YZ100 '82-83

7/11/2016 7:23am
You can put the piston and cylinder off the 82 it175 on the bike easy as pie as thats what mine is. You do need to make a pipe though
pakala
Posts
42
Joined
2/7/2010
Location
Yorba Linda, CA US
7/11/2016 11:55am
Wiseco 52mm is the largest over bore that is off the shelf. I think you will be at 108cc.
SouthwestMfg
Posts
280
Joined
2/9/2007
Location
Diamond Springs, CA US
7/11/2016 1:10pm
Wandell wrote:
In the early 1980's, aftermarket, oversized "stadium" front number plates were very popular.
Giant billboard number were put into the AMA rules in 1981. They relaxed them a little smaller in 1982. Hence the reason you see a lot of national bikes in that period with crazy big numbers and plates. 1981 they went way to far, look for pictures from that season.
7/11/2016 1:20pm
pakala wrote:
Wiseco 52mm is the largest over bore that is off the shelf. I think you will be at 108cc.
Hey thanks. Just checked using this calculator http://www.mk5cortinaestate.co.uk/calculator2.php and that gives me 106cc. But leaves no room for later maintenance rebores.

It’s a shame that the 1980 YZ125 cylinders exhaust is offset to the side because that would be an ideal direct bolt-on without going to the mad IT175 cheater cylinder.

Has anyone ever heard of anybody managing to sweat a 125cc iron sleeve into a smaller base cylinder? That would give a starting point of 56mm (123cc) with plenty of room for overbores.

The Shop

7/13/2016 12:49pm
Hey thanks. Just checked using this calculator http://www.mk5cortinaestate.co.uk/calculator2.php and that gives me 106cc. But leaves no room for later maintenance rebores. It’s a shame that the...
Hey thanks. Just checked using this calculator http://www.mk5cortinaestate.co.uk/calculator2.php and that gives me 106cc. But leaves no room for later maintenance rebores.

It’s a shame that the 1980 YZ125 cylinders exhaust is offset to the side because that would be an ideal direct bolt-on without going to the mad IT175 cheater cylinder.

Has anyone ever heard of anybody managing to sweat a 125cc iron sleeve into a smaller base cylinder? That would give a starting point of 56mm (123cc) with plenty of room for overbores.
If I was you I'd concentrate on the suspension and brakes first, as even with 100cc's you soon reach the limits of those first!



7/13/2016 1:24pm
If I was you I'd concentrate on the suspension and brakes first, as even with 100cc's you soon reach the limits of those first! [img]https://p.vitalmx.com/photos/forums/2016/07/13/143442/s1200_image.jpg[/img]
If I was you I'd concentrate on the suspension and brakes first, as even with 100cc's you soon reach the limits of those first!



Sure thing fella, you make a very good point. Nice photo by the way, going by the soil it looks like Farleigh which is two miles down the road from where I live, However I can't make out where on the course that would be.
7/14/2016 6:59am
I found out very quickly last night the limits of the front forks. Now I am looking for some upside down forks with disc to swap on to it.
7/14/2016 9:31am Edited Date/Time 7/14/2016 9:32am
I found out very quickly last night the limits of the front forks. Now I am looking for some upside down forks with disc to swap...
I found out very quickly last night the limits of the front forks. Now I am looking for some upside down forks with disc to swap on to it.
Why don't you try a set of 43mm 1986 IT 200 forks, seems the hot ticket with these bikes.



7/15/2016 12:08am
Farleigh pic is from 4th corner, 2013, Pre83 125 class.
Regarding the forks, i think the disc is a bit of overkill. Given the nature of the bike and the power delivery, the more you can stay off the brakes and carry corner speed, the better you'll go! Maybe the earlier 175 forks could be an option, then make a twin-leading shoe front brake fit? See the guy in the pic above has fitted the IT swing arm, i might give that mod a go.
wfoyz250
Posts
410
Joined
1/19/2011
Location
Spring, TX US
7/15/2016 4:41am Edited Date/Time 7/15/2016 4:43am
As far as the twin shoe deal, I swapped the 36mm forks and triples and used spare 38mm forks and triples from my '79 YZ250,along with the brake setup. This also requires using the front wheel with the typical YZ conical hub.
I too thing think the disc is overkill but looks trick as hell.
Watch the youtube vids of those former factory riders on these bikes and it seems they never use the brakes.
7/15/2016 6:08am
I could do the IT200 front end but why not be a little more different and go with USD forks. As of right now mine has the 81 125 swing arm to get rid of the heavy steel swing arm. I am looking at trying to swap in a KTM 125 swing arm with the rear disc as well.
wfoyz250
Posts
410
Joined
1/19/2011
Location
Spring, TX US
7/16/2016 10:38am
wouldn't the usd forks have an impact on weight? Are they heavier?

