I own a 1992 Nighthawk CB750, and these maintenance tips work great for me. Hope you all can put them to use. First comes the life blood of our dependable stallions...the oil. I'm running Castrol Syntech (100% synthetic 10 W30), along with a Fram oil filter (number PH6017A). I purchased the oil at Wal-Mart for about 3.65 per quart. You can purchase the filter at an Advanced Auto Parts, Twin Bee, etc. for about $4.00. The big thing is, substitute a quart of oil with the DuraLube oil treatment ($13.00). You only have to do this every 50,000 miles or so, and does it ever make a difference. The motor literally purrrrrs at highway speeds. Also, I do regular oil and filter changes every 4000 miles. Next is the fuel system. The DuraLube fuel system treatment ($7.95) is absolutely wonderful. It comes in a 16 oz bottle and says to use it with a full tank of gas (10 to 20 gallons). Since our mighty steeds have about a 4.7 gallon tank, it stands to reason that 8 oz is sufficient. The nice thing is that you don't need to add it again until the next oil change. And yes, with the DuraLube products I did notice better gas mileage and performance.

The chain is the next item. What can we use to clean our chain?? "Dawn takes grease out of your way!" That's right, Dawn dishwashing liquid is a mild degreaser. Use some HOT water, Playtex dishwashing gloves, and a brush. Scrub the chain and cogs down real good, rinse with fresh water, and let dry. No harm done to the O-rings, and you're ready to lubricate. After I deep clean the chain, I'll spray the inside with STP White Lithium Spray ($2.25). Then at least once a week I'll lubricate it with WD-40. How often do I deep clean the chain? Every oil change. Also, when I do this I'll remove the chain guard, rubber chain rail (the rubber piece that the upper portion of the chain rides on), and the front drive cog cover and clean them too.

Now for the front fork struts (the shinny part that goes down into the forks). Spray those with WD-40, and wipe it off. This will clean and lubricate the fork struts, allowing it to easily travel through the shock strut O-ring and help prevent dry-rot. This will also help prevent bugs from sticking to it (sort of like cooking with PAM). For those of you in aviation maintenance it's the same as wiping down the landing gear struts with hydraulic fluid.

Last, but not least. If you have a Shop-Vac, invest in the little attachments (about $12.95) that allow you to vacuum in small tight areas. Not only is this great for detailing, but for when you change your spark plugs. This allows you get those pesky little pebbles and keep them out of your engine when you take the spark plugs out. It also works great for cleaning out your air filter between changes, not to mention the inside of your computer.

Oh, and one final thing. Buy the sticky back Velcro, and a small cheap water proof watch. You can attach this on the ignition switch plate. Now you don't have to dig through gloves to find the time.

Guess that's it for now. Anal??? You betcha, but it works for me. Let me know how it works for you. E-mail me at: rdu@home.com or r_upchurch@hotmail.com

A Response from another rider:

  FYI--

I noticed the latest tips you posted from rdu@home.com and wanted to mention something. I definately know that you do not endorse whatever people suggest, you just post them. You may want to pick up the April 99 Cycle World magazine, and take a look at page 149, Service Tips. Someone wrote in asking about the benifits of adding Prolong to their oil, and the author basically said that manufacturers spend millions of R&D dollars and if a better running engine was just a bottle of that stuff away, wouldn't at least ONE of them recommend using it?

Also, don't you think something like that would cause clutch slippage, and possibly faliure? I don't know. I've read in Consumer Reports that the stuff does absolutely nothing for car engines, and Dura Lube, I believe, had to pay large sums of money for false advertising. (don't quote me on that though.... )

Just thought it was worth mentioning.

I have owned a 1991 CB750 and a 1993 CB750 Nighthawk. Both were excellent machines and gave superb service before I sold/traded them (20K on the 91--- 26K on the 93) --- Except for one minor thing: The bushing for the shift lever bolt, that serves as a pivot, has two weak rubber seals that are there to hold grease in and NOT keep moisture out. Water invades the grease, corrodes the bushing and the whole thing will start to sieze-up. When downshifting, owners will find the lever not returning to the "home" spot so the next gear may be selected. Imaginations will conjure up bent/broken pieces inside the tranny itself and a huge repair bill to follow, but fortunately the fix is much simpler and cheaper.

