Cam chains

[Anonymous]

Hi all please confirm my supicions. My cam chain makes a hell of a noise so after checking things I have decided to replace said chain, I removed the carbies and using a spanner rolled her over to no1 TDC then removed the tensioner as per the manual, its ok. Then just for fun rolled her back again so the chain was lose and the rear tension guide was in the fully back position (no tension on the chain) then I used a screwdriver and carefully pushed the guide forward so there was tension on the chain again. The guide was quite 'tight' to push forward needing more pressure the spring of the automatic tensioner could provide. Is this normal, is the guide stuffed (in dire need of replacement)
Any Ideas ?

[earlfor]

Re: Cam chains

The amount of tension the automatic tensioner exerts on the cam chain is not extreme and does not need to be. Does the tension guide move forward to engagement freely and then become more resistant as it engages the chain, or is is resistant to any movement even when the chain is slack? Did you check the tensioner operation to see that the spring and rod release and move out smoothly? If the auto tensioner is working correctly, when you loosen the jamb nut and turn the slotted screw to release the plunger, it will spring out smoothly. Due to the beveled end on the interior end of the rod, it will not be pushed back in my increasing cam chain tension. Once it takes up the slack in the cam chain, it should hold that setting. In pushing the rod in and realeasing it, do you see the spring wind and unwind under the large knurled nut on the outside? When the plunger is released to set chain tension, you should still see some gap in the springs under the large knurled nut (that shows there is still remaining travel and tension available)

I'm assuming you know to lock the plunger down to install the cam tensioner and once bolted up, the jamb nut is loosened, the plunger released with about 1/2 to 1 turn on the slotted machine screw and then the jamb nut retightened. (I dont want to overlook anything....:-) )

You may also be able to rewind the spring beneath the knurled nut to increase available tension slightly.

Since the cam chain tensioner is self adjusting for chain slack, there is no reason to have to position the engine at TDC to remove or install it.

Earl

Hi all please confirm my supicions. My cam chain makes a hell of a noise so after checking things I have decided to replace said chain, I removed the carbies and using a spanner rolled her over to no1 TDC then removed the tensioner as per the manual, its ok. Then just for fun rolled her back again so the chain was lose and the rear tension guide was in the fully back position (no tension on the chain) then I used a screwdriver and carefully pushed the guide forward so there was tension on the chain again. The guide was quite 'tight' to push forward needing more pressure the spring of the automatic tensioner could provide. Is this normal, is the guide stuffed (in dire need of replacement)
Any Ideas ?

[Anonymous]

The guide itself is the culprit I think, it seems to be sticky either way without tension on it. The automatic tesioner moves in and out freely.

[earlfor]

If the tensioner seems to work correctly, that only leaves the guide. The only thing I can think of there would be a worn out mount pin on the guide.

Earl

The guide itself is the culprit I think, it seems to be sticky either way without tension on it. The automatic tesioner moves in and out freely.

[Anonymous]

yep that's where I thought I'd end up, just needed another opinion

thanks. I shall go and dissasemble a bit. I have got the gaskets and I was planiing on chaning the chain regardless so at least now I have an excuse to go right through the old girl (she needs a birthday)

thanks

[Mr. Jiggles]

I'm not sure that I'm clear on what's going on here - you said that you rotated the crank backwards and then noticed that the tensioner would not advance? If so then this would make sense since backward rotation would increase tension on the rear portion of the chain.

Or did I read your post wrong?

[earlfor]

I believe you are reading it correctly. The tensioner has, on the outside of the housing, a large knurled nut with a spring under it. As the internal tensioner rod advances into the cam chain guide, you will see the knurled nut rotate. That verifies the tension rod is moving inward when released from the jamb nut. It is common practice to rotate the crankshaft backwards from normal rotation while observing the knurled nut. It should rotate backwards slightly and recoil/rewind its spring. If it does, then it is working correctly. In this example, the cam chain guide appears to be stiff/sluggish in exerting return pressure on the tension rod. That isnt how it should be. As you note backward rotation would increase tension on the rear portion of the spring and the knurled nut would reverse its rotational direction.

Whether we call that advance in both directions or advance and retract, I dont know. :-)

Earl

I'm not sure that I'm clear on what's going on here - you said that you rotated the crank backwards and then noticed that the tensioner would not advance? If so then this would make sense since backward rotation would increase tension on the rear portion of the chain.

Or did I read your post wrong?

[KEITH KRAUSE]

The fine, outside spring can also lose it's strength over time. This will not allow it to keep pressure on the rod. If you look at where the spring end inserts into the hole in the knurled knob, the "range" of advancement will be about 7:00 to 5:00. My spring had got weak and stopped advancing at 1:00. This allowed the chain to become slack. Before re-assembly, I pulled the spring end out and wound it counter-clockwise one full turn and re-inserted it. Now the knob/spring advances through the entire range and the chain noise is gone.

[Dink]

If the guide is stiff of tight , you will need to remove the inlet cam to get to the bolt that mounts the guide as it is deep in the cases.
Dink

[Mikael]

Hi,

I experienced a similar problem as you describe on my bike. I am currently
in the process of putting my 1150 together, and when I was trying to lower the
head in to place something made a resistance. As it turned out the tension guide
was a bit enlarged just where the tensioner applies its pressure. As a result the
tensioner was just too large to fit comfortably in the camchain slot in head.

I don?t think that the pressure of the tensioner would be able overcome that friction,
so the guide would most like have gotten stuck. I grinded both sides of the guide
so it could swing freely, problem solved.

At least on the 1150, you have to take both the head and the cylinders of in order
to free the bolt for the tensioner guide.

/ Mikael