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Bluethunder3320 07-14-2012 10:49 PM

YZ125 project
picked this up today. has a siesed bottom end.

here is how i think it went..

it had carb problems, the main jet was partly clogged and it was running lean (hot) OR they ran straight gas

this wore out the rod bearings and killed the top end

the last owner bought it, cleaned the carb, and rebuilt the top end

it ran for a while, then the rod bearings got so worn out that it started rubbing on the crank. metal shavings went up into the cylinder and left a ton of pitting on the piston&head

the bottom end finally got so worn out that the rod got completely stuck against the crank

and here we are now

cylinder doesnt look too bad

my friend has tools to take the clutch off and flywheel and stuff. i just need to save up for a top and bottom end rebuild now

Bluethunder3320 07-14-2012 11:01 PM

there we go, $300. that would make it a $300 bike with a completely rebuilt engine

OzFab 07-15-2012 12:39 AM

That piston crown & head have definitely taken a beating.

How much would a good used engine cost? You also have to think about the condition of the bore; if it's too pitted, you may need to bore or even resleeve it, which may not be cost effective.

bighead 07-15-2012 01:11 AM

Is the head going to need any machine work? Will the gaskets in the kit work if so?

bighead 07-15-2012 01:28 AM

looks good

Not sure of the years but hey!

Bluethunder3320 07-15-2012 12:11 PM

i think i will need a head, piston, crankshaft&rod, gasket kit

im trying to figure out if any other year engines will fit. it seems very hard to find a 1992 bottom end rebuild...

if i had spent money on this i would be worried

B.M.800 07-15-2012 12:22 PM

Looks like fun. I like the blue...

I may be able to get a couple bikes of some sort, been in a shed for years. Not sure what they are...

r97 07-15-2012 03:30 PM

I know there is a website that can tell you what other year/model motorcycles share a certain part from your bike. Unfortunately I can't find it... but you seem to be doing fine finding parts anyway. If I could find a rebuild kit like that for my motorcycle I would probably buy it, new pistons, rings, con-rods, and many other parts for my bike are made of solid unobtanium :ack2:

What is up with the cylinder? It looks like someone went through it with a hone, but only once. Good luck with your project!

brandongeiger2 07-15-2012 03:43 PM

Looks a whole lot like a 95 except for the rear fender i wouldn't machine the jug head though id get a good used one try to keep the engine stock or use good aftermarket parts it makes everything easier

Bluethunder3320 07-15-2012 04:33 PM

i think the cylinder is new.

the front fender is a newer one, i think he said 2003? the rear fender is stock. used to be white and someone painted it

pic with the fenders mocked up

Ghanem 07-15-2012 04:40 PM

hey Blue i was wondering how many bearings are in a 125cc quad engine?

Bluethunder3320 07-15-2012 05:02 PM

a lot. needle bearings on both sides of the rod, ball bearings on the crank, and all of the transmission, kick starter, shifter, all ride on ball bearings

you dont see any bushings like a small engine

a 4 stroke has more moving parts so they have more bearings than a 2 stroke...

brandongeiger2 07-15-2012 05:32 PM

Those are shrouds and number plates not fenders :roflol:
but anyway is there a decal on the steering tube with the year on it? I'm interested in this also what are you planning on doing with it just getting it running?

Bluethunder3320 07-15-2012 05:53 PM


Originally Posted by brandongeiger2 (Post 219594)
Those are shrouds and number plates not fenders :roflol:
but anyway is there a decal on the steering tube with the year on it? I'm interested in this also what are you planning on doing with it just getting it running?

i plan on getting it running and ride it alot.

theres a vin number on the steering tube i didnt see a year at a first glance i will look again

fenders, shrouds, number plates, whats the difference? lol

brandongeiger2 07-15-2012 05:56 PM

Haha just thought id throw that in there if you need shrouds and ask for fenders at a shop guess what you'll get? but yz's are the best id trade my bike in a second for one.
And you would have seen the year if the decal was there most bikes have them but the vin will do just as good with a bit of research

Bluethunder3320 07-15-2012 06:01 PM

also, someone seems to have painted the frame. the paint is scratched away where the VIN is.

gonna go take a picture now

Bluethunder3320 07-15-2012 07:02 PM


Jimbo86 07-15-2012 08:22 PM

You put the vin# in incorrectly.

JYA4DDW04NA008401 - what you said it was
JYA4DDW94NA008401 - what you put in

brandongeiger2 07-15-2012 09:30 PM

1 Attachment(s)
Nice im suprised i was within +-5 years hahabut normally there's a decal that looks like this........ its a phone picture sorry but its not that hard to see

Bluethunder3320 07-15-2012 10:30 PM

yeah my friends xr100 had a stamp like that

jimbo, oops, i thought it was a 9...

EDIT: doesnt work either way

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