The fix is simple: Remove the whole lever BEFORE this happens and dress the bushing with fine grit sand paper or a wire wheel. Next,apply liberal amounts of a waterproof grease to the bushing,bolt and inside the lever pivot. Reassemble as before and Ride! Traitorous as it may be, I personally used a nice blue grease made for Yamaha personal watercraft. A tube should last the average backyard wrench for years.

I have talked with other Nighthawk owners and a couple have had the same problem. It's an annoyance at worst and can be fixed in minutes at best.

Happy riding!

Eddie transalp@mindspring.com

• Problem with Needle Valve -
  • I checked out your web site on Honda 750's and I have a problem. Maybe someone else has run into this one. I bought a 1992, 750 Nighthawk new from a dealer two years ago. When I got it home, it stalled on me a few times and the dealer told me he had to clean out the needle valves on some the carbs. Everything ran OK for a about two years. Now, the number 1 cylinder runs dead and she leaks gasoline. If I change plugs, it will run clean for a bit and then foul out. No matter what I try, it continues to leak gasoline and foul the plug.
  • The Solution - It turned out to be the main needle valve seal for the cylinder! It was "floating" having come loose from its press-fit. It has been glued in and works like a champ. It was discovered by using air-pressure to examine componenets/parts. Hope no-one else runs into this as it is quite disturbing to clean it out several times, change plugs and have it flood again and again.

   

• Randy Get's Stranded - Learn from the original "Wrench Dummy" how not to troubleshoot a fuel system problem.

• Modifying the Vacuum Petcock -
  • "After learning what did happen to you with the automatic petcock, I decided to take some action in order to avoid that it would happen to me.

    I dismantled the petcock of my Nighthawk and got rid of the spring that pushes the first diaphragm against the petcock gas outlet, stoping the flow when the engine is shut down ( it's a straight forward task, you don't have either to remove the valve ass'y. from the tank nor tha tank from the frame). Now I have a petcock that works a a standard one, i.e. there is a constant flow of gas to the carbs if you leave it open. That means you can't get stranded anymore because of it. The only drawbacks is that if the first diaphragm wears out or gets damaged in time, you would loose some gas through the assembly's vent but plugging it would solve momentarily the situation while you get a new diaphragm and, if the second diaphragm fails, you would only loose some vacuum in No. 2 cylinder, wich would be remedied by plugging the vacuum hose while you get the replacement, but you would never get stranded anymore.

    Be only careful of not losing the spring when removing the 4 screws that hold the ass'y. together as it is prone to jump and get out of sight very easily. Also be careful to assemble the 2 diaphragms in their beds, as you might pinch them, ending either with a a spill of gas or an air leak wich would lead to rough idling."

    The Wrench Jedi

• Mark's Fuel Problem -
  • Randy,

  You might remember an e-mail that I sent you about a month ago about my Nighthawk leaning out and stalling on me. My bike had very similar symptoms to one of your fuel troubleshooting articles and the article pointed out that the vacuum petcock may very well be the culprit. Well, I opened that sucker up, and both fuel screens were spotless. The diaphragms seemed to be in good shape. (No dry rot) Even the fuel bowl in the petcock was clean! I still could not figure how in the heck crud was getting into my fuel bowls with a clean petcock. When I looked at the air box, I saw that right where it divides into the branches that feed a pair of carbs, there was a band of black sealant. The sealant hand split in a couple of places and other spots had a few holes! I guess this would explain how the crud could get in my fuel bowls, and not in or on the petcock screens. My guess as to why it was leaning out may be explained by extra air (and crud) getting sucked in through the gaps in the air box. Too much air, and not enough fuel would give you a lean mixture, and I'm guessing this was my problem. Since then I have sealed the cracks with a tube of black caulk from Wal Mart, and my fuel bowls are clean, and the bike runs like a champ! I was wondering if the sealant around the airbox ports was a factory thing or if the previous owner had done this himself. Hopefully this is may help out other riders as well. Mark

