1978 RM125 Restoration

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7/7/2017 11:29 AM

Hi everyone...I've been lurking for a while reading posts on here and thought it was time to post my new project. Dating back to when I was 12 or so I got my first dirt bike, a 1975 Honda XR75, which I quickly outgrew. My next bike was a '79 Yamaha IT175 that I rode until I wanted a car so away it went. Between those two bikes I always wanted an RM125 but never got one. Fast forward to 1985 and I bought a brand new Honda ATC250R which I still own and race occasionally in CALVMX events. About a month ago I picked up a '78 RM125C from Craigslist. It's in decent shape but needs a lot of TLC, although new parts have been arriving frequently from Vintage Suzuki, eBay and Rocky Mountain. When I'm finished with it I may keep it to ride and or race or sell it and buy another project. It's a lot of work but a lot of fun too. More posts to come as things progress.

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7/7/2017 10:12 PM

Badass. Looking forward to your build. I have the exact bike in multiple tubs and storage bins. ☺

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7/9/2017 9:32 AM

Fun factor is off the chart. I had a '77-'78 hybrid that was awesome to ride. It was a ''77B with a '78C forks, triples and swingarm. Fox Airshox on the rear. Wish I was light enough to have raced it. Good luck with your build. Looking forward to it.

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7/10/2017 10:44 AM

Great project, really a cool bike, I have a few misc. left over parts if you need any. Here are a couple of pictures of mine last week at Red Bud,Photo


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7/10/2017 11:21 AM
Edited Date/Time: 7/10/2017 2:08 PM

Very nice bike Mike! Slowly but surely mine is coming along. I have the majority of the parts I need at this point but the list of everything I needed grew daily as I stripped it down and decided what needed replacing and what could be saved or refurbished. Cleaning off almost 40 years of gunk, grease, dirt and crust is what is most time consuming. As soon as I'm done with that part of it I can start reassembly. What parts do you have available and do you know if the rear shocks can be disassembled and or rebuilt (I haven't checked my manual yet)? Thanks, Greg.

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7/10/2017 2:20 PM

The shocks are NOT rebuild able, I built this bike to sit in my office as a display (for now) I have a number of other vintage race bikes that I ride in AHRMA events regularly. If I was ever to get this bike back in racing form I would replace the shocks.

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9/21/2017 11:53 AM
Edited Date/Time: 9/21/2017 10:08 PM

Update...I've tracked down and received 99% of all the parts I need for this project and list went from long to longer to extensive and expensive. I was originally only planning on cleaning the bike up with new plastic, and some painted parts but the further I got into it the more it needed and I wanted to do it right. It reminds me of when the wife wants to buy new family room furniture, pretty soon you also need new curtains, wall paper, carpet, paint, etc. The snowball snowballs in a hurry! That being said, after much research, the following parts were purchased from Rocky Mountain, Vintage Suzuki or eBay...Front number plate & background, left & right side number plates, front & rear fenders, air fork cap, rubber fork caps, gas tank, gas tank strap & rubber mount cushions, tank decals, rubber lever covers, foot pegs, rear shock reservoir rubber mounts, front & rear motor mount bolts, front & rear axle nuts, swing arm thrust washers, swing arm bearings, center spacer & pivot slider, rear axle seal, rear wheel spacers, swing arm seals, front sprocket cover, rear sprocket, 428 chain, chain tensioner, grips, seat pan cushions, rear fender mounting spacers & cushions, front brake lever & cable, front & rear Tusk wheels laced with Dubya spokes, front & rear tubes; tube protectors, front & rear IRC tires, complete gasket and seal kit, petcock filter and rebuild kit, fork seals, fork boots, kick start lever, rear brake pedal, seat foam & seat cover, kill switch, air box & UNI air filter, stainless bolt kit, spec bolt kit, front & rear hub bearings, rear hub, rear brake stay rubber mounts, front & rear brake shoes. The majority of the parts are genuine Suzuki and with the exception of the air box, rear hub, motor mounts, and gas tank, all of the above parts are new or NOS. It amazes me what's still available for a 40-year-old bike. $1900 later, not counting what I bought the bike for I am close to starting re-assembly. Thankfully, I was able to get a small crack in the swing arm pivot welded up and the frame powder coated at no cost (other than a twelve pack) through a friend. I'll still need to work some dents out of the pipe and repack the silencer. I may also attempt to change the rear shock oil and add Schrader valves to the reservoirs so they can be recharged with nitrogen. Once it's back on two wheels, I’ll tear into the motor to see what kind of work and part$ it will need...stay tuned!

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9/22/2017 6:33 AM

Your 78 looks factory fresh Mike. Looking at the pics makes me want one even more.

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9/22/2017 8:56 AM

I remember going to Bohners Suzuki in Fresno after they returned from L.A. with 2 of these still in crates in the back of a pickup. The first 2 in Fresno. They were already sold.

They were so badass. They put Fox Airs on one during assembly. I was a junior in H.S. I wanted one so bad.

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9/22/2017 11:00 AM

Nice Build! I'm curious to see what you find for shock therapy. I've got the same dilemma on a '79 KX and '79 KLX. Non-Rebuildable and nobody offers anything close with reservoirs. I have seen Arctic Cat showmobile shocks made by FOX that may be worth considering, but nothing exact.

