1986 CR125 alive again! she is done!

I almost forgot. It has a Pro Circuit pipe. It was rusty so I put metal rescue on it and after two days the transformation was dramatic!

I'd throw down for the OEM plastics. Live it up a little.

One more question. A person near me is selling a 1990 CR frame for $50. It has inverted front shocks with the entire tree. It has a front wheel with the brake. The rear shock and the foot pegs. Would those inverted shocks from the 1990 work on the 1986?

Not sure about the shock but the frond end would be worth it. you can buy a bearing conversion kit from All Balls. But I am thinking it will bolt right up.

no, don't do it.... those forks sucked ass in comparison to the 86 cartridge forks.

BR8ES wrote:

no, don't do it.... those forks sucked ass in comparison to the 86 cartridge forks.

+1

Thanks guys

Brian_Bowles wrote:

So while I am working the 1986 YZ125 I also have this CR125. Both were dying in a back yard with no love.
When I first got her she was really crusty. Notice the electrical tape in place of the boots on the shocks...



We brought her home. Cleaned out the carburetor then then blew the carburetor out with compressed air. We changed the transmission oil and checked the radiator fluid. Then we put a new spark plug in and this happened:
">CR125 comes alive!

Next we checked for the dreaded corrosion in the water pump area. It was full of corrosion thatvlooked like white toothpaste. After digging it all out and checking the water lines there appeared to be very little damage.

We replaced the water pump gasket and put it back together. Unfortunately the radiators were full of white corrosion sludge. It took them to a radiator shop and for $20 they were able to clear them out. We then filled the bike with Evans waterless coolant so hopefully corrossion will not be an issue in the future.
The screw in the throttle housing on was completely seized and we were unable to drill it out. So I got another one off eBay for $8 shipped.


I have been sanding the plastic to restore it so it is starting to look better. The back fender is not OEM and no amount of sanding will help it.

I painted the handlebars and added new grips and a new throttle cable.
The bike has good power but is on the lower compression end.

I have some questions:
1. I can get a new front and rear fender from UFO for $54. A new OEM front and rear fender from Partzilla is $90. Is it worth the difference in price. I ask that because I will also need new tires, case gasket (leaking a little oil), new sprockets, new shock boots, maybe new clutch plates, and new decals.
2. If the compression is low I assume I either have to get new rings or possibly a new piston and rings. If the cylinder wall is marred up can the bike be bored, plated, or is it sleeved? when examining how is all of this in #2 determined.
I would like to do a big shout out for my brother. None of this would have been possible without his help.

BTW I got both bikes for free. I think the previous owners had no more use for them. They were happy to get rid of them and happy that someone might save and use them.

For plastics, I’d go UFO. They make a good product and it won’t make a bit of difference when your done. There are a lot of items I think OEM makes since. I’ve probably got $500 in OEM parts for the 87’. Still can’t believe you got that bike for free !

Brian_Bowles wrote:

One more question. A person near me is selling a 1990 CR frame for $50. It has inverted front shocks with the entire tree. It has a front wheel with the brake. The rear shock and the foot pegs. Would those inverted shocks from the 1990 work on the 1986?

I’d keep the 86 forks also....JMO

Thanks Mark,

I hear people say you can spend so much on one of these and easily outspend the value of the bike. It makes it a lot better when you got the bikes for free.

So what about the piston. I figure I will check the compression tomorrow. When I first tested it the compression was at 110lbs. Now that was before it had been run and had sat for 5 years. I expect it would be a little higher now. I will say the previous owner told me how he rode the CR125 FOREVER EVERYWHERE when he in his teens. I asked him if he ever put rings in it and he said no. So my question is what am I looking for when I take the head off. I was thinking of the following:
1. Check for scaring on the cylinder wall. If there is no major scaring I can probably have it honed and get a new piston and rings.
2. Check for play in the crank. I know it will move side to side but should not move up and down. How much movement is ok?

Should I take the ring off and put it in the cylinder and measure the gap with a feeler gauge?

