Building the

Building the:
Installing the
popular Lifan 200cc
engine in a 1971
Honda SL-100
Gerry Langwell
July 2009
Acknowledgements
Special thanks to all who helped and supported this
project.
 My wife, Vicki for her patience and understanding while trying
to finish this project.
 David Moore for donating the project Honda.
 My brother Brian at Unique Services for helping modify the
exhaust. And my brother Jim at Gumby’s Cycle Werx for his
technical guidance when I would find myself up against a wall.
 And finally, Larry Hooper and Daniel from Hooper Imports
for engaging in lengthy discussions with me while trying to
troubleshoot the wiring.
2
Some Things You Will Need

A 200cc Lifan engine. You can get these from places like eBay, but Hooper
Imports will include everything you need for this conversion. Their
engines come with carburetor, starter relay, coil, rectifier, and CDI unit.
Also, you will not find better customer service anywhere.

Some 18 gauge wire. I used red and green.

Sheet metal for fabricating brackets.

A 12 volt battery. I used the XL4L-B from Batteries Plus

A pod type air filter

A starter button (I used the lower switch housing from a Honda CB-350)

A choke cable and lever ($5 on eBay from a Honda CM-185)

A section of 1.25” ID pipe to modify the exhaust pipe.

A 10 watt 3.61 ohm resistor or 12 volt light bulbs.
3
The donor bike… A 1971 Honda SL-100.
This bike was given to
me by my good friend,
David Moore who rode
this bike while he was in
college back in the early
eighties. The last time it
was running was 1984.
After a little carburetor
work and a battery, it
started right up.
Unfortunately, the
transmission wouldn’t
shift. Since I was
restoring the bike for my
wife, we elected to install
a Lifan 200 engine with
electric start.
4
A couple of shots of the SL frame cleaned up, painted,
and ready to accept the new engine.
5
Fresh out of
the box and
ready to
install!
The new 200cc Lifan engine from
Hooper Imports
6
Left and right shots of the newly stabbed motor. All of
the lower mount bolts lined right up – no drilling/cutting
required. I could be wrong, but I think this engine
actually went in easier than the Honda engine came out!
7
Uh oh! This won’t
work. I’ll have to
make a bracket for
this. Maybe I’ll try
running it for awhile
without it and see if
it really needs one.
Top engine mount
8
The choke linkage just barely clears
the frame. Connect your choke cable
and fuel line before mounting the
carburetor, or you will have to take it
back off like I did.
The new carburetor is larger than the
original so you will have to either
modify the boot or use a pod style
filter. I went with a Uni.
Carburetor issues
9
With the head pipe seated and bolted
tightly in place, the muffler mount
doesn’t line up.
Mainly, because it hits the oil level
indicator bubble on the right case,
which the original Honda engine did
not have.
Exhaust pipe alignment issues
10
How I fixed the exhaust pipe clearance problem.
First I cut out a section of the pipe
and bolted the two pieces in place.
Then I cut a piece of curved 1¼” ID
exhaust pipe to “slip fit” over the
existing pipe, tacked it in place, then
removed the exhaust as a whole and
welded it up.
11
Oops! The stock
Honda clutch cable
housing is too long.
You’ll either need to
shorten the housing
by about an inch, as
I did, or order a
replacement Lifan
200 clutch cable.
Honda clutch cable doesn’t fit.
12
Miscellaneous brackets
I fabricated these out
of .040” aluminum.
The one on the left is
for the rectifier and
the one on the right
is for the coil. The
rectifier will mount
to the battery box
and the coil mount
will attach to one of
the original holes on
the frame backbone.
13
Well, as it turns out I could not find a
12 volt battery small enough to fit the
original Honda battery box. I tried
modifying it, but didn’t like the results.
Since I was going to have to do
something about the air filter anyway, I
scrapped the whole idea and decided
to fabricate my own.
I use manila file folders to make
patterns. They work great, they’re
cheap, and it allows you to make
mistakes until you get the pattern
right. Once you get it how you want,
transfer it to your metal, and bend it
up. The tabs sticking out are to mount
the CDI unit and starter relay.
Battery box/air filter housing issues
14
Here’s how the battery fits.
And here it is installed in the bike.
New battery box
15
Electrical

The next slide is an adaptation of the wiring diagram found on Hooper Imports’ website. The
only difference is that the Hooper diagram does not depict an ignition switch. I followed their
wiring diagram exactly but could not get any spark. After several lengthy phone calls with Larry
and Daniel at Hooper imports and a new CDI unit, we determined that I had a bad ground. I
returned the CDI unit, fixed my ground and viola! I had spark.

