1988 yz125 issues

89'cr dude
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89'cr dude
Edited Date/Time 1/27/2012 12:59pm
My cr125 is currently out of commision, so i decided to look at the REALLY crappy '88 yz125 i have. My yz125 runs like a four stroke, it actually has no powerband at all! The engine now needs rings, but even before the low compression it ran like crap. I was wondering what you guys think. Currently my cr125 is my rider and prized bike so the yz125 is going to be a project for when everything else is done.
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ThePipe
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ThePipe 4/26/2010 5:59pm
4/26/2010 5:59pm
Don't expect much.
Those bikes were Super Slow off the showroom floors back then.
A stock CR would smoke the modded YZs in that era
1984 through 1992 were Dark years for YZ125s
89'cr dude
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89'cr dude 4/27/2010 4:11am
4/27/2010 4:11am
hmm, i might just throw rings in it, gaskets, a set of bars and some of the other random parts it needs then sell it and hope for the best.
89'cr dude
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89'cr dude 4/27/2010 4:12am
4/27/2010 4:12am
Oh, by the way i was wondering what the best way to get paint off of plastics was, because someone went crazy on this bike with spray-paint.
ThePipe
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ThePipe 4/27/2010 7:44am
4/27/2010 7:44am
Spray on paint remover From WalMart
Don't get that on your skin though. Be careful with that stuff

The Shop

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lumpy790
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lumpy790 4/27/2010 8:46am
4/27/2010 8:46am
I recall something about a different intake waking them up.
89'cr dude
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89'cr dude 4/27/2010 4:47pm
4/27/2010 4:47pm
would the kind of paint stripper you apply with a brush work, or would it melt the plastics. speaking of intake, i was just stripping my bike down and the airbox is jammed in with no way of getting it out thanks to a one-piece frame.
Sandberm
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Sandberm 4/27/2010 9:33pm
4/27/2010 9:33pm
Squish that airbox and pull it out through the top, it can be done....I think thats how i used to do it on my 87 yz 250...

Your power valve isnt "unhooked" is it. That would make it run like crap. Take the pipe off and that power valve cover on the right side and see if that bolt that holds the linkage is even loose. Happens sometimes.

I think Larry Ward once said that his 88 YZ 125 was his favorite bike of all time.
project racer 4/28/2010 12:24am
4/28/2010 12:24am Edited Date/Time 4/17/2016 10:27pm
Also check to make sure the power valve is not 180 degrees out of phase. I believe there is a dot on the end of the valve where the linkage attaches that needs to be lined up with the dot on the linkage piece that attaches to the end of the PV.

If the linkage securing nut has been tightened or loosened without using a holder in the notch of the linkage into the little hole in the cylinder, the arm could be tweaked also, fouling the operation of the PV.

Decarbonize the PV, PV chamber, and the pipe/silencer while you are at it.
89'cr dude
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89'cr dude 4/28/2010 3:41am
4/28/2010 3:41am
That theory seems very likely, especially seeing some of the repairs the previous owner did. The more i look at it the more of a project it becomes. currently i want to strip the paint off the plastics safely, but then im going to do the topend, clean and check the powervalve, and see what i can do to the suspension.
Cygnus
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Cygnus 4/28/2010 5:40am
4/28/2010 5:40am
I don't know . I had an 89 YZ125 and that thing was a screamer. One of the only decent Yamaha's I ever had.
lumpy790
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lumpy790 4/28/2010 6:22am
4/28/2010 6:22am Edited Date/Time 4/17/2016 10:27pm
The YZ's KYB suspension was pretty good right out of the box. Put some fresh Golden Spectro suspension fluid (125/150 forks & Ultra light shock) in it and ride!
89'cr dude
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89'cr dude 4/28/2010 6:11pm
4/28/2010 6:11pm
my YZ's suspension is SOFT, VERY SOFT. when youre riding it you can almost bunny hop bumps. on the plastics issue though, i'm still wondering if brush-on paint stripper will eat away at plastics.
tunedlength
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tunedlength 4/28/2010 8:42pm
4/28/2010 8:42pm
89'cr dude wrote:
my YZ's suspension is SOFT, VERY SOFT. when youre riding it you can almost bunny hop bumps. on the plastics issue though, i'm still wondering if...
my YZ's suspension is SOFT, VERY SOFT. when youre riding it you can almost bunny hop bumps. on the plastics issue though, i'm still wondering if brush-on paint stripper will eat away at plastics.
re-charge the shock. Nitrogen is probably long gone.
project racer 4/28/2010 9:20pm
4/28/2010 9:20pm Edited Date/Time 4/28/2010 9:23pm
I've used the brush on paint remover as well as the aerosol on plastics. I have never had a problem with it eating or softening the plastic. It may take more than one application of the stripper. Be sure to wash the plastics with soap and water after stripping.

