Topic: First bike: 1978 CB750 K8. Let's turn this piece into a solid runner.

[therobbstory]

There is some good information on this thread! I am watching this because I too am building my 78K.  The honda man ignition, can it be used with the moto gadget stuff though?

I went through your build thread the other night, and I'm pretty sure that's what made me decide to go with a raw tank. Kinda reminds of The Rocketeer in a way.

No idea about the Motogadget compatibility. I imagine it'd work, though. The control module wouldn't know the difference between breaker points and transistor switching.

[greyghost18t]

I am up in the air about the raw tank.. i like the raw look..but then i see some amazing paint jobs and makes me second guess.. now i am thinking about an early to mid 70's tank or a F tank because of this thread.

[Restoration Fan]

There is some good information on this thread! I am watching this because I too am building my 78K.  The honda man ignition, can it be used with the moto gadget stuff though?

Sure.  I don't see a reason why not.

[calj737]

There is some good information on this thread! I am watching this because I too am building my 78K.  The honda man ignition, can it be used with the moto gadget stuff though?

Sure.  I don't see a reason why not.

It can without question. Use the AUX output to power Hondamans box. Simple and done.

[greyghost18t]

Thanks for the responses - Didn't mean to hijack your thread.

[therobbstory]

Stellar weather this weekend, so I got out on the road with some friends. Rode DC > Frederick, MD > Baltimore, MD, DC yesterday, about 150 miles of country roads.

Some things I noticed:

When pulling in the clutch and coasting, I felt and heard a little k-chunk k-chunk sound. I know what bad wheel bearings feel like on a 15lb bicycle, and this felt like the same thing but increased by a magnitude of 650lb motorcycle with rider. I'm going to order some replacement bearings. All Balls seems the way to go from what I've read.

I'm also going to swap the chain and sprockets for peace of mind. There was considerable slack when I bought the bike, so much so that it would slap the swing arm. Not sure if that was a stretched chain or just poor maintenance. The drive drain sounds really noisy despite cleaning and lube.

Fork seals are leaking so much oil, I wonder if there's any left in there at all. Even small bumps at speed would send a shockwave down my spine. I've got the seals, I just need to engineer a way to hold the front end off the ground. I don't have a garage, so I may attempt the cymbal stand hack I saw in another thread.

The engine ran great all day, though! Most of my riding has been stoplight to stoplight in the city, and I rarely get to stretch it out in 5th gear. Cruising down the Baltimore Washington Parkway at 70-80mph was a real treat. Especially with a new headlight

In other news, I found a local powder coater who has grand ambitions for my raw tank. Should be able to get that to him this week. Still need to figure out a seat solution. Stock one is all ripped up, but functional. I'll likely move the hinges back to accommodate the super sport tank until I think of a better idea for replacement.

To recap next steps:

• Replace fork seals
• replace wheel bearings, front and rear
• replace chain
• replace sprockets
• install shorter clutch cable
• powdercoat new tank

Here are a few photos from yesterday.

[calj737]

You would be well-served to also replace the steering head bearings while the forks are apart. Butter smooth, and not jolts when riding or steering  All Ballz makes those too

[therobbstory]

You would be well-served to also replace the steering head bearings while the forks are apart. Butter smooth, and not jolts when riding or steering  All Ballz makes those too

Will do, sir!

Just came back from a quick ride. Noticed a little bit of smoke coming out of the crank case breather tube which exits next to my muffler. I know these 78's had some kind of smog pump under the battery tray. This seems to be bypassed on my bike. The tube comes out the top of the breather cover, under the tank, and exits down under the bike.

Is the smog pump (correct me if it's called something else) essential? Should I reconnect this? And what could be causing the smoke? Oil level seems normal and I haven't had to add any since changing it about 500 miles ago.

[Stev-o]

Smog pump?  I don't think so.

[HondaMan]

It has (had?) an oil separator for the engine breather tube(s) and the oil tank. If it's still there, it is a little plastic container, about as big as a coffee cup, under the battery, above the front "U" part of the swingarm.

