1979
Honda CM185T Twinstar
Go to online Shop Service Manual Page
History of my Twinstar Including
some Fixing and Maintenance Tips.
This bike is a 180cc street
bike. 2
cylinder. 4 speed. 6 volt system.
(185cc is inferred by the model
number but
the engine block says 180cc. BUT then the spec sheet in the service
manual
page 1-2 states 181cc)
I got my Twinstar in 2000.
The story is that the bike was bought
new by one of my coworkers. He got married soon after he bought it
and his wife wouldn't let him ride.... Sat in a garage for many
years.
Coworker 1 gave it to
coworker 2 in
perfect running condition with only about 1000 miles on the odometer.
coworker 2 and his buddies messed around with it broke things and
lost things. The bike was being stored at a 3rd coworkers house
where I first saw it. Coworker 3 told me I could have it. Said all
it needed was a carburetor. So I loaded it up in my truck and took it
home. Lucky for me I found the title on the bike in the pocket
behind the side cover. The title was still in coworker #1's name. I
checked with him then got the title transferred to my name.
I got it home one of the
things that
coworker 2 lost was the carburetor. I bought 2 carburetors from 2
different bike salvage shops via Internet. I bought some internal
parts from a Honda dealer and still had to fabricate one part. I am
missing the needle cap plate shown on page
4-4 of service manual. Out
of all that I was able to get enough parts to get 1 carburetor
working.
Now for the broken parts.
After a lot
of tinkering around I found that I wasn't getting any compression so
I tore down the cylinder head and found all 4 valves leaking. How
those guys blew out the valves in a few hundred miles I'll never
know. I took just he cylinder head in and
had the valves redone at the Honda dealer for about $400.00 (about
the blue book value of the bike at that time).
I was able to get
a new gasket set
from a Honda dealer. I followed a tip from the Honda
mechanic - There is enough room to lift up the cylinder block some and
disconnect the
piston rods without removing the pistons from the
cylinders. This saved a lot of work
messing
with rings and stuff as all I wanted to do is put in a new lower head
gasket.
I was also lucky to receive
the Honda
shop manual along with the bike published Dec 1977, I have scanned
that entire manual for you to download
if you wish.
Now it is running well with
only 3000
original miles on the odometer.
This is a my first bike and
it has been
a great bike for learning. I did take MSF course a couple of years ago.
The bike is barely freeway
legal. I
think 150cc in the min. in my state. I can get it up to 60-65mph or
so on flat terrain, but that is pushing it. Not really enough power
for freeway use.
Riding at night is a bit
scary for me.
I have the newer 35/36.5 watt headlight but it is a bit dim for me. I
am
thinking of adding some driving lights if I can find something in 6V
and not too much power draw.
Misc. Repairs
Other items that I have
replaced.
Ignition switch. New from Honda dealer. Now I have to have 2 keys One
for ignition and the original key for tank, fork and helmet lock. The
old
ignition switch was kinda flaky.
New internal (petcock) tank
filter screen and tube.
Turn signal bezel (One day
I parked the
bike behind the car my wife wanted to drive, Somehow she tipped the
bike over while trying to move it herself). Lucky a local motorcycle
shop still sells these. They were used on several other bikes.
I had to fix the brake
light switch in
the handlebars. Was able to re solder internal parts and get it
working.
Battery/Charging System:
I am on my second battery.
I bought a
battery at a Honda dealer, he sold me a 6N12A-2C, but it was supposed
to have a 6N12A-2D.
I didn't find this out until I went to buy my second battery. The
only difference in these 2 batteries is the location of the drain
tube. The correct one (-2D) has the drain on the back side. The -2C
has the drain on the front (Terminal) side. Didn't make much
difference, you
just have to route the drain tube differently, but no big deal. So the
6N12A-2C can be substituted for the -2D version.
The charging system on this
bike is
somewhat primitive. There is no electronic regulator so it relies on
the battery and headlight etc to regulate. The battery MUST
be
in good shape in order for the charging system to operate properly.
Even with everything operating as it should the bike just doesn't
charge well unless the engine is going over a certain
RPM. So if you are
just puttering around the neighborhood, the battery will not get
charged much. I find that I need to put the battery on an external
charger once or twice a month to keep a good charge.
Not sure if this is
folklore but a
lot of people say to charge the battery off the bike or disconnected
from the bikes electrical system. On this bike the rectifier block is
directly connected to the
battery even with the ignition switch off. Also the stator windings
are indirectly connected via the 2 reverse diodes in the rectifier
block. See wiring diagram.
