For our purposes carb syncing is the process of setting the individual carb's butterfly valves to open at the same time and same amount. The effect is to provide the same amount of air (and thus fuel) giving us the most power and smoothest operation. This is a crucial step in tuning any multi-cylinder engine, but especially highly tuned, high-performance ones like the V4 Interceptor.

It's a simple concept with the only difficult part being actually getting to the set screws. That's where the Motion Pro 90-degree Hex Driver comes into play.

(Below) In the case of the VFR, I snap on a 7mm socket to fit the adjuster screw. A straight blade screwdriver socket will also fit but is much more difficult to actually use. The reason is that we'll need to fumble around in the dark under the carb set to find the adjuster. The socket is just a more positive engagement. The tool doesn't hold the socket very well (seems to be common with Motion Pro socket tools) so I wrap a bit of teflon tape on the base to help out.

With the engine warmed and idle set at about 1200 RPM, and using number two carb as a (non-adjustable) base, adjust the other three to match. I do this at idle and at a steady higher RPM, about 3000. When I'm happy with the adjustments, shut the engine down, allow it to cool a bit and remove/plug the vacuum ports. There's some good video tutorials on YouTube for more tips. Job done!

Last month I began the process of resurrecting Project 17, an unloved, forgotten VFR750. Starting with a basic stripping and cleaning, I continued with mechanical checks, including valve clearance, compression test and carburetor rebuilding (see previous posts). At each stage the old girl gave me the thumbs up to continue and now we've arrived at the moment of truth: will it run? Here's how it went....

Success! After some initial smoking from oiling the cylinders, the engine ran smoke-free and pretty smoothly, considering I'd yet to sync the carbs. Throttle response was good and no unusual noises. More good news; no leaks and all the lights and tach are functioning normally — things you don't really know about till it the bike's up and running. Next, we'll sync the carbs and continue moving forward with Project 17.

What: 1997 VFR750F
Where: Eldridge, Iowa
Why: Fully optioned, known history, great value
Price: $2800

Last fall I sold this bike, Project 22, to Scott in eastern Iowa. He gave it his best shot, but his knees are not letting him enjoy the VFR experience. It's a real shame as Scott was very excited to get his Interceptor. So, it's back up for sale at a genuine bargain price. His ADVrider ad has it currently listed at $2800.

This VFR has been refurbished by myself, and has a laundry list of farkles. Some highlights:
DMr suspension upgrades
Two Brothers slip-on
Carbon fiber front fender
Reg/Rec upgrade
Bar risers
Throttlemeister
Pazzo levers
Seat cowl
NOLOGY ignition wires
Heated Grips
...and much more.

A great-looking, final year VFR750 ready for many years of enjoyment. Contact Scott via the ADVrider PM link (may require registration), or directly:
Scott Grunder
563-650-7946
cyberhog9@yahoo,com

The photos shown here are from my photo album:
https://flic.kr/s/aHsm8E3hT6

As your shop manual likes to say, "installation is the reverse of disassembly." Which is true, but here's a few tips I've learned over the years.

Note: I will be syncing these carbs once the engine is running, so before proceeding with this install, I've connected the sync tool's vacuum hose adaptors and hoses — see a previous post ("Preparing For Carb Sync") for details.

Note: Check your carbs for leaks before installing: see my technique at the bottom of this post.

If your carb insulators (manifold boots) are hardened with age, simplify your life by installing fresh boots, which are still available from Honda. First remove the lower clamps and, with a large pliers, give the old boot a firm tug to remove. Clean up the area and push the new boot into place, noting that the groove adjacent to the word "Carb" is oriented to 12-o'clock (below). Install all eight boot clamps, oriented to the left, and tighten the lowers.
(click on any small image to enlarge)

(Below) I wipe a film of grease or something similar on the lip of the boots to help the carbs slip into place. Place the carb set square to the front boots and push firmly down till seated in the front boots, verifying that they're seated with a flashlight. To get the rears in place I maintain downward pressure with my left hand while running the blade of a flat screwdriver along the inside of both rear carb boots with my right hand. If your boots are fresh and supple they will "pop" into place after repeating the screwdriver trick two or three times. Tip: if you're in a cold environment, adding heat to the boots with a heat gun will help soften the boots.

(Below) Tighten the upper boot clamps making sure that the clamp is square in its groove all the way around. Use a flashlight to verify this as you tighten the clamp. The 1990+ clamps have an upgraded design to hold them square, but the earlier models don't. Install the throttle cable ferules, then the cable bracket's two screws. Install the choke cable ferule, then tighten into its clamp. Tip: A long screwdriver is invaluable to reach the right side carbs...and a JIS screwdriver is always recommended.

​(Right) At this point I'll connect the fuel I.V. direct to the carb intake line in preparation for engine start. If you do this, disconnect the fuel pump power supply at its connector just above the pump. The pump relay can remain connected.

​You can also use the fuel tank and pump with all its plumbing hooked up.

With the radiator reinstalled (and filled), double check all your connections, hook up the battery, and we're ready to hit the magic button!

I've seen these guys before. They're a really dedicated riders group in Hungary who call themselves Club Hungary Sikonda. Here's a shot from one of their recent gatherings. Near as I can tell, they run their club rides the same way we do: Ride, admire, eat, drink, repeat. They can be found at:
http://www.hondavfrclub.hu

After my haircut appointment this morning I decided to take the long way home. While it's not the easiest proposal in the northwest suburbs of Chicagoland, I managed to find some back roads in a westerly direction and ended up in the picturesque little town of Woodstock, IL. If you're even passingly familiar with the 1993 movie, Groundhog Day, you'll remember the quaint town square portrayed in the movie as Punxsutawney, PA — but it was actually Woodstock, IL.

