I really have to stop throwing out internet bids on “interesting”
bikes and forgetting that I did it until I receive notice that I have
“won the auction”.
Those of you who have followed my ramblings over the past 10 years
(or more) might recall that I acquired a somewhat troublesome Benelli
Sei (750 six-cylinder) machine from a local seller who had had it
since the 1970s. That bike was fun to ride and sounded amazing…
when it would start. Even a $500 ignition system never insured that
the engine would fire up easily. That, along with the factory
defective transmission gearset (there was a recall that the bike
never received) led me to let it go to a local Italian bike dealer
who had the bike restored.
So, here we are again, with almost the same bike, but with fewer
cylinders this time. The Benelli Quattro 500 is the Honda CB500
engine clone in virtually the same chassis as the Sei. The big
departure is that instead of a double-disc Brembo front brake, it has
a double-sided drum brake system with 4 brake shoes upfront.
The bike caught my eye on some Internet link to a big auction in
Wisconsin in mid-Oct. It was open to internet bids a few weeks ahead
of the actual date, so I thought I would test the waters to see how
much interest there was in this rare machine. Benelli updated the
models with the double-disc brake wheel later on, but few of these
bikes were probably ever sold in the US in either form. I do recall
seeing one for sale locally a number of years ago and visiting the
seller’s place to see it in the flesh/metal. It, too, was a
drum-brake model, but it wasn’t running and I shied away from it
due to lack of parts and general knowledge of the series.
By the time I paid for this bike, plus a hefty 18% buyers fee and
rounded up a U-ship guy to haul it out for $450, the initial bid cost
had increased by 50% again. All that was shown in the auction page
was both sides of the green bike and a short sentence about the frame
number and perhaps the mileage on the odometer. The auction company
did provide a WI title a few weeks after the bike arrived, which is
helpful for getting a CA title for the bike, but you still have to
jump through the DMV/CHP hoops to finalize the paperwork.
The main source for replacement parts is a company in Germany, which
seemed to have gathered up all the remaining Benelli parts for all
the models they could find. They have microfiche illustrations
on-line and generally ship parts out quickly and at reasonable
prices, all things considered. I did inquire about the H-shaped
molded fuel hose connector in advance of receiving the bike and they
did not have a replacement part for that item. There are four
carburetors and two petcocks to connect all the plumbing together so
I will have to round up T-fittings to get it all fueling properly.
Arrival…
The bike arrived within 10 days from the auction, riding tail-gunner
on the back of a long, double-axle open trailer. At 20 feet, it
doesn’t look TOO bad, but as you got closer the condition issues
became more and more apparent. Fortunately, it did have some air in
the tires and the 4 shoe front brake did function to a point. The
friendly driver helped me push it up the driveway and into the
awaiting bike lift for future repairs and a deeper inspection of all
systems. It was one of those heart-stopping moments where you say to
yourself, “What did I get myself into now?”
The first look revealed that there were NO spark plugs in the engine,
no ignition switch key provided and the engine was LOCKED UP solid.
The first thing to do was to squirt WD40 penetrating oil down each
spark plug hole and hope that it would work some magic on the stuck
pistons.
The design of the battery box is such that you cannot remove the backside of the air filter box to service the filter. Removal of various
attached electrical components finally allowed the battery box
removal. At that point, the bolt holding the filter cover turned out
to be part of the inside of the housing, not accessible unless you
remove the carburetors and airbox. The carburetors are connected with
intake manifold rubbers which attach to intake manifolds which are
bolted onto the backside of the cylinder head. The air filter box
connects to the carburetors with short connectors, which unlike the
outside angled versions on a CB500 Honda, are all straight-back
designed parts. Pulling the connectors off the airbox and back off
the carburetors allowed for carburetor removal. One of the carburetor
tops was missing and the throttle cable had already been
disconnected. SOMEONE had been in there before, probably trying to
get it running sometime in the past 10-20 years.
