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1986 RM125 Modern Restore

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Alright, so I was browsing the good ol' craigslist one day and I ran across a beautiful 1986 RM125. It definitely needed some work but was a great little bike for the price. :) $175 and no it did not run at the time of me picking it up. 

 

so i popped open the engine and found that the bike had been over bored to 55.5 mm and the guy tried to put a 54 mm piston in the bike, (I guess this is why it didnt run lol) Luckily the cylinder wasnt scored at all and the bike only needed a good hone to get her back in tip top shape. I ordered a Wiseco over-sized piston and the crank shaft seemed to be perfectly in spec with no play in the shaft, the rod actually looks like it is brand new! 

 

So initially I though that I would have this bike just for my wife to learn to ride, but the more I worked on it, the more I fell in love with this bike. So I have come to the conclusion that I will be restoring this bike back to new again, but I will be changing just some minor details along the way. 

 

Here is the sleeping beauty put away from last winter and ready to enjoy a nice little refresh!

 

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Edited by blbiker56
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Started Some Disassembly of the bike, So far everything looks pretty good. The FMF pipe looks like it was from a modern 125 cc bike, and the inlet pipe is cut off a bit, but thats ok, I will be looking for a DG system to install later on in the build. The rear shock is low on nitrogen, and I will be having it rebuilt by a shop, Anyone know of any good shops for these older bikes? I have heard Pro-Action-Suspension is fantastic.

 

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Should be a fun project!  As for the shock, in your case your just going to rebuild it, so I wouldn't worry too much about who does the rebuild.  Maybe look for a shop that was around in '86 but honestly, any decent shop should be able to do it.  Oh, and don't forget about rebuilding the forks too.

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So I did a little work to the bike this past weekend, and I am finally updating the post.

 

The carburator was dirty and full of pre-mix oil in the float, so I started to do a full rebuild. I purchased a carb rebuild kit that came with all new seals, but before I rebuilt the carburator it was in desperate need to have a little cleaning performed on it, so I soda blasted the carb (which turned out really nice) and then put her back together.

 

JETTING- can someone help me with getting the jetting right for a 1986 rm125, high altitude?

 

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would that make a difference? Im not quite sure how big the stock carb is?

The PWK is a better carb, so isn't the air striker. Id figure out stock jet sizes, run that in the new PWK or airstriker and go from there. Do plug chop tests to see if its too lean or rich.

Bad spark, too hot or cold of a plug, bad reeds, and worn top end would make jetting tricky too. Make sure all of those are in order before trying to jett. Pick a ratio, like 32:1 and jett accordingly.

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I am on a business trip at the moment, I have another carburator so I will have to see what kind it is. It came with a cr125 that I purchased a couple of years ago. Im not looking to build a real monster machine, but monstly a very nice restored rm125 that can be a blast to ride/race for enjoyment.

 

on a couple other posts I have made here on thumper talk, I spoke about how the crank shaft was leaking coolant into the transmission oil. This is the main reason for a copmlete engine rebuild. You can see the pitting and groves on the crank shaft before polishing it. I had the shop down the street help me polish this, Wane helped me with a lathe and crank shaft polisher. Turned out pretty good, hopefully this will fix the issues.

 

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Here is it after the polish,

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You can see one little grove that Wane just could not get out of the crank shaft, but it is so tiny that it will not be an issue. But now this thing is almost brand new, and has a new connecting rod as well.

Edited by blbiker56

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Did some more soda blasting this morning, and was able to assemble the transmission along with getting the crank shaft installed. I really like the bare aluminum engine with the painted internal surface areas. For a lot of performance car engine heads this would be an extra expense to allow the oil to flow evenly, Does it really work??? I DONT KNOW, but it sure does look awesome.

 

I was able to find a complete engine oil seal kit that I will be installing on the bike. This will give the bike a brand new look and provide the benefits of a completely leak-less engine :) The kit also came with all copper washers to replace as well. All o-rings have also been replace.

 

I cant wait to get this engine going and hear it run for the first time.

 

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I was able to get the clutch side of the engine assembled and cleaned up. My clutch tool had a hard time getting in between the clutch basket, so I was able to fabricate up a nice little tool from some left over little steel. Gave me a reason to use my new flux core welder, tuned out pretty good looking for a flux core if you ask me.

 

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I also was able to soda blast and clean up the head, which is in very, very good shape.

 

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So the frame was stripped of all paint and then re-coated with a high gloss black and several clear coats. The paint turned out really great and is going to look fantastic with the stripped engine. I also had the chance to rebuild the rear brake and get the brake pads installed (pictures will come later). I am getting the rear shock rebuilt by a guy here in Denver hopefully this week, will need new oil and nitrogen refill. 

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did some work today on the RM and I am looking at doing a vintage graphics kit but I want black lettering, does anyone know of a well priced custom vintage graphics dealer? I was thinking about printing some off at Kinkos and putting their HD 3mil clear liner on top of the graphics.

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I am currently rebuilding the forks and have put the new fork seals and dust caps in,

 

does anyone know the correct amount of oil to be put into the forks?

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You're getting it done pretty fast looks great

 

Thanks,

 

Yeah, I have been spending most of my free time working on it. The other bikes are waiting on parts so it may slow down when i get those in. :)

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Hey Guys here is a quick update,

The bike has been put on the back burner due to another customers bike to be worked on, but...
I have rebuilt both forks and put new fork seals and some fresh oil has been put into them, they look and feel great! Also I spent a ton of time working on the radiators. They were bent up and many of the fins bashed in and not facing straight. Took a long time but the radiators are looking fantastic now and are cleaned and heated cleaned to burn off all oil deposits. I will be high head coating them with flat black to bring back the shine!(Flat Black) grin.gif . I also received both motion pro cables and the new UFO front fender. I should be able to polish and use all the other original plastics on the bike. I also finished the rear brake pedal.

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Hi - I live up in Evergreen CO. and am rebuilding a '84 rm125.  Who helped with your rear shock? I need help with mine.  Thx 

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