Is the #4 still sputtering? Often, riding these awhile will smooth off the carbon that collects on the valves, making the engine miss if it hasn't been ridden often (and fairly, umm...briskly...). I've also found that splitting up a can of BG44K into 5 or 6 "portions" for a series of gas tank fills helps to clean these off, too. Compression goes back up afterward.

How's the charging system doing? Do you have OEM type coils, or maybe some 3-ohm type instead? The latter can drag the battery voltage down when ridden for 3-4 hours in slow traffic.

After I restored the K8 on my patio the later "K" bikes have grown on me somewhat. I still think the "F" tanks do look a little better on them, though, even if the K8 tank can get you halfway across Colorado on a single fill! That's kinda important out here where fuel stops can be 100 miles apart... 

[Desert-SOHC]

I just need to engineer a way to hold the front end off the ground. I don't have a garage, so I may attempt the cymbal stand hack I saw in another thread.

You can run a 2x4 under the pipes and use a floor jack to lift the front off the ground while its on the center stand.

[therobbstory]

Oil separator! That's what it is. Yes, it's still there on my bike, just seemingly bypassed. Looking for a diagram on how it's supposed to be routed now. There's also a port on the top of my airbox with nothing connected to it.

Haven't had any backfire issues on #4. That was happening after I pulled the carbs and replaced the gaskets on the float bowls which were leaking. While I had them off, I sprayed through the jets with carb cleaner. No blockages that I could see.

Charging system is actually fine. Looking back, I didn't know how to start this machine and likely killed the battery with an unknown charge state with the starter. PO put a new battery in it shortly before I bought it, but I really don't think he knew the first thing about simple maintenance, and rarely even rode the bike. "About once a week in the city" is what he told me.

The coils are branded 'TEK' if memory serves me. I measured them just shy of 5 ohms, so they're either stock or stock replacement.

I'm going to keep the K8 tank for long hauls. The SS tank just has nicer curb appeal, and it was cheap. You're not kidding about capacity. One of the dudes I rode with on Sunday has a HD Sporster with a 2.5 gallon tank. He stopped at nearly every gas station to top of 'just in case.' I wasn't even close to reserve at the end of 140 miles.

Brake lines should arrive today. That's the big project prior to the weekend. New bearings are on order.

[therobbstory]

Not much action this week as I've been spending more time riding and less time tinkering. Got a good deal on a set of Renthal bars this week, so I threw them on. Vibration at the wrists is gone, and they offer a bit more pullback than the generic superbike bars I had.

Got all my new bearings this week. Going to attempt that next weekend.

Dropped my super sport tank off at the powder coater's house this morning. While doing aobut 70 on the interstate, I noticed my speedo bouncing around. When I got off the freeway and my hearing returned, I heard what sounded like a tortured cat under my front end. The sound went away when I covered the speedo with my ski-gloved hand. So I guess I need to inspect the cable. If that isn't the issue, I'm going to try a little denatured alcohol in the speedo body. If that doesn't work, I'll guess my speed by counting highway lines. Kidding.


Afterlight by Robb Hohmann, on Flickr

[Stev-o]

I have a nice set of gauges if you are in need

[therobbstory]

I have a nice set of gauges if you are in need

Thanks! I'll let you know. I'm going to pull these off in the next hour.

[therobbstory]

Well, the inevitable happened.


Boxy Brown by Robb Hohmann, on Flickr

I picked this up in northern Michigan on Friday, and rode it back to DC.

I'm keeping my 750 as it's frankly more fun around town. The BMW only has 20k miles on it and is just a fantastic long-haul cruiser. For my ferry ride, I had it loaded down with side bags and a large dry duffel with all my camping gear and tools I didn't end up needing.

The 750 is going to get all new wheel and head bearings soon, as well as chain/sprockets and fork seals. I really like where it's at. It's a joy to ride and I've no reservations about doing 200 mile days on it.