How'd this happen? Timing chain slip

K I'm gettin to a point where I'm ready to sell my xl6's cuz of the constant headache they are, so I got it with bad rings and it smoked bad, fixed that, 300 miles after break in and my wrist pin clip pops out destroying my cylinder, fixed that, 50 miles in the break in on the new cylinder and my timing chain slips??

I'm more curious how it happened to prevent it again, I rode it to work, rode it home from work, stuck it in a trailer to take camping, road was bumpier then I though so my bike tipped over in the trailer on the kickstand, picked it up went to kick it and something was jamming the engine up, sometimes, checked valve clearances and my intake were way way out.. if I put them to where they should be, then the bike jams up

Well I finally got the engine out again this morning and pulled the cover and this is what I saw, my piston is in top dead center in the pic, look where my cams at?? I can understand it slipping a tooth or two but not this much

Already have new replacement chain, tensioner is still tight.. I think I'm gonna need new intake valves and let's hope not a piston or a head considering this is the third piston in this engine since I got it

Forgot the pic

1379542923319.jpg

If you indeed have it at TDC you are out on the timing a plie.........

 

Change the tensioner and pin that goes through it,,,,,,,and the chain...

 

Have you checked your choke plate to see if it`s OE,,they fracture,,get swallowed and nuke the top end too..

 

You may have bent the valves...take the chain off,,set the cam and crank to TDC..........lock the crank with a powerbar with a 17mm socket on the crank through the removeable cover on the stator.........wire the powerbar to your footpeg so it can`t move..

 

Get an adapter from a compression tester and hook it up to shop air pressure.......air the cylinder up........

 

Now take a bic lighter and hold it up to the exhaust outlet...........and then the carb inlet.........if the flame flickers badly or goes out you know which,,if any,,,valves are NOT sealing well.........

 

B

Ya, its way freakin out, so I already have a new chain, but I should get a new tensioner and pin? I was think just a new tensioner spring?

Sorry, I know two valves are bent, I just think it was the intake because the were so out of wack, I can turn the engine over by hand with all the valves shut, theirs no compression... :(

I just wish I could figure out how it happened, because no matter how hard I try i can't get the chain to move around on its own, the tensioner still has it hard

Were the sprockets in good shape?  Check the shear pin/key on the flywheel.  When it was tipped over in the trailer was it leaking fuel?  If so, could the cylinder have filled up with fuel and hydro-locked (seams like a long shot).  Stranger things have happened though.  If so, then the oil would have gas in it as well.

 

ME

Edited by kmequint

If you indeed have it at TDC you are out on the timing a plie.........

 

Change the tensioner and pin that goes through it,,,,,,,and the chain...

 

Have you checked your choke plate to see if it`s OE,,they fracture,,get swallowed and nuke the top end too..

 

You may have bent the valves...take the chain off,,set the cam and crank to TDC..........lock the crank with a powerbar with a 17mm socket on the crank through the removeable cover on the stator.........wire the powerbar to your footpeg so it can`t move..

 

Get an adapter from a compression tester and hook it up to shop air pressure.......air the cylinder up........

 

Now take a bic lighter and hold it up to the exhaust outlet...........and then the carb inlet.........if the flame flickers badly or goes out you know which,,if any,,,valves are NOT sealing well.........

 

B

Brianhare, I don't think the XL6's have a choke plate.  Don't want to confuse anyone.   I know its a rarity that I think.  :lol:  

 

ME

Edited by kmequint

Oh ya, I meant to ask what the choke plate was..

So if I remember right, when it fell over, it was on its kickstand, and some of my camping gear, but the kickstand made it higher so the carbs were lowest on the bike, but I can't remember exactly

I'm afraid it was the bottom sprocket now that you mention that, well actually I mean, I hope it was that so I can fix it, I did notice when I tried to pull the chain tight by hand and I would also try and center the piston at tdc by pulling on the chain by hand and it would slip, a lot, when I pulled hard

All the problems you are having is the reason why whenever I rebuild an engine I replace all wear parts period.  I also do a bunch of research and find out what other parts fail on whatever engine I am working on.  That way I know everything is new inside and the odds of something else breaking is slim.  In order for you timing chain to slip it must have a bunch of slack in it.  When you put it together the second time did you check the chain for stretch?

Oh ya, I meant to ask what the choke plate was..

So if I remember right, when it fell over, it was on its kickstand, and some of my camping gear, but the kickstand made it higher so the carbs were lowest on the bike, but I can't remember exactly

I'm afraid it was the bottom sprocket now that you mention that, well actually I mean, I hope it was that so I can fix it, I did notice when I tried to pull the chain tight by hand and I would also try and center the piston at tdc by pulling on the chain by hand and it would slip, a lot, when I pulled hard

I think you might have answered your own question.  One of the sprockets is no longer available from Honda.  I used the chain and sprockets for a 1990 XR600.  You'll have to replace both sprockets because the chain is not as wide.  I would also replace both chain guides with the original "new" ones.

