cam chain tension

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paul-haggis

Guest
Hi Maurice,

rather than thinking of an absolute engine position, it is easier to observe the cams themselves.

by slowly turning the engine you will be able to see a position where the valve springs are pushing on the cam lobes in such a way as to force the cam wheel 'tops' towards each other - this will be the position where the chain between the cam wheels is the loosest and chain tension is easiest to read.

Remember to complete at least 2 full rotations of the crank to see all the possible cam positions.

Hope that helps, Paul H.
 

Rob

Hero member
Location
Midlands, UK
The factory handbook indicates that cam chain tension should be checked with the inlet & exhaust cam lobes on the primary drive side of the engine facing away from each other.  In practice there are a couple of other positions where the chain is not heavily loaded and tension can be checked.  For peace of mind I like to check at these points too for tight spots, in the same way as you would for a rear drive chain.
 

johnwh

Full member
Hi Cam,
You got me thinking because I usually rotate over TDC on center piston a couple of times until I get the one with the most slack.I would guess probably compression.
John
 
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paul-haggis

Guest
Hi Maurice,

If you have fitted a new tensioner blade it will not yet have settled into a fully conforming shape and will be acting a bit like a spring, against which the cam lobe force pushes and pulls - this can contribute slightly to an apparent variation on cam chain tightness as the cams roll over. However the variation in cam chain tightness is due to the way the inlet and exhaust cams work against each other - through the chain - pulling through it or pushing it together.

Paul H
 

nick7

Hero member
Well, maybe I got it wrong :embarrassed: As readers of the ILOC forum will know, my tensioner is in 2 pieces, one bit in the gearbox preventing selection of first gear...though as per the article posted there, this is by no means unknown. As my engine is coming out for other reasons anyhow, its not a big issue, though i am hoping to fish the thing out with a magnet once it is on the bench rather than split the cases..looks in one untouched piece from the view of it through the side of the crankcase (too small to fish iy through....)
Consensus seems to be that there are some duff tensioners about...for sure this one not very old.
Nick7
 
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noneglibob

Guest
Nick, Have you considered disconnecting your cam chain tensioner altogether...it isn't really doing very much........ :D :D
 

Rufustbear

Hero member
Location
Manchester
Nick if its in half it means you have worn through the metal part, split the crackcase,s clean out the crank bearings you will reget if you don,t
 

laverdakeith

Hero member
I recon it will have snaped clean in half rather than worn through, got one here out of Reggies' RGS that has been fitted backwards at some point in its life, I'll post a pic later.

    Keith
 

nick7

Hero member
Bob,
No, it differs from accelerator pumps in that respect :kiss: Btw, did you test your bike with/without and if so with what results?
And Rufus, it did not wear through but I am sure there is merit in rinsing out  because the chain is dragged over the remaining end and into the metal...mind you, that will have dumped less crap than when my middle piston disintegrated a while back because of  massive pre-ignition caused by a short in a pick up (all that old wiring will be going too as the Redax sourced ig system will be fitted this winter too).
Nick7
 
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