Fixing problems with new (old) bike. - Running

[MeanGreenMachine]

I recently got a 1990 KX500, and after riding the bike just enough to fall in love with it, I'm finding out that the previous owner was not all that honest about it's condition.

Things I've found so far:

- Water in transmission, milky oil: I found that the water pump seal was bad, and in fact, had silicone over a crack in it... Minimal shaft play, unable to feel any groove in the shaft with a screwdriver or a fingernail, so I just replaced the seal. Milkiness returned once, but it'll probably take another change or two before I know if it's gone for sure.

- Frame crack at the top near motor mount: Ground/notched, MIG welded and painted over. Seems to be holding fine.

- Stripped out drain plug: It came with a cut off 1/2-13 bolt in it, which then stripped. I made a guide jig and put a Perma-Coil in it to bring it back to 1/2-20. Then I installed a Fumoto F101 drain valve with about 1mm of metal "wall" left. It seems like it'll hold, though I don't exactly want to torque it too hard. The valve is well constructed and protected by my skid plate, so it should be safe. Should make changing oil easy, anyways.

So ok, it looks like I got it under control. I come home today and check the bike over in preparation for some badly needed riding time tomorrow and discover:

- Oil leaking from output shaft/chain sprocket: Must be a seal, unsure if installed from the outside or inside.

- Whirring noise at idle: Sounds suspiciously like the kind of noise a roller bearing makes when it's worn out. I pull the stator cover off and push/pull on the crank and notice that it wiggles up and down and side to side very, very slightly, though you can feel it and hear it tick when it moves. Also, the crank has some end play as well, when pushed or pulled directly. I turn the flywheel with my hand and notice that there's a very slight slack before the piston/rod move as well... Looks like I need a full rebuild. d**n it!

So, it looks like I won't be making it to Pismo after all. Further more it looks like I'll be sitting out on riding season trying to get this thing put back together. Does anybody have any ballpark estimates on how much I'm looking at to go through the entire engine, bottom end and top end rebuild, with crank, rod and new piston? Even though I got the bike for cheap and have become completely addicted to it, I could use some encouragement... I'd appreciate any information!

[sandblaster]

The good thing and the bad thing about a K5 is that they can run a long time completely worn out if your not too hard on them but yours sounds like it is really in need.
At a minimum.... a crank rebuild, top end plating and piston, bearings, and seals, your looking a 1K minimum and of course, that's doing the work yourself and the sky's the limit on cost.
If you find out that 3rd gear is bad which is common, there's a couple of hundred more, if the exhaust valves are worn out, there's a few hundred more, ect, ect..
You really won't know until you get into it.
If I were you I would read this build..
http://www.kxriders.com/forums/index.php/topic,8717.0.html
And
http://www.hallbergs.net/kx500/
And
http://www.kxriders.com/forums/index.php/topic,8890.0.html
Of course, this is the right site for K5 info and rider sympathy  
Oh.... save a few bucks and buy a Clymer Service manual...

[MeanGreenMachine]

Yeah, I figure that my biggest problem right now is the crank mains and the rod bearings. It's funny since I compression tested it and ice cold, I was getting ~145 PSI, and looking through the exhaust port, the bore looked undamaged and KIPS valves moved freely. Obviously if I go through the bottom end, I'll send the top end for plating and get a new piston as well.

The pisser is that we were supposed to go to Pismo in two weeks... There's no way I can get parts out and back in time to have it ready. The guys are hounding me to "just ride it till it breaks", which IMO is probably a great way to end up with 10 times the damage and parts costs.

So what places do you guys recommend for plating? Millennium? US Chrome? Powerseal? What about crank rebuilding? I read about a place called Crank Works, but could use some recommendations. Probably time to start planning...

[sandblaster]

K5's are notorious for wallering out the left main bearing journal on the case.
The more you ride it loose, the greater the chance of damage.
Also, if you ride it enough with a loose piston, the greater chance of breaking off a piston skirt and munching a set of cases...
But hey, new cases are available for about 450 bucks 
For a crank rebuild I would sent it out to Pinsonnault Racing for a rebuild, weld, true, and balance.
http://pinsonnaultracing.com/
Your engine and hands will thank you from the reduction in vibration.

Plating?
I'll let other chime in...

[81cr450]

US Chrome +1

Jug came back beautiful within .0002 , the finish was sweet, sealed up quick

[MeanGreenMachine]

Alright guys, aside from starting the day breaking off the kickstart lever (how much stronger is the improved part? Guess it's time for one), I bit the bullet and tore down the bike today. I've never taken a bike apart, but there didn't seem to be much to it. No unpleasant surprises so far, everything looks ok.

I currently have the engine out sitting on the bench and will start taking it apart tomorrow. The top end seems fairly straight forward. As for splitting the case halves, do you need a puller tool, or is there another way if your kx-fu is good enough? If the main bearing journals in the case are pounded/spun out, can the case be saved or is it time for new parts?

[sandblaster]

There is all sorts of ways to split your cases...
I do it this way...
http://www.oem-cycle.com/forum/viewtopic.php?f=40&t=66

The newer kick lever design is stronger...

Get it apart and measure the bearing journals in the cases and tell us the measurements.... Then we can give you options 

[Motorrad]

leakdown test before you take appart.

[MeanGreenMachine]

Ok guys. As I expected, the top end came apart without any problems. The piston is an "ART" piece, size "A" that showed some light scratches but no apparent problems. There was no chamfer on any of the ports... Could the plating be stock?

