86-92 YZ80 differences??????????

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5/20/2018 6:09 PM

I read 86-92 YZ80 parts alot interchanges...surely there where changes along the way? If your where looking forone or parts,,what would you use??

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5/20/2018 8:54 PM

Not many changes made during those years. Any of those years would be a fun project, maybe they added a rear disc brake towards the end of that run? Not 100% sure.....

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5/20/2018 9:16 PM

No disc brake out back until 93.... just done some checking. 86-92 had a ton of BNG type changes.....

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5/21/2018 8:05 AM

I found the 88 went flat top piston and different dome,,,read in MXA changes in 86-87 pipe,,I I know wheres a basket case '89' with K10th digit,, with motor in box all apart..missing pipe, silencer, carb, and probably more. Wondering what will interchange and to look for If I get and would build it
All suggestions welcome

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5/21/2018 12:15 PM

My first race bike was a new 87 that I got in 88. A couple years ago I was given a basket case 87 that my son and I restored for him to ride. There were a few very small changes between 86-88 and then I believe the 88-92s are identical except for graphics...not too many racers rode them in these years as they were slow and smaller than the other brands. Lots of parts are the same back to 84....ask me if you have any specific questions as I’ve been through the whole bike in the last year. I used an 85 DG pipe on mine....little different shape but they fit.
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5/21/2018 12:16 PM

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5/21/2018 12:17 PM

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5/21/2018 12:20 PM

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5/21/2018 12:21 PM

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5/21/2018 12:41 PM

WOW That looks awesome!!!! Is there plastics out there nos, or repoed? Seat cover? Was the shock& forks same 89-92? is there better perforance in any of the newer pieces to search out. I will be racing this,,,,against a spunky 86 CR80 and a couple other 80s ..adults acting like kids..so performace upgrades a plus. Hunting through my old books I found 86/87/88 80 shootouts,,,,but not the 89 or newer. I saw how it was a begginer bike,,,but they tweaked it each year,,88 being the flat top change.

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5/21/2018 2:49 PM

I was able to clean up and use the original side panels. With some help from vital here I did a Yamaha nationwide dealer search with the part numbers and I found a new front fender/front number plate and rear fender in inventory at different shops around the country. Yamaha no longer has the parts available so it's either find a dealer that still has them like I did or eBay. There is repo plastic available but it won't look as good as OEM...probably fine for racing. My seat cover came from eBay (company from Thailand and the quality is good and they are only 35 bucks shipped). Yamaha does have new tanks in stock or there are aftermarket Clarke tanks. My tank was cracked and yellow but I bought a used tank on eBay and cleaned it up. Graphics came from Wicked Tough on eBay also.

Ebay was fun on this project...I found a ton of new parts cheap and collected for a year and a half until I had everything to build the bike. I found NOS cables, front rotor, brake lever, Answer Radialite sprockets. I paid 30 bucks for a rusted DG pipe that I cleaned up. I used all Moose bearings/seals/brake pads/air filter. Pro Wheel rims.

If I was concerned about performance Pro Circuit still makes a pipe and silencer and some port work can make these keep up with the RM/CR/KX. One of my buddies raced 80 Expert from 89-91 on them and used PC motors and Suspension. Barrs Competition on the East Coast was another company that I think is still in business and was known to build good YZ 80s.

I went from this bike to a 89 KX 80 and immediately picked up speed and went from Beginner to Intermediate in about a year...I remember my Dad asking me then if I thought I could go back and ride as fast on the YZ 80...and I told him I could....but for some reason I didn't think I would have been able to progress that fast if I'd stayed on a Yamaha...something about getting on the KX 80 made me figure out riding and pick it up quicker.

It was a sentimental project for me because I'll have a replica of my first race bike and I'm really nostalgic about that time period when I started racing. My kid doesn't ride much and I figured it would be a cool project for him to help work. Until he can learn to ride this YZ 80 right....keep it on the pipe.....use the brakes...and jump with good technique...I see no reason to spend 3-4K on a new 85.

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5/21/2018 2:52 PM

riv187 wrote:

WOW That looks awesome!!!! Is there plastics out there nos, or repoed? Seat cover? Was the shock& forks same 89-92? is there better perforance in any of the newer pieces to search out. I will be racing this,,,,against a spunky 86 CR80 and a couple other 80s ..adults acting like kids..so performace upgrades a plus. Hunting through my old books I found 86/87/88 80 shootouts,,,,but not the 89 or newer. I saw how it was a begginer bike,,,but they tweaked it each year,,88 being the flat top change.

I could be wrong but I believe Suspension was never changed...might even be the same all the way back to 1984. I thought it would be cool to build one with some different forks. I've seen pictures of some in Europe with USD WP forks. And there are often modern Marzocchi USD mini forks on eBay.

