1989 YZ125W build.

Dekon
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Edited Date/Time 12/27/2017 3:21pm
Just wanted to post up a build I have been working on since I picked up a total basket case '89 YZ125. It was literally a basket case; when I picked it up every part of the bike was in four large Tupperware bins. It was missing the cylinder, carb, clutch, and electronics. Oh yeah, and almost all of the bolts. This build is an extreme budget build. Started the build on August 31st after rounding up 90% of the parts. I like the parts chase.
Sanded and rattle canned the frame, it is going to be a rider not a garage queen.



All new linkage and swing arm bearings. Didn't use the Pivot Works grease, I used a marine grease(forgot the name).
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Dekon
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11/5/2017 8:41am
I got real lucky and found a used cylinder and piston on ebay. Apparently the cylinder had just been replated and matched to the piston. It was never used, person found it as left over parts when he cleaned out the garage. Measured everything up and it was in spec. Had the crank rebuilt by Ken O'Connor racing, all new bearings and seals in the motor.


Dekon
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11/5/2017 8:44am
Dropped the motor in the frame.

Installed the rear shock, linkage, and swing arm.

Then installed the air box.
Dekon
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11/5/2017 8:47am
Then tragedy struck. Somehow one of the straps came undone and it fell over onto the kicker which resulted in this.

Luckily in the pile of parts that came with this there were four kick shafts, so I replaced it and went on from there. I still can not believe how the shaft snapped right in half.
Dekon
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11/5/2017 8:53am
Installed the forks(new seals, bushings, and oil), wheels and tires(new bearings in the hubs).

Cleaned out the silencer core, all the holes were totally blocked with carbon/oil residue. There are 800 holes in the core, 50 rows with 16 holes in each row. I punched out each one individually, I was amazed at the pile of carbon/oil I had when I was done.

The Shop

Dekon
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11/5/2017 8:56am
That brings us up to this weekend where the radiators, exhaust, tank, and seat were mounted.

Dekon
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11/5/2017 9:00am
Like I said this is an economy build, if you can really call any bike build economy, but I had to go for the gold D.I.D. chain, I think it adds a little bling to the build, besides, I think they are cool looking. Also, as I was working yesterday, the postman stopped by with some more goodies I had ordered, new swing arm slider and chain block, and a new petcock and fuel line. You can see the old slider under the bike, it was ugly looking.

Dekon
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11/5/2017 9:03am
Finished up the day mounting the front and rear fenders, front number plate, and the radiator shrouds.


And my assistant for the build; I think he can not wait to go roost on this, LOL
Dekon
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11/5/2017 9:08am
All that is left to do is:
Mount front and rear master cylinders and brake lines
Bleed the brakes(I hate doing this)
Mount up the side panels(haven't arrived yet)
Install the foot pegs
And then the graphics, not sure if I am going to go stock or do a Donny Schmit Chesterfield bike. This can wait for the winter months.

Oh yeah, I almost forgot, start it up.
cvm
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Monrovia, MD US
11/6/2017 3:12am
Dekon wrote:
That brings us up to this weekend where the radiators, exhaust, tank, and seat were mounted. [img]https://i.imgur.com/G6gFhaR.jpg[/img] [img]https://i.imgur.com/vrpw26t.jpg[/img]
That brings us up to this weekend where the radiators, exhaust, tank, and seat were mounted.

Fantastic Bike / job. I Did a rider build on a 92, and doin a 93 this winter.

Lookin back @ the hrs I spent on my tank, & the pic of yours at top of this post, I'd love to see a close-up.
Why the absence of yellowing that is under where the radiator shroud mounts to the tank? Test spot?
Not disputing that premix yellows them, but if yours is orig that means that UV rays are a major force in yellowing also. Which they have to be to some degree. But rt side seems more consistent. Hmmm.
A pic of mine in the EVO thread, a great place for graphics.
Again, great job. Take extra pics now cuz they're a little different after 30+ track days Smile
Dekon
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11/6/2017 6:02am Edited Date/Time 11/6/2017 6:15am
Thanks sandman.