On the plus side, the odometer only showed 1506 miles and the
original Pirelli branded tires were showing little wear, which seemed
to verify the miles shown on the speedometer. There was rust
everywhere on chromed parts, other than the fenders, which were
unaffected for some reason. There was surface rust inside the fuel
tank, of course, but the carburetors were clean inside the bowls. The
plastic meter box, which mounts to the upper fork bridge with a
couple of bolts was broken at both attachment points. It was déjÃ
vu all over again, as the basic architecture of the Quattro 500 is
nearly identical to the 6-cylinder Sei. The Sei had double disc
brakes up front, but both bikes shared the same rear hub and
suspension. The Sei has alloy rims, where the cheaper 500 was left
with chrome steel hoops, which were both rusted badly on this
machine.
The fork ears had been chromed, along with the front brake hub stays
from the factory. The brake stays were suffering from peeling chrome
and the fork ears were in similar condition. The chromed headlight
bucket was somewhat better, but the headlight rim chrome was badly
pitted. The 4into 4 mufflers were solid, but with surface rust and
pitting down in the creases. The header pipes were still in
remarkably good condition, however.
Once the carburetors were removed, work commenced on getting the top
end of the engine removed for damage assessment. Unlike Honda,
Benelli engineers used #1 Phillips head screws to retain the top
rocker arm cover. Fortunately, they mostly loosened with a few blows
of the impact driver with a matching driver tip. More challenges were
revealed when two of the Allen screws that hold the top cover end
caps wouldn’t come out, stripping the hex heads of the 5mm screws.
After trying various methods of removal, the heads were drilled off
so the caps could be taken off. The end caps cover the last two end
screws that hold the top cover to the cylinder head. The screws
thread into the ends of the rocker arm shafts and there was no
apparent reason for two to come off and two to be firmly entrenched
in their positions. It took about a half-hour of careful drilling the
screws out of the ends of the shafts, then rethreading the holes
successfully. The cover then came off easily revealing shiny metal
parts inside. The rocker arm pads were all like new and the camshaft
lobes appeared to be barely broken in.
The camshaft is secured to the camsprocket with two bolts, but
somehow the engine had stopped with both bolts lying right at
horizontal positions. It’s tight quarters in there, so although the
camshaft bolts could be accessed (remember the engine was frozen),
you can’t back them all the way out of the camshaft sprocket as the
heads hit the inside of the cylinder head opening. I tried to loosen
the camsprocket bolts with an open-ended wrench, but they didn’t
budge at all. I figured that the bolts had been installed with
Lock-tite thread locker, so the only option was to try to loosen them
with a large sharp chisel. The chisel was able to catch a corner of
the bolts at just the right angle, but it took considerable amount of
hammering to get them to begin to rotate loose from the camshaft bolt
holes.
Eventually, both bolts were loosened successfully, but couldn’t be
removed due to their proximity to the edges of the cylinder head. A
Dremel tool with a cut-off wheel was used to cut half of the bolt
head away just enough to allow the bolt to be removed from the
forward bolt hole. The rear one remained in place, however. Using a
long-handled adjustable wrench, I applied some torque on the
crankshaft bolt, hoping that the engine would give just a little bit.
Suddenly, the crankshaft turned about 10 degrees and the camshaft
bolt was then clear of the cylinder head for removal. With the
camchain free of the camshaft, the engine was turned back and forth a
few times, finally allowing for full rotation of the crankshaft and
full movement of the pistons.
The camchain tensioner bolts to the back of the head and cylinder
with 2 bolts, but unlike Honda’s design, the mechanism can’t be
locked in place for removal. When the bolts were removed, the
tensioner spring wanted to push up against the back of the camchain,
preventing removal of the camchain from the sprocket teeth. The
tensioner was pulled upwards, but hit the frame backbone tube before
it was clear of the cylinder head. Finally, it appeared that the
tensioner could be compressed with my fingers and the whole unit
rotated 90 degrees, which then allowed the top to be tipped over and
just clear of the frame tube.
Once the camchain was off the camsprocket, the camshaft was removed
and a wire attached to the camchain to prevent it from dropping too
far into the engine. The cylinder head is attached with a series of
flanged nuts and washers, some of which are sealed off by little
rubber plugs in the head. With all the nuts removed, the head pulled
up with a little nudging here and there. The valves had quite a bit
of soft carbon on them, but showed little signs of use. The
now-exposed piston crowns showed some signs of varnish, carbon and
moisture corrosion. The cylinder bores had some pitting around the
edges of where the pistons were sitting for so many years. The
corrosion had eaten into the bores just enough to catch a fingernail
on the edges, so the choice was to pull the cylinders for a re-bore.