I mean.......you want to keep these bikes light as possible.
7/20/2016 2:46pm
yes, obviously. But could do the Pre85 Smile Have you got the bike yet, pretty rare, I only know of another 2 in the UK!
MaxPower
Posts
2646
Joined
8/15/2006
Location
NJ US
7/20/2016 6:54pm
I could do the IT200 front end but why not be a little more different and go with USD forks. As of right now mine has...
I could do the IT200 front end but why not be a little more different and go with USD forks. As of right now mine has the 81 125 swing arm to get rid of the heavy steel swing arm. I am looking at trying to swap in a KTM 125 swing arm with the rear disc as well.
USD forks discs and a 200 cylinder.
Why is it you want a old yz100 again? They make bikes with all those things on them already
billyslad
Posts
544
Joined
12/31/2014
Location
GB
7/20/2016 10:31pm
Your bike looked super sweet Gary at mildenhall
It was a great day up there with the evos although a bit warm for me
7/23/2016 5:32am
billyslad wrote:
Your bike looked super sweet Gary at mildenhall
It was a great day up there with the evos although a bit warm for me
yeah, it was hot (for UK), we're not used to that big round yellow thing in the sky hey! We're you parked up in the shade? Jumping off the 250 on to the 100 was probably not a good idea, felt a bit under powered to say the least!!
billyslad
Posts
544
Joined
12/31/2014
Location
GB
7/24/2016 1:31am
Parked in shade to start but yes strange yellow thing in the sky made for a hot day

The YZ 100 is my secret desire a couple of friends had them in schoolboys but I ended up with a Kx 80 to then upgrade to a cr in 84
There are very few about
hedgehog.237
Posts
2
Joined
11/28/2016
Location
Burleson, TX US
11/28/2016 11:30am
pakala wrote:
Wiseco 52mm is the largest over bore that is off the shelf. I think you will be at 108cc.
Still got any 100's for sale?
newmann
Posts
24444
Joined
4/1/2008
Location
US
11/28/2016 2:29pm
pakala wrote:
Wiseco 52mm is the largest over bore that is off the shelf. I think you will be at 108cc.
Still got any 100's for sale?
I have a friend here in Southeast Texas near Beaumont who is wanting to part with a 1983 model that he is quite far along on the rebuild. I know the lower end is built and he has a new piston kit, cylinder needs bored. Frame and swingarm is freshly painted with epoxy primer and urethane black, new plastics, plastic tank needs restored/polished, fresh build on original rims with Buchanans spokes, $1100.00 in Race Tech suspension. Think he has about $2800.00 tied up in it at this point and is asking just under $2000.00 for the unfinished project as is. He's a machinist and a tad bit OCD...no junk work. PM me if you are interested. I can get you his contact info.
TTperra
Posts
311
Joined
9/15/2015
Location
SE
11/28/2016 4:01pm
Hey thanks. Just checked using this calculator http://www.mk5cortinaestate.co.uk/calculator2.php and that gives me 106cc. But leaves no room for later maintenance rebores. It’s a shame that the...
Hey thanks. Just checked using this calculator http://www.mk5cortinaestate.co.uk/calculator2.php and that gives me 106cc. But leaves no room for later maintenance rebores.

It’s a shame that the 1980 YZ125 cylinders exhaust is offset to the side because that would be an ideal direct bolt-on without going to the mad IT175 cheater cylinder.

