…musings of one easily amused

1972 Honda SL125 – Alive again!

It started out as an abused Frankenstein bike, containing parts from a ’71 Honda CL100 and a 1972 Honda SL 125.  One of my periodic scans of Craig’s List turned up this $125 beauty.

Most of the controls were missing, the bars were bent, the shocks were missing, pegs
were way out of wack having been broken a re-welded off-center.  The 100cc engine
had a sheared kick start shaft.

The tank was off of a ’71 CL 100, I believe, and had half a tank of 2-year old gas.
The carb was trashed.  The CL pipe had been wire wrapped in place because there
was not mount plates for it on a an SL frame.

This was obviously going to take some new/used pieces to get it running again.
I started with eBay and soon realized the pipe and tank were not going to come cheap,
even if I could find them.  I lucked out about three weeks after picking this
one up when I spotted another SL125 on Craig’s List.  It was the year I needed
and it had the tank AND the pipe!  The tank was in rough shape but nothing that
“Pore” couldn’t take care of.

With the two bikes I now had enough spare parts to potentially make one functioning
motorcycle.  I stripped the “real” SL125, cleaned and painted the frame and started
putting it back together with the better parts from the stockpile I now had.
I was able to repair the handlebar controls and switches, thankfully.  The wheels
cleaned up nicely and some more contributions from my eBay slush fund helped make
completion a real possibility.

I now had the basket case engine from the second SL, the eBay engine and the 100cc
engine that came in the original frame.  Both the eBay and basket case engines
had top end issues due to being left uncovered outside.  I ended up using the
lower end of the eBay engine and the head off the original 100cc engine.  I found
a used cylinder on eBay and also purchased a new piston, ring, pin and bearing kit.
The carb from the basket case was salvageable (after a full week of soaking and a
full day of cleaning).

Additional parts needed included shocks, pegs and levers (eBay) and a clutch cable
(local bike shop).  It was now ready for firing.  Unfortunately, the first
time I pressed the shifter down to first it would not come back up.  Why do these
things always work perfectly on the bench and fail after you have mounted the damn
thing in the frame?

I laid the bike on it’s side and pulled the clutch cover.  It seems the previous
owner of that eBay lower end also had an issue with it shifting.  The shift fork
was worn and was slipping over the cam instead of engaging and rotating it.
Instead of replacing the fork, they added washers to apply more pressure.  Having
plenty of spare parts, I pulled the cover on the basket case engine a removed the
needed shift assembly.

The final “re-fix” would be the engine cut-off switch.  I ended up taking it
apart and re-soldering one of the wires to the contact plate.

Everything re-assembled, it was time to try again.

On the fourth kick there was life, albeit short lived.  I advanced the timing
a few degrees and tried again.  This time it settled into a fast idle immediately.


I rode it around the back yard a bit.  The ground is like a slick wet sponge
right now with the semi thaw we’ve had the past couple of days.  I rode it enough
to put one of those stupid grins on my face.  This bike is very similar to the
one I learned to ride on back when I was in elementary school.

To-Do list includes finishing the front fender and installing new speedo and tach

Updated 3/15/2009 –

New Speedometer and Tach cables installed and a new 6V tail/brake light bulb and the
SL is 100 percent.

23 Responses

  1. Keith

    Wow I have had my SL 125 since 92 & still cant find parts for it. I need help with seat,tank,carb. Everything else was stripped off by my uncle years ago. No lights or gauges would really like to find all those parts also. Any help would be good. Thank you. Keith

    April 6, 2010 at 1:16 am

  2. The tank and working gauges are going to difficult unless you scan ebay constantly and don’t mind spending allot of money. Anything else is readily available on auction sites or craigs list. The carbs I have are in rough shape but I do have an extra taillight assembly.

    April 6, 2010 at 8:35 am

  3. Jim

    Great job! I found your post researching CL100’s as I’m thinking about getting one for my girlfriend. Wanted to know something about them before plunking down the cash.

    Great job on the restore, resourceful, etc. Nice bike, neat as a pin and well done.

    June 16, 2010 at 11:09 am

  4. bob sovacool

    Hi- nice job on the SL125! I will need to sandblast my frame (also a 1972 SL125) and am wondering what paint you used on yours, and if you recommend it, or something different. Again, yours looks raelly nice; congrats on a good job.

    January 1, 2011 at 11:17 pm

  5. Thanks Bob. The paint is nothing special. I used a can from my local auto supply. I was not going for a museum piece. Bikes are meant to be ridden and not placed behind a velvet rope, right? 🙂

    January 7, 2011 at 10:10 am

  6. Tony

    So, I’m in Twinsberg Ohio on business. I’m lounging around my hotel before going out to eat and decide to look for parts for my 1971 sl.

