight I picked up with a chicken cage over it and a side spot. We'll see. Also got my eye on an Acewell that's not too spendy, a seat and some fenders. Anyone with some direct knowledge about the breadbasket with a baffled 4-1 feel free to chime in with jetting advice.

That's all that springs to mind just now, I'll see if I can figure out how to add some pics of the poor dear to this post.

[mrbreeze]

 A 750 is pretty much of a lump for a dirt bike but if you plan to be on pavement more than dirt it should be ok. How about something like an old 450 twin? Would be better in the dirt and strong enough for the road too. What kinda tank is on there?

[Killman]

I hear what you're saying about the 450, but I have this on hand, I'm "sturdy" and there's usually a fair bit of highway to eat on the way.

Not looking for anything too ambitious, just like to keep my spine and teeth intact during some of the non-paved and bumpy stuff.

[Killman]

Forgot to answer your question. Pretty sure the tank is from the early 80's. I'd looked it up, but I forget which model. Cool paint, huh? Really really wrinkly 

[seanbarney41]

Yup, cb750 is possibly the worst in the dirt of anything I have ever ridden...but hey. its fun to try...you will want to up your main jets one or two sizes  with the breadbox...seriously, the stock airbox is better than anything, but if you seriously can't stand the looks, 115 mains will get you in the ballpark with a reasonable length and baffled exhaust

[Killman]

Thanks for the info, you're the second person to tell me that about the mains, so it sounds like a winner. If the breadbox turns into a pain, I'll either tape the inside, or find an airbox. Got a kz440 with cv's that much prefers the stock box, too. The breadbox came with stock triples and stem, lights and a chrome front caliper, so if I've got it I may as well give it a go. Can't be worse than the crushed pods that are already on there.

[mrbreeze]

You seem to be big enough to ride it in the dirt but the big problem is ground clearance. I don't know know what kinda terrain you're talking about riding in but I agree about having the 750 for the highway portion of the ride. I had a 500 twin back in the 80's but never rode it more than maybe 50 miles on the highway at a time.

[calj737]

The Carpy exhaust (if I'm thinking of the unit you ordered) will reduce your ground clearance over the stock exhaust, and the fork clearance to the header. I envision a great deal of conflicts with the stock bike components (fender on front, fork travel, fork twist, front end compression/conflict to exhaust, etc) while riding "off asphalt". I saw that you said "light off road" travel, so I'm not envisioning you leaping through the air doing kickies and bar stands, but still, converting a fairly heavy bike into a decent handling dirt traveler is "ambitious" on a tight budget.

I would strongly encourage you to add a front fork brace, replace the steering bearings with tapered type, and do a full fork rebuild. And buy some very good quality adjustable rear shocks (yes, I realize you said you were "not rich") but "why screw around", right? These components will do more for your stability and safety, not to mention your comfort, while traveling on differing terrain. Probably some Rental type bars would also be a good investment for handling, and different foot pegs to offer better clearance.

Lastly, a breadbox is probably the worst induction type for any "rural" travel do the constant dirty air and dust and debris. So pay regular attention to it for servicing.

[Killman]

All good advice. I am leery of the clearance on the header, (Sidewinder version) but until I can find an option for some decent higher pipes, they're what I'm rolling with. I should clarify the terrain I'm thinking of, dirt and gravel roads, easy fields, light mud and the possibility of what would equate to gentle singletrack in my mountain biking days. Airtime would definitely be frowned upon.

Some of your suggestions I'm already on. New tapered, needle and sealed bearings are on the way for the neck, swingarm and wheels. I was wondering if a fork brace was in order in addition to the fender brace, if you're worried about something it's usually better to just take care of it, so on the list it goes. Just so happens that I have an assortment of off roady type bars in the shop. Even a couple of sets of Renthals that I figured might do nicely. Got some Oury grips inbound, too.

Now although I'm not looking at a Concours budget, I will be throwing some dollars at it, just not a grand for shocks. Recommendations on shock makes, models, spring rates, etc. are exactly the type of info I'm looking for.

In the end, if all else fails, it'll still make a very nice paved road tripper. Seriously appreciate the info, I take it all onboard as I have an aversion to non-ink related body modifications nowadays.

[Killman]

Forgot to mention, the forks will be completely redone with new seals, springs and gators.

Like to hear any recommendations you might have for footpegs. Teeth would be nice for grip, but rubber would help with comfort.

[Killman]

Had an interesting chat with Dave Moss today. He recommended progressive springs for the forks, as well as cartridge emulators and air assist. Sounds like I'd have to do a front end swap, (possibly for an F model assembly?) to accommodate all that, if what I've been seeing is correct.