So as a precaution, instead of disconnecting the battery, I
just disconnect the silicon rectifier (diode) block connector before
charging. This is
much easer than disconnecting the battery terminal(s). The silicon rectifier
block is easy to get to behind the left side cover. Note that
I have
charged the battery without disconnecting anything and have not had
any problems, but if the diode(s) were to fail it could toast the
stators in the alternator.
Lucky the bike has a kick
starter. BUT
I have found that if the battery is severally discharged then I can't
get it started with the kicker. A dead battery acts too much like a
dead short I'm guessing. If I charge with an external charger
for a few minutes then I can get it going with a kick or push start.
Fork Seal Replacement:
Finally got around to getting new tires put on (Nov. 2005). My bike had the
original factory tires with a 1978 date code! At the same time I am
doing the fork seals. One of the forks has been leaking for quite some
time.
I raised the bike up using a floor jack to jack the rear up enough to
put a jack stand under each side. Locate them under the muffler pipe
where the frame weld is. I then put a bottle type jack under the down
tube to lift the front wheel off the ground. I found it necessary to
use the jackstands because I was removing the rear wheel and needed the
clearance to work the chain off of the sprocket etc. If you are
not removing the rear wheel then you can just uses blocks of wood under
the frame 4x4's and/or 2x4's will work.
Supplies and Tools:
New Fork Seals: Brand I got is: K&L Part number: 15-1428, Size: 31x43x10mm. I purchased these fork seals $7.99 from a local motorcycle shop.
Fork Oil: The
service manual says to use regular ATF fluid. I bought a 16oz of 10wt
Fork Oil on recommendation of the shop sales guy. You will need 4.2 Oz
(125cc) for each fork
Liquid Measuring Device. I
bought a syringe type device from an auto parts store. It was sold as a
device to measure 2 cycle oil in different ratios but also has
graduations for CC and OZ.
Thread Lock Compound. I got 'Locktite Blue' at an auto parts store.
Large 6mm Allen Wrench. If
you use a socket mounted 6mm hex bit then the 6mm hex driver part
needs to be > 3" long. The ones I saw were shorter than that and
would not work.
Fork Seal Driver: I
improvised and used a 1" PVC pipe fitting. The fitting I found in my
junk box was a slip on one side and female pipe thread on the other but
I think any 1" slip union should work. Find them in
plumbing/sprinkler pipe section of your favorite hardware store. Note
that different brands may have a different OD or ribbing that may or
may not work for you. Sand the edge smooth if it has ribs, raised lettering, or molding imperfections.
Bench Vise. Soft jaw or use padding of some sort.
Misc Tools: Wrenches 10mm x2, 12mm, 17mm. Large screw flat blade driver, Mallet or hammer etc.
Gun Cleaning Rod: I used a shotgun cleaning kit to clean the old oil from the insides of the tubes.
Heat Gun: For heating the area metal around the seals to make it easier to pop the old seals out.
Cleaning Solvent : I used spray can brake cleaner
Steps for fork seal replacement:
I pretty much followed the instructions in the shop service manual (Chapter 11) with a couple of hints below:
Remove front wheel as detailed in manual page 11-8
Remove front fender as detailed in manual page 11-14.
Note: Loosen the fork top cap (17mm nut) while the fork tube is still
on
the frame. Just loosen about a 1/4 turn. This will save
having to put the upper tube in a vise to loosen the top nuts later on.
Loosen the top hold bolt with two 10mm wrenches. Page 11-14
Hold onto the tube with one hand and loosen the 12mm hold down screw behind the side reflector. Page 11-14
Slide the fork assembly down and out. Page 11-14
Follow rebuild as stated in manual. Pages 11-14 to 11-20.
Hints on removing the 6mm bolt from the bottom of the fork housing
(11-16). The
threads are sealed with Locktite and could be very difficult to break
loose. Also the piston rod that the 6mm bolt is attached to can spin
inside the housing. I was able to break mine loose with just the
Allen wrench and a piece of small diameter pipe to give leverage.
The short end of my Allen wrench was not long enough to reach the bolt
so I had to use the long end with a piece of pipe on 90 deg. short
end. Other ideas that may work if you have trouble: Use a Dremel
tool to cut a 3" piece off of the Allen wrench and then chuck that into
a hammer drill or impact wrench.
Hint on snap ring removal. The manual (11-17) says to use special snap
ring pliers. I just used a screwdriver. It was pretty easy to remove.
Install with fingers.
Hints on removing the old seals. Use a heat gun to warm the metal area near the old seals.
Hints on driving the new seals. As stated above I used a 1" PVC union
fitting. It is not an exact fit, something slightly larger in
diameter would be better, but it is good enough to get the job done.