 

ME

Edited by kmequint

If I remember correctly the 1990 XR600 upper sprocket has "out" stamped on it.  You'll have to put it on backwards to get the chain lined up correctly. 

 

14401-MN1-671 Chain, Cam

14312-MN1-670 Sprocket, Timing 19T

14321-MN1-670 Sprocket, Cam 38T

 

ME

Edited by kmequint

looking at the manual it looks like neither the top nor bottom gear  could slip in the shaft

 

the top is bolted to the cam  and the bottom is on a splined  shaft

 

i feel your frustration

Well ive got a second engine with hopefully a good sprocket, ill compare them, that was is getting a full xr top end with xr chain.. just curious, I've heard a few people say to replace the chain guides

1. I've only ever seen used one

2. How do they really go bad, I thought the chain just kinda glides across the top of it, both my sets look the same, there's no pressure on them, as that's on the tensioner, sorry if I sound snobby, I'm just honestly curios why'd they have to be replaced

And if I were to take them completely out, both chain guides, the engine should still run just fine right?

If I remember correctly the 1990 XR600 upper sprocket has "out" stamped on it.  You'll have to put it on backwards to get the chain lined up correctly. 

 

14401-MN1-671 Chain, Cam

14312-MN1-670 Sprocket, Timing 19T

14321-MN1-670 Sprocket, Cam 38T

 

ME

 

 

Good stuff Quint..I was trying to recall what has to be done to use that later model top sprocket the other day..Knew there was something odd about the setup of it..You're correct,,Has to go on back the front..

 

It's nearly always that bottom sprocket that gets worn out,,tops seem bulletproof..Still to be on the safe side do the lot excluding guides though I did have one of them come apart where they fit in the head on one of my older twin carbs...I'd get the chain ,,both sprockets,,a new spring for the tensioner (they wear on the end where it sits against the head,,don't risk them in an old motor),,guides,,your choice on the danger/risk front with them..I've compared heaps of old with new and can never see any discernable difference..Think I have a bag of old ones around somewhere..

Edited by Horri

Well ive got a second engine with hopefully a good sprocket, ill compare them, that was is getting a full xr top end with xr chain.. just curious, I've heard a few people say to replace the chain guides

1. I've only ever seen used one

2. How do they really go bad, I thought the chain just kinda glides across the top of it, both my sets look the same, there's no pressure on them, as that's on the tensioner, sorry if I sound snobby, I'm just honestly curios why'd they have to be replaced

They get brittle with age.  Also, the one that the tensioner pushes against wears on the back side.  Also the tops of the guides wear a little as well. 

Edited by kmequint

And if I were to take them completely out, both chain guides, the engine should still run just fine right?

The guides keep the chain from slapping around.  Without the guides the engine would eventually self destruct.

Edited by kmequint

I've rebuilt a handful of engines and anything that appears in good working order I usually just leave it, I've learned my lesson, this has been such a big headache.. but I've done this so many times that I surprised my self today, I went out and had the whole engine removed from the bike in just over 10 min without tryin, ya, I've takeing it in and out that many times...

Yeah, I did that the first time I rebuilt this one.  Like you I have had my engine in and out several times.  I should have replaced anything that could have been wore the first time around.  After several head gaskets and two timing chains later plus numerous other parts, I have finally been able to put several thousand miles on mine without a hiccup.  Since I just jinxed myself I will have to tear mine down tomorrow, god I hope not.   :rolleyes:

 

ME

Edited by kmequint

Yes there's hope! Knock on wood.. so I got the rest if my head off, and surprise surprise, my intake valves smashed my piston, so they're bent, luckily I have an extra set.. just hope it didn't hurt my head..

So something very fishy is goin on with my cam chain bottom sprocket, I pulled my tensioner, and then went to untighten those two cam bolts and as soon as I put any pressure on them, the cam would spin and the chain would just slip around the bottom sprocket, now I know there was no tension, but it still should grab right? If its a good sprocket, I haven't gotten to him yet because I can't get that stupid bolt off behind the clutch again.. i need an impact drill..

I sure hope that sprocket is my culprit..

Just curious if you think this sounds fishy, but with my tensioner, I don't have a vice to squeeze the spring to put a zip tie on it, so what I do instead is I took a flat head, and bent the tip into a curve so I could push the spring under the tensioner, I can't really guarantee that I got it right, the spring was still down when I took the head off though, but I could grab slack in the chain with my finger.. I could have also put my old spring back on, I got them mixed up :(

Sorry for the huge post, but one last thing, is there a way to tell when the chain guide needs to replaced? Maybe measure its depth? Because I dont wanna buy another used one, and I could only find one new one for $75

No vice,,I suppose a decent sized pair of vice grips may suffice for the spring crush,,or maybe a G clamp if you're careful..the%

 

Given up trying to edit this,,sites a pain tonight,,see the next post..

Edited by Horri

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