Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,838
16,902
Chicago
Shift shaft seal is usually replaceable from the outside so that won't pose any problem. It helps to put some electrical on te end of the shift shaft before you slide the new seal on so you don't snag the new seal and damage it.
 

Okiewan

Admin
Dec 31, 1969
29,555
2,237
Texas
Update? Have you got that thing in a million pieces yet?
 

DavidR8

Member
May 13, 2018
64
30
Vancouver Island
Update time.

I gradually stripped the bike to the point of pulling the head and cylinder in anticipation of doing the top end job the ad said it needed.

It has GPIMotocross rads in good shape
IMG_3890 2.JPG
.
More evidence of lousy 'paint job'
IMG_3892 2.JPG


Popped off the powervalve cover to discover it is completely pristine.
IMG_3895 2.JPG
IMG_3896 2.JPG


Off with your head!
(far more clean than I expected)
IMG_3893 2.JPG


Next the cylinder.
(looking pretty good. So far. <-- see what I did there? That's called foreshdowing :)
IMG_3894 2.JPG


Cylinder is off!
IMG_3897 2.JPG


IMG_3898 2.JPG


When I got the bike it wouldn't kick over. I put this down to a stuck ring thus the need for a top end job.
If only that were the case.

Oh look! Errant plastic!
IMG_3899 2.JPG

IMG_3900 2.JPG


Looks like it came from here:
IMG_3901 2.JPG


IMG_3902 2.JPG


The rod is almost immovable.

I'm mulling over what I'm going to do. I did text the PO and tell him that his advertising was false. It does not need a top end. It needs a new crank.

He said it was running. I told him there was no possible way it was running. It wouldn't kick over.There was 2 cups of gas in the pipe. Every motor mount was loose. I asked for $400 back for a new crank and rod.

He said it was more expensive to do the top end than the bottom end.
He sent me this picture as evidence.
IMG_3726.PNG

I told him it that was a big bore kit and was irrelvent as it doesn't need a new cylinder. It needs a new crank.


He said had another buyer who was upset it sold. I told him I'll gladly put the bike back together and give it back for a full refund.

If that doesn't happen I'm in the market for a used oem crank so I can put this thing together and decide what to do next.

Ask me if I'm annoyed.
 

truespode

Moderator / Wheelie King
Jun 30, 1999
7,978
249
Check out Eric Gorr Racing - Home

Eric sometimes has complete rebuilt engines for a fair price and other services. He is a big supporter of DRN but also is very busy.

I know you may feel a bit disappointed but honestly, even if you rebuilt the crank, top end and re-valve the suspension you will have a bike about the 1/3rd the cost of a new one and one you know is put together right.

Looks like you are pretty mechanically inclined and that is a good thing.

I like how you called the guy out on the false advertising and trying to get your money back... let us know how that works out.

Ivan
 

DavidR8

Member
May 13, 2018
64
30
Vancouver Island
Thanks Ivan,
Yeah last night I was pretty bummed.
I will wait and see if he calls me back. Honestly I'm not expecting much but even during the text exchange last night he was feeding me a line. So not exactly on the up and up.

Oh well, live and learn. And you are right, I am mechanically inclined so except for machine work, there's not much I can't deal with.

So my line of attack is thus:
Find a decent used OEM crank ( I have a line on a crank)
New bearings
New top end kit
Rebuild carb
Flush and renew all fluids
Rebuild calipers and master cylinders
New pads F/R
Remove and lube swingarm bearing and linkage
Rebuild forks/shock
New chain and sprockets
New grips
New cables
New tires

If I feel ambitious I might paint the frame.
 
Last edited:

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,838
16,902
Chicago
You can see evidence of the crank bearings coming apart in the pock marks in the cylinder head. One of the said truths about buying a used dirt bike is people either don't tell the truth, or they don't have the mechanical skills to know how bad their used bike really is. Unfortunately as the buyer you get short changed either way. Most dirt bikes this old will be in similar states of dis-repair so maybe you can get him to refund part of what you paid to help cover the cost of repairs. I think if you get it to a good state you'll have a bike that you will really enjoy.
 

DavidR8

Member
May 13, 2018
64
30
Vancouver Island
Thanks Rich,
That's also my feeling. There are essentially no YZ125s for sale anywhere within 200 miles of me.
So a bit of cash and some sweat equity will yield me a decent bike that I'll enjoy.
 

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,838
16,902
Chicago
When the basics are right they are really outstanding bikes. Given a reasonable bit of maintenance they can last an incredibly long time and be trouble free. You clearly have the right approach going in, so I'm betting your time and money will net you a load of good fun down the road.
 

DavidR8

Member
May 13, 2018
64
30
Vancouver Island
More progress tonight.
My manual arrived today. Great timing.

Pulled the subframe and air box as one unit to avoid having more loose parts about.