He gave me a list of affordable suppliers of dual spring rears that he likes, WP, Nitron, Works Performance and suggested an additional inch in length over stock to deal with the extra travel and load. What a nice way of describing my sturdy butt. 

Awesome guy, I've been really happily surprised at just how many experts have been willing to lend me their brain power when I've approached them for advice on my thoughts for this machine. Making my life so much easier.

[754]

What year do you think motor is ?..I think you said 72 in your introduction..but that head is 73 and up..
a few of us have a trip planned near Merrit in May. along the old railbed. I will try to take my CB750.
 Mostly guys from BC Classic MC Club... search Bcclassic.. one word to find the site.
 The Island bunch have trip planned to Gold River in a few months too.. if you want to join the fun..

[calj737]

Had an interesting chat with Dave Moss today. He recommended progressive springs for the forks, as well as cartridge emulators and air assist. Sounds like I'd have to do a front end swap, (possibly for an F model assembly?) to accommodate all that, if what I've been seeing is correct.

He gave me a list of affordable suppliers of dual spring rears that he likes, WP, Nitron, Works Performance and suggested an additional inch in length over stock to deal with the extra travel and load. What a nice way of describing my sturdy butt. 

Awesome guy, I've been really happily surprised at just how many experts have been willing to lend me their brain power when I've approached them for advice on my thoughts for this machine. Making my life so much easier.

Some GL's had air-assist forks, but many yanked them off due to reliability issues. The cartridges are a very good recommendation, but typically they're used with single rate springs, not progressives, unless that's an off-road trick?

[Killman]

Good point. Very good point. Thank you. I'm going to have to go over those emails again to make sure that I haven't misquoted him, or combined two different suggestions in my head. Let's just assume any errors are mine for now.

I've heard of the GL mod, but what are these reliability issues? If I decided to swap out the front end, I think I'd be tempted to just go with some usd's. Sounds like I should give some progressive springs a shot to start, and decide how much farther I need to go from there.

Anyone got any thoughts about the different makes of rear shocks in that list?

Just thought about how much fun the shakedown is going to be. 

[calj737]

With USD forks, you've already got cartridges. Just have them sprung for your weight. Works, YSS and Nitron are all very good shocks. Choose your poison.

[Killman]

The day is starting off right. The Oury grips and engine oil seals kit came in yesterday, and I'm expecting the new sealed battery today. Hondaman is finishing off my electrical toys and Carpy has my  header and centre stand on the way. Not to mention the raft of assorted other run-good goodies that are coming over the next couple of weeks.

Checked out the BCClassic site, very cool, looking forward to doing some digging when I've got a few moments. The rides sound great, just got to get this old girl in decent shape first.

Thinking that I'll keep things simple on the front end for now and put the progressive springs in with the new seals and see how I like it. Got an offer to trade my front caliper for a side stand, but I'm still not convinced that this single disk is going to have the best stopping power with a heavy bike and rider. I do have a chrome caliper, with new pads, that I was going to swap in regardless. No idea about rear shocks yet, as I've spent the wad for the moment, and need to replenish funds before my next shopping spree. Although I am getting sick of looking at the ass end sagging down, makes it hard for me to visualize what I want when the stance is so yuck.

I'm pondering how to proceed with the engine. Need to run a compression test. There are fluids leaking everywhere at the moment, and I'm thinking about getting the engine vapor blasted in advance of powder coating the jugs and crankcase. So if it turns out that I have to pull it apart for gaskets and seals anyways I may as well get it blasted unassembled. Not really looking for the extra time involved if a teardown is needed, but we'll see what happens.

So far my evil plan is to wait until the new ignition, Denso plugs, NGK caps, copper core plug wires, Dyna 5 ohm coils, etc., get here and get the electrical up to snuff. Probably pull the carbs and give them a nice ultrasonic bath and rebuild, (reminds me, I still need to get some jets ordered) in the meantime. With new sparky bits and fresh carbs the battle should be mostly won, (knock on wood) we shall see what we shall see. Wish the weather would turn, my little shop's a lot more pleasant when I can open up the bay door and let the sunshine and fresh air in.

Thanks for the advice guys, hope you're all having a great week so far!

[calj737]

You might hold off buying jets until you determine the jetting needed with the breadbox and exhaust combination. At a minimum, retain the stock jets and buy original Keihin pieces when you do. And lots of extra plugs for chop tests.

