Hey all,

I talked with Srinath a bit about this, but wanted to hear your opinions and keep ya'll updated with pics and progress and such.

Got an 86 with what I call a knock. It's more like a loud clank/bang bash / what-the-h3ll-is-going-on in the top end. It sounds like the piston is smackng the head cover (which we know it really can't run that way, but still sounds that way). Odd thing is, it runs great.

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So, I throw it into TDC to check the decomp and valves. When I begin turning the engine over, every 15-20 degrees or the turn there is an audible click from the top end. And it turns over hard.

So, off come the valve covers. Get this: the intake valves are locked in the 'up' position, no matter how much I turn it over, and the exhaust valves start to descend but snap back up (aftter 15-20 degrees of a turn) making the loud clank.

Again, the bike runs without an issue down the road. But, how can it run decently in this condition? I gotta assume the cams still turning. Busted springs? a random loose nut got in the top end jamming things up?

Next begins the tear-down to figure it out.  I'm going to try to pop off the head cover while still mounted due to time and laziness factors. Might as well fix the plug/cap leak too. *sigh*

Any hints/tips/suggestions appreciated.

gotcha. On the intake side, the rocker arms don't move at all. On the exhaust side, the arms start down then snap back up. If the top end seems ok, then the chain and tensioner are next. At least a new chain is on its way I believe.

What might be happening is the cam journals are completely worn out.
Great big egg shape allowing the cam to move forwards and back.  The cam due to rotation will run up against one side.  As soon as the lob comes up it starts to open the valves then shoots over to the worn side dropping the valve.

Very interesting

BTW, there was a head on ebay for $100 might still be there.

I'd get in there and find out whats wrong.  that might be what you need.

If it is not in the head or cam chain adjuster then check your con rod bearings, top and bottom.  I have never heard of an issue with this engine but the old 230 quad sports used to spit them left and right and when they did it sounded very much like you are describing

Guys, you're gonna love this. I wanted to update all here reading this, as I've learned a ton from reading other people's posts.

I finally got around to actually working on my own bike again! only took a month...

recap:

So, as said before, got a mad loud clang bang on the top end. Not a tick, or knock, a downright "Oh my god shut that thing off" noise. When I took the valve covers off and turned the engine over, the front rocker arms push down the exhaust valves about half way then snap back/pop back up, making the rocker arm smack against the head cover stop, causing the noise.

The rear, intake valves don't go no where. This is where I was left at, as I adjusted the decomp and valves at TDC and still had the same issue.

Finally, I got around to working on it, and got the head cover off. While in there, (this is an 86) I found what was left of the hardened, cracked cap to be laughable, so at least that was one easy fix. I was hoping to find something easy; something broken.

The rocker arms, slightly worn, look and act fine. The cam is smooth, not too worn, and everything likes pretty decent, considering. I was disheartened.

As said, the rear valves weren't moving with head and rockers on, so I turned over the engine now with the cover and rockers off. The cam turns fine, with no wobble or lifting etc. So, I'm asking myself, wtf is making these rockers/valves not work correctly?

Stuck valves, I say to myself. So, a little ball peen hammer and some breath holding minutes later I tap all the valves enough (so I think) to maybe break 'em free if sticking. Then, I put the head cover back on but with no bolts, just holding the cover on as best I can while turning the engine over. Of course, when coming around, the head cover lifts up (a heck of a lot harder than my hand can handle), so I use the one main bolt in the center to hold the head on. When turning it over it acts, the same, but with a little bit more movement.  

I'm getting to the point, I promise.

I loosen up the top bolt so there's 1/4-1/2 inch of play, and turn it over again. This time, the head cover lifts, but not much, and to my shock both intake and exhaust valves push up and down freely, with less tick/clang/slap when coming around, as the rocker arms isn't baning very much against the head.

whoo hoo, valves aren't stuck at least. It seems to me (an IT guy, not a mechanic) that there isn't enough "oomph" or power/pressure to push the rockers/valves down with the head on tight. To test this out for sure, I back out the valve adjusters in the rocker arms nearly flush with the arms so that there's only a millimeter or two coming down, slap on the head over and turn it over. This time, with the head cover on relatively tight, the rockers, cam and valves act as the should.

I do the opposite as a test: I adjust the valve adjusters the opposite way (down/in/tight) really darned far, and try to turn the engine over. Click bang snap, the rockers and valves aint moving.

So, I conclude with decent certainty that there's not enough torque to turn the cam/rockers strongly enough to push down the valves. Keeping in mind, though, this whole time in this condition I ran this bike up and down the road for a few minutes through all gears.

I think to myself over the next couple days...wtf...

Last night,m staring at it, choking on a few Marb reds, I get to thinkin' about my riding mower I fixed Friday. The darned thing wouldnt move, even when in gear, but nothing was broken. Turns out the drive belt was so worn and loose it wasn't engaging. Once I replaced it, the mower races around the back 40.

So, applying that useful info here on my forth or fifth smoke, I'm thinking...cam chain?

no..it cant' be the cam chain...that would be too f'ing easy. But, just in case, I drain the oil and pop off the right side engine side cover.

Upon removal, a spring falls on my foot. The cam chain adjuster is shredded and dangling in two pieces.

So, ironically, I never heard the chain slapping because the top end noise was so loud. Turns out a loose chain won't turn the cam worth a dam.


Versy wrote "---Gonna guess, the adjuster fallen apart, the cam chain is slack and it takes 15° to take up the slack when it sloshes forward."

You win.

...you got an adjuster? I'm a needin' one.

-Kit