A set of .50 aftermarket Honda CB500 pistons/rings were ordered up
from Japan for $125 and the cylinders will go off to my favorite
machine shop for $160 of machine work. Lots of scraping was involved
to get the leftover gasket material off the engine cases, all the
while trying to keep the loose bits from entering the open bores in
the crankcase. The pistons all came off of the pins with little fuss,
so there is no concern about damaged pin bores in the rods.
Progressing slowly…
The a/m pistons came in from Japan in about a week. My machinist
bored the cylinders and noted that one piston was a bit smaller than
the other three, so bored the holes accordingly. After some
wire-brushing to clean off excess corrosion, the cylinders got a bit
of color added back. Benelli actually painted the cylinder blocks
gold and the heads black from the factory! After an hour of careful
prepping and assembly, the cylinders glided onto the pistons and the
assembly awaited the completion of the cylinder head.
The cylinder head was disassembled and de-carboned. All the valve
faces and seats looked great, but valve stem seals were hardened, so
were replaced with gasket kit parts. In the process of reassembly one
of the valve stem keepers dematerialized and could not be recovered
despite an extensive search of the immediate area. I discovered that
the valves were 5.5mm stems like the Honda valve stem sizes, but
Honda keepers didn’t fit, so replacements have to come from
Germany.
I was ordering parts from Benelli-Bauer anyway, as they are one of
the last couple of resources for NOS Benelli parts. They can supply
replacement instrument cases and most everything else that I have
asked for so far.
In the meantime, I decided to go the poor man's route and have the
rims powder-coated satin black, along with the formerly-chromed fork
ears. Some new tires were ordered and after all the spokes were
cleaned up, the finished rims were re-spoked back to the de-rusted
hubs. There was extensive amounts of rust inside the drums, however, it did clean off with extensive use of wire wheels and abrasives. The
brake shoes were glazed and had a thin film of corrosion embedded
into the faces. A little light sanding brought back the original
surfaces.
Rather than purchase all the Benelli gasket parts, one-by-one, I
just ordered up a whole CB500 Four gasket kit and installed all of
those parts without issue. Apart from the slightly-angled forward
cylinders, much of the top end components are exact dimensions of
Honda’s OEM CB500 designs.
The parts order from Germany took almost 2 weeks to arrive, so to
speed up the assembly process an OEM Honda exhaust valve was ordered
to match the keepers that were already purchased, but didn’t fit
the groove pattern on the Benelli valve stem. Problem solved and the
cylinder head was bolted down, torqued to specs. Two new camsprocket
bolts were ordered to replace the butchered ones and the rest of the
original parts reinstalled.
My experience with the Benelli Sei mirrored the current one of the
Quattro. The intake manifold rubbers were broken/cracked causing
obvious air leaks. On the Sei, I ordered up OEM Honda manifolds and
installed a set on the Sei, which did not have the original airbox
in place. The manifolds were a little longer than the originals, but
it didn’t matter because of the pod filter installation. The
Quattro carb/manifold/airbox combo is a REALLY tight fit; even worse
than a standard CB500-550 setup.
Sadly, after the long wait for the box of parts from Germany, it
became obvious that the intake manifolds shipped were of two
types/lengths. Three might have been actual Sei units and one an
actual Quattro replacement part. A message back to Germany,
accompanied with photos, confirmed the mistake and a promise to ship
the correct parts came back quickly.
Eyeballing the manifold situation, it seemed that the “wrong ones”
could be used in the interim but because they were of a thicker
material the original manifold clamps wouldn’t reach around to fit
the increased diameter. Also, the process of wedging the carburetor
rack in between the bolt-on manifold stubs on the head it became
apparent that there was left no room for the carburetor rack to fit
between the two components. I would imagine that the “correct”
way to remove/replace the carburetors is to loosen the engine mounts
and tilt it forward, which is required on a CBX Honda Six.