Has anyone ever heard of anybody managing to sweat a 125cc iron sleeve into a smaller base cylinder? That would give a starting point of 56mm (123cc) with plenty of room for overbores.
If the 125 sleeve don't fit the 100 cyl, you can sleeve-down the 175 to 125.

I would go for the 175cc, its only cheating if you win..
newmann
Posts
24444
Joined
4/1/2008
Location
US
11/28/2016 8:46pm
Hey thanks. Just checked using this calculator http://www.mk5cortinaestate.co.uk/calculator2.php and that gives me 106cc. But leaves no room for later maintenance rebores. It’s a shame that the...
Hey thanks. Just checked using this calculator http://www.mk5cortinaestate.co.uk/calculator2.php and that gives me 106cc. But leaves no room for later maintenance rebores.

It’s a shame that the 1980 YZ125 cylinders exhaust is offset to the side because that would be an ideal direct bolt-on without going to the mad IT175 cheater cylinder.

Has anyone ever heard of anybody managing to sweat a 125cc iron sleeve into a smaller base cylinder? That would give a starting point of 56mm (123cc) with plenty of room for overbores.
TTperra wrote:
If the 125 sleeve don't fit the 100 cyl, you can sleeve-down the 175 to 125. I would go for the 175cc, its only cheating if...
If the 125 sleeve don't fit the 100 cyl, you can sleeve-down the 175 to 125.

I would go for the 175cc, its only cheating if you win..
If you're not cheating you're not trying.

You've got cheaters and you've got losers.

LaughingLaughingLaughing
hedgehog.237
Posts
2
Joined
11/28/2016
Location
Burleson, TX US
11/29/2016 9:16am
pakala wrote:
Wiseco 52mm is the largest over bore that is off the shelf. I think you will be at 108cc.
Still got any 100's for sale?
newmann wrote:
I have a friend here in Southeast Texas near Beaumont who is wanting to part with a 1983 model that he is quite far along on...
I have a friend here in Southeast Texas near Beaumont who is wanting to part with a 1983 model that he is quite far along on the rebuild. I know the lower end is built and he has a new piston kit, cylinder needs bored. Frame and swingarm is freshly painted with epoxy primer and urethane black, new plastics, plastic tank needs restored/polished, fresh build on original rims with Buchanans spokes, $1100.00 in Race Tech suspension. Think he has about $2800.00 tied up in it at this point and is asking just under $2000.00 for the unfinished project as is. He's a machinist and a tad bit OCD...no junk work. PM me if you are interested. I can get you his contact info.
I PM you
wfoyz250
Posts
410
Joined
1/19/2011
Location
Spring, TX US
3/5/2017 8:16pm
I have a question for the johnstone contingent or anyone else that runs the bikes.
Seems that the inner bronze bushing within the clutch basket/hub is just a bit worn, The clutch assembly rocks/wobbles on the spriral grooved insert as a result of the bushing wear. It's ever so slight but it's one of those things that bugs me. Now then, is there a way to press the bushing out of the hub and replace it? If not, maybe the bushing can be knurled to "tighten up" the tolerance and eliminate the wobble. FYI, the grooved insert fits nicely over the drive shaft and is not a cause of the problem.
wfoyz250
Posts
410
Joined
1/19/2011
Location
Spring, TX US
3/6/2017 5:57am Edited Date/Time 3/6/2017 5:58am
...
vetmotoxer34
Posts
152
Joined
10/24/2008
Location
Mansfield, TX US
1/15/2018 4:31pm
Finally found me one after a lengthy search. First ride this past weekend was awesome.



Looking forward to a few upgrades from this post.

wfoskir
Posts
181
Joined
6/11/2017
Location
Half Moon Bay, CA US
2/12/2018 7:09am
I just got a 1982 YZ100. Overall it is there, not quit as nice as some of the bikes I see here though, maybe in time. I added a few pictures, just because. I do have a few questions. The black protection plate on the suspension linkage, is it the same as a YZ125? Mine is cracked and I was looking to get another one.



avmechanic
Posts
209
Joined
2/13/2016
Location
Langley BC CA
2/12/2018 10:58am
Sweet bike. That should fix up nicely. I wish I still had mine from back in the day.
Greg

Post a reply to: YZ100 '82-83

The Latest