Hitchcocks Forum

I have been servicing my Twin Enfields for years but I am not happy about the timing chain
adjustment Manual states a 1/4" movement at the tightest spot. When turning the engine over the chain is as taught as a bow string on most of the revolution when the cams are under load from valve springs this to me is its tightest spot but it cannot be slackened off even by slacking off the adjuster completely .To me the chain is far too tight when under load and does cause a slight howling when throttling off .When the load is off the cams the chain is then a bit slacker and can be adjusted I am not concerned about this it is how excessive tight the chain is under load which cannot be good . Has any one out there had the same thoughts or even modified the adjustment to give a bit of slack when the chain is under such load
Duffel

Hi Duffel, the cam chain will appear to be very tight at certain points, because the cams opening and allowing valves to close again will put considerable weight on it. If you try the 'slack' on several rotations where there is any slack between the crank sprocket and the exhaust cam - you might be able to get as many as three valves closed at any one time - you should get a good idea of where it's at. The top run of the chain will appear to be bar tight when the inlet valve of a cylinder is opening as the exhaust valve fir that same cylinder is closing, don't be mislead by this. There will probably be tighter spots in even a new timing chain, that is why I like to check the adjustment over several revolutions of the engine. Too much slack is just as bad as too little, so follow the manual regarding this! Regards, Paul.

I really hate to state the obvious, you are checking the slack in the middle of the bottom run of the chain?

My sympathy. I detest setting the adjustment. Just done mine on an SIA Interceptor. I have set it without the heads fitted (this time) & will be rechecking once heads are refitted, but should not need readjustment, in theory. However, I have one suggestion. Find the slack spots in the chain, pull it hard towards the cases at the two points at which a slack chain usually wears the inner case away. If it touches the case then it will touch when running. If you can't get it to touch the case then it should be OK. TTFN Jack

If it is a new chain there will be some initial stretch, don't worry too much and sort it (check it,) on the first big service. REgards, Mark

Thanks to all that have replied and given tips and suggestions.Hi Papasmurf I was checking the slack in the middle of the bottom run .Thanks Cleggy I made sure the chain was not touching the cases in the slackest run,good tip for the primary chain also let me know the result when you get the heads back on . Mark it is a new chain fitted 500 miles ago to a S11 and will check it after this years Summer after its got a few more miles on it as I will need to have the timing cover of to see if the Oil feed seal is still firmly in place

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Be honest guys, have I got this right, or am I cocking it up?

You do need to turn the engine to find the tightest spot but as you had it both chains looked a little on the slack side to me.

Slackville City, as it was. You didn't show after adjustment. TTFN Jack

Both of those chains are way to slack. She must sound awfull on the overrun.

Ed