Here’s a few tips to help keep you out of trouble:
1.
There’s a convenient bolt just below, and on, the stock Honda battery box that looks like it
would be a perfect ground. Don’t be fooled…the battery box/air filter is mounted with
rubber bushings so it is isolated from the frame (ground). Use a bolt directly to the frame
and make sure you scrape the paint where it makes contact. ALWAYS confirm your
grounds with a meter.
2.
I have had solder-less (crimp style) connectors come loose and give me fits to try and
troubleshoot. Now I always solder my electrical connections and protect them with heat
shrink (electrical tape works too, but will eventually come off).
3.
Use a good meter to check continuity of your connections (especially your grounds).
4.
The way the stock Honda ignition switch is wired in, won’t prevent the Lifan from starting.
If you wire it in to the starter circuit, you can still kick start the bike without the key. I
wired mine into the kill switch wire. The only problem with this is that the electric starter
will still crank with the key in the off position. The bike won’t start, but it will crank. A
different ignition switch may fix this.
5.
Most important….DON’T DEVIATE FROM THE HOOPER DIAGRAM! (except maybe the
starter button. Will discuss later).
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Wiring the Lifan 200cc Vertical Engine
(all greens go to ground)
Kill switch
Starter
button
Key
Starter
relay
(optional)
CDI
Not used
Coil
Starter
Rectifier
Black/Red
Blue/White
Black,
not used
Red
Yellow
Green with white stripe
Engine Connector
Pink
-+
Battery
12 Vdc
17
Wiring Continued (starter button)
The Hooper wiring diagram depicts a starter button that
completes the (hot) power wire to the starter relay. This works
fine and is how I wired the bike initially to get it running, but if
you want to keep the bike looking stock you can use the lower
right switch/throttle housing from an electric start equipped
Honda CB/CL-175, CB/CL-350, etc. However, the Honda
starter button is wired so that when you push it, the switch
completes the ground, not supply power. So the change is to
run the hot wire straight to the starter relay and connect the
wire from the handlebar switch to the starter relay ground
connection.
Starter
button
Stock Honda
Button
Starter
relay
Starter
-+
Battery
12 Vdc
Change in wiring to use
Honda switch
18
Wiring Continued (kill switch)
If you plan to use the stock Honda kill switch, you will have to
re-wire it where it connects to the system inside the headlight
bucket. Remove the headlight and locate the two wires
coming from the kill switch (one black one black w/white
stripe) and unplug them.
Connect one of the wires to a new wire coming from the CDI
unit (per the Hooper diagram) (through the ignition switch if
you use one) and the other wire to ground. Check your
connections and function of the switch with your meter.
19
Wiring Continued (Lights)
The Hooper diagram has no provisions for lights. The stock
SL-100 uses a 6 volt system. The new Lifan 200 uses 12
volts. There are no issues with the wiring (it can handle the
extra voltage) but the bulbs, however, can’t. If you apply 12
volts to the bulbs you will blow them all, and the headlight is
not cheap. I see two ways that this can be handled:
1. Replace all the bulbs with 12 volt rated bulbs, or
2. I found an XL-125/Lifan 200 wiring diagram on the Yahoo
Honda Clone group that depicts a 10 watt 3.61 ohm
resistor connected to the white wire on the back of the
headlight bulb and going to ground. This appears to be
the only change. In theory this would reduce the amount
of voltage applied to the lighting system. I’ll try this option
and let you know how it works out.
20
The Finished Product
(almost, I’ll tear it down this winter for new paint and re-cover the seat)
Left side
Right side
21
First Impressions

With the exception of the wiring issues, this was a fairly simple
conversion.

The staff at Hooper Imports was very helpful and their customer
service is over the top.

The bike starts right up and runs great. Plenty of power with a
good positive shift.

Even though the stock Honda engine would start on the first or
second kick, the electric start is wonderful when you have bad
knees.

I would recommend this conversion to anyone who has the basic
mechanical/wiring skills to work on motorcycles. There is no frame
modifications required and only requires a little fabrication of a few
brackets.

I welcome suggestions and comments and you can email them to
me at [email protected]. I will update this information as I
come across new items (such as the lighting when I figure it out).
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