I picked this bike up, along with a 1985 YZ125 for $1300 from a guy in NC. We drove 10 hours 1 way to get them. They also came with literally $700 in brand new parts. I had to order a new carb for the 250 as the original Mikuni was pitted pretty badly inside. I went with a Keihin 38mm PWK Air Striker. It started after 7 kicks. Compression before starting was only 140psi, and after I ran it for a bit it went up to 154psi. That's borderline for a new top end. I'll probably do a piston/ring in it. The plan is to strip it to the frame, and replace what's necessary. Here's a short video of it running:
https://www.youtube.com/shorts/2xYi3Rxf6yI
Here's the bikes loaded up:
What a trip. My best friend's first new bike was an '85 YZ125 and his second was an '87 YZ250. I'm looking forward to the rebuilds!
Got my new stand from Vevor in yesterday so I put it to use today. I took the 87 YZ 250 down to the frame. I spent about an hour getting the top triple clamp off, and another hour getting one of the lower swingarm linkage bolts out. The rest of the bike was a breeze. In the next few weeks I'll try to get the frame stripped, and I'm planning on building my own powdercoating oven to do the frame.
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I shot a small video of an easy way to get linkage bolts out when you have limited room:
Good stuff. I have a 86 YZ250 that I've raced at the local Harescramble series the past few years. I'm on my 3rd overhaul of it and it's been a great bike. The 87 is nearly identical to the 86 with different cylinder porting for more low end power (no Boyesen transfer ports) and a white frame and white radiator shrouds. The whole bike shares a lot of commonality with the YZ490 that ran from 86-90 and the TRI-Z 250 had the same motor so motor parts are pretty easy to get. Talon makes a clutch basket, ProX has rods and main bearing kits. ProX does pistons along with Wisceo and Vintco cars some stuff for it also like clutch kits. UFO has all the plastic but the radiator shrouds but DC plastics has those but aren't great quality.
I bough mine because I had a 86 YZ125 in High School and since I was racing vintage stuff a 86 YZ250 was on the bucket list. Mine has 88 YZ250 cartridge forks for better performance and I ditched the KYB compression valves for RaceTech Gold valves and swapped out the rebound valve from some Showa 20mm units from a 87 CR250. One of these days I'll finish adding rebound control to them as the YZ85 compression caps thread right in. Mine has a Ohlins rear shock but I played with a modified 86 version with out BASS and KYB ditched BASS in 88 but it's the same basic shock. I did build a 88 shock with 90 rod/clevis as Yamaha liked to use oriface rebound well into the 80s and would make the back end busy when you run decent rate springs the 90 rod/clevis is more like the modern day unit bypass. I also ditched the rear wheel for a 81 YZ465 unit as it has the large axle setup and give a much larger braking drum. I could wear out a set of pads in one vintage harescrambe to the point the brake pedal would hit the frame. Not fun on some of the courses with hills! It also got rid of the Z-spokes!! I've tried stock, PC and FMF pipes and I like the FMF best as it cleaned up the bottom end and has a nice broad power range. FMF still makes the pipes too. Great bikes and I have really enjoyed racing mine the past few years.
I ordered a PC pipe for it. It was the only one I could find in stock. The factory pipe on it was bent in a few places and not sealing well against the exhaust port.
Thank you very much for all of the information!!!
Cleaned up the kick starter today. I use a soft brass brush on the aluminum. It works great at removing caked on grime and leaves a nice finish. Then I hit it with some Mothers Mag and Aluminum polish. It looks brand new other than some dents. I scrubbed the rubber boot and massaged some Adam's tire shine on it.
I'm about 5 hours into the frame now. I've hit it twice with paint remover, and scraped it off after work 2 times. Today I sat down with a bunch of equipment and started scraping/sanding. The best method so far is a wire wheel on a drill. It's slow and methodical but it works. I have a few different sizes to work with to get into the tighter spots. I've sandblasted a frame before and it also takes a lot of time. Anyone that tells you they can PROPERLY blast a frame in an hour is likely full of you-know-what. Frames have so many brackets, gussets, braces, nooks and crannies etc. The only way to blast one that fast is with a large industrial size blaster. A smaller blaster at home is going to take you hours, not to mention you'd need a huge cabinet for a frame like this that doesn't have a removable subframe. Anyways I figure I have about 2 hours left.
Well I broke down and I built a cabinet big enough for the full frame YZ. I spent about $100 for materials, but it came out great. The best part is that I can take it apart in 5 minutes and store it in a corner so it's not in the way when not needed. https://www.youtube.com/shorts/Z42-CCgeKfw
Here's the finished result after about 2 hours:
Built the powder coat oven today. I used 2 sheets of insulating board from Lowes and 1 roll of tin tape. The tape is VERY important. I got the idea from "Chase builds bikes" on YouTube. I built 2 small wooden ends that rest on the side to support the weight of the frame/bar assembly. It's about 40lbs total. I got 2 heat guns for $65 on Amazon. Today I gassed the frame out. That means you heat it up fairly high to get any residue off of it. Next weekend I will powder coat it. Can't wait! The oven itself weighs about 5lbs lol.
