84 Rm 125 rebuild (the basket case bike)

[chillywilly]

So about a month ago i picked up an 84 rm 125. I brought the bike home in pieces in the box of the truck, as i said in a previous post, some assembly required. with the bike i also got a extra frame with swing arm, forks, front wheel, and bars with triple tree. The main bike is missing the top end, and i do mean top end. It needs cyl, head, piston, pipe, and carb. I also need throttle assembly, levers and perches, and kill switch. I have recently aquired a cyl, so i can scratch that off the list. I pulled the remains of the motor out and split the cases, and found that it must have sat outside with the missing top end and requires all new bearings, nice. So i am waiting on two bearings to arrive then i can reassemble. The seal surface on the crank flywheel side is pitted so i guess it will have to be resurfaced. I have started to work on the rest of the bike, by repacking the headset, painting the bars and steam cleaning the whole thing. Next is checking wheel bearings, swing arm bushings and then reassembling the chassis and awaiting the motor to be done. Oh yes did i mention that i am doing this on a tight budget, so it might take all summer to get it done.

 

[rmc_olderthandirt]

The seal surface on the crank flywheel side is pitted so i guess it will have to be resurfaced.

I hate to tell you this but I suspect that you need a new crank!

Have you separated the crank halves and inspected the rod bearing? If the main bearings were toast and the seal surface pitted then I would expect that the rod bearing is in similar bad condition. It could be a real disaster if you manage to get this bike running again and then throw a rod due to a bearing failure.

As for the seal, are you sure that the crank can be resurfaced? The usual process for resurfacing a rod or journal bearing surface is to grind them down to a smaller size and then use oversize bearings, but I have never seen this applied to the seal surface.

 

[2strokerfun]

I'd find another engine and use parts from both. Otherwise, I'd recommend you stop this madness now. It sounds like a black hole of money.

 

[chillywilly]

The crank can easily be saved, the crank bearings were fine well kind of, and the seal surface on the clutch side is perfect. I talked to the local machine shop and they said that they can grind the seal surface down to 16mm from 18mm to remove the pitting. Then i get a 16-30mm seal from the local bearing shop and all is good. I am going to split the crank and do the rod bearing as well, cheap insurance. I also thought about a speedy sleeve for the seal surface, but it will be cheaper to resurface it.

 

[John.Jr]

Hello my friend Im not trying to discourage you but DO THE MATH FIRST!!!!!!! before you get started. Add all this stuff up first before you get started,check on Ebay for an whole motor .But I know you are looking at this skeleton and you are hyped to get it going butit might be REEEALL EXPENSIVE for this project I wold buy a nice RUNNING BIKE FIRST then work on that Suzuki later, keep me informed JohnJr

 

[chillywilly]

A running bike like this up in Canada is worth aprox $1000- $1200, i paid $200 for it the way it sits. The cylinder cost me $75 shipping included, bearings will cost aprox $100 for the whole motor and trans. Tha rest will be pieced together slowly. I have been watching stuff on flea-bay, but the shipping to canada is easily double than in the US, that blows. I have added the stuff up and i will be into it for less than a runner.

 

[John.Jr]

Hey Chilly that great brother I had an 1986 YZ 250 and a motorcycle shop gave it to me, I want to give them something for it, they told me to take,according to them it would cost over $1000.00 to get it running ,when I bought it home my brother and dad said it was a piece of junk,needed piston and rings,carb.,coil,exhaust, one side cover,FOOLED THE NEYSAYERScost me to get it running about $400.00 found parts here and there this thing was reliable.I sold it like a fool and bought a 01 KX500,I miss that bike. Its a lesson in this story, keep me informed, JohnJr

 

[gregorious77]

You can get it going again cheaply enough.
Mine is ready to run now first ride this weekend hopefully.
Mine cost £300 for the bike then I spent another £250 on it to get it all sorted. still cheaper than a decent runner and now I know everything about the 84 RM125 inside and out.
When you come to put the cases back together that spring loaded thing on the gear selector drum is a right pain in the ass to get located. I had to use a piece of fishing line to hold it back while sliding the cases back together.It doesnt mention how to do it in the book. took me a knuckle scraping 1/2 hour or so to get the cases back together.

 

[chillywilly]

Thanks for the warning. At least when i am having troubles now i won't be thinking wtf am i doing wrong. By the way, if you are riding this weekend, what is the temp over there. I woke up to -38 and a wind chill of -50. But it is going to be a balmy -13*c this weekend, perfect sledding weather.

 

[gregorious77]

It will be about 10 deg C this weekend
not to bad at all.
http://www.metoffice.gov.uk/weather/uk/se/se_forecast_weather.html

 

[zoommx]

Chilly, I have used a speedy sleeve on the flywheel side of a crank. Works fine. Turning it down should work good also. On a couple transmission cv output joints of an old car, I had a machine shop turn them down and resleeve back to original size also, another good option when wanting to keep original size seals. :clue:

 

[chillywilly]

Just a quick update, the crank has been split and sent out for grinding. The rod and pin have some small pits in it, so i guess a new rod kit is in order. Finally got the last bearing for the trans, so that is in the case and waiting for the crank to come home. Pulled the swing arm pivot apart, and the bearings in there are as dry as a popcorn fart and need replacing as well. I guess as long as i keep reminding myself that this is suposed to be a fun project it will keep me from going to tears with all the money i will fork into this basket case. Oh yea if my wife asks, the parts were only about $20!

 

[gregorious77]

hurry up and get it going!! did you see my vid and pics?

 

[chillywilly]

yes i saw them and enjoyed them. Money is tight right now with the wife only working casual and in university full time. But when she is done and making use of the degree it will be time for daddy to go on a shopping spree!!!!

 

[gregorious77]

ha ha fair enough. I still need a seat cover but cant find one in the uk. can find em in the usa but too pricey for me.

 

[chillywilly]

Yea i hear you, most stuff on e-bay with the shipping ends up being the same cost as new stuff here.

 

[chillywilly]

More updates, the crank is home from the machine shop, and a new seal is in the case. The rod kit was put on hold, as i bought another parts bike. This one is also a 84 rm 125, with no motor, rear wheel, or swing arm, but is otherwise all there. And it does have a good carb and a pipe, two of the key pieces that i need. I payed less for the whole thing than i would have the two pieces that i needed on e-bay. And it was only 2 hours from me. So if anyone needs some 84-85 125 parts let me know, as i have one complete rolling chassis minus rear wheel, and one frame and front end.

 

[sr5bidder]

chillywilly
what parts do you still have for the rm125? I have an 85 rm125 I think I'm going to put a yamaha rt180 engine in if the deal goes through, so if it all works out I'll have a complete engine needing only the 3rd oversize piston and crank bearings/ seals to run

I rebuilt this before and sold it and it came back to me for free after several fixes over a year for the previous owner they had finally wore it out and messed up the suspension.

I remember it was one of those light switch powerbands and thats why I sold it in the first place and do not want to rebuild it again, but put some fun grunt for a woods/ loaner bike/ learning bike...I really hope the rt180 goes in without to much fab!!

 

[chillywilly]

Wow long time no post. I have not done a single thing to the bike since back in the spring. Thinking on getting started on it again. I need to sit down and look at, compile parts lists and get shopping.