The little square hasn't changed much in the 25 years since filming there, and these days the town uses the provenance to market itself as a shopping destination. Today, the farmer's market was in full swing but I managed to find a cup of coffee and a park bench a few feet from the bandstand. Lots of people watching and a pleasant diversion before heading home.

Near downtown I came across this well-kept former gas station. I thought it would make an awesome little vintage bike shop...but then I think that about a lot of old gas stations. 

The carb set is ready for installation on Project 17, but in anticipation of syncing the carbs I'll want to attach the tool's adaptors and hoses. This is much easier with the carbs off the engine.

I use a Morgan Carbtune. After struggling with mercury and mercury-substitute devices I discovered the Carbtune and it's found a permanent home in my toolbox.

(Below) The adaptors are screwed into the intake manifold vacuum ports. Remove the screw in each manifold. On California-spec models and 1990+ models, two or more of the ports will have hose adaptors in place for the emissions hardware. Remove and replace with screw plugs if you're removing the emissions hardware, as I am on this California-spec 1986 VFR750.

The adaptors are lightly screwed in place; no need to compress the rubber seal beyond what's needed to make a seal. I then connect the hoses to the adaptors, which I've labeled #1 through #4, and plug the ends with golf tees.
Ready for carb installation.

Progress continues on Project 17. With valve clearances checked and cylinder compression verified, it's time to clean, inspect, assemble and install the carburetors.

I first completely disassemble the components, scrub the carb set in the sink with degreaser and hot water rinse, then give the small parts a dunk in the ultrasonic cleaner. All the passageways are given a blast with compressed air and verified clear. As a matter of course I replace the fuel tube o-rings and fuel lines (see the Maintenance page for a detailed tutorial). 

​(Right) ​This carb set was pretty grungy on the outside, but surprisingly clean inside. Someone had replaced the float bowl screws with generic allen screws which have since acquired a lovely rust patina.

(Right) In order to remove the pilot screw adjusters, the factory caps need to be removed. This is made easier by applying gentle heat from a small torch while gently pulling on the cap till it comes off. The caps are an emissions thing (to prevent owner adjustments) and don't need to be reinstalled unless desired. The screwdriver groove will have some grunge in it so clear that out with a small blade.​

​(Below) Turn out the screw, being very careful to avoid losing the spring, washer and o-ring inside — these little parts are NLA from Honda, though I have sourced replacements for the o-ring and metal washer. I use a small nail with a bent tip to dig for the washer and o-ring if they're left stuck inside the hole.

​(Right) This needle is stock OEM, which tells me that no jet kit was installed in this carb set.

(Below) After reassembly, the five California-spec vent tubes will need to be capped. I source rubber (not cheap plastic) caps from NAPA; four 3/16" and one 7/32". Install them using the original OEM spring clamps.
(click on an image to enlarge)

(Below) An additional aspect of California-spec bikes is the method of fuel tank venting. Instead of venting through the filler cap the CA bikes vent through a tube in the underside of the fuel tank. DON'T PLUG THIS VENT. Run an open hose downward in the front area of the frame and terminate somewhere that fuel vapors won't ignite on a hot engine part.
Ready for installation!

Spark plugs are simple-looking little devices, but in reality they're highly-engineered components lying at the heart of an engine's combustion process while living in an unimaginably harsh environment.

Fortunately for us home mechanics, they're simple to deal with. I'm re-installing the plugs in Project 17 in preparation for test running the engine, and my basic tools are a plug gapper and an old tube of anti-seize lubricant. I've had this tube for at least 20 years, so a little goes a long way.

The idea behind the plug gap is to afford the largest gap that your ignition can fire, thus giving the largest flame to ignite the combustion mixture. But with use, the spark plug gap will increase so it's best not to go with the widest gap at initial setting — give the plug a little extra to work with. The range on our plugs is .03-.04" so I set mine at .035".

A word about heat range. The specified NGK plug for the '86-87 VFR 700/750 is DPR9EA-9. The letters and numbers are fitment and resistance values, but the middle number, 9, is the heat range value. NGK numbers their plugs higher for "colder," lower for "hotter" (some manufacturers are the opposite). Hotter vs colder is simply the ability of the plug to dissipate heat. A hot running engine needs a cooler plug, and vice versa. Honda specifies either a number 8 or 9 for this model. Why would you choose one over the other? If you run consistently in an unusually cold environment you may want to choose the number 8 if your engine exhibits some carbon fouling or sooty deposits. This was much more of a concern in the old days of air-cooled motors, not so much anymore. What you don't want to do is run a hotter plug 'cause someone on the internet said it's "higher performance" or some such nonsense. Not true in any sense and too hot a plug can cause engine damage. To consider a plug heat range change for performance modifications is unlikely — it would require an increase of about 75 HP to warrant a cooler plug. So, a K&N air filter, slip-on mufflers and a jet kit DO NOT require a plug change. This is a case where the engineers at Honda are smarter than us.

After checking the gap, I smear a bit of anti-seize on the threads, being careful not to allow any near the tip which could cause a hot spot and pre-ignition. To make certain that I don't cross-thread the plug I use a short piece of rubber hose to thread the plug in place. Dealing with a cross-threaded plug hole in your cylinder head will have you rethinking your life decisions.

Final tighten with a socket wrench. If you don't have a feel for proper spark plug torque, use a torque wrench till you do. See the life decisions discussion above. A stripped plug hole from over-tightening or a popped plug from too loose a plug will also ruin your day.

I like to put a big dab of di-electric grease on the end of the plug wire. This lubricates the fitting making it a little easier to remove in the future and also forms a water and humidity seal.

Next up; carburetors.