CVM, I found it funny too that under the rad. shrouds there was no discoloration. I think you might be on the something about UV. Could it also be that the plastic is thicker on that side of the tank? I just don't know. All I did to the tank was wipe it down. No sanding or anything like that on it. Also, the pictures make it look lighter than it is, the tank is pretty yellow. I think it is original to the bike, it came in the pile of parts(it is a OEM Yamaha one).

CVM great looking build, really like the rear fender and side panels with the hand holds in them. Wish Yamaha did that in '89 instead of starting in '91.
Banana_oil
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11/6/2017 1:01pm
Those bikes are so good looking! I built a 1990 some years ago and it was nice to ride. I vote for stock graphics as the Chesterfield builds are so common but sure they are very nice.

One flaw with these bikes is the magnesium outer clutch cover but maybe you already know. It is too weak which makes the clutch drag. Go for a 91-93 cover instead, they are in alu and stiffer.

Good luck with the build!




Dekon
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11/6/2017 2:06pm
Banana_oil wrote:
Those bikes are so good looking! I built a 1990 some years ago and it was nice to ride. I vote for stock graphics as the...
Those bikes are so good looking! I built a 1990 some years ago and it was nice to ride. I vote for stock graphics as the Chesterfield builds are so common but sure they are very nice.

One flaw with these bikes is the magnesium outer clutch cover but maybe you already know. It is too weak which makes the clutch drag. Go for a 91-93 cover instead, they are in alu and stiffer.

Good luck with the build!




Great looking build! I like the red upper tubes on the '90's.

Did not know about magnesium clutch cover issue, thanks for informing me. Just so I get this right, the rest of the components from the mag. cover will drop right in with no mods.?

One issue I found is no one has fork springs for the '89.

And I'm really leaning toward the stock graphics as they just have a clean look to them.
Sully
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JP
11/6/2017 5:29pm
Nice looking bike. There's something about the giant radiator shrouds on the '88 - '92 YZ 125 & 250 that I really like.
Mdesmond
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Melrose, MA US
11/6/2017 5:37pm
Very nice!

Did you leave the engine as bare aluminum? I'm getting started on a rider build of an 88 RM250 and don't like the blue engine. I was thinking about going bare aluminum....wondering if that works OK?
Banana_oil
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11/6/2017 9:41pm
Dekon wrote:
Great looking build! I like the red upper tubes on the '90's. Did not know about magnesium clutch cover issue, thanks for informing me. Just so...
Great looking build! I like the red upper tubes on the '90's.

Did not know about magnesium clutch cover issue, thanks for informing me. Just so I get this right, the rest of the components from the mag. cover will drop right in with no mods.?

One issue I found is no one has fork springs for the '89.

And I'm really leaning toward the stock graphics as they just have a clean look to them.
Yes, no other parts need to be changed.
Dekon
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11/7/2017 4:08am
Mdesmond wrote:
Very nice! Did you leave the engine as bare aluminum? I'm getting started on a rider build of an 88 RM250 and don't like the blue...
Very nice!

Did you leave the engine as bare aluminum? I'm getting started on a rider build of an 88 RM250 and don't like the blue engine. I was thinking about going bare aluminum....wondering if that works OK?
I just cleaned up the engine, it is still in the factory silver color. I wouldn't see any problem if you left it bare aluminum. The only thing I can think of keeping it bare is that it might be tough to clean because it is cast and not so smooth that the dirt will get into the roughness.
Dekon
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11/7/2017 4:09am
Banana_oil wrote:
Yes, no other parts need to be changed.
Awesome, thanks for the tip.
Dekon
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12/25/2017 7:49am
OK, so I am basically calling this build complete. Other then installing the OEM style graphics and bleeding the brakes, the YZ is complete. I added a little premix to it and it fired on the fourth kick. Really wanted to take it for a blast down the street but the brakes are not bled. Was having an issue doing it. So here it is.



Don't mind the right side foot peg. Cheap Chinese crap that broke when my boot hit it when I was kicking it over. Good thing that happened now rather then when I was riding it.