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5/21/2018 3:07 PM

Thanks for info! I'm not familiar with how too dealer search here? Is there a forum to post part numbers or something?
I had a 1985 Barr Competition engine in my KX125 back in the day. Yes it ran awesome...broad power band. Your not alone with the nostalgia. I have collected several of the bikes from the 70s/80s I either had, or wanted. I race them in SSVMX.
Thanks

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5/21/2018 3:15 PM

Is that a 88 WMX125 in background ? I had a the 88 125 for a summer back then....quick machine ! Hated the little kicker and delerotto though.... I would've kept it longer but our local dealer had closed up..Had to go directly to his house for pistons and such & was drying up fast from his shelf. Rare and pretty machine..

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5/21/2018 3:35 PM

You can take the part numbers to a yamaha shop and they should have access to search the parts inventories of dealers nationwide.

That’s a WMX 250 but I do have a 125 (an 88 and 83). They are my main hobby and I’ve been racing them in the Northwest for the last 4 years. I get rid of the Dellorto and use Mikunis off the modern Italian Husqvarna 125/250s. The YZ was the first Japanese bike I’ve restored.
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5/21/2018 6:27 PM

AWESOME!!!!!

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5/21/2018 6:37 PM
Edited Date/Time: 5/21/2018 6:37 PM

83-85 similar to same bike US color changes in 85 aside
86-87 front disc, boxed swingarm, new gas tank and shroud, significant motor revisions were long rod plus cylinder and porting changes. Basically a copy of the 85 KX80 powerband.
88-92 head and flat top piston otherwise BNG

The pipe design changed quite a bit, look at the shape of the 86-92 vs 83-85. Engine basic design is just a water cooled 81 YZ80.

Popular here through 87, forget it once the 88 KX and 89 RM came out. Motor was easy enough to make fast enough. 33mm damper rod forks atrocious. Unless you were small or a beginner, all of the other bikes did most things better. 89 CR80 was 7 mph faster top speed, and that was with the YZ having 15/46 gearing.

They spent at least three years testing what became the 93 YZ80...

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5/21/2018 11:30 PM

Another thing I found out was that in 86 they added a couple clutch plates and the clutch cover is a few mm bigger to compensate. I bought a nice 85 cover thinking they were the same...but it just touched the clutch enough that it bound up and wouldn’t turn over. I had the cover off 20 times thinking something was wrong with the kickstarter mechanisms before I realized the clutch/cover change on the 86 and up.

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5/22/2018 8:09 AM

meant to include in my post - 87 YZ80 was my first race bike,.too. I also had an 88 or 89. And I was tiny for my age (11 in 1989) so the YZ actually fit me just fine.

Drilling out the airbox, like quarter sized holes, and using fine mesh helps it breathe better. There was a heavy duty shock spring available, I remember we got it from dealer. We also had problems with stripped shift shafts.

I remember we got my 88 or 89 as a leftover for not much more than a thousand dollars or something. We had a little backyard track that the neighbors would tolerate me putting in laps on with the super quiet S-II silencer, but I liked how the blown out stock one sounded and would swap it. Cops would be there in 10 min every time.

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5/22/2018 5:14 PM

The Sneak wrote:

83-85 similar to same bike US color changes in 85 aside
86-87 front disc, boxed swingarm, new gas tank and shroud, significant motor revisions were long rod plus cylinder and porting changes. Basically a copy of the 85 KX80 powerband.
88-92 head and flat top piston otherwise BNG

The pipe design changed quite a bit, look at the shape of the 86-92 vs 83-85. Engine basic design is just a water cooled 81 YZ80.

Popular here through 87, forget it once the 88 KX and 89 RM came out. Motor was easy enough to make fast enough. 33mm damper rod forks atrocious. Unless you were small or a beginner, all of the other bikes did most things better. 89 CR80 was 7 mph faster top speed, and that was with the YZ having 15/46 gearing.

They spent at least three years testing what became the 93 YZ80...

the sneak...you said they 'where easy enough to make fast'....how,,28mm carb instead of the 26mm,,barr or other porter,,more compression and dg pipe? I may sell my 86 cr80 with DG pipe to focus on this bike. Don't want to sell the CR and end up with a slower bike. Thanks for replies!

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5/22/2018 6:56 PM

The CR80 was a monster and I don’t know how close you will get that YZ80. If I recall correctly, Barr’s did Colin Edwards’ YZ80s so they would know what to do. I thought the 93 onward YZ80 still had a 26mm carb so I am not sure that a larger one would be needed.

There was a good thread on Planet Minis where a couple of guys were building old YZ80s and one mentioned he had the hot porting specs for those motors. It may be worth reading through and trying to get in touch with that guy, not sure if he is on Vital:

http://planetminis.com/forums/2-stroke-pitbikes/166079-82yz80j-also-83-84-85-86-yz80-s.html#/topics/166079

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5/22/2018 7:27 PM

Just to add....although all the pipes are interchangeable, the new DG pipes are the 84/85 style and not the 87-92. Pro Circuit sells the right pipe. I’ve been trying to find the Yamaha branded YZR pipe they sold back then (made by PC), as this is what my buddy had on his modified 91. Seriously by 90/91 nobody who was very serious was racing these unless their Dad owned a Yamaha shop. Guys who never rode anything but YZs switched (mostly to Green) until the new 93 came out. That 93 was really a game changer...one of my best buddies even went to a 125 for 92 then back to minis when the 93 came out.