• My original battery only lasted about 18 months on my 95 NH. I bought a cheaper one as a backup, but when I just couldn't rely on either one of them, I bought the original, a Yuasa. I discovered that testing voltage means nothing. You can get 13 volts on a meter and it won't have enough juice to start. Bacause of problems in hot weather, I bought a Battery Tender (very convenient to use, with a connector that stays on the bike) and used it daily. I found that after a ride when I attached the charger, it would charge for a period of time. With my new battery, after a ride, it doesn't charge at all. I also found out that the little syringe testers work OK, but I never got a full charge reading (four balls floating). I think motorcycles must eat batteries because they are so small and there is so much vibration.

  Motorcycle Consumer News has a very complete Battery Maintenance guide that I printed out and found very helpful. Jim Finch

• Kragen Exide 12N12A-4A-1 M2221B
  • The battery fits nicely and has the proper polarity orientation. The terminals are slightly different so the terminals are not locked into position by the metal tabs on the crimped lugs but this is not a serious problem.

   

• Champion 14LA2 (Also sold as a Walmart label)
  • Even though the manufacturer says it works, and even though they fit physically, the + & - terminals are reversed, and the wiring harness isn't long enough to accomodate that.

 ATTENTION ALL OWNER'S---Share your information. Let me know if you've replaced your original battery with something other than Honda's. Were there any problems? Longevity? How many miles or months can we expect out of a "properly maintained" original Nighthawk 750 battery??

 Electrical

•  from Jeff W. - Had to order a new right handlebar switch housing/assembly and wiring harness today. Apparently, one of the four wires insides the housing is the headlight cut-out for when the electric starter is pushed. That wire broke on mine. Honda of Jacksonville is ordering a new one and a private shop at the beach is installing it for me. Should have it back by Wednesday. Cost from the dealer is only $53. Not too bad!

  Couldn't figure out why my headlight went out on me. New bulb (that's not it), fuse is okay (that's not it), continuity check says there is current into other headlight shell wiring but not the headlight plug. Ah ha! problem must be in wiring harness. Sure as shit, there it was when we opened it up. Oh well, I'll be back on the road by Thursday.

• Update: It wasn't the bike's wiring harness, it was just the control assembly on the right handlebar -- that contains the kill switch, starter switch, and and electrical cut-out for the headlight when the started is pushed. There are 4 wires inside there. One of them broke. That's what caused the problem. Cost was only $53 so it's not too bad of a problem.  

• Honda Manual Wiring Diagram Error?? This past Saturday I installed several items onto my '93 including a Rifle fairing, Fiamm horn and a KRISS headlight modulator. The modulator's installation sheet called for it to be installed in the high beam headlight circuit, which is fine. What I mean by install in the circuit is find the appropriate wire going to the headlight bulb socket, cutting it, and then connecting the cut ends to the appropriate wires coming out of the modulator. No big deal, went to the factory service manual (Honda p/n 61MW306 "91-98 CB750 Nighthawk") and looked at the wiring diagram (drawing number 0030Z-MW3-6700) on page 17-1 and found the headlight. Although the printing on the diagram is VERY small, it still clearly indicates that the white wire goes to the high beam terminal on the lamp, and the blue wire to the low beam terminal. I cut and spliced accordingly, then tested the headlight operation. Guess what! The factory's own wiring diagram had it backwards. The correct wiring is as follows:

  White wire - Low Beam

  Blue wire - High Beam

  Green wire - Ground

  I wasn't too happy about finding out about it this way, since I hate to cut on wires that don't need to be, and I had to remove the fairing to get to the headlight again. The Rifle fairing was a bear to install because of the unique "universal" mounting system they use (it's really strong and stable, but the trial and error effort trying to find the optimal combination of brackets, holes, and strut orientation is a real pain. I've already e-mailed Rifle about this.) Fortunately, the fairing was very easy to remove and replace after all the grunt work of initially mounting it was done, but in this case the fairing was taken on/off needlessly...all Honda had to do to prevent this was to make sure the wiring diagrams are correct.