84 KX250 reassembly

[bishboy]

Finally got around to putting my 84 KX250 back together.

I bought from the states in October 2011 and after missing a couple of boats it finally got here in June 2012

If you've got 4 minutes, here's a video from the seller, which gives a good run down of the bike.

https://www.youtube.com/watch?v=DvlxgZw_55U&safe=active

When I got here, I couldn't get it started, found it had no spark, worked out it wasn't earthing properly, got that sorted and got spark.  Then I decided to pull it down to give it a good clean, it was pretty clean, just some dirt and grease etc where you would expect it.  Then it sat in its pulled down condition, bagged and boxed ready for time to put it together. 

So now after nearly 3 years and moving interstate twice I've got some time off got around putting it back together.   

Because it's in such good original condition, I've decided to not restore it, only replace consumables etc.
I've replaced so far:
- swingarm, uni strut, top shock
- chain rollers and sliders

On order and going to replace
- wheel and steering bearings
- fork seals and I have a set of fork valves to put in
- front caliper seals and the master cylinder seals (if I can find a kit for it)
- grips and levers
- wide footpegs

Once I get these bits done I'll put the plastic on and put up some more photos.

I also found a few non genuine bolts on it and I've managed to order some oem replacements through partzilla and a I got a few original style flanged bolts and nuts from a local place, only thing is they're a light gold colour instead of silver.  They only ones that I've had to use hex head bolts are the bottom engine mount and the front tank bolt. Maybe I'll find some on ebay???
I'm also missing the shock splash guard and I'm sure the uni strut guard is the wrong one.

I put enough bits on it try to start it, didn't want to putting plastic on and then off and then on and then off.......

First I pulled the plug and turned it over gently a few times and then checked I had spark, which I did after a few moments of worry before I realised the plug wasn't seated correctly    Plug back in, make sure full flowing into carby etc.  Then off the bench, via a piece of wood as a ramp as I lent my ramp to someone and didn't get it back. 

After a few kicks with a normal boot on and no result I decided to go put a motocross boot on and three kick later it roared into life     

Little video of it running
https://www.youtube.com/watch?v=geqhvjBOpVQ


Now that I've got it running I have no clutch. 
Would the most likely answer be that they have sat around for 3 years and have stuck together??  If so, is it a simple matter of soaking them in some oil or similar or do I need all new clutch plates?


Here's a couple of in progress pics.

[Paulos]

Coming along, no point rushing these things.

You'll probably find the clutch frees up after 10 minutes of riding around getting the motor warm.

[tony27]

Clutch plates will have stuck together over time, getting the motor warm may be enough to break them free although there is no guarantee of it & you'll have to manage to get it moving first
Modern trials bikes are well known for doing this, most owners will rock the bike backwards & forwards in a high gear before starting. Sometimes I will get mine started on the work stand with the rear wheel in the air & getting it running in a fairly high gear while standing on the brake with the clutch pulled in until it breaks free, can take a while so I wouldn't suggest it
Best thing you can do is strip the clutch & pry the plates apart which shouldn't take much, give the drive plates a quick rub with coarse wet & dry to remove any glazing while you're at it

[mick25]

You can put a zip tie around you handle bar grip and around the clutch lever and pull the clutch lever in 10mm.
This takes some pressure off the plates and stops sticking while the bike sits between race meets .
It's only compressed the springs a bit so shouldn't do any long term damage .

[pokey]

You can put a zip tie around you handle bar grip and around the clutch lever and pull the clutch lever in 10mm.

Bingo mick, i do that little number on my Barn finds (chook house mostly) before picking up the spanners and leave it over night. i pull the lever all the way in.

 the plates are suppose to have a thin film of oil between them even when they are running, This gives enough drive and enough slip when plates separate and more oil flows in. Sitting for an extended period allows the plates to dry out and they tend to grow together. just releasing the tension can often be enough to loosen things up a bit, it wont be perfect first up but that comes soon after things get shaken up.

[Dave Mc]

I had this Happen on a KX85 I bought my son a few years Back. A Change of oil and a 10 Minute ride freed it up.
Good to see another 84 KX250. Mine is back together but it needs a new rear wheel/Rim. the alloy is all Flaking apart on the inside.

[bishboy]

Pulled the clutch cover off and the plates were all stuck together.  Pulled them out and separated them and cleaned them up and gave the friction plates a bit of a sand.