    And I find groberts.com you got to be kidding me, I have to good 600 miles to see a guy who lives 4 miles from me has the same bike.

    Tony Lasaracina

    May 9, 2011 at 6:43 pm

  7. Gotta say, that is pretty funny. I don’t have the bike anymore but I do have some bits and pieces. Give me a call when you get back.

    May 10, 2011 at 10:02 am

  8. daniel

    wow, i got two of these bikes from my grandfather. both have working gauges, i found a seat, one of them has the entire carb assembly and working lighting wires. they dont need a alot of work but some.

    July 24, 2011 at 4:40 pm

  9. James C

    Nice job. I have a 1972 SL100, red in good shape. I put a 125 top end and crank in it and a 200X carb that looks factory. Unfortunately I had to use the stock SL100 pipe so it doesn’t run as good as it could but I still enjoy it. I gave 50$ for it in 1983.

    August 29, 2011 at 11:08 am

  10. Bill JIbben

    i have a honda sl 125 (1972). it was last riden in 1980. been in a shed since, could use input on takin off the seat and the take still has gas in it.

    September 24, 2011 at 12:34 pm

  11. Mike c

    That looks exactly like the one I just picked up. The bike I have is also a 72 SL125 had sat in a garage since 72. Piston was siezed from sitting, so I was patient worked the engine back and forth with a little Marvel and 2 weeks later it was free. Put the compression tester to it and 0psi. Tore theengine out and found a bent exhaust valve and the rings were busted.

    September 28, 2011 at 8:49 pm

  12. All fixable. Bring her back to life. I promise it will bring a smile to your face.

    October 4, 2011 at 8:40 am

  13. Mike c

    been waiting on engine parts from thailand, got the last of them tonight.

    October 14, 2011 at 7:03 pm

  14. Craig Hunter

    I’m trying to buy rear shocks for my 75 sl125 but I seem to find two lengths -350 or 400 mm. Which length is correct??? Thanks for your help

    December 16, 2011 at 8:06 am

  15. karl

    I have a 72 SL 125 and my story looks similar to most. Bought it for $50, found bits and pieces here and there, repainted, new decals. Starts and runs great except for a metallic clacking noise coming from the top end. I’ve already adjusted the valves… could it be worn rocker shafts? I don’t want to pull the cylinder if it’s something simple like top end parts.. any ideas? I know it’s tough without being here to hear the noise in person. Any help is appreciated.

    April 15, 2012 at 7:43 am

  16. Tires wer mint when I got the machine but very quickly dryrot. I can not find anyone who makes a 3.25X18 tire for the rear, will a 3.5 tire work?

    June 13, 2012 at 7:22 pm

  17. Eric

    Nice job on your 125, I have three of these bikes, and am in process of getting one done,

    July 3, 2012 at 8:17 pm

  18. T Dee

    Fine resto ,I build SL125 classic motocross versions from wrecks. Great little fun bikes, cheers from Australia

    November 2, 2012 at 3:53 am

  19. daniel

    I have the two bikes and decided to make one. I want to take all lights off and just use it as a dirt bike. Any suggestions on how to desire from an on off switch to the condensor and alternator. Have plenty of wiring, just don’t want to have to start it with a battery. Any one with a suggestion or diagram for this sort of thing, let me know.

    July 3, 2013 at 8:51 pm

  20. Macie

    Could you tell me how you replace the intake and exhaust valves? I’m having huge problems replacing them with the C-clamp valve spring compressors, it keeps compressing the collets off of the valve and never staying in as I compress the valve to install the new valve.

    January 15, 2014 at 6:16 pm

  21. Strong thumbs, patience and a third hand? 🙂 Seriously, third hand does come in handy. Use of a very small set of needle nose pliers or a small magnet to place the retainers back into position.

    Some specialty tools are more effective than others. Search Amazon for “Motion Pro 08-0247” and there will be many options ranging in price from $15 to $215.

    There are also some homemade techniques as well-

    Good luck!

    January 22, 2014 at 8:31 pm

  22. rtl

    I have a 1971 Honda sL125 that I bought for a winter project. Mostly there. Looks good. I’m concerned about if the clutch is engaging and other minor problems. Would like to hear the motor running. )( it turns and is not frozen up ). Lots of new Honda Parts. If I can’t go further without a big investment would like to donate to some kid to learn about these as I did. Merry Christmas.

    December 23, 2014 at 5:31 pm

  23. I am starting a project next week with a 72 SL125.if I remember correctly back in the day it eas ok to run a 100cc head on a 125 honda gaining a little compression boost along the way. If read your post correct, did you use a 100 head on a 125 cylinder? If that works it sure would save me a lot of searching for a 125 head in good condition. I have a 100 head in the shop. Great job on your bike. Very nice little 125 you have to show for the work you put into it.



    April 3, 2017 at 1:23 am

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