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9/22/2017 4:49 PM
Edited Date/Time: 9/22/2017 4:55 PM

Did you go with a 428 chain Sandman?
For a few thousand dollars you get to have a total blast racing a perfect 78 RM125 and the personal satisfaction of doing killer restoration . Even if its 3500 with a trick motor and a new set of shocks It's my opinion it's worth more than every thing you spent. Obviously you love vmx or you wouldn't be on vital posting about your project. I have zero regrets of what I've put into my bike

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9/22/2017 5:50 PM

Yes, I went with the 428 chain. It and a new rear sprocket were delivered today. Maybe you can explain it that way to my wife, and talk her into letting me keep it in the living room too!

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9/23/2017 6:00 AM

Can't help you with justifying a rm in the living room until you are on your own. We are here for a short time. Don't deny your dreams

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9/23/2017 7:37 AM

It’ll have to stay in the garage with plenty of other Japanese speaking company or I will be on my own. I don’t want to flush 25 years of a great thing down the toilet.

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10/1/2017 8:43 PM
Edited Date/Time: 10/1/2017 9:00 PM

Weekend update...front and rear hubs have been fully restored, i.e. bead blasted, new bearings, shoes and paint. Off to Dubya they go this week for new spokes / lacing into my new wheels. Stay tuned!

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10/1/2017 8:56 PM
Edited Date/Time: 2/27/2019 9:06 PM

More goodies...new IRC knobs and a NOS sprocket.

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10/2/2017 6:30 PM

Nice bike to build and great performer for it's time. I have a couple and have modified the snot of them,,if you go for power I can make suggestions from experience. One thing to watch out for...the tanks commonly split inside across blind nuts. Before you go spending any time on tank...look inside carefully to insure there are no cracks developing on back of humps where the blind nuts are molded first. Also... because the cylinders interchange with 77 and swapping happened alot...the 78 has a pair of trapezoid shaped exhaust ports, \_I I_/ ,,not square(75-77). Part of secret to it increased power. When they port them they make the top even wider

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10/6/2017 3:43 PM

Mike 29 wrote:

The shocks are NOT rebuild able, I built this bike to sit in my office as a display (for now) I have a number of other vintage race bikes that I ride in AHRMA events regularly. If I was ever to get this bike back in racing form I would replace the shocks.

Yes, you are almost correct, they are not easily rebuildable.

Years ago i had a shop here in Australia ( Krooze tune ) modify and rebuild my RM125 N shocks,
Seals, bladder and oil, yes it was expensive, with the rough black paint average Joe could not tell.

There must be someone in the US that could do that if you wanted to keep it OEM looking,

Of course they were still 1989 technology.

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10/7/2017 6:47 PM

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Two brand new ones in '78 for me and my brother.
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10/8/2017 11:18 AM

Very nice! Love the racing slick on the trailer too! smile

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10/8/2017 11:19 AM
Edited Date/Time: 10/9/2017 10:53 PM

Dubya just called and said my newly laced wheels are ready for pickup. I’ll post some pics up as soon as I return from vacation.

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10/8/2017 6:35 PM

Mr. Sandman wrote:

Dubya just called and said my newly laced wheels are ready for pickup. I’ll post some pics up as soon as I return from vacation.

We got some retreads not long after this. If my memory is correct, but it probably isn't.

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10/9/2017 6:57 AM

Give this guy a try for your shocks. http://www.mxrestoration.com/carsl.html

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Yeah, I have no clue !!!

10/13/2017 8:56 PM
Edited Date/Time: 10/14/2017 11:05 AM

I picked up the frame from the powdercoater and my Tusk wheels with new, freshly laced Bulldog spokes from Dubya today. I'm finally, almost ready to begin reassembly.

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10/18/2017 9:52 PM

Proof that 40 year old legs clean up nicely and can be sexy and shiny again. I'm just waiting for new reservoir hoses to be made.

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12/14/2017 3:19 PM

So things have slowed down a little on this project but I hope to get going again after the first of the year. Currently, I need to refinish the lower fork tubes and triple clamps (blasted, polished and powder coated clear). Once they're done I can reassemble the forks, mount them and the swing arm, which had a small crack that needed to be welded, and I should be able to get it back on two wheels.

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12/16/2017 6:10 PM

Thought I would share a picture of one I built up last winter.
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Oldmxer95

1978 KX250A4, 1995 KDX200H, 1998 KX300K5, 1982 CR480R (for sale)

12/19/2017 3:02 PM

Beautiful bike Oldmxer.

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12/22/2017 11:16 AM

Love the old RMs, I have 3, 2-125s and a 500. But my 1st race bike was a 77 125B so I had to have one in my collection except instead of the old beater my dad bought me when I was 16 I had to have the Full Pimp package this time with 80T model suspension and wheels and the Fox Airs I never got to have. Photo

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Old Vintage Gold Rules

12/22/2017 4:56 PM

yzweldon wrote:

Love the old RMs, I have 3, 2-125s and a 500. But my 1st race bike was a 77 125B so I had to have one in my collection except instead of the old beater my dad bought me when I was 16 I had to have the Full Pimp package this time with 80T model suspension and wheels and the Fox Airs I never got to have. Photo

The 1977 RM125B was the first real MX bike I ever rode. They were the bike to have back then. This picture brings back some memories. Really nice bike here.

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