The jug appears to be in good shape, but has a small area of flaking coating and 2 fine cracks between the main exhaust port and the 2 small KIPS booster ports on each side... The plating guys can weld these before plating, right? The KIPS parts have some carbon buildup but moved freely. There's a little bit of gear wear but it doesn't seem like it will effect much.

The rod has some slight movement on the big end if you pull up and down on it, but also rocks and slides side to side noticeably. That's probably part of the bearing noise I was hearing at idle. I haven't been able to split the case yet, but the crank has noticeable play on the clutch side bearing, which I guess makes sense since that's where power is taken off the crank.

Somewhere along the way I found another problem that concerns me - the splines on the output shaft that the chain sprocket goes on is very badly worn... I missed it until now. Do I have to replace the entire shaft/gears to fix it? Honestly, at this point, I'm afraid to split the cases and see what's inside, as it's clear that every part on this bike is worn completely out...

[MeanGreenMachine]

Ok guys, I've made some progress today. I bought a couple 75mm long M6x1.0 bolts with the idea of screwing them into the stator holes, and using one of those crows foot shaped harmonic balancer pullers I had laying around. Problem was that the bolts were too short and the 2 opposing slots in the puller weren't long enough. I ended up cutting the head of the M6 bolts then threading them to make a stud. Then I put a 3/8x24 bolt on the lathe, drilled a hole into the end and tapped to accept the stud. Or you could just buy longer bolts, but I was bored at work. Then I went to Autozone and for $15 bucks picked up this: http://www.autozone.com/autozone/accessories/OEM-Timing-gear-and-pulley-puller/_/N-26b8?itemIdentifier=231208&_requestid=1684868

I used an open end wrench and carefully applied pressure, and sure enough, the cases popped right open, no problem. Try this at your own risk: I can't guarantee that 2 bolts will be strong enough, or won't strip the threads out of your cases or even break them. Use common sense and be careful!

[MeanGreenMachine]

Honestly, I was dreading what I'd find inside to the point of dragging my feet, but it appears that everything looks pretty good so far. All transmission components appears to be in good working order (except that output shaft splines - I'll need to replace the shaft).

The output side crank main where the looseness was most noticeable doesn't look catastrophically failed. The core moves a little bit when prodded with a screwdriver and it's a little noisy when turned by hand, but thankfully the OD of the bearing appears firmly pressed into it's bore in the case. There's even a cast in iron sleeve that it rides in, which is a reassuring touch, especially with the mighty 500. I think that the problem is the crank journal - it slipped out of the bearing without any resistance, and the journal surface looks a little chudded, like it's been rolling/spinning a little. Will most crank rebuilders be able to spray/weld/sleeve/chrome and grind this back to spec?

I will need to investigate the engine and transmission innards in detail before I know for sure, but so far the damage tally is:

Topend:
- Possibly stock, 23 year old bore needs a replate.
- Cracks between KIPS booster ports and central port
- Pin shaped extension on one KIPS drum valve broken off, but seems to be holding the valve in place anyways
- Exhaust spring mount worn completely through in one place

Bottom end:
- Rod/bearings worn out
- Output side crank main bearing worn out, corresponding crank journal worn
- Transmission output shaft/sprocket splines damaged
- Kick start idler gear bushing wallered out

External
- Needs new fuel tank
- Kick starter broken
- Need to investigate rims/spokes for tension/true
- Front pipe mount broken off next to engine
- Threaded insert for side plastic missing in subframe

- Whatever else I haven't discovered yet!

Time to tally up the damage one last time in detail, start planning/budgeting, getting parts shipped out, and doing other work while I wait for them to come back...

[sandblaster]

Be sure to get all new cir clips for your trans...
Replace them all...

[MeanGreenMachine]

Oh yeah! That's a good idea... Any other must change/problem parts while I'm in here? Are worn circlips usually the cause of losing 3rd gear and other problems?

Also on another note, does anybody know if a crank rebuilder typically offers a service to weld or chrome up bad journals and regrind?

[bansheedave]

I just rebuilt my kx250 bottom end due to a circlip breaking apart. Took out a gear and allowed the gear to rub the shift for. Grooved the fork but didn't damage it to bad. New clips equal cheap insurance.

[MeanGreenMachine]

Ok guys... This is the part where I sacrifice (the remains of) my wallet to the great entity that is Kawasaki. I've fully disassembled the trans and every last bit of the engine, and prepared "KX Casserole" - I had a pretty easy time getting all the bearings removed from the case halves with the oven method.

It turns out that I spoke too soon, and found more damage in the transmission. As you know, the output shaft is boned due to badly worn chain sprocket splines. Ok fine. I found today that 4th gear (labeled 13260-1020 on the exploded diagram) is wallered out and the input shaft is galled in between the 2 circlips where it spins. So it looks like I need input and output shaft, and 4th gear... There is a trans assembly out of a 91 up on eBay right now for less than it'd cost for the shafts and gear. How common is this problem? Where does 3rd fail? How likely is it that these parts could come with the same problem?

[edit]: The bearings that I extracted from the case halves are the same as Motorrad mentioned in his thread:

Main: 2x Koyo 6306
Trans (L): NTN 6305, NTN SXO391 (OEM#     92045-0013)
Trans (R): NTN 63/22C3 (Plastic cage, of course...), Bushing (OEM# 92028-131)

Shift Drum: NSK 6905
KIPS governor: 608 (Make unk.)