1972 SL100 Lifan 200CC 163FML Engine Swap and 12V Upgrade


Bikes: 2014 Honda CB500F, 1972 Honda SL100
Hello DTT forums. I'm a new poster here. I started this thread to chronicle my installation of a Lifan 200cc 163FML motor into my 1972 SL100. I intend to use the finished bike to bushwack around the unimproved roadways and alleys (of wich there are many) here in my home of Southeast Portland, Oregon.

Below is the bike before I started the Lifan engine install.

A couple years previous, I purchased the bike from a couple in White Salmon, Washington for $500 running with clean title. Its not in awesome shape, but it is solid overall. Major drawbacks were a Kreem-coated tank and some dents and other bruises from a few thousand miles of trail-time. I test road the bike at purchase, but neglected to shift above third at the time. Back at home, I did some sprucing up, then took it for a ride around the neighborhood. As soon as I shifted above third gear, it would not for its life come back down without me stopping the bike and hammering the shifter. With misplaced hope, I pulled the side covers and troubleshot the problem away from the shift linkage (which I had prayed it would be) to inside the engine cases. Naively, I pulled the engine apart and found the problem to be in the shift drum and forks. Never was able to pinpoint the cause, but the project ended up back-burnered and languishing due to my idle disinterest in engine work.

A year or so back, I found online that one may swap in a 200CC Lifan 163FML engine with relative ease. Added horses, electric start, 12v system, and a fresh motor for $550 was tempting. A couple weeks ago, I decided to pull the trigger. I ordered the crate motor from PCC Motor via eBay and received it a few days ago.

The following will be my attempt to log the whole installation, break-in process, and then my review. When I've finished, I may publish an Instructable or similar on this topic as there seems to be a relatively scant quanitity of info about these motors (though I may be corrected by DTT members here).

By way of introduction to the DTT forums, I'm a 31-year-old, business jet mechanic from Portland, Oregon with an awesome, motorcycle-friendly wife, two daughters and a mutt. Thanks!


Bikes: 2014 Honda CB500F, 1972 Honda SL100
I ordered the "SET" version of this Lifan crate motor, which meant I received a carb, CDI ignition box, coil, kickstart lever, shift lever, regulator/rectifier, starter solenoid and wiring harness for the motor as well. Here's the extras unboxed.

On opening the box, one is greeted by the distinct aroma of Harbor Freight Tools (also known as Chinese/Thai industry). I think this is produced by a combination of the fresh rubber, and the preservative oils they lather on everything, for wich I am glad, considering these machines plow through the salt-spray of the Pacific to get here.

But! Keep in mind when unbagging the engine that it will be slicker than snot. I wiped the whole thing off before attempting to mount it in the frame. The motor after unbagging shown below.

Once de-oiled, my wife and I wrestled the lump into the SL's frame with ease. Well, as easy as ever, anyway. The new motor's jug is sizably larger than the 100cc original, so it was a tight squeeze.

I was able to bolt it in with the rear mounting holes and the front mounting plates, no problem. However, due to the Lifan motor being a push-rod OHV affair (unlike the OHC original Honda motor), the top mount point on the head is nowhere near the original. I've seen others simply ignore this, which is probably fine. Personally, I'll be fabbing up some new brackets for the head which will include some of the new electrics as well.

This is the very old school shift lever included in the set. :)


Active Member
i am just doing the final tweaks and dial in on a 1971 cb100 with the same lifan200
i got the set motor but the supplied carb sucked
so i have now replaced it with a vm28 mikuni
i have a custom exhaust while the jetting dial in is not perfect yet
the thing goes like hell we clocked it on gps friday at 68mph in fourth gear and not anywhere near redline
it even wheelies
it will bring a big grin to your face when you ride it

you need to make a upper motor mount set up or the motor will turn the frame into a vibrating tuning fork
also drill the back two bolt holes out to 10mm and use 10 mm bolts the size the lifan holes are made for


Bikes: 2014 Honda CB500F, 1972 Honda SL100

Good to hear you've had success with this motor. I am, indeed, looking forward to riding it.

I've got some 1/8" mild steel plate I'll be making new upper mount brackets from. Interesting about the rear mount bolt size. I'll be looking into that. Frankly, the front bolts seemed similar, but the stock bracket's holes are oversized quite a bit. Wide manufacturing tolerances, I'm guessing. Didn't know the holes in the Lifan engine case were actually larger than original. Been a while since I had the original engine out of storage.

As for the carb, I'll run with the cheapy for now and see what happens. I intend to use the stock exhaust header, if possible, and put a more size appropriate slip-on muffler in place. Can't use the original airbox boot (different size), so I'll run a pod filter.

For all interested, it should be noted I received absolutely no information with this motor. No parts breakdown, break-in guide (aside from a sticker on the side cover), no mount point dimensional drawing, nada. Just the packing slip from PCC Motor.

Below are some pics of the supplied carb.

"HONGDA" huh? A mark of high quality somewhere, I suppose... You can find these carbs online for $15-$20 new, so I'm not expecting much.


