KLX650 Cam Cap failure!

[KevTM]

I have a 1993 KLX650C1 which was running great and had been sitting for 2 days as I was waiting for new tyres etc.

I started her up only to hear a "crack" so shut her down. Took the tank, panels off etc so that I could start her up briefly to pinpoint the area of the now "tapping" noise. Sounded like it was coming from the cams so I took the cam cover off to check timing (which looks ok) but I did notice the leg that picks up the oil from the head on the cam cap had sheered off!

pic:
https://img.photobucket.com/albums/v407/Project_Sapphire/klx650_kev6_camcap.jpg

Is this a common failure? Anyone know any reason as to why it would do this? The galleries don't appear to be blocked.

Do you think having it welded back on would be do-able if I can't find a replacement?

[finpos]

That's very odd indeed, seen as that bit shouldn't be moving, so shouldn't be tapping! were the bolts loose at all? My guess would be it's a secondary failure after something much more hideous like a dropped valve.

You may have trouble with a replacement, that part will have been machined in place on the head to fit the cams, so you can't easily mix and match. (Look at the side of the cylinder head, it'll have two half moon cut-outs where the milling tool went in)

f.

[KevTM]

the leg that's broken off just rests on a o-ring. As you say though it shouldn't move! the tapping noise is only evident now as there's no oil feeding the cams? either that or it was the leg moving around

I don't see how it's possible for anything to even move/jump/etc to break that off.

All the bolts were still very tight, got the usual "crack" undoing them.

The leg fits on nice to the rest of the cap so I don't think a weld would be too difficult and the only pressure on it should really be the oil pressure.

[finpos]

[KevTM]

I'll see if I can get a machine shop to weld it back on tomorrow and try it out and see if the tapping still occurs.

[finpos]

Just a thought - it may have cracked a long time ago if somebody had it apart and didn't follow the correct bolt untighten/tighten sequence (assuming you did )

f.

[KevTM]

Yeah I checked the sequence from the manual before I took it off, and then noticed the sequence is stamped on the cap as well

The last guy that had the bike didn't have much of a clue to be honest. I posted about my battery not charging in here before. Turned out he had it wired all wrong!

[KevTM]

On closer inspection I may have found out why it failed. It seems like someone has used a screwdriver to prise the cam cap up at the base of the "leg" where it seals against the head.. you can see the little notches on both the head surface and the surface of the broken off "leg" possibly caused a hairline fracture?

Don't know why they tried that though as it's fairly easy to pull off without having to prise it to that extent.

[stinkwheel]

[KevTM]

probably which probably means they never bothered with the tightening sequence either

I'd rather have Stevie Wonder working on it than the people before.

[finpos]

[KevTM]

Nah dowels are there but it's still easy to pull it off without tools, done it several times now.

Got it welded ok, started it up and the ticking was still there. Took the head off and there was a small piece of copper or something?! It's a deep plug "cylinder" and I reckon it must have been below the hex on the old plug so when I took it out the bit fell in without me seeing it (changed the plug the other day) - Anyway, minimal damage done, little mark on top of piston and a little on the head but wont cause any probs.

Put it back together but having difficulty getting the slack out the upper cam chain, bit of a nightmare. Chain guides are correctly in place so no idea what it is.. will try again in the morning.

[KevTM]

All back together and sounding fine, exactly as it was before. Only had it ticking over with a few mild revs thrown in until the fan kicked in - all ok. Will take it a run later, fingers crossed!