As far as the suspension, the shock probably needs a rebuild and oil change. Possibly a new seal head for a bike of that age.
89'cr dude
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89'cr dude 4/29/2010 12:24pm
4/29/2010 12:24pm
thanks guys, im going to try the paint removal now. As far as the suspension goes im not sure how much i want to invest in this.
onenastynotch
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onenastynotch 5/4/2010 8:12pm
5/4/2010 8:12pm
gumout carb clean eats spray paint....just spray and wipe
killerdwarf 5/5/2010 2:27pm
5/5/2010 2:27pm
paint stripper will eat plastic! Use easy off oven cleaner. Spray it on, and leave it for a few hours. Use a brush on it while rinsing it off with COLD water. Wear gloves, as the shit burns skin, and watch your eyes. I've stripped paint off plastic countless times like this, and is the only thing that works without harming plastic.
vino3
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vino3 5/9/2010 9:05am
5/9/2010 9:05am
89CR dude,

It sounds like you need to put some money into your YZ to get it running good. I had an 88 YZ 125 that I bought used from Paul Thede at Race Tech back in 1989. It was his personal bike from the previous year. That bike was a "ROCKET"! It had such a broad meaty powerband. It would pull all the way through from bottom to top. The mods it had were Race Tech porting and head mod, air box mod, jetted carb, cases were stock, stock pipe and stock silencer.

When the new 1990 CR125 came out later that year, me and another guy at the shop drag raced our two bikes and my "whipped" 88 YZ would stay dead even in a drag race with the new CR. I had put allot of time on that bike and the motor needed maintenance, (was worn out).

The 86 through 88 YZ125's had great ergonomics and handled really well. You have cartridge forks on your 88 and the 46mm steel body KYB shock, ( Yamaha copied Ohlins) is bullet proof and you can still get parts for it.

Those cylinders (88) are boreable so you could build a 134cc, (56mm piston). I would also try a set of carbon fiber reeds. You could make that YZ faster than your 89CR. Your CR cylinder is Nikasil plated and cannot be bored to a 134.

You can also get the 89YZ125 to run just as good. The 90 and 91 YZ 125's were turds.

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xnationalwrench 5/9/2010 12:59pm
5/9/2010 12:59pm
project racer wrote:
Also check to make sure the power valve is not 180 degrees out of phase. I believe there is a dot on the end of the...
Also check to make sure the power valve is not 180 degrees out of phase. I believe there is a dot on the end of the valve where the linkage attaches that needs to be lined up with the dot on the linkage piece that attaches to the end of the PV.

If the linkage securing nut has been tightened or loosened without using a holder in the notch of the linkage into the little hole in the cylinder, the arm could be tweaked also, fouling the operation of the PV.

Decarbonize the PV, PV chamber, and the pipe/silencer while you are at it.
Check the power valve for sure I have heard people forgeting to remove the the holder when they rebuilt a top end also.
89'cr dude
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89'cr dude 5/22/2010 9:31am
5/22/2010 9:31am
OMG!!!!! whoever did the topend before me should be shot!!! I took the powervalve cover off before i removed the cilinder, and there is NO POWERVALVE!!! I double checked the exploded diagrams to be sure, and the barrel with the notch cut in it to varie the exhuast volume is completely missing. this bike is a piece of SH*T. Im going to put rings in it and get rid of it.
project racer 5/23/2010 3:21am
5/23/2010 3:21am
killerdwarf wrote:
paint stripper will eat plastic! Use easy off oven cleaner. Spray it on, and leave it for a few hours. Use a brush on it while...
paint stripper will eat plastic! Use easy off oven cleaner. Spray it on, and leave it for a few hours. Use a brush on it while rinsing it off with COLD water. Wear gloves, as the shit burns skin, and watch your eyes. I've stripped paint off plastic countless times like this, and is the only thing that works without harming plastic.
Have used paint stripper for years on a lot of plastic .Never have seen it eat or soften it. Of course, you do not leave it on for hours. Just a tip, never use any oven cleaner on a coated metal surface. Saw a friend ruin his rear wheel spokes using EZ Off as a degreaser.

The cad or zinc plating was rinsed right off, leaving the spokes a nice shade of coal black.
89'cr dude
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89'cr dude 5/23/2010 10:41am
5/23/2010 10:41am
on the up side the paint stripper did work, and someone put on aftermarket red radiator shrouds, but im still pissed about the missing powervalve.
Wayne_VintageMx_87_Yz125 7/1/2016 11:17pm
7/1/2016 11:17pm
89'cr dude wrote:
My cr125 is currently out of commision, so i decided to look at the REALLY crappy '88 yz125 i have. My yz125 runs like a four...
My cr125 is currently out of commision, so i decided to look at the REALLY crappy '88 yz125 i have. My yz125 runs like a four stroke, it actually has no powerband at all! The engine now needs rings, but even before the low compression it ran like crap. I was wondering what you guys think. Currently my cr125 is my rider and prized bike so the yz125 is going to be a project for when everything else is done.
Have a 87 yz 125 strong if not stronger (being in a lot better shape some of them) as some of the later year yz 125's I've had. Either way it's beasty enough to keep up with any 125 that's for sure definitely not a slouch by any means

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