To override that necessity, I removed the manifold stub bolts and
replaced them with bolts, so I could slide the whole assembly in
laterally and fit the carb inlets to the new air cleaner box
connectors. I could only use 2 of the original rubber manifold clamps
on the one correct manifold that was supplied, so the other three
were clamped with 2” hose clamps that I had on hand. The two rubber
manifold types have different ribbed patterns, but they were close
enough to allow a tight fit once paired with new clamps.
Another couple of hours were spent doing R&R on the meter box
installation, which was a snug fit for all the components. All the
wiring connections to the instrument warning lights needed to be
disconnected so the harness could be pulled through the small slit on
the bottom of the meter box housing. The wiring diagrams found online
were all in German or Italian and of very faint and small drawings.
That had to be reworked on the computer and printed out to help with
the wiring installation. The recommended replacement Yuasa battery
had side posts instead of top posts, so some angled adapters were
fabricated. Fortunately, apart from some blown-out bulbs and some
that had melted the plastic upper meter housing plate, the electrics
mostly came to life without blowing any fuses. The fuse block is
typically mid-20th Century design with little bullet-ended
ceramic fuses and flimsy fuse holder tabs. Corrosion had built up on
the ends, so everything needed cleaning to promote good electrical
connectivity.
The ignition points were corroded, so required more cleaning and
adjustment. I hesitantly tried the starter button and the engine
began to spin over, somewhat slowly, but the result was encouraging.
The fuel tank was cleaned and sealed with 2 part Caswell epoxy
coatings. New generic Italian-style petcocks were located and
installed to complete the fuel tank repairs. Some ¼” T fittings
were purchased at the auto parts store and little pieces of 5.5 OEM
Honda fuel line were cut up and fitted to tie the fuel system
components together.
Initially, the engine spun over, but wouldn’t fire up, even with the
choke fully applied. There is a lot of friction with new
pistons/rings and a lack of ring sealing in the beginning which
caused some difficulties in getting the engine spun over fast enough
to get everything synced up, but with a jumper system in place, the
long-dormant engine finally fired up on all cylinders, sounding quite
like a copy of a Honda CB500 Four with 4 into 4 exhaust pipes. The
carbs were fussy, at first. The idle speed was erratic, either too
low or too high, probably owing to a sticking spark advancer unit.
The engine does start and run, but not idle well. The charging system
light stayed ON, so the left generator cover was removed for
inspection. The Bosch charging system uses a set of brushes to
contact the slip rings on the end of the rotor shaft, not unlike an
automotive alternator. While the components all appeared to be in
good condition and electrical wiring checked okay, the whole outer
brush/stator assembly was basically just floating on the end of the
rotor shaft because the four 5mm mounting bolts were MISSING! Long
5x45mm bolts are not easily found locally, so a quick look online
gave some clues about where to find them. I called local
hardware/bolt stores and discovered that there were some in stock…
45 of them in a box! I only needed 3, but the whole box was only $6
and change, so I bought the box and have more than 40 to share with
anyone out there who might need such a fastener.
The bike continued to be hard starting, didn’t want to idle and one
carburetor began to overflow due to a failed plastic float assembly.
Carb kits were ordered and the wait continues for replacement intake
manifold rubber connectors. All the spares will go with the bike,
which has been put up for sale now.
As has happened several times in the past, I am facing surgery
again, this time for a worn-out ankle. The recovery requires 3 months
of non-weight bearing on the right foot, so getting this project
wrapped up and ready for sale has become a race against time.
A quick trip to the CHP office for verification and then back to DMV
to push through the completed paperwork was successful, so the bike
can be officially titled in the state of California. Having a titled
bike helps the sales process immensely so I always do the legwork to
get the paperwork in order for the next owner.
I have to promise myself NOT to repeat this process again,
especially with another rare Italian Honda copy model, such as the
Quattro 500. In an eerie coincidence, during the Quattro project, I
was contacted by a man who I met at the January 2018 Mods and Rockers
ride event. He had bought a storage unit full of bikes, including a
silver 1976 Benelli Sei! He wasn’t going to sell it right away
(although there is always a price that works in the end), but needed
someone’s help to get his running properly. I offered to help, but
warned him of my upcoming surgery and lack of ability to do
motorcycle work for at least three months afterwards. Unfortunately,
the sands of time have about run out on that offer…
Bill Silver aka “MrItalianHonda” for the end of 2018.
