1982 RM 125 Rebuild

[jb_dallas]

Hello All

I am getting back into riding after about 8 or 9 years. I rode trails from the time I was about 9 until I was about 25. I bought a 1982 RM125 for $400 (not the best trail bike I realize, but I wanted to find out if I was interested in riding again, cheaply). It was missing the brake assembly needed a few other parts. I ended up buying a brake assembly, rear wheel bearings, both sprockets, chain, and brake pads ($250 in parts). When I got the bike home, I did a quick compression test (cold) to see what I was dealing with. The motor tested 90psi, which seems low. It is also spitting out oil from the tailpipe. My mix is 30:1...apparently, opinions vary on the mix ratio as well. I suspect that I may have a crank seal leaking, but Im not sure. I put exactly 800ml of oil in the bike and I have ran about 2-3 hours since. I am going to drain the oil and measure it tonight to see if it has burned any. I consider myself mechanically inclined and have worked on motorcycles in the past. I think I can handle a top end rebuild, but I am not sure about splitting the cases. How big of a job is splitting the cases and putting in new seals? Should I just ride it until it blows up?

I bought a '99 YZF400 on Saturday, so this is my backup bike.

Thanks

 

[gregorious77]

No need to split the cases for crank seals. you only have to drain oil and remove clutch cover then remove clutch basket and the gear from the end of the crank for oily side and the other side is done by taking off the magneto.
special tools required are clutch basket holder and flywheel puller.
I have a 1984 RM125 and had very similer problems to you. mine turned out to be very worn cylinder and wrong piston (flat top instead of domed)
check out this site for exploded views of the engine click here and get yourself one of these click here

 

[jb_dallas]

Yeah, I probably need to buy a manual.

Thanks for the advise.

 

[jb_dallas]

I drained and measured the gear oil. It burned almost 100 ml of gear oil in 2-3 hours of riding. It probably needs crank seals and top end.

 

[gregorious77]

yep sounds like crank seal is leaking this will cause the smoke and oil out the pipe for sure. check the play in the crank by taking off the magneto cover and giving the magneto a wiggle because if your crank bearings are worn out the crank seals wont last long and you will need to do the bearings.
This does require splitting the cases which is not that hard to do but you will need that manual.

 

[jb_dallas]

If I want to run the bike a few more times before the rebuild, could I run a 50+:1 mix? Apparently, it is drawing plenty of gear oil to lubricate. This may help my plug fouling problem. I realize a rebuild is inevitable.

Thanks

 

[2strokerfun]

Many have tried this and failed. By running less oil in your mix, you're actually running more gasoline which is richening your gas/air mixture and will likely only worsen your fouling problem. Just keep a few clean plugs with you.

 

[jb_dallas]

I think I will ride it until it blows up or sell it. It may be good for another 10 hours. I really need something more trail friendly.

 

[_JOE_]

The clutch debris in the tranny oil is abrasive. If the moving parts arent junk now they will be in short order.

 

[jb_dallas]

I drained the gear oil twice in the short time I have owned it. I did notice this last time I drained the oil that it was very dirty for only 2 hours of operation. What makes you think there is clutch debris?

 

[_JOE_]

Any clutch creates dust. Since the dirt bike has a wet clutch this dust goes into the oil. The dust is from the plates wearing. Lots of bikes have aluminum discs which create even more, metallic, debris. This metallic dust can build up on the piston/cylinder if the tranny oil gets into the combustion chamber.

 

[jb_dallas]

This is a continuation of my thread about the clutch and this thread.

I blew the clutch yesterday and I have suspected bad crank seals for weeks. With this being said, I wanted to pull the head and cylinder to check their condition. The piston has "080" printed on it, so I am assuming that it has already been bored .080" over. The piston had quite a bit of play in the cylinder, so I removed the cylinder. The rod (to crank) had some play as well. It sounds like the motor needs a complete overhaul. The problem is that the bike isnt worth a major rebuild. If the cylinder has already been bored .080", isnt that the max tolerance? Would it be better to part is out and cut my losses, attempt to fix it myself, have a shop fix it...ideas? I have about $650 in the bike with new sprockets, chain, wheel bearings.

Thanks

 

[gregorious77]

Up to you.
Engine will need a new sleeve, main crank bearings, big and small end bearings, possible con rod, new piston/rings/wrist pin full gasket set, new seals, new clutch and some man hours from you. price it all up and see what you think.

 

[jb_dallas]

As Joe said in my other thread, I think the problem may be availability of parts, especially the clutch. What about a conversion? I see 90's RM 125s on Ebay for sale quite often. What would be some complications that may cause? I am assuming parts would be more readily available for the new models. The cylinder bore measured 55.70-56.0 mm, so it has been bored.

Thanks

 

[gregorious77]

That bore is done then deffo needs a re sleeve have you looked on ebay.
Parts are available for my 84 but I live in the uk.

 

[jb_dallas]

I think I am going to sell or trade it...I need somthing more trail friendly anyway.

 

[SMMWest]

Where are you located? I would love to own a 1982 Suzuki RM125 again. This was my favorite bike of ALL TIME! I have owned Matt Maximoffs' Team Suzuki Factory 1993 RM125 and David Pingrees SplitFire/Pro Circuit 1996 Kawasaki KX125 and would say I liked my 1982 Suzuki RM125 a lot better then either of those bikes.

Don't split the cases on this year bike yourself, there are these hidden bolts and if you don't get them and try to open the cases they will be damaged (I did it before).

I will slap an old Krause Kannon Pipe or DG Pipe on there, Krause Kannon Silencer or DG Type II Silencer, go down 1 tooth on the Rear Sprocket (for Motocross) get the Ceet Safety Seat Kit for it, Stiffer Fork Springs and ride that bike for the rest of my life.

 

[jb_dallas]

I am in Dallas, TX. I would imagine shipping would be expensive for you.

 

[SMMWest]

I am in Dallas, TX. I would imagine shipping would be expensive for you.

Crating and Shipping would be like $300. Lets stay in contact. I want it, gotta make my next Child Support Payment and then I will know what I have to work with.

 

[SMMWest]

If you still have this bike and are willing to crate it up, lets do this deal at the end of this month.

 

[jb_dallas]

Since this thread, I have fixed all of the problems and spent more money. I currently have over a grand in this bike, so there is no way I could let it go for under $850...which I am aware it probably wont bring.