1974 Honda CB750 Four K4
Mechanical Service with some Cosmetics
Owner & Writer: Randy Creel, Jr., Owner & Restorer of Randy's Cycle Service & Restoration
Revitalize the Spirit & Beauty of your Classic Bike
Located in beautiful Central Virginia since 2001
8175 Black Walnut Run Road, Rhoadesville, VA 22542 USA
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The Mid-Atlantic Region Premier Restorer of Vintage Motorcycles
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This page was last updated on: August 6, 2013
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COMMENTS: This page is an ongoing write-up of Randy's mechanical & cosmetic service to the bike he'll personally be riding starting the spring/summer 2010. Write ups - some technical some personal - will be posted along with pictures & a video of the progress. Notifications of new entries will appear on Facebook, so please join us on Facebook by clicking on the icon above.
Blog Entry 7: Posted June 15, 2010
The engine sure looks a LOT better residing between the frame rails than on my bench where it's been for the last couple of weeks! With the painted frame and the painted and polished engine unit surrounded by the fresh bodywork, it really looks quite nice if I do say so myself.
Lifting it into the frame in one large chunk isn’t an easy task however, as it makes the bulk of the weight of the bike at around 260 lbs and required the assistance of one of the guys in the shop here with some very careful maneuvering to avoid damaging the new paint. It went in perfectly and without so much as a scratch, then new hardware was used to mount it into place. As with most of the bike I went with stainless steel fasteners wherever possible to avoid any corrosion issues in the future. Nothing ruins the appearance of a fresh restoration in my opinion, quicker than cheap hardware that rusts the first time it is subjected to moisture. The eye is drawn to it. I opted not to polish any of the stainless to keep it as close to the original cadmium plated hardware originally used by Honda at the time the bike was built. I did however remove the markings on the heads of the bolts to keep everything consistent. Again, a small detail, but one I see overlooked too many times. Also whenever stainless hardware is used, particularly in alloy casings, a small amount of anti-seize compound should be applied to the threads to prevent them from galling due to the fact that the stainless bolts are somewhat softer than other types of fasteners. I also do not use stainless on critical components that require high shear strength bolts.
After standing back and admiring the shiny lump situated in the frame for a bit, I figured it’d be best to get it functional, so all of the major connections followed the install. The electrical connections were first, all getting a liberal dose of dielectric grease in the plastic connectors, and then followed by the grounds (nice and clean), the oil tank hoses, the breather hose, ignition HT leads, and finally the electronic ignition. I did opt for a Dyna electronic ignition unit for several reasons: First, the maintenance that comes with points is constant and honestly not something I want to fiddle with every 3,000 miles these days. Point-type ignition is antiquated technology. Second, the Dyna is a self contained unit that eliminates a lot of moving and wear-prone parts and doesn’t alter the appearance from the outside of the engine. Third, the increase in performance is noticeable. Not a giant horsepower increase, but quicker starts, smoother idle and consistent timing across the RPM range. A small boost in fuel mileage isn’t a bad benefit either. And for all the folks who approach electronics on a classic as heresy, I can say honestly say this with real-world experience: I’ve yet to replace a failed Dyna unit I’ve installed on any bike in the past due to failure on the side of the road. One of the early units I had on my GL1000 had over 50,000 trouble-free miles and it is still going to this day. And that without ever having to be adjusted, lubricated, any gaps set, or advance weight springs replaced. I’ll take my new fangled gizmo any day.
Carburetors were the next thing to tackle. I thought this would be the easy part. It would have been, had everything gone according to plans. As we all know, sometimes plans change abruptly. This bike had sat for many years idle, and before I’d purchased it, it had sat then too. In fact the title reflected that it hadn’t done but a tick over 1,000 miles since the title was issued in 1987 and I bought it in 1999. The carburetors that originally came off of it were in such poor shape both inside and out, that I knew they were really only parts donors, so in the corner they went. The set I grabbed off of a donor bike that “ran when parked” with the intent of rebuilding looked almost as new on the outside. They still had that purplish sheen to the bodies and the rubber boots on top were soft and pliable. Looks can be deceiving however . . .Inside of each bowl, revealed such horrible corrosion that the bowls were full of aluminum oxide powder to the tops, and the float mounting posts were completely rotted away. So were the main jet holders, and pilot jets in two of them. If it “ran when parked” that must have been somewhere around the Carter administration or so. No problem I thought. I parted down a lot of these bikes in the years we used to do salvage, and I kept a big box of carburetors to fit the CB750 SOHC engines. I’ll go get that box. In it, were approximately 20 carburetors, not including the set from the bike originally and the aforementioned, DOA’s from my donor. Out of those 20 I managed to select about 6 decent bodies, linkage, bowls, slides, and other assorted hard parts. All of the floats, jets and small parts of course were replaced with new. All told I have about 10 hours in that set of basket case carburetors, and I really don’t want to think about parts cost. They are a very good set of carburetors to be sure, and will function perfectly, but it was a good reminder to me that what you see on the outside of any part isn’t what you will end up with once you inspect it further. Keep that in mind when considering a basket case bike that “ran when parked.” Full disclosure may not necessarily be on a sellers’ mind when the money is about to change hands. It was also a good reminder that I shouldn’t keep some things “just because.” At least after this it made some space for more parts. I’m not sure if that is a good thing however.
Once all of the parts were ultrasonically cleaned, thoroughly (and I do mean thoroughly) inspected, and reassembled, I did a quick bench synchronization, (they will get the real deal once the bike is running), float level check and static adjustment before they too were mounted onto the engine with new rubber intake boots both on the intake side and the air box side. All of the jetting is stock as is the factory air box for simplicity and reliability.
Next update: handlebars, controls, final wiring, and let’s hear it run!
Carburetors rebuilt
&
cleaned
Dyna electronic ignition
Dyna electronic ignition