Brian_Bowles wrote:

Thanks Mark,

I hear people say you can spend so much on one of these and easily outspend the value of the bike. It makes it a lot better when you got the bikes for free.

So what about the piston. I figure I will check the compression tomorrow. When I first tested it the compression was at 110lbs. Now that was before it had been run and had sat for 5 years. I expect it would be a little higher now. I will say the previous owner told me how he rode the CR125 FOREVER EVERYWHERE when he in his teens. I asked him if he ever put rings in it and he said no. So my question is what am I looking for when I take the head off. I was thinking of the following:
1. Check for scaring on the cylinder wall. If there is no major scaring I can probably have it honed and get a new piston and rings.
2. Check for play in the crank. I know it will move side to side but should not move up and down. How much movement is ok?

Should I take the ring off and put it in the cylinder and measure the gap with a feeler gauge?

Yah I’d first measure the cylinder and see what you got. If the cylinder looks good and is stock 54.00 bore, id buy the Weisco piston, ring, and pin on EBay for $99. It’s the only one I see and looks like you can’t get stock OEM piston anymore, only 1st and 2nd over. So it really depends on what you find when you open it up. I would definitely do a top end while you have it open if it were mine. Up and down play on the rod should be almost none. If you feel any up and down play doing it by feel, then you probably should split the cases. However, I’d avoid that if I could unless you want to spend some time and money. So see what you got after open up and go from there...you’ll know when you see the piston and cylinder walls

Mark did you have to do a bottom end on yours?

I do not have the tools to measure it so maybe I can take it to a machine shop and have them do it. Then I can get the piston needed online and take both to the machine shop.

Brian_Bowles wrote:

Mark did you have to do a bottom end on yours?

No....Mine was good, and I'm glad I didn't want to dig into it

Brian_Bowles wrote:

I do not have the tools to measure it so maybe I can take it to a machine shop and have them do it. Then I can get the piston needed online and take both to the machine shop.

You need to decide what your going to do with it BEFORE you buy a piston. Make sure you have your direction of stock bore, or first over if your going to have it bored. I say that because I bought stock piston before I tore it down....and they didn't want to take it back,,haha. So I bought another stock bore cylinder

Time to get going. My other project the 1986 YZ125 is running well. I took the head off today and this is what I found. What do you think?

cylinder looks good, hone it and measure it!

Well the piston looked good. It had one mark near the front. It is being bored and then will have a piston ordered to match it. In the mean time I was working on the top of the cylinder. The paint was looking really bad.maybe a natural look would look good.

What a great find!!
Go with the UFO plastics. They do everything apart from the side panels. (87 rad scoops are the same as the 86) The UFO plastics are actually a better colour match than the OEM ones you can get! (Yes, really) The mix must have been changed slightly over time and the OEM fenders are a little bit pink. It's quite noticeable when they are next to original "orange" side panels. The UFO stuff is spot on for colour and fits perfectly, it's also cheap!!
Stevie

Double post.

Thanks Steve, I plan to order some fenders today. I need to find a front chain slider. Mine does not have one so it is carving the swing arm away. I found some but they are $50+. Anyone know a cheaper alternative?

Brian_Bowles wrote:

Thanks Steve, I plan to order some fenders today. I need to find a front chain slider. Mine does not have one so it is carving the swing arm away. I found some but they are $50+. Anyone know a cheaper alternative?

Sadly, the only things available are the Hot foot Moto stuff. They are ok, (they need a bit of work to get them fitting correctly) and they are quite expensive. But there isn't anything else available.

I had some luck finding an oem piston ring by calling my local dealer. I guess they share inventory databases and had one ordered from a dealer in Kansas. You might give that a try. Good luck!

Thanks Bonseff, I will try that. It cannot hurt.

I took the rear shock off today. That was easy. The bolt that holds the swing arm on was another story. I think I will have to get a longer tool with more leverage to get the bolt unscrewed.

The process continues......