Also, I ordered up the '93 outer clutch cover like Banana_oil said but it did not fit. The clutch push rod was to large for the hole in the cover. Looks like I need to drill out the cover. No big deal. I can not wait to go rip on it.
Banana_oil
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12/25/2017 8:52am
I'm sorry I fooled you, I must admit I assumed all other parts fit as I read about the swap in another thread. I know the clutch assembly was changed in 92 or 93, so maybe 91 is swapable without mod.
Nzpatch
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NZ
12/25/2017 1:40pm
Hi guys , they changed the clutch in 93 ( 1 more plate etc)
So 91 and 92 are the same, the actuator shaft is different in 92 to change the leverage rate
Your yz looks mint by the way! Ps I would keep the stock graphics.
Dekon
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No. Prov., RI US
12/25/2017 3:37pm
Banana_oil wrote:
I'm sorry I fooled you, I must admit I assumed all other parts fit as I read about the swap in another thread. I know the...
I'm sorry I fooled you, I must admit I assumed all other parts fit as I read about the swap in another thread. I know the clutch assembly was changed in 92 or 93, so maybe 91 is swapable without mod.
No worries. Just glad I got some input about the clutch issue. Looking at the parts fiche, it looks like 91-92 will work as the push rod is large like the 89-90. 93's push rod is smaller in diameter.
Dekon
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12/25/2017 3:39pm
Nzpatch wrote:
Hi guys , they changed the clutch in 93 ( 1 more plate etc) So 91 and 92 are the same, the actuator shaft is different...
Hi guys , they changed the clutch in 93 ( 1 more plate etc)
So 91 and 92 are the same, the actuator shaft is different in 92 to change the leverage rate
Your yz looks mint by the way! Ps I would keep the stock graphics.
Thanks. And yes I am going to go with the stock graphics.
Dekon
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No. Prov., RI US
12/25/2017 3:40pm
Great build!! Love those years
Thank you. I always wanted that bike back in the day. I was finally able to get it.
12/25/2017 4:46pm
Great build!! Love those years
Dekon wrote:
Thank you. I always wanted that bike back in the day. I was finally able to get it.
I raced one back in 89 the stators on the first shipment were bad and always prone to failure. Yamaha fixed the problem. Apart from cylinder and head work one thing i did was run an 1988 model YZ FMF pipe and silencer it was way better than the 89 model fmf pipe it also looked identical in shape to what Bradshaw was running.
Bent206
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Coventry, RI US
12/26/2017 7:20am
Dekon wrote:
Installed the forks(new seals, bushings, and oil), wheels and tires(new bearings in the hubs). [img]https://i.imgur.com/AYEt6s5.jpg[/img] Cleaned out the silencer core, all the holes were totally blocked...
Installed the forks(new seals, bushings, and oil), wheels and tires(new bearings in the hubs).

Cleaned out the silencer core, all the holes were totally blocked with carbon/oil residue. There are 800 holes in the core, 50 rows with 16 holes in each row. I punched out each one individually, I was amazed at the pile of carbon/oil I had when I was done.
Cool build. I’ve always liked the ‘89’s.

Use a map gas torch the next time you have to clean the perforated core. In a safe location heat the core until the oil catches on fire an burns off. Then clean off the leftover ash (it comes off easy). It sounds crazy but I actually saw this in an old Suzuki two stroke street bike manual. I’ve done it many times since.
nicko-31
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12/27/2017 3:21pm
Nzpatch wrote:
Hi guys , they changed the clutch in 93 ( 1 more plate etc) So 91 and 92 are the same, the actuator shaft is different...
Hi guys , they changed the clutch in 93 ( 1 more plate etc)
So 91 and 92 are the same, the actuator shaft is different in 92 to change the leverage rate
Your yz looks mint by the way! Ps I would keep the stock graphics.
Check out EVO MX in Great Britain, they have a lot of graphics and Costom work, especially a full gas tank cover with breathing holes so graphics don't bubble.

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