Honda CX500 - "fantastinen" Finnbox FBG47 CDI ignition

Problem Statement:

Honda doesn't produce the CDI ignition module for the early CX500 motorcycles.  The capacitors and semiconductors are now over 30 years old and probably not performing as they did when they were new.

These are the symptoms my CX500 was beginning to experience:

• Hard Starting
• Misfire while on choke
• "Flat" spots in the rev range
• Hesitation from idle
• Misfire while accelerating hard
• Total loss of power in the rain

As a benchmark, the bike was getting around 48mpg with backroad and commuting to work type of driving.

Naturally the carburetors were eliminated as a culprit.  They have been cleaned, rebuilt, balanced, and tweaked repeatedly.  The spark coils were replaced with new modern ones from an ATV.  The spark plugs were changed to a resistor type plug and the resistors were eliminated from the caps.  These upgrades only provided marginal improvement.  The bike no longer ran on one cylinder at start, but still had all the other problems.

I also checked the stator and source coil winding to make sure they were healthy.  

I had the whole engine out over the winter, so checking the resistance readings was easy.  The insulation was good, so I had no doubts that the G47 stator was in good health.

I started reading about the ignition module and found this post on the CX/GL500 forum.  This seemed like the appropriate solution.

(There was also a Ignitech option, which was computer programmable, and cost several hundred dollars.  This wasn't something that I was interested in.)

The Solution:

I contacted "Andy62" from the forum and he replied swiftly confirming that he could happily make a Finnbox FBG47 for me.  Like any good engineer he had decided to make what he could not purchase.  The result is a re-engineered version of the CDI ignition module similar to the original, but unique with modern components.  A few short weeks later it showed up in the mail from Finland.  The exchange of emails between Aki and myself was pleasant and I'm very grateful for his dedication and stewardship to support the Honda CX500.

... and was promptly installed

It is a well engineered product, for something that wasn't supposed to be a commercial venture.  As enthusiasts we are indebted to people like this that use their talents to support old equipment.  The board is professionally created, and the components are thoughtfully arranged and packaged.  The whole module is enclosed in a tough water-tight enclosure, with the leads coming out sealed nicely.

Hook up was easy, and he even supplied a set of mating barrel connectors for the flying leads.

From top to bottom:

White = Right Coil

Yellow = Left Coil

Blue = Kill Switch

The source wire pairs were White and White / Blue.

If you put a thin screwdriver down alongside the original twin connector you can push the original spades out and re-use the housing with the new connectors.

The ground was obvious, and went under the original hold-down screw on the left side of the bike. 

(The mounting screw on the right side of the bike was eliminated so that the new Finnbox would sit properly.)

The stator connector was also obvious, and fit directly into the original place, and secured with hook-loop "Velcro" to the inner fender.

The whole Finnbox enclosure was secured to the bike frame with "Velcro" and also zip-tied securely in place.  (Belt and Suspenders) Wires were just the right length to be routed to the original locations, and tied securely in place.

(Ignore that little cube relay, that's for my tail-lamp flasher module.)

Results:

The bike fired up easily after the final termination.  I couldn't wait to test it so I went out right away.

The initial results were very noticeable.  The bike ran evenly on both cylinders while warming up.  There was no misfire present at all.  The requirement for choke was perhaps even shortened as I rode off up the road.  The acceleration at around 4500 rpm went straight through past 5000 rpm with no flat spot or hesitation.  These are all very good results and brought a wide grin to my face.

• Improved - Less misfires when cold
• Solved - No flat spot on acceleration from idle
• Solved - No flat spot or misfire at mid-range engine speed.
• Solved - Pulls like a mule when accelerating hard.... (now I notice the clutch slips a little)
• I haven't been in the rain yet, but I'm fairly sure that was due to weak spark, and should be fine now.

The 300 mile trip I took over this past weekend yielded a respectable 60 miles to the gallon with mostly highway riding.  I don't think I ever could do better than 55 mpg before, and I was keeping up with traffic and the rest of the motorcycle group who all had >900cc bikes.

