Got defeated this weekend

[trbig]

Right before the Bob Jones rally last week, Bohn Frazier went to adjust his cam chain tensioner. He put the timing on mark on the C, removed the tensioner, pushed the plunger in all the way, re-installed, loosened the set screw and heard a "click", then tightened it down. When he went to start it, it didn't sound right he said. So he was told to try to adjust it again.. so he was turning the crank back to the C and said it felt "Notchy". Then it wouldn't start at all. He called me to ask my opinion, and I told him the notchy feeling was probably the crank gear jumping teeth on the chain and it is now out of time with the possibility of bent valves.

He brought the bike down to Texas to John and Kat's for me to work on. I took off the valve cover, loosened the cams, put the crank on the "T" and re-installed the cams in time, got everything tightened back up, held tension on the adjuster bar and turned the crank enough to check the clearances on the cams to see if anything was way too wide which would mean a valve hung open. (Bent) Most of the valves were too tight which was a good sign. I checked them all, removed the cams again and reshimmed correctly(Easiest to just remove the cams since all but two needed shims) then re-installed. I then spun the crank to the C and pushed in the plunger and installed the adjuster, let it off, heard the click, tightened it back up, then went to roll the motor around a couple times... and it felt notchy again. Checked the timing, and the crank had apparently jumped a couple teeth AGAIN.

I removed everything and started again.. got everything back in time an cams re-installed, adjuster re-installed, and rolled the motor around a couple times. Everything still looked in time, so we did a compression check. A little low, but it was a cold motor. So I assumed we really lucked out and no valves were bent. Looked at the chain again and it looked loose. I pulled on it, and it was. Rechecked the timing.. and it was off again!

So.. thinking maybe the adjuster spring was bad(There weren't any burrs on the shaft) or a chain guide bad, we quit for the evening. Next morning, I took off the cams again and looked down at the chain guides. We did notice that the front one wasn't centered in the adjuster hole.. but I couldn't remember if this was normal. Sometimes when I would push in on the adjuster, it felt notchy.. other times smooth, but I couldn't see what would cause anything. I could see two of the bolts holding the chain guide and they looked fine.

So... cams back in again.. everything in time.. again. This time I pushed in on the chain guide with a ratchet handle to be sure all the tension was out of the chain. I swapped the adjuster shaft and spring on the tensioner with one I had brought with me. I left the adjuster fully extended this time but with the set screw loose and installed it. There wasn't a lot of adjustment left in the plunger, but there was a bit. I thought maybe a stretched cam chain, but when one gets stretched, the dots on the cams don't line up exactly with the arrows on the caps.. these do. I then tightened the set screw and started putting it back together. We cranked the motor a few times to check everything and it looked good.

When we got it together, we went to start it and try to synch the carbs.. but when we started it, it sounded like there was no adjuster in the motor and the cam chain was grinding against the valve cover... and it popped and backfired a couple times.

SO.. assuming it either jumped time again, or there was a valve slightly bent. He's taking the bike to a guy that actually works on these motors and rebuilt the bike innitially (Also who did all the work to Maximan's old XJ). He'll pull the head to check things out better and check the valves, but this one has me absolutely bumfuzzled. I just can't figure out what was wrong. Timing and chain adjustment is pretty straight forward, but this one is kicking my azz. It really really bothers me that Bohn is taking it to someone and he'll have to spend all that money on it, but we are supposed to take a trip to Colorado in a couple weeks, wants his 1100 ready, so time is getting short.

Sorry so long, but just wondering if any thoughts on this to pass forward to Bobby. (The mechanic)


Tod

[Russ79]

Hey Tod,

It sure sounds like a stretched cam chain to me. If the adjuster is all out of adjustment the chain must be stretched to the point that the slack cannot be taken out of it. Bohn rides a million miles a year, so it would not surprise me it is just worn out. Something else to consider is what do the sprockets look like. A worn out sprocket could cause it to jump time on you, or broken off teeth on the crank shaft sprocket could also cause the chain to jump. I'm just grasping at straws here, so take it for what it is worth, Ha Ha. Also what does the cam chain guide look like? is it worn out or broken, this could also cause the cam chain to be unable to be adjusted. Sorry to here of your butt kicking, but it sometimes happens to the best of us! If there is anything I can do, just give me a shout. Hope this helps

Russ

[oldyam80sg]

No thoughts to pass on,but i assumed i had this cam chain tensioner procedure down pact the last time i adjusted it.Went to start bike and would not start.Finally started it and heard the sound i didn't like.Kind of a oh --it moment.Stopped what i was doing and looked at the manual and this site and tried it again.Finally stopped making bad noises and think that the XS11 Gods were looking down on me.Also RTV'ed the little rubber plug and have not had a drop of oil since then.Good luck!

[79XS11F]

This is not likely the cause but I did have a similar situation on the first rebuild I did and as it turned out the cam chain was not on the blasted crank sprocket. It would turn with the crank because of the tight fit between the crank sprocket and the crank but would slip with a few turn overs. The marks would line up on set up and the chain would have its tension removed by the tensioner as you describe. I only solved this and saw the prolbem when I looked down the cam chain tunnel with a strong flash light.
Rob

[Big Daddy Funk]

Just thinking out loud...

To the best of my knowledge Tod, you did it all exactly right. The only thing that comes to mind is if the chain and the chain gear on the crank become more like fish hooks than teeth from excessive wear. I have seen this on cars but not a bike. The crank cam gear holds the chain past the point where they would normally separate. That makes the chain tighten and then loosen quickly between the crank and cam gears. Easy to set up in the static position but goes out of whack when turned over. It could skip a tooth.
Just thinking out loud, maybe help a little. I would be interested what the problem was when you find out. Thx Rick

[Big Daddy Funk]

Happened to me too

A little embarassed at time but I did this too.

