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Dekon Dekon
11/5/2017 8:36 AM

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.

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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 Dekon
11/5/2017 8:41 AM

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.

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Dekon Dekon
11/5/2017 8:44 AM

Dropped the motor in the frame.
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Installed the rear shock, linkage, and swing arm.
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Then installed the air box.
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Dekon Dekon
11/5/2017 8:47 AM

Then tragedy struck. Somehow one of the straps came undone and it fell over onto the kicker which resulted in this.
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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.

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Dekon Dekon
11/5/2017 8:53 AM

Installed the forks(new seals, bushings, and oil), wheels and tires(new bearings in the hubs).
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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.
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Dekon Dekon
11/5/2017 8:56 AM

That brings us up to this weekend where the radiators, exhaust, tank, and seat were mounted.
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Dekon Dekon
11/5/2017 9:00 AM

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.
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Dekon Dekon
11/5/2017 9:03 AM

Finished up the day mounting the front and rear fenders, front number plate, and the radiator shrouds.
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And my assistant for the build; I think he can not wait to go roost on this, LOL
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Dekon Dekon
11/5/2017 9:08 AM

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.

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sandman768 sandman768
11/5/2017 4:08 PM

Nice job....

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cvm cvm
11/6/2017 3:12 AM
Dekon wrote:

That brings us up to this ...more

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

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Dekon Dekon
11/6/2017 6:02 AM

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.

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Banana_oil Banana_oil
11/6/2017 1:01 PM

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!


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Dekon Dekon
11/6/2017 2:06 PM
Banana_oil wrote:

Those bikes are so good ...more

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.

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Sully Sully
11/6/2017 5:29 PM

Nice looking bike. There's something about the giant radiator shrouds on the '88 - '92 YZ 125 & 250 that I really like.

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Mdesmond Mdesmond
11/6/2017 5:37 PM

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?

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Banana_oil Banana_oil
11/6/2017 9:41 PM
Dekon wrote:

Great looking build! I ...more

Yes, no other parts need to be changed.

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Dekon Dekon
11/7/2017 4:08 AM
Mdesmond wrote:

Very nice!

Did you leave ...more

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.

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Dekon Dekon
11/7/2017 4:09 AM
Banana_oil wrote:

Yes, no other parts need ...more

Awesome, thanks for the tip.

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Dekon Dekon
12/25/2017 7:49 AM

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.
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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.

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Banana_oil Banana_oil
12/25/2017 8:52 AM

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.

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Harm_Van de Bunte Harm_Van de Bunte
12/25/2017 11:59 AM

Great build!! Love those years

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Nzpatch Nzpatch
12/25/2017 1:40 PM

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.

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Dekon Dekon
12/25/2017 3:37 PM
Banana_oil wrote:

I'm sorry I fooled you, I ...more

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.

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Dekon Dekon
12/25/2017 3:39 PM
Nzpatch wrote:

Hi guys , they changed the ...more

Thanks. And yes I am going to go with the stock graphics.

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Dekon Dekon
12/25/2017 3:40 PM
Harm_Van de Bunte wrote:

Great build!! Love those ...more

Thank you. I always wanted that bike back in the day. I was finally able to get it.

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Richard Tease II Richard Tease II
12/25/2017 4:46 PM
Harm_Van de Bunte wrote:

Great build!! Love those ...more

Dekon wrote:

Thank you. I always wanted ...more

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.

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Bent206 Bent206
12/26/2017 7:20 AM
Dekon wrote:

Installed the forks(new ...more

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.

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nicko-31 nicko-31
12/27/2017 3:21 PM
Nzpatch wrote:

Hi guys , they changed the ...more

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.

Yeah, I have no clue !!!

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