Running with worn/damaged cam chain guide

[Mitch81special]

I was talking to a local mechanic about replacing my cam chain guide. I found a few pieces of it in an oil change, I can also hear some ticking. He said I was crazy for running it if I knew it needed replacing. Am I taking a big risk running it?

 

[5twins]

It's hard to say. It depends on how far gone the guide is I guess. Unfortunately, there's no way to know unless you take it apart. There's no way to see in there and inspect it with the motor together. If the rubber bits were just from the lip along the sides of the guide, you're probably OK for a while longer. If the whole rubber strip has come loose and fallen off, maybe not. Then the chain would be running against the bare aluminum guide base and grinding into it. You could dump and inspect your oil. If it's all full of metal flakes, that usually means the chain is grinding into the aluminum.

So I'd say at least start collecting up the needed parts because a cam chain guide replacement is in your future.

 

[Mitch81special]

a cam chain guide replacement is in your future.

Thanks 5twins, that's my plan. This winter I'm going to pull it apart. It's my first time doing it so I'm sure I will be posting on here frequently looking for advice. Do you think theres anything other than the guide itself I'd need?

 

[5twins]

If the motor has anywhere near 20K on it, I usually replace the chain too. If it's never been apart before, you usually want to replace the valve guide seals. They're rubber and now like 40 years old. Other things will depend on what you find once you get in there. Rings may need replacing if the end gaps are too big (and they usually are). If the cylinder to piston wear is past the limit then you'll need to do more, have it bored out oversize instead of just rings. Most I've been into were able to get by with just rings. But the next time they're gone into, a bore will probably be needed.

Some of the valves may be leaking but that can usually be fixed by just hand lapping them back in. Bottom line - it's quite a bit of work just getting into one of these so it's best you do all that needs doing while you're in there. Figure about $150 to $200 in parts if you don't have to bore it, maybe another $150 or so if you do. Of course, this is doing all the work yourself save for major machining operations like the boring.

 

[Rasputin]

Speaking of cam chains. Can anyone confirm the number of links. The chain out of my 447 engine has 106 links.

 

[5twins]

Yes, that is correct for all '74-on "447" motors. The early '70-'73 "256" motors used a different shorter (102 link) chain.

 

[Mitch81special]

Would that be the same number of links on my 4M4?

 

[5twins]

Yes, all motors from '74-on are referred to as "447" motors, even though the beginning of their serial number may start with something else. They all had the same cams but more importantly, the the same cam and crank sprockets for the cam chain.

 

[Rasputin]

Thanks for that.

 

[jetmechmarty]

FWIW, my original to me XS650SK is approaching 60,000. I had to take the bottom cover off this year. Years ago I found a bunch of those rubber bits in the sump. I can see the guide from the bottom. Where the chain tracks is good. I’m not ready to overhaul, so I’m going to keep going. There are other projects I want to do with my precious little time.
Also, experience tells me, when the rubber is gone you’ll be out of adjustment on the chain. You’ll hear it as well. Right fellas?

 

[thuban]

FWIW, my original to me XS650SK is approaching 60,000. I had to take the bottom cover off this year. Years ago I found a bunch of those rubber bits in the sump. I can see the guide from the bottom. Where the chain tracks is good. I’m not ready to overhaul, so I’m going to keep going. There are other projects I want to do with my precious little time.
Also, experience tells me, when the rubber is gone you’ll be out of adjustment on the chain. You’ll hear it as well. Right fellas?

I don't know but I'd bet money on it! 60,000 Wow, that's great. JMM, do you change the oil every, what, every two months if your not riding. I've forgotten.
( Don't want to start a fight with the other fellers either!)

 

[jetmechmarty]

I don't know but I'd bet money on it! 60,000 Wow, that's great. JMM, do you change the oil every, what, every two months if your not riding. I've forgotten.
( Don't want to start a fight with the other fellers either!)

I am not very organized. I’m not good at keeping records. I am however, very good at running machines far beyond their life expectancy. I drove a Dodge Neon 300,000 miles after three teenage girls had their way with it. I sold it, running perfectly, ac and all for $400. So, yes. I change oil with regularity, but I’m usually just guessing that it’s time. My XS650SK has been well used, loved, and cared for.

 

[MaxPete]

If the front timing chain guide fails (the black plastic slipper channel fails off the metal shoe), you will likely hear a knocking sound like a conn rod. You will also find a lot of black plastic chunks in the sump.

I described all of this in “Lucille pulls another one on me” in this forum.
Pete

 

[YamadudeXS650C]

FWIW, my original to me XS650SK is approaching 60,000. I had to take the bottom cover off this year. Years ago I found a bunch of those rubber bits in the sump. I can see the guide from the bottom. Where the chain tracks is good. I’m not ready to overhaul, so I’m going to keep going. There are other projects I want to do with my precious little time.
Also, experience tells me, when the rubber is gone you’ll be out of adjustment on the chain. You’ll hear it as well. Right fellas?

I am very impressed with the longevity of your SK !
I also have an SK in my collection, and it has recently turned over the 20,000 mark.
I've begun to worry a bit about what is going to maybe wear out.
It has been well taken care of by the PO, never sat idle in a barn, and I've maintained it like it was my child,
and it isnt making any peculiar noises,
So, your experience supports letting go of my worries. I think its going to give me 80,000 miles with nothing major occuring.

 

[jetmechmarty]

I am very impressed with the longevity of your SK !
I also have an SK in my collection, and it has recently turned over the 20,000 mark.
I've begun to worry a bit about what is going to maybe wear out.
It has been well taken care of by the PO, never sat idle in a barn, and I've maintained it like it was my child,
and it isnt making any peculiar noises,
So, your experience supports letting go of my worries. I think its going to give me 80,000 miles with nothing major occuring.

View attachment 176457

Yes, no worries. I am my own PO. I got my new bike when I was 24 years old. I am so much smarter now!

 

[MaxPete]

when I was 24 years old. I am so much smarter now!

...aren't we all Marty..aren't we all.

Pete