Put them back in, misread the torque settings for the clutch spring bolts and presto snapped a bolt off 

Took the clutch hub off and in the drill press and drilling nice and slowly and the chuck/drill decided to move sideways enough to damage the threads.   

Options:  Get someone to drill out the bolt and tap it for a bigger bolt or get another hub, anyone got one (I believe the 82 & 83 also fit)

Thoughts....... besides using the drill press for a boat anchor. 

[Momus]

Can you drill the bolt from the back of the hub? 

If it was not bottomed when you broke it, drilling from the other side is quite likely to unwind it.

If you can do this use a drill bit smaller than tapping diameter and then tap through to M6? and use a longer bolt.

[bishboy]

If it was not bottomed when you broke it, drilling from the other side is quite likely to unwind it.

You're a genius, went from the back and it screwed out enough to grab it with a set of pliers. 

Thread was hardly damaged and bolt goes in normally.   

[bishboy]

Took the front end off to rebuild forks and the brakes.  Forks will get new oil, seals and emulators from Walter.  Caliper will get all new seals.

What weight fork oil should I use.  I've got the amount from the manual.

I think the caliper has seen better days.  That is not surface rust, that is some serious pitting 




I put most of the plastics on just to give some inspiration......the old girl doesn't look too bad 

[bishboy]

As I don't have an impact gun or anything else to fit in the damper rod (its about 37mm across), I made up a little fork damper rod removal tool.

I found a washer that would fit just inside the damper rod and then went and got some nuts that where just bigger than the washer.  Ground a couple of nuts down until they just fit inside the damper rod (one to go in the damper rod and a lock nut), put the nuts on a threaded bar and a couple of standard nuts to hold it in the vice, inverted the fork and voila, easy as 

[bishboy]

Forks all cleaned up, new seals, some new 10W fork oil, extra holes drilled in damper rod and spacer cut down by length of PD valve (not in picture) and ready to go back together. 

Because the forks require 550ml of oil per leg, I had to buy 2L of oil   




I also made up a seal driver, I must admit I pinched this idea of you tube.

Got a piece of poly tube that was the size below the diameter of the fork tubes and by sheer miracle it was a nice fit on the fork tube. 

I cut two pieces, one about an inch longer than the other, the longer piece was also cut length ways (both pieces would be needed to be cut length ways if it wasn't a snug fit) .  If you had to cut both pieces of pipe then a couple of U clamps to the hold them together would be needed. 

All the edges where sanded smooth and the longer piece place over the shorter one, a bit of silicon spray on the fork tubes and seals in.   

[alexbrown64]

I love a good rebuild.  Great job.. love the seal driver.  I rebuilt my 125K forks like you have, with emulators etc.  However, i didn't use a seal driver and i think i damaged them.  I went to Bunnings and got a nice length of PVC which was the perfect diameter.  I redid the forks with new seals and my fancy seal driver... just like yours, works great.
You may of already, but i found i had to check the spring tension on my emulators (race - tech).  I was only supposed to have 3 turns of compression, but they came with 6 turns. 
I found the best way to set the sag was to have the fork fully rebuilt and extended but without the spacer.  Then measure from the top of the spring to the top of the fork. Then subtract the distance the fork cap screws in. This will give you the "free space" where your spacer would normally sit. At first, i made the spacer so that the fork springs would "preload" 10mm.  Unbelievably, my forks were really stiff with zero sag and i did not like the initial feel.  I cut the spacers down so that i had about 2mm preload on the spring (just enough so it would not rattle) and the difference was amazing.  I had a small amount of static sag and the forks felt much more compliant in the first 3-4 inches of travel. For the fork sag and spacer length, you can use heavy wall PVC pipe as well.
Keep the pics coming, its a great rebuild.
Cheers,
Alex

[bishboy]

Did the top steering bearing, it was still good but as I had the new bearings I thought why not.  There was only a tiny lip under the race and the drift couldn't get a grip, so I got the dremel and made the lip just big enough to get the race out.  The bottom race has not lip at all and as the bearing and race are still good, didn't replace them at this stage.





The rear end might be bit harsh, not much adjustment either     Shock off getting rebuilt.  Just need it back and the new brake piston to arrive and good to go.

[tony27]

Couple of small beads of weld about 10mm long opposite each other is the easiest way to remove the bearing shells, often they fall out as the weld coils
Nice looking bike