Just be sure to drive slowly and evenly. Tap a couple of times then
look..tap look... If it starts to go unevenly then tap on the
high side etc...
Tune-up Hints
Tune-up consists of 3 main procedures.
1. Valve adjustment (3-4)
2. Point gap check/ adjustment (3-5)
3. Ignition timing (3-5)
The valve and point gap are done as stated in manual but the timing instructions needs some help.
Engine Timing Steps
(Note: Point gap must be correct before the engine timing can be done. See page 3-4)
Tools required:
Screwdriver
Battery - 6V lantern battery or old 6V motorcycle battery etc *
Light bulb 6V - A
bulb with pigtails (wires) would be ideal. (Radio Shack has these, Catalog # 272-1140) OR use an automotive test light found at an auto parts store. (Has light
bulb inside a screwdriver like handle with has a pointy probe on one
end and a ground wire with clamp on the other end and works at 6V
or 12V).
Jumper wires with 'alligator'
clips on ends. 2 or 3 needed. (Radio Shack Catalog # 278-1156)
* Other batteries/ light combinations can be used. Just don't use anything over 6 Volts. I have used a partially discharged 9V battery.
Batteries with some kind of terminals are the easiest to work with as you can clip the jumper wires to the terminals.
1. The battery must be charged and the coil, condenser, and the rest of electrical system must be in working order.
2. Remove metal ignition cover on left side of bike.
3. Turn ignition switch to the ON position and the engine kill switch to RUN. (This step was not mentioned in the manual but is very important)
4. Clip one end of a jumper on the timing plate (ground) and the other end to the (-) terminal of your test rig battery.
5. Using appropriate clip lead jumper(s), attach one side of the light bulb to the (+) terminal of the test rig battery.
6. Attach the other end of the light bulb to the (+) side of the
breaker point. (This is the side which has the terminal/black wire
attached to it. Do not remove the black wire from the terminal).
7. Rotate the engine by turning the crankshaft bolt Counter Clockwise with a 17mm wrench. (Be sure tranny is in NEUTRAL before turning)
Note: With this setup the test
light will be ON when the points are CLOSED and will go OFF when the
points are OPEN. See Timing CAM operation below.
8. As you are turning the crankshaft , the test light
should be on and then go off when the F1 mark is aligned with the
timing mark.
9. If adjustment is needed then loosen the screws on the base
plate and rotate one way or the other as described on page 3-5. Tighten everything back down and retest.
Alternate Timing Method (No external battery required)
Tools:
6V light bulb with wire leads. (I used an automotive 6V-12V test light).
Jumper wires with alligator clips. 1 or 2 needed.
1. Do 1-3 above. (Ignition switch to the ON position and the engine kill switch to RUN)
2. Clip one side of the light bulb to the timing plate (ground).
3. Clip the other end of the light bulb to the (+) breaker point terminal. (This is the side which has the terminal/black wire
attached to it. Do not remove the black wire from the terminal).
4. Rotate the engine crankshaft bolt C CW. (Be sure tranny is in NEUTRAL before turning)
Note: The test light illumination will be opposite of the above. The light will be OFF when the points are CLOSED. The light will go ON when the points are OPEN.
5. As the crankshaft is turned the test light should be off and then go on when the F1 mark is aligned with the timing mark.
6. If adjustment is needed then loosen the screws on the base
plate and rotate one way or the other as described on page 3-5. Tighten everything back down and retest.
Timing CAM Operation
The points will open up
when F1 reaches the timing mark and close back down when F2 is at
the timing mark. When F1 ( cylinder 1) is set correctly, then
F2 (cylinder 2) will also be correct. If F1 in not correct then F2 will
be off by the same amount. So we only need to look at and
adjust for F1.
F1-------------F2--------------F1-------------F2.....etc
| Points Open | Points Closed | Points Open |......etc
|<------ One Revolution ------>|
With
this setup both plugs fire at the same time. One cylinder will fire in
the compression stroke while at the same time the other cylinder will
fire in the exhaust stroke.
This is how the one set of points control both plugs without having to
have a distributor of some sort.
Things
that still need to be done:
- Gas tank is rusty on inside. I cleaned it out best I could
and then installed an external automotive glass tube fuel filter. I
have to clean out the filter from time to time. Reserve does not work
reliably because of sediment in tank. My carburetor float gets stuck
once in a while.
- Want to clean the oil filter screen but most of the cover
hold down screws are seized.
- Missing one of the orange reflectors on fork.
Kevin
Ricks -
Last updated 12/05
klricks@prodigy.net
