1980 RM125 Project

Kidkawie
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9/4/2013 5:01am Edited Date/Time 2/1/2016 1:05pm
Plans are to turn this into a solid rider. It runs and is supposed to have a "new top end", great compression. The bike looks stock and overall doesn't seem to have been ridden much. Pegs, kicker and cases arent worn out or anything, pegs still tight, etc.

I'd like to get into the suspension first so I need some pointers on that as far as tuning or tips on setup. Hopefully some of you guys will weigh in. I'm guessing I need to compress the springs to get at the dampers?

Any other pointers are welcome, thanks!

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MXM
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9/4/2013 6:35am
There is another guy who is just finishing a 1980 rm 125 project on thumpertalk under " Suzuki 2-strokes". He will have much help for you on this I am sure.
newmann
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9/4/2013 6:42am
Those bikes look really good. Run pretty good too! My brother had a nice one stolen in Dallas a few years back with a few trick bits on it. F'n thieves....
Kidkawie
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9/4/2013 7:51am
Thanks, my knowledge is in the 90's green bikes so this is all new to me. Been going through it and am having some issues with: torque link, rear brake adjust rod, silencer and chain guide. I'd like a serviceable silencer and maybe a newer chain guide with less pieces, a chain block-type guide.

Besides that, the bike seems pretty solid, mechanically. Can't wait to flog the snot out of it.
berniepiet
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9/4/2013 8:33am
I am curious, where did u get it? I recently sold one similar to it

The Shop

Kidkawie
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9/4/2013 8:52am
berniepiet wrote:
I am curious, where did u get it? I recently sold one similar to it
Central Jersey
Kidkawie
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9/4/2013 12:20pm
If anyone has any parts I'm looking for: chain guide, case saver, torque link and rear brake adjusting rod. Thanks!

Just been going over the controls, cables, etc. Straightened and painted the bars.





Pipe is mint



Whats left of the guide.





newmann
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9/4/2013 2:07pm
I was pretty impressed with OEM parts availability on the 77 RM125 when I was hunting parts. None of those available new?
9/5/2013 3:42pm Edited Date/Time 9/10/2013 4:35pm
whoops, double post...url sniffer delay
9/5/2013 7:36pm Edited Date/Time 9/10/2013 4:34pm
whoops, double post...url sniffer delay
9/5/2013 7:41pm Edited Date/Time 9/5/2013 7:47pm
As stated above by my brother you will be surprised how many parts are available. You can find numerous parts lookups on the inter-web to get you going, but unfortunately your brake torque rod and chain guide parts aren't available but I do have some suggestions.

Google Alpha-Sports. They have an awesome Suzuki parts lookup.
(*The link sniffer is not allowing me to post the actual url)

Also, if you haven't checked out Mark's Swapmeet page you need to. A great resource and I recommend just posting a wanted ad for the things you need if you don't buy new.

Again, Google Marks Swapmeet.

Suggestions and how my previous 1980 RM125 was set up. I found an aluminum brake torque rod in a bone yard that probably came off a mid to late 1980's YZ model. Find one that matches the length or is very close. They are out there! As for the chain guide I bought a Fredette Racing model for a late 90's model RM125. A little shimming and some minor grinding and it fit nicely. It was anodized blue to top it off. I can't remember the correct year model though so you may have to just watch that auction site for a used one. The suspension setup I ran was 16.5 inch Works Performance shocks and I used a 43mm 1984 RM model front end with Race Tech springs. As for the motor I had to correct the horribly matched intake ports from the reed valve. If you're good with a Dremel you can do this yourself. I had a struggle with getting the carb setup for some reason. I used new carbs, old rebuilt carbs, carbs off other running bikes, and nothing worked well. I found a NOS 1983 RM125 carb and it ran perfect. Set it up to stock specs with a slightly larger main jet. I ran a DG head, Jemco exhaust, digital PVL ignition, and all the ports were cleaned up. I even modified the petcock as the diameter is super small and it just doesn't flow enough gas when the bike is wound out.

I'm still pissed about it being stolen...it was a nice bike.

You can message me if you want. I have a box of parts somewhere in my attic that I could part with.
Tdub13
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9/6/2013 11:55am Edited Date/Time 9/6/2013 12:00pm
I love that bike! Hopefully you got a good deal on it. When I was looking for a 125 up in the northeast, they were a little scarce for reasonable pricing. The good ones got bought same day off of CL.