I’ve built plenty of bikes that I just thought were cool and weren’t the fastest....unless you really want to do the YZ for some sentimental reason or challenge it’s going to be hard to beat the CR you’ve already got.

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5/23/2018 10:22 AM

wpark89 wrote:

Just to add....although all the pipes are interchangeable, the new DG pipes are the 84/85 style and not the 87-92. Pro Circuit sells the right pipe. I’ve been trying to find the Yamaha branded YZR pipe they sold back then (made by PC), as this is what my buddy had on his modified 91. Seriously by 90/91 nobody who was very serious was racing these unless their Dad owned a Yamaha shop. Guys who never rode anything but YZs switched (mostly to Green) until the new 93 came out. That 93 was really a game changer...one of my best buddies even went to a 125 for 92 then back to minis when the 93 came out.

I’ve built plenty of bikes that I just thought were cool and weren’t the fastest....unless you really want to do the YZ for some sentimental reason or challenge it’s going to be hard to beat the CR you’ve already got.

I jumped in and ordered a DG pipe for it,,supposed to be 89 NOS. Will be hunting a matching silencer . My piston is std,,,,and needs bored. Looking for a reasonable 48.25mm flat top kit ???? I see Wiseco jumps right to the 48.5mm,,may go there if someone has a deal on one. The connecting rod kit -which part number or source >> I see 93 up is listed different...but no ebay listings for 88-92. Anyone help on one?
wpark89....I bummed this wasn't fast model...but I too have saved a few slow bikes for the niftyness or sentimental purpose. I raced a 85 rm125 briefly that year....pretty bike...but I clearly remember being passed on a straight during practice by a little kid on a white/red 85 YZ80 !...That's when I KNEW that RM was slow..
Looking at the cylinder....I see some room for improvement,,maybe even some boyesen boost ports. I appreciate any and all help to find the connecting rod,piston kit, silencer

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5/23/2018 10:43 AM

Pictures of the white ghetto turd
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5/23/2018 2:05 PM

There are lots of OEM oversized pistons on eBay. My cylinder was worn so bad I had to use a 49 Wiseco. Your bike looks pretty low hours so you may be lucky if it’s still on the original bore.

I used a Pro X rod kit. Part number is 03.2104 (84-92 YZ 80) they don’t come up on the Pro X site but I found one on eBay.

You can still get a silencer from DG, but I don’t think the new DG quality is anything like the parts they sold in the 80s. The pipes aren’t bad but in my opinion the silencers are cheesy. I’d get a PC silencer if it will work with the DG pipe. I’ve seen nos Answer silencers on eBay and DynoPort is an option.

Just for fun I went through the Loretta’s Vault. 87/88 there were decent numbers of YZ 80s. By 92 there were only a couple of them in the results...and only in the 7-11 stock class. The last fast mini rider to have top 10 results on a mod YZ 80 was Matt Maximoff in 1990. Might be worth it to find out who built his bikes. For some reason Michigan kids kept racing them when nobody else was.

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5/24/2018 7:26 AM

Im still kind of scratching on connecting rod,,,from charts i've found the 1982-83 86-91 was 94mm long,,,,but the 84-85 was 90mm,,,,,then 92 up went 96mm long. When you where finished was the piston at top of cylinder or down in the hole 2mm? I saw another Mitaka rod kit I just purchased from UK for 72 shipped. The only prox was $122!! Here's picture of pipe I just got,,,hopefully work and fit. Photoind Photo

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5/26/2018 8:41 PM

I’m not sure on the rod. Mine fit right...the Pro X kit I got may have been labeled 88-92? That pipe has been on eBay for quite awhile. It will work but like we mentioned earlier it’s more the 1985 shape and not the proper 87-92 pipe.

I have no experience with Mitaka parts. Just research and be careful, a lot of aftermarket companies have the years wrong for fitment. I used the chaparral site a lot and you can look up part numbers and then also see what models that part is used on.

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11/18/2018 6:18 AM

Im in the process of restoring a !990 YZ80. Yours looks awesome! Were did you get the footpegs?

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11/18/2018 7:36 AM

Pegs came from eBay....not the best quality but they are wide and bolt right up. Seem to be working fine so far for the little bit the kid rides it.

FYI Friday I saw Pro Circuit has 87-92 YZ 80 pipes on sale for 100 bucks. Only the plated version is available, but it’s a great deal.
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11/18/2018 7:49 AM

Had to throw a couple of 87's in the trash in the early 90's. Could not give them away. Robbed both ignitions, and rolled them to the curb. Crank tapers on those is the same as 78-88 YZ250. Used them for my Champion framed dirt tracker.

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