Rebuilding my 1987 KX 250

[sandblaster]

You may have something as simple as a broken transmission snap ring.
You will need to disassemble a bit more to know for sure.

[bens87braap]

nice I love old school builds keep us informed on how everything goes

[dinkyguitar]

You may have something as simple as a broken transmission snap ring.
You will need to disassemble a bit more to know for sure.

Yeah, I'm planning on taking everything apart. I'm working on it in my spare time.

Engine wise, I don't think a lot is needed....but frame wise is another story.

For instance, yesterday I was spinning the back tire to see if it was true, and sure enough I found an area on the rim, almost where the bead lock thing is, where the rim lip is bend. It doesn't seem like much since the back tire still holds air, but I'm sort of a perfectionist so it bothers me.

And then 2 days ago when I was measuring the ignition coil I was 1 ohm low of being within spec's. So I might have to replace that as well. The good news is, there's plenty available....the bad news is, it's just another thing I have to replace and spend money on.

dinky,

[dinkyguitar]

I managed to remove the motor. Pressure washed the rolling frame and part of the motor.

Here's some before shots:







And after:







I have a feeling the top end was rebuild. Check out the cylinder:





I don't feel any scratches in the cylinder, and you could see the cross hatchings.

The piston and head had carbon, but it came off easily. BTW, I looked up the numbers on the piston and it's a Wiseco std. bore.









That's it for now...

dinky,

[dinkyguitar]

Another update...

So I finally split the case and found out what the trans problem was. The previous owner said he lost either 1st or 2nd gear (don't remember which one) so he decided to skip the gear and shift up. Well, the shift fork pin had broken which is why there was no 1st/2nd.

You would think he should have took it apart to look why this was happening...but no...he kept riding. Well, that pin eventually logged into a gear and broke 2 teeth off. There was also a missing circlip, and very loose/wobbly gear.

So I bought a used trans which was good considering it's an 87. I had to replace a questionable gear with one from my old trans.

I also bought a primary gear cause the teeth on mine were worn as well as the splines on the crank...which is why I needed another crankshaft.

Then I had my mechanic install the new connecting rod.



Plus, he recommended honing cylinder.





I then repaired one of my silencer brackets that was broken off with aluminoid weld rods.





My mechanic also said only to replace the main bearings in the case. The other bearings usually don't need to be replaced unless you can see that they are bad...

Would you agree?

Anyway, I'm trying to raise more funds for putting the motor back, plus getting the frame back together with new bearings and odds and ends. I can honestly say this isn't a cheap hobby.....

dinky,

[sandblaster]

Mains are a must.
I won't say you couldn't get away with riding with your other bearings but for the cost of replacing them all why not?
Your already there and you can prevent other problems from happening.

[Goat]

I agree with Sandblaster. Plus if that snap ring turned to dust, fragments of teeth, or shift fork rod particles went through those bearings then are beat up junk that will cause more damage in the future. Just because they "look" fine to the naked eye doesn't mean they are good.

[Oblivious Maximus]

 The 87's aren't the most economical bikes to work on for sure. I was lucky to buy mine for $600 from a thumper talk guy who impressed me as genuine. I cleaned the entire fuel system and rode it for 6 months.  Fortunately I had no motor problems and it still runs better than it did when I bought it.

 Then.. Brake rotors, sprockets, sub frame, tires and a few other wear items. Found an oem pipe for 120 bucks then a few months later bought a PC platinum for 140. Brake rotors are pricey, I paid 45 for a good used one. Refitted a powercore II from a 2002 Suzuki with a little cut and weld for 37 bucks. And on and on it goes as with any bike.

 But the kicker is, IMHO, you'll have one of, if not, the most grunty, responsive 250 cc 2 stroke motors out there. I ride in the woods with the kids with the 450f's and they never have to wait for me.

 Stick with it and you'll enjoy the results.

 

[dinkyguitar]

Thanks guys...

Progress will be slow, but eventually it will be done.

The 85's, 86 & 87's models are the models I grew up with. I remember moving at 11 to a neighborhood all with woods. There were no neighbors behind my house....just woods. So I saw dirt bikes, 3 wheelier's (yup, just gave away my age) and stuff. Mom never let me get a dirtbike  , but I drove everyone else's  , and that's were I got some riding experience....

I eventually got a moped, 89 CR250, KLR 250, FZR 600, but got rid of them. Wish I held onto something. I find myself getting rid of this I later want again...So now with 3 kids I finally got the opportunity (my wife being the biggest hurdle) to have another dirt bike for free, a la my cousin.

Now all I have to do is throw away my savings and retirement fund to get it running again  .

dinky,

[dinkyguitar]

Here's an update....getting closer 

I want to finish the frame somewhat so I can put the motor in and start it.

I have all new bearings for the entire motor, new rod, piston, cylinder honed etc.

I know it will be a pain changing all those bearings and pressing to 2 case half's together so any suggestions would be appreciated.







dinky,

[bens87braap]

How did u go Dinky u get ur cases back together?

[sandblaster]

Chassis is looking great!

[dinkyguitar]

Chassis is looking great!

Thanks...hope it lasts...it's not power coated.

[dinkyguitar]

How did u go Dinky u get ur cases back together?

Haven't touched the motor yet, but I do have all the bearings and seals.

I was thinking to use heat and the freezer to get the cases together.

The manual I have says to put the case in the oven at 200 deg. or so to get the bearings in.

dinky,

[Goat]

I usually just freeze the bearings for a few hours and they drop right in the case halves. Never had to use heat.