This is not likely the cause but I did have a similar situation on the first rebuild I did and as it turned out the cam chain was not on the blasted crank sprocket. It would turn with the crank because of the tight fit between the crank sprocket and the crank but would slip with a few turn overs. The marks would line up on set up and the chain would have its tension removed by the tensioner as you describe. I only solved this and saw the prolbem when I looked down the cam chain tunnel with a strong flash light.
Rob

[Ken Talbot]

Sure sounds to me like camchain wedged in beside the crankshaft sprocket rather than on it. Getting the chain properly on the sprocket and held on while you get the cams in and lined up is tricky at best, but is a bit easier if the bike is on the centrestand.

[wa407mpp]

That is not the way to adjust the cam chain, they are self adjusting, all you have to do is line up the marks and loosen the lock bolt and it will adjust it's self. Doing it the way you did will put undo stress on the chain and if it is an old chain you probably damaged it or a least stretched the h out of it. It sounds to me like the damage was done before you worked on the bike, so don't feel too bad.

[thewiz]

Agree with Mr Talbot

on this one Tod. Had a similar thing happen on the last one I was working on. Chain was wedged between the crank sprocket and case. Bedeviling.

[trbig]

That is not the way to adjust the cam chain, they are self adjusting, all you have to do is line up the marks and loosen the lock bolt and it will adjust it's self.

If you read through the post, you'd see that doing it the "right" way didn't get the slack out of the chain. Installing an adjuster with the plunger all the way out and not locked, will NOT put too much pressure on the chain. It makes it harder to install by screwing in the bolts against the spring pressure, but the pressure would/should be the exact same as doing it the "Right" way. By doing it this way, I could guarantee that the plunger was extended and not hanging up.

It sure sounds like a stretched cam chain to me.

The chain wasn't too stretched out.. the plunger wasn't extended completely out and all the timing marks lined up perfect. As an old chain stretches, the cam timing marks will start seperating. After a while, the intake dot will be slightly towards the rear of the motor and the exhaust in front of the arrow towards the front of the motor due to the longer length of chain between the cams.

The first time I ever changed out a cam chain, I also had the problem with the chain being BESIDE the crank sprocket.. and got a head full of bent valves. This is one problem that I am very aware of and triple check... and wasn't the problem here. Also.. the crank gear and teeth looked just fine... looking at it from the top of the motor anyway.

The one thing that I'm uncertain of, is when he started the motor the first time and the chain was loose, it could have damaged the rear chain guide since the chain is getting slung that way first. It is also more difficult to see. Also, one time when I went to remove the cams, I removed the tensioner, but the chain still had tension on it somehow. I would rock the crank back and forth to try to get some slack and finally would after a jump like it came loose from something.

I don't know.. it sure has me scratching my head. I'm sure all will be revealed when the head comes off. In the great words of the Queen of Hearts from Alice in Wonderland... "Off with yer head!!!"

Tod

[Crazcnuk]

This is exactly what happened to the 80G, last time I killed it. (It's still dead).

I was replacing the tensioner because the plug on the end fell out somewhere on the road.

My cam chain was never off the sprockets, but the first 'click' didn't actually put any pressure on the chain. After cranking it over, and noticing the wrong sound immediately, I let off the lock bolt and heard a 2nd, louder click.

By this time the timing was out about 160deg.

Later, when I took the head off, I didn't see any bent valves, although I don't know how that would be possible.

[79XS11F]

I would rock the crank back and forth to try to get some slack and finally would after a jump like it came loose from something.
Tod

Hey Tod, Now that's really starting to sound like the cam chain beside the sprocket. I have built a few of these engines now and would swear on some builds that it's on at the bottom when it proves to not be. I have found that even across the short distance of the cam chain sprocket on the crank, the cam chain can be 1/2 on and 1/2 off. Feels real good when setting up but then goes loose as soon as the crank is turned. There's not really much else that could cause this situation.
Rob

[Ivan]

I think there is something causing the chain to tighten up and push the adjuster back.

After talking to you and understanding your abilities, I am reasonably sure you have done everything correctly. So the only conclusion is that something is causing the cams to bind up and pull a bunch of tension on the chain forcing the tensioner to retract. I am at a loss as to what might cause this, as the tensioner is on the slack side of the chain, and the crank should be pulling the other side. Battery hooked up backward maybe? Longshot but it almost seems the engine is turning the wrong way.

I am truly as befuddled as you.

[trbig]

LOL.. No, the motor isn't/wasn't turning the wrong way and the chain was on the crank sprocket. We cranked it without the plugs in it with the valve cover off to make sure everything looked good and had some compression before putting back together the last time.

It's a big mystery that hopefully this other mechanic can enlighten me on. I don't mind finding out I did something wrong and was a dumbazz because I can learn from it.. and I like to make fun of ME as much as the next guy.. but after all the times of working on these and doing the things that have always worked before, only to have them not work here and not see any problems... bugs me pretty bad.


Tod

[XJOK2PLAY]

Tod...

Wow... man I'm sorry to hear this things become a "B"!
If I understood your last post, you could crank the thing over and over and watch the chain and cams work perfectly for many rev's w/o the plugs in... and all was well? But as soon as the plugs went in and compression was restored, it all went South? Ivan may have somethin' there. That is wierd. If anybody, (other than you) can find it, surely it'll be Bobby. To me it sounds like something's off track, down on the bottom, where ya can't probably see, and pressure causes it to jump. But you'd think it would jump regardless. Sorry for Bohn... startin' to sound expensive now. Tell him I've got my fingers crossed for him...