Anyway, it looks like you could bolt a solid block of nylon or HDPE into that chain guide and be on your way. Obviously Lonestar's retrofit idea will take more time and effort, but potentially way better looking outcome, maybe work better too.

On my 1982 RM125, the silencer was blown out hollow. I cut the back end off and packed it with insulation and machined an aluminum cap to slip-fit into the end and bolted it on. Worked great. Answer, FMF, etc... silencers are getting expensive on ebay!

And what's up with the full-floating rear brake rod? If it's loose, you can get bronze bushings at Aubuchon Hardware to tighten it up. Drill to fit and install.
Kidkawie
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9/6/2013 12:56pm
Thanks for everyones help and input so far. Tdub13, great minds think alike. I was browsing Ebay only to find nothing or high priced stuff. I had a bunch of parts on-hand and McMaster Carr is 30 minutes away. I picked up some hdpe 1"x1" bar for a couple bucks, made the brake stay from some alu flat I had and the case saver from some 1/4" plate. I might drill some lightening holes in the case saver. I also modified the rear brake adjuster by welding a longer bolt on the end, so it works as it should now. :D

Finally rode the bike and glad she shifts through the gears. There is a "clunk" when I lock the rear wheel and another clunk when I release the brake, have to check into that. Shock (pushing down on seat) feel decent with good damping. Forks are like pogo sticks, I can bottom them just slamming on the front brake. lol I have new tires and grips coming next week.










Tdub13
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9/6/2013 1:19pm
Those are all perfect period style fixes. Nice work!

About the forks: Old skool tuning in my shop goes like this: I usually fill to spec with ATF. Knowing that I will need more oil than stock and probably higher viscosity, I usually add heavier oil on top. Suzuki actually suggests this method in their GS models. Add 10-W40 to raise and thicken the oil and you can get some pretty good action out of the old boingers. This method will get you on the track while you're saving up for emulators. (you might want to install a crossbar pad though!)

Let me try to upload a photo of fork oil viscosity chart for ya in case you're interested....
Kidkawie
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9/6/2013 1:35pm
Thanks for the tips! I need to get a manual then I'll get into the forks. They need seals as it is and I'm sure the oil is over 15 years old.

I want to pick up those emulators for my Z1, only heard good things about them from road racers.
Tdub13
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9/6/2013 1:43pm Edited Date/Time 9/6/2013 1:56pm






Holy crap it worked LMAO! this is a good chart to use for comparison.

Mobil 1 ATF is right in the middle of the chart. It's about 12 weight.
Tdub13
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9/6/2013 1:58pm
Gotta LOVE the cheng-shin meats too.
notme
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9/6/2013 5:53pm
I bought one of these back in the day, a dealer was closing and got it below cost. It was very decent, nothing outstanding about it though.
Jay (?) do you still have the 96? Your thread on tt was a very inspiring build for me,a spraybomb special to solid runner! Ive done 4 builds like that one but none of them were in worse shape...but close!

Good luck on your parts sourcing.
Kidkawie
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9/6/2013 6:08pm
notme wrote:
I bought one of these back in the day, a dealer was closing and got it below cost. It was very decent, nothing outstanding about it...
I bought one of these back in the day, a dealer was closing and got it below cost. It was very decent, nothing outstanding about it though.
Jay (?) do you still have the 96? Your thread on tt was a very inspiring build for me,a spraybomb special to solid runner! Ive done 4 builds like that one but none of them were in worse shape...but close!