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More progress done on the '87 YZ250. My first attempt at powder coating. It came out amazing! I'm very happy with the results. I had a few tiny issues though. The bottom steering stem plug that I made fell out during the cure and landed right in front of a heat gun. It started to smoke so I panicked and opened the oven up to get it out. Then the sides of the oven started to fold inward and they rubbed the powder off of the edges of the footpeg mounts. Next time I will build a slightly wider oven to solve these issues. I did everything you see here for under 200 bucks total. I bought 1lb of powder and I probably used 1/4 of it. The frame has 2 coats. I did 1 coat on the low voltage setting, then did another coat with the higher voltage setting. It's cool to see it in action. The powder comes out in a super fine mist, and just gets drawn onto the part. There's virtually zero mess when you're done.
Dove into the engine today amongst other things. Found that it has a Wiseco 1mm over piston (.040"). I pulled both rings and checked the gap. The top ring is .014" and the bottom ring is .012". There is very little visible le cross hatch in the cylinder. I'm gonna send it lol.
Got the front wheel torn down. All of the spokes came right off. The tire was mounted backwards too. I'm going to powder coat the hub next weekend. I cleaned each spoke by spinning it in a cordless drill while wrapping it with sandpaper (320 grit) and a dab of polish. Unfortunately there's nothing I can do about the rims themselves. They have a lot of scratches. If I were keeping the bike I'd strip the anodizing, polish them up and re-anodize them. But it won't be cost effective for me to do that to sell the bike. The spoke nipples will be polished too.
Here's a short video of me doing the spokes:
Man you're spending a tremendous amount of time and energy on the chassis but I'm surprised that you'll just send it on the motor. You can get larger pistons from wiseco and woosner for it. All the way up to 2mm over stock.
I'm about to wrap up my 86 build as I have a race this coming weekend that I need it to be ready for. I doubt I'm going to get much testing in before hand but that's what I get for putting family first. Lol
Pit Row
The motor ran good, and based on the lack of wear on everything inside it looks fairly fresh. The rings look fresh, there's green gaskets under the jug, the piston top had a small spot of carbon on it that wiped off. Both rings check out well within spec. There's zero play in the crank up and down. My guess is that the bike was put together and run for 4-5 hours or so. The guy who's likely buying it, is a vet guy that will woods ride it mainly. I'm trying to turn a small profit on the bike, Adding a new piston/ring kit plus a bore, will add $350-$400, then you enter into the "while I'm in there I might as well do this too...." scenario. Then I'm in an extra $800-$1000 and I'm upside down in the build. I don't mind the labor at all. I like to reuse whatever I can if it still has shelf life.
The next bike is either my '85 YZ 125 or the beastly 1983 CR 480R I just picked up!
Did some powder coating this weekend. Did the rear spring in racer red, and did the footpegs, upper triple clamp, and front hub in gloss black. Everything came out great!
Rear spring
Got some more stuff powder coated and did the first assembly. Got the footpegs mounted and the bike is officially on the stand now! This weekend i will polish the spoke nipples and reassemble the front wheel.
Built the front wheel yesterday. I got the spoke pattern wrong and had to redo it lol. Took my time truing it and got it near perfect. Also installed the new headset bearings and triple clamps.
Got the engine together mostly and set it in the frame. It's not fully together yet, but took the opportunity to mock the pipe up. Won't be long now until it's running!
Got a few pieces on yesterday. The stock rads were a bit trashed so I picked these up for $65. Had to modify them to fit. The bugs were at the wrong angles and hitting the frame. Got the forks on. Took a chance with some cheap boots from DC Plastics and they were very close to factory. Saved myself 30-40 bucks. Hit some of the plastics with a few different grits. Before amd after pics below. Ordered some crazy strong hydrogen peroxide. Going to mix with powdered bleach and/or baking soda to see what it can do.
Yamaha plastic from that time period is an off white. You can still get OEM front fenders and you'll have though they have yellowed but in reality it is the OEM white.
The bike came with new bright white plastics from UFO and Maier. The number plates, and front and rear fenders. I have 3 shrouds for it. 2 are aftermarket that are fairly dirty (in the post above) and the other is the factory one for the left side. The crispness of the factory piece is far better than the aftermarket ones, but it is very discolored. The tank is very discolored. I will throw every trick I have at it lol. Last resort will be to paint it. I did some work this morning on the radiator hoses. They very caked with grime. Hit the with Adams' tire cleaner and a soft brush, then worked some hose dressing into them. The clamps I cleaned with a small wire wheel.![]()
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Got the hoses all routed. What a pain in the ass lol.
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