ionbeam
2 FUN
^^^^ But what about the CCT?
FWIW, my cam chain slippers showed zero wear at 40k miles, wanna see them?
FWIW, my cam chain slippers showed zero wear at 40k miles, wanna see them?
Cam timing experts needed
- Thread starter Harald
- Start date
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Look at page 7 of this FJR document for a drawing showing the chain and guides. Only the front guide (exhaust side) might affect timing.
https://www.fjrforum.com/files/fjr1300guide.pdf
Looking at this drawing I don't understand how fiddling with the automatic chain tensioner could let the chain move about on the crankshaft sprocket.
The lower end of the guide is fixed in position by a pin or dowel. As long as the pin is in place the tensioner has little effect on the guide and chain near the sprocket. In fact when the tensioner is retracted it would appear that the guide would push the chain in tighter to the sprocket since the guide extends down below the pin.
Maybe when you remove the cover it's possible for the pin to come off with the cover allowing the guide to move about.
If the cover isn't removed I don't understand how the chain could move on the sprocket.
https://www.fjrforum.com/files/fjr1300guide.pdf
Looking at this drawing I don't understand how fiddling with the automatic chain tensioner could let the chain move about on the crankshaft sprocket.
The lower end of the guide is fixed in position by a pin or dowel. As long as the pin is in place the tensioner has little effect on the guide and chain near the sprocket. In fact when the tensioner is retracted it would appear that the guide would push the chain in tighter to the sprocket since the guide extends down below the pin.
Maybe when you remove the cover it's possible for the pin to come off with the cover allowing the guide to move about.
If the cover isn't removed I don't understand how the chain could move on the sprocket.
The CCT takes up any added slack on the back (intake) side between the back side of the crank sprocket and the intake (rear) cam. That's what it's there for. The timing is determined by the taut run of chain from the crank sprocket up to the front exhaust cam and then back to the intake cam. If either the chain stretches (wears) or the curved front guide wears, or the sprockets wear, any of those will cause ******** cam timing. The crankshaft sprocket is milled into the end of the crankshaft itself, so you want to assume that is not the problem.
The front and top chain guides are not under a lot of pressure into the chain. I'd guess it is the chain itself that is wearing internally and stretching. I wish we could find a reference on what the allowed wear limits are. The difference between 40k miles and 110k miles may be significant.
The front and top chain guides are not under a lot of pressure into the chain. I'd guess it is the chain itself that is wearing internally and stretching. I wish we could find a reference on what the allowed wear limits are. The difference between 40k miles and 110k miles may be significant.
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RossKean
Well-known member
Didn't realize that. I guess that means that the crankshaft sprocket cannot be changed when the timing chain is replaced. I noticed that the FSM says to change the cam sprockets when the chain is replaced.
Correct. Some other engines have replaceable crank sprockets. Yamaha apparently had high confidence the sprocket would last the life of the engine.
Oh oh. In my search of references on the measuring of timing chain wear, and determination of when replacement is indicated, I turned up this gem:
Timing Chain Wear Assessment with Different Types of Oils - SAE Technical Papers
While this may push this thread into the NEPRT zone, those fellows that have noticed their timing retardation after 100k miles may want to compare notes on their oil choices.
Oh oh. In my search of references on the measuring of timing chain wear, and determination of when replacement is indicated, I turned up this gem:
Timing Chain Wear Assessment with Different Types of Oils - SAE Technical Papers
While this may push this thread into the NEPRT zone, those fellows that have noticed their timing retardation after 100k miles may want to compare notes on their oil choices.
You may not see enough clearance, but it is definitely there. Removing the tensioner allows the guide arm to pivot in and create enough slack even with the pivot pin still in place. There is room at the bottom sprocket for the chain to skip teeth on the crank sprocket. The fact that It happens all the time (I have observed it) is all the evidence you need.
ionbeam
2 FUN
I can attest that this is true. In fact with the original CCT the crank sprocket can skip teeth with the CCT still installed.
The crank sprocket is press fitted on the crank shaft but still can't be changed.
I did not know this, and not sure how you know it, though it certainly makes all kinds of sense. The sprocket needs to be fairly hardened, while the crank only needs to be hardened in the bearing journals, not the masses. If I were making crankshafts I would certainly make it replaceable. Not sure how much Yamaha saved by not doing so.
ionbeam
2 FUN
It was pressed on my '04 anyway. I have held my crank in my own hands
Very interesting. Rotella 15w40 has been used every 5,000 miles on my FJR except for maybe 3 oil changes with Yamalube once and a couple with Rotella 5w40.
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