Pulled the carb.
62C3F76C-90CC-4DD2-A5B3-E6E70CE786A0.jpeg


Pulled the chain and rear brake pedal.
The rear master cylinder is only attached by the lower bolt.

Pulled the shifter. Discovered the shift shaft is bent. Really bent. Likely have to get it back to semi-straight to have any hope of getting it out.
4F917464-CEAC-4693-AE8B-F1FF812864AA.jpeg


Had a text exchange with the PO.
“Im an honest seller if not why did I deliver the bike and give you my personal details like my drivers license? As i said when we check the bike it was top end that need to be done and it was checked by certified bike mechanic”
I told him that he also got ripped off.

Upshot is no cash but is giving me all the other parts that came with the bike including a new rear tire.
So at least that’s something.
 

DavidR8

Member
May 13, 2018
64
30
Vancouver Island
Quick update:
I bought a NOS crank today. The existing crank is completely toast.

Now that I’m over my annoyance it is fun. Actually it’s more fun. It was already fun :-)

Let me say how grateful I am for everyone’s support and guidance.
 

DavidR8

Member
May 13, 2018
64
30
Vancouver Island
Totally agree. I haven't tackled a teardown/rebuild like this since my 1978 Yamaha XS400 needed a rebuild.
And I've never done a two-stroke so a lot of new stuff for me.
For example, I was surprised that the crankcase was full of fuel. Took about 5 seconds to figure that out!
 

DavidR8

Member
May 13, 2018
64
30
Vancouver Island
I wasn't going to turn any wrenches tonight but I had to pop out to the garage to get some tools for a quick home repair. Did the repair and upon returning the tools to the garage, picked up my socket set and took out the swingarm pivot. Took all of 3 mins maybe. Popped off the upper shock mount and undid the rear master cylinder in anticipation of rolling the swingarm back but I forgot about the linkage bolts. Gave a half-hearted go at the lower shock bolt but no dice. Dosed it up with AeroKroil and will have a go at it tomorrow.
OSHA alert: I was wearing my slippers!
 

DavidR8

Member
May 13, 2018
64
30
Vancouver Island
This is a great thread! I can't wait to see the final build!
Thanks!
I’m throughly enjoying the process. I’ve put down my annoyance with the PO.

One thing I’m enjoying is how easy it is to do the work.
My street bike a Honda ST1300 is a bit of a bear to work on because it’s so much engine in a small space. Four cylinders, etc make it much more complicated. Even getting to the engine is a 20 min exercise in removing plastic.

Last night I learned that I can rebuild the YZ shock. By myself. That’s amazing to me. And appeals to my diy attitude.
 

truespode

Moderator / Wheelie King
Jun 30, 1999
7,978
249
Last night I learned that I can rebuild the YZ shock. By myself. That’s amazing to me. And appeals to my diy attitude.

You can use an air compressor and air for the shock but it should be nitrogen. Once you rebuild it you may be able to take it a shop to have it filled with nitrogen for a fee. That is how I would do it but I had a friend that used his air compressor without any issue but I don't recommend it.
 

DavidR8

Member
May 13, 2018
64
30
Vancouver Island
You can use an air compressor and air for the shock but it should be nitrogen. Once you rebuild it you may be able to take it a shop to have it filled with nitrogen for a fee. That is how I would do it but I had a friend that used his air compressor without any issue but I don't recommend it.
Why nitrogen vs air?
Just curious.
 

DavidR8

Member
May 13, 2018
64
30
Vancouver Island
Last night’s progress:
Tonight’s progress:


Swing arm off.


Easy peasy, lemon squeezy!
Pesky electrical connector to the stator yielded to my mind power.
Singing “Ain’t nothing tight on this here machine!” to the tune of “Ain’t no sunshine when she’s gone” as I popped off the countershaft sprocket.

Engine is out!
EB703100-5569-4F5D-8F22-05E2D12BFACE.jpeg

Piston is off. I had to really work to got the pin out. I’d say there was some overheating in this pistons past.

9EE81F64-8565-4B70-83E2-83755A012709.jpeg


Wrist pin and bearing were very tight in the small end.
07A1E9F1-5E4C-4228-AF8A-857CEB1A3DB0.jpeg


I don’t know how I’m going to get this out. I tried to bend it back a bit with zero success.

AE691E93-1CA9-49A3-A8D3-FE1818FBCDB3.jpeg

I have a new one on the way. I might just cut the bent end off.
961B413B-0256-4951-B8D1-284413CA041E.jpeg
6F8336A4-6B23-4ED2-A998-3AF79CF4E570.jpeg

Some random shots of the not so pretty frame.


I discovered that the lower right stator cover bolt had aluminum in its threads. Not a good omen. Might be a helicoil in my future.
 
Top Bottom