Long term results of fuel economy are improved, but negligible.  The around-town fuel economy remains about the same in the mid 50's mpg.

Overall a successful and simple upgrade for the average rider, with all the really hard work done by friend and benefactor in Finland Mr. Aki "Andy62" Lötjönen.

Sunbeam S7 Deluxe - swag

I try to snap up any Sunbeam cycle swag whenever I see it.  Paper products are ok, but the condition is usually poor.  Items like this are much more durable and can be enjoyed daily.  The previous owner was kind enough to include the Pioneer Run pennant with the purchase of KYL95.  I keep that hanging in my pool hall.  I picked up the pocket watch a year or so ago on eBay.  (The crystal was missing, so I got it cheap.  Replacement was a snap for an old instrument repair tech like me.)  For a promotional item its hard to beat for uniqueness.

The t-shirt was one of my own creations via an online printing company.  Representing your brand is essential at any bike meet.

The latest addition is the pin.  Its relatively small, and the color is slightly off, but the detail is nice.

If its not Norton, BSA, or Triumph its not something we see on this side-of-the-pond.

IMP - exhaust in the cabin - fuel delivery

The major complaint from my wife is that the cabin of her car tends to smell of exhaust fumes, and makes her sleepy.  While this is a good thing to keep her from shopping excessively, it cannot be healthy for the long term.

Things we have tried include:

• Plugging all passages in the rear quarter panels above the wheel wells
• Insuring that the rear hatch seal is sealing correctly
• Taping over the vents above the rear hatch

None of these have completely cured the problem.  Putting duct tape the vents actually made it worse, even though I don't know how that would be possible.

The suggestion was made from some club members to extend the exhaust out beyond the body of the car.  This seems to make sense, but will have to be tested.  The limitation is that this car has to be able to climb up on our car trailer.  I already scrape the tailpipe as it is, so it can't get any longer.  It will have to go out the side.

I cut off the tailpipe and welded a piece of 1" EMT elbow to the stub after expanding it.  We will do some testing on this setup to insure success and the health of my bride.

The car has been known to cut out for no reason.  Even on a cold day.  I was thinking that there must be an obstruction in the fuel tank.  That turned out to be an incorrect assumption.  The tank is flawlessly clean.  I did however discover some tar-like substance running down under the fuel tank.  That was easily cleaned by using some parts washer solution and a little elbow grease.

before

after

I may investigate placing the fuel pump in the front of the car like I have on my '66.  This helps fuel delivery tremendously.... however the ticking noise of the pump can be heard from the driver's seat.

The luckiest break that I got was the clutch slave cylinder.  I was worried that the clutch had a worn friction disc, due to the juddering and grabbing that the clutch exhibited the last time the car was driven 2 years ago.  The slave cylinder was found to require a rebuild and a new hose.  Now it works fine.  We won't be pulling the engine this winter!

"Project Bantam" - First Ride

Its been a long year.  Patience and skills have been tested along the way.  Gumption levels both plummeted and rose to new heights in the past few weeks.  Quality was balanced between practicality and schedule.  Stewardship overall was the name of the overhaul.  My hope was to have the Bantam 5000 available for my son to enjoy the same way I enjoyed it, and will continue to enjoy it.

The last new part to be installed was a new plug.  The original was the culprit responsible for hard starting.  A quick trip to the hardware store provided sweet and immediate rectification.

The float bowl still leaks, I'm told this is an inherent issue.  I haven't given up trying to make it correct just yet.  The fuel shutoff is a necessity.

Here we have a slideshow of the entire process as it arrived to our workshop, and finally completed to a level where it moves under its own power.  Sit back and relax, it takes a while to go through all 50 photos.

And finally the triumphant First Drive together.

There will be more reports on further detail work and fiddling...

"Project Bantam" - Fan Shroud

The Briggs and Stratton 14-FB fan shroud was completely rotted through on the bottom.  Even back in the 1980's it had a patch pop-riveted to the bottom.  This repair stretched my bodywork skills (or lack thereof).

The electrolytic de-rusting process got the part down to what was left of the base metal.  It was pretty ugly.