Good luck on your parts sourcing.
Thanks man. Sadly, I had to sell the 96. The original idea was to fund a 74-76 KX. That didnt happen so I came full circle with another RM. haha Its not hard bringing these old bikes back if you have the patience. I just hope the bikes I save continue to be ridden and not neglected again. Can only keep so many....if you want to stay married.
slotsquid
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9/8/2013 6:28pm
I raced the "N" and the "T" models, loved them. Here is my '80 "T" model.
1
Kidkawie
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9/9/2013 7:10am
Anyone know the model carb on this? I need to find a choke knob. Looks like a plastic press fit knob would fit.
yzvet426
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9/9/2013 1:33pm
I love that white RM and really like the fender/plates. Apparently I'm the only one that liked the fender design. What shocks are those?
slotsquid
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9/9/2013 7:39pm
yzvet426 wrote:
I love that white RM and really like the fender/plates. Apparently I'm the only one that liked the fender design. What shocks are those?
Thanks, It was easier for my family to spot me on the track amid the sea of yellow bikes ! I really liked the M. Robert rear fender. "D.C." plastics makes a nice copy in all the colors. Those shocks were call " Motosport" air shocks. They had a 1" shaft and worked well for me. Troy Lee painted the tank for me!
9/9/2013 9:34pm
I want to see a full picture of the little yellow Toyota pickup in the background too! That truck looks old skool cool. Interesting on the shocks. I never heard of Motosport air shocks. Any other tricks to the motor you can remember?
slotsquid
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9/10/2013 5:26pm
If I remember, a different ignition, major porting, scavenged works pipe ( from the US Suzuki dumpster) R&D air box with UNI weenie air filter, 36mm carb, & Trick Reeds... It was bloody fast !
Craze
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9/11/2013 2:49am Edited Date/Time 9/11/2013 2:52am
Kidkawie wrote:
Anyone know the model carb on this? I need to find a choke knob. Looks like a plastic press fit knob would fit.
The carb is a Mikuni VM32.... I went with heavier fork springs in the front with 10 wt. fork fluid, not oil & 16.5 inch Progressive suspension shocks on the rear, boyseen reads and left the motor stock so far on my racer....It's plenty fast stock .....I'm also building another 1980 RM125 that I'm installing 43mm forks w Race tech emulators, using 1984 rm125 clamps and Ohlins remote reservior shocks (16.5) and a (32mm or 34mm) flatside carb and modified cylinder, head and pipe (1/4 inch cut out of the mid section)....Parts are available, but I've bought 3 other RM's (1-1980 &2-1979) parts bikes..for super cheap.
Kidkawie
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9/11/2013 6:13am Edited Date/Time 9/11/2013 6:18am
Thanks for the info.

I rode the bike out in my lot and it seems to be a dog. I feel the power come on right before it redlines. Before that is all flat. I'll pull the carb (maybe can twist it in there?) and see what the jetting is. But right now I think my KD100 could whoop it. lol It's as if the powervalve (if it had one) was stuck open.

What's the stock fork height setting?

Installed new rubber and cleaned up the plastics a little. I think the side panels are a lost cause so I'm just going to spray them yellow for now.

Tdub13
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9/11/2013 7:07am
That's how they run. No powervalve = power in only one area. I believe the 1980 RM125 was a piston port motor and had all it's power up top, at least the 81 liquid motor was like that. Another thing that would exaggerate this would be a worn out motor with low compression.

I remember the RM's always blowing through fiber disks. Maybe the riders were fanning the clutch all day long to stay on the pipe. Regardless, with an old skool 125, you're going to need an easy clutch pull.
Craze
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9/12/2013 6:23am
Kidkawie wrote:
Thanks for the info. I rode the bike out in my lot and it seems to be a dog. I feel the power come on right...
Thanks for the info.

I rode the bike out in my lot and it seems to be a dog. I feel the power come on right before it redlines. Before that is all flat. I'll pull the carb (maybe can twist it in there?) and see what the jetting is. But right now I think my KD100 could whoop it. lol It's as if the powervalve (if it had one) was stuck open.

What's the stock fork height setting?

Installed new rubber and cleaned up the plastics a little. I think the side panels are a lost cause so I'm just going to spray them yellow for now.

It's a case reed motor and it's mostly on the top end screamer....The main jet should be a 250-270 range, make sure the float level is set...very finicky ....you can alter the ign to 5 degrees BTDC...seems to help....replace the stock petcock with a newer model (83-87) or similar year yz...more flow....make sure you have plenty on compression...or it will suck arse....I run the forks at 5mm up in the clamps
Tdub13
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9/12/2013 8:03am Edited Date/Time 9/12/2013 8:13am
What's wrong with the plastics? You can sand / scrape the chalk and scars. Might be better than painting. I've brought back some very nasty plastic to look very nice. Takes some time though....

Case reed? Way ahead of it's time I guess huh! I do remember the piston port motors and when they changed to the cylinder reed in '82 the "punch" was missing...
Kidkawie
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9/12/2013 9:07am
Thanks for the info Craze.

Tdub, refurbing the side panels is more work than I want to get into. I plan on buying new plastics but the nasty side panels killed the look of the bike. I lucked out as the paint color matches well.

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