[Killman]

Figured at $2-$5/jet I'd bring in some of the 115's that keep being recommended to me. Be nice if I got lucky. Going to have to grab a bunch of cheap NGK plugs at Canadian tire for chop tests. The Denso's, are not free to order in up here. Although I did get a decent price at Rock Auto.

[Killman]

Cool beans Batman! Looks like I've got a side stand, place holder OEM rear shocks and fork brace lined up. Finally need to nail down a tank and then it'll just be wrench, spend, repeat.

[754]

There is a good vaporblasting place in Chilliwack

[Killman]

That's exactly who I was thinking about. 

One of the owners stopped by my booth at the Motorcycle Show to see if we were going to Vintage In The Valley this year, we are, but I can't remember his name. I think I've got his card on my desk somewhere. Got to drop him an email with some questions about the vapour blasting, so hopefully I can find the thing, failing that I'll just get in touch with Wally as I need some info about the show as well.

Maybe some of you guys will know. I've got new engine oil seals, but I don't know if it's the best idea to install them before I get the engine blasted, not sure if I'd just have to replace them again. Can they blast an intact engine, or do I need to disassemble the whole thing? I'm not really interested in stripping another frame and engine by hand, so if vapour blasting won't work I might go with soda.

[Stev-o]

Best way to blast is totally disassembled.

[Killman]

Got a line on a complete front end for a '76 GL1000. Which would appear to open up some new possibilities for me, re: dual disc and suspension mods. I'm in the middle of reading roughly a bazillion threads regarding everything from dual disc mods for the k model to cartridges for the GL front end:




The same dude with the GL assembly, who has been super quick and helpful, also has a couple of modern packages available, including this 2009 Kawasaki zx6r front end for US$250:


Now I don't want to dick this guy around, but I have to tack on roughly an additional 40% to each purchase from the US, due to the exchange rate. Which means I have to be careful what I pull the trigger on, because it adds up fast, and having to resell bits due to design changes isn't a great way to economize what cash I have. So measure twice, spend once is my mantra right now.

I already have a new front tire on the way that should also fit the GL rim, (100/90 19) and tapered bearings (that I'm hoping would work for the stem?) but I guess the fork brace I just ordered would wind up useless for that application. From what I've been reading, using the GL front end, rather than farting around trying to make the dual disk conversion work with the '72 forks, which supposedly wouldn't take a cartridge setup if I wanted to go that way, would wind up being a more efficient use of time and money. Pretty much plug and play, and it would allow me more options regarding suspension down the road, (cartridges, etc.) however there's apparently a difference in fork length to consider. I was already considering using a bit taller shocks in the back, so possibly this wouldn't be such an issue, but I don't know the actual difference that I'd be dealing with yet. Still snooping for info. Looks like I could put some prog springs in there for under USD $100, or cartridges for USD $400+. I could probably swap in a modern front for the price of just the cartridges and with any luck have the same or better internals for less.

If I went the with the zxr assembly, I'd still need to source triples, an mc, figure out bearings and races and find a wheel that would hopefully allow me to use the tires that are already coming. All of this sounds like it could get really spendy really quickly. It would give me some modern internals for the suspension, although I'm not sure how much street racing components are going to benefit me, when what I'm trying to put together is a bike that will let me handle long stretches of highway with the capability of bumping around in more rural settings without needing new kidneys.

Seeming so far like the GL front end with the dual rotors, prog springs and some decent rear shocks would be the most bang for my buck. Assuming I can get the fork length issue sorted, which I'm thinking shouldn't be too much of a pain in the ass.

Lots to consider. Feel free to chime in with any thoughts, experience, advice or to point me in the direction of more reference materials. Be nice to keep any errors and backtracking to a dull roar. Parts are starting to arrive and the weather is getting nicer, got the new header in and it's gorgeous, things are looking pretty good so far.

[SOHC4 Cafe Racer Fan]

The entire GL front end is a plug and play solution.  You will want to use the GL rotors, calipers, forks, triple trees, etc.  The only thing you will likely want to do is re-spring for the lower weight of your bike (vs. the heavier GL).

I am not sure as to the compatibility of that year Kawasaki.  As for modern fronts, you might be better off with a Suzuki GSXR or Honda CBR__RR front. Check the Cognitomoto set ups, as you will also need to alter the steering stem (length) and you will need to use a modified hub to use the modern brakes.  This conversion will offer better performance (dampening and brakes) but cost more than the GL.

[calj737]

Since you are looking to do some "light" dirt roads, I think I would steer clear of the USD forks, personally. The GL is a much simpler conversion in terms of $ spent, and affords you better options of tires mated to a stock sized hub.