Active Member
you should post or forward me some pics of your wiring harness when you get that far

mine i had to change the ground pin position at the cdi to get it to fire and apparently this is common

i dont know about the front mount bolts as mine were missing so i just used what fit i believe i also used 10mm there

i did nit have the stock pipe so i fabbed one up using 1 3/8 then 1 1/2 to the muffler and used a aluminum flange


Active Member
yours is a lot nicer looking lol but mine will get there

i will take a few when we do some testing tomorrow


Bikes: 2014 Honda CB500F, 1972 Honda SL100
The included carb won't install in place unless you loosen the screws securing the boot to the head.

Not much room between the choke mechanism and the frame.

The original battery holder and air box assembly is removed. I'm doing a full 6v to 12v conversion, so I'll be fabbing a custom battery and electrics holder.

Next, I'm going to carefully correct the bolt size problem cxman pointed out, then start working toward a first start on the engine.


Bikes: 2014 Honda CB500F, 1972 Honda SL100
I looked into the bolt size issue and here's what I found. The mounting holes in my Lifan measure not quite 9mm inner diameter. This is consistent with a loose fit for an 8mm bolt, which is the Honda original size. Curious, I grabbed the box with the cases from the Honda motor and found them to be basically the same, if not slightly larger. As such, I'm sticking with the original hardware.

I couldn't even get a 10mm bolt through the Lifan's mounting holes.

Here's a pic of the original top bolt going through the Lifan top mount hole, just to see the fit.

This, from my experience is a pretty typical fit for bikes of this age.

I wonder, cxman, if our Lifans are just a bit different here. I've already been surprised at the number of little differences there seem to be among these engines.

Case in point, mine has no "LIFAN" on the right hand side cover.



Active Member
well 10 mm slid thru on mine

and the carb that came with mine was not like yours

i also dont have the decal near the dipstick


Bikes: 2014 Honda CB500F, 1972 Honda SL100
As I recall, that decal has the "run in" instructions. Pretty basic and in poor English. Basically says only 35mph or less for first 160 miles, then change oil. I'll get a photo of it later.

Sent from my iPhone using DO THE TON


Active Member
i ran mine for 1 hr nice and easy then changed oil

since then it has run about another 3 hrs and has hit 70 mph a few times lol


Bikes: 2014 Honda CB500F, 1972 Honda SL100
Here's that "break-in" sticker. Pretty amusing.

The original exhaust, unfortunately, no longer fits. The Lifan engine's side cover includes a sight glass where the original does not.

As a result, the header contacts the engine there and prevents the header flange from sitting flatly on the exhaust port face. Oh well.

Being forced into fabbing a new header may be a good thing, anyway. Referencing a CB350 header and SR185 header in my shop, both measure 1.5" OD and at least 1.38" ID. The original SL100 header measures 1.25" OD and about 1.1" ID. If a 160cc and 185cc cylinder both use exhausts above 1 3/8" ID, a 200cc will need similar.

All this means I can justify the price of a new die set for my tube bender, ha ha.

In the mean time, I was able to "reconfigure" in order to test start the new powerplant.

Got things hooked up for the first start, then realized the battery I was going to use was almost dead. So I threw it on the charger.

In the meanwhile, I had received some goods to refresh the wheels and brakes.

Up went the front end, and I will get the wagon wheel ready for the wet, muddy, jungle-like tracts of eastern Portland that are in fact, public roads. :)


Bikes: 2014 Honda CB500F, 1972 Honda SL100
1. Pull off wheel.

2. Remove tire, tube, rim strip.

3.Examine rust.

4. Remove rust.

5. Do a lot of cleaning, polishing, and other stuff I forgot to photograph.

6. Install fresh brake shoes and reassemble. I used EBC 303G grooved shoes.

Next, first start of new engine.


Bikes: 2014 Honda CB500F, 1972 Honda SL100
On to the first start!

Below you will find the wiring diagram I found most useful.

This is the pin-out of the CDI unit provided.

These were useful in large part because there were two defects in the supplied wiring harness. Thanks goes to cxman for warning me of this.

One was the apparently common mis-pinned four-pin CDI connector. The ground needed to be moved to the originally empty location. The winning arrangement is shown below.

The second defect was at the stator connector. See if you can spot it.

A quick re-pin corrected the misplaced exciter coil wire. After that, I started getting spark.

Ready to run.

Jerry-rigged electrics.

I put a little go-juice in the tank and fired it up! A little video is linked below.


Seems to work well. Only start hiccup was a leaking petcock strainer bowl, which turned out to be due to a missing backup washer for the o-ring.

Next up, I will fab the new battery and electrics holder and start work on the exhaust fab. Other tasks include refreshing the rear wheel, new chain and rear sprocket, massaging the Chinese wiring harness, and converting the lighting to 12v. Stay tuned!


Active Member
just an update

i re used the 14 tooth front sprocket from the cb100 and its to tall for the lifan gear spread and ratios /power band

i have a 13 tooth and 12 on its way

the motor lugs in 5th

and will only do 75 in 4th now that i have it jetted right


Bikes: 2014 Honda CB500F, 1972 Honda SL100
Interesting. I just planned on using the front sprocket included with the Lifan. We'll see how things go when I get there.

Sent from my iPhone using DO THE TON


Active Member
mine did not com ewith one or t got lost how many teeth does it have?

from the pics i see its a 14 tooth as well so may be on no help to me
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