The patch was made of comparable gauge material with the worse of the rusted sheet metal cut away.  The back plate was used to hold the correct diameter and curve of the fan shroud.  I kept it bolted in place while the patch was tacked into place using oxy-acetylene and a brazing rod.  The brazing rod wicked pleasantly into the new patch material and surprising well onto the original part.

Here's the finished part after all the brazing was completed.   Brazing was certainly a much easier option than straight welding, but still it resulted in some distortion of the sheet metal.  I ground off the excess material and hammered any distorted surfaces flat.  The Bondo stage and glazing putty is always the hardest for me.  The Bondo sets up too fast, so I have to work in small batches.  When it is sanded it always sticks to the sand paper.  The glazing putty is easier to work with since it dries harder, but only covers small areas at a time.  Altogether its not too bad considering what I had to start with.  Its by no means perfect, but I did it myself, which is what counts for me.  Its only the bottom, which is obscured when the engine is installed in the tractor anyway.  You can't see straight into the shroud for this reason as well, so imperfections will be difficult to see.

The current plan for the exhaust and muffler is to use the original.  It went through the de-rusting electrolyte tank and actually came out without any holes in it.  The EMT conduit fitting is still serviceable into the exhaust manifold elbow, so instead of risking cracking the block, I'll just keep it.  I can always make a new exhaust later if I want.  I have no idea what the stock Bantam exhaust was like.  My father fashioned the current muffler from a spent propane torch tank.  It slings neatly under the floor board and attaches to the bolt holding the transmission in place.  The nice thing about this exhaust arrangement is that it keeps the heat away from the driver.

"Project Bantam" - Engine fires off

I stayed up a little later than usual to try to get some more work done on the 14FB engine. The axial float was easily obtained by making a slightly thicker gasket. The backing plate for the fan shroud hadn't been painted, so I did that before going to bed.

The rest of the tinwork went on easily and looks sharp.

The head was torqued down and carb mounted. All that was left was to set the ignition timing and points. The Magnematic is so simple to set. Gap the points, use a test lamp to watch for the points just opening. Then set the coil to point at the arrow on number 14.

I bolted the engine to a plank for stability. Shooting some ether, and pulling the cord yielded a satisfying BANG! I'm grinning.

The fan shroud still needs some structural repair.... The next task.

"Project Bantam" - Arts and Crafts

I've finally amassed all the parts required for the Briggs&Stratton 14FB engine overhaul.  The main bearings look good, and the piston ring gaps are within spec using new standard size rings.  One of the exhaust valve keepers was rattling around in the tappet chamber when I opened the tappet cover last month.  The exhaust valve seat was rather rusted and required significant lapping to get down to good metal.  A quick grind on the valve stems put it back within gap specification.

exhaust = 0.015"

intake = 0.008"

The gudgeon pin is still tight and the piston looks good as well.  It can be put back in with the new standard size rings.

I went with a two-tone paint job on the block.  The fins were rather rusted, so I wanted to make sure they got painted and stayed painted.  So they got a 1200'F rated exhaust paint in silver.  The crankcase got a 500'F rated engine paint in black.  The exhaust elbow was rusted fast, but the threaded adapter to the exhaust pipe still had good threads, so that's staying.  I just need to obtain a new mating nut and olive for the exhaust.  It looks like an electrical fitting.

I had my son help with the arts and crafts.  Making measurements and cutting gaskets is a tedious task, but still enjoyable.  I started with some relatively thick gasket material for the tappet cover, point cover, and oil pan.  The bearing housings require some adjustment based on axial float of the crankshaft.  I made them out of thin material as templates.  I can go back and duplicate these easily when I get the crank set in, if the float needs increased to meet spec in the manual.

On closer inspection there are marks on the inside of the timing gears.  It looks like someone has had this engine apart before, since the cam gear has a awl scratch on it pointing to the correct place between the timing teeth.  The manual says to set the timing based on the outside of the gears, which is presently obstructed by the main bearing.  Timing will have to be set by the inside viewing through the bottom of the crankcase.