The Triumph Dolomite Club - Discussion Forum

Hello its tractor boy again. Struggling with a rough idling problem.Engine starts and runs ok when cold but when warmed sounds like a valve has gone off .Took plugs out all correct colour except no 3 which is verey white with no deposits on the nose. Engine doesnt burn oil and runs quietly no tappet noise. It does however appear to sound off a cylinder at the exhaust. Any clues please??

A compression test would seem to be a good starting point here. Its possible there is a tight tappet, the effect would get worse as the engine warms up so do the test with the engine at normal running temp.

Steve

Steve, adjusting valve clearances isn't as easy on the 1850. Valve seat recession isn't really an issue either (the 1850 has hardened valve seats due to the head being made of alloy) but a compression test is definitely worth doing to eliminiate worn piston rings or HGF. The next thing to check is the ignition system and don't assume that new parts are perfect. There are some poor quality new parts (such as as condensers and rotor arms) so make sure the parts are 100% known to be working. Use a strobe light to check the timing. The book figure is a good place to start for the ignition timing. Once you know that the ignition is 100% then you can move on to the carbs. The Dolly Wiki has a good guid for setting up the SU carbs.

Thanks for advice i will do a compression test over the weekend and see what this throws up. Will keep you posted. Thanks tractor boy

I know the tappets are shimmed on the slant, that doesn't mean they have not been incorrectly set by a previous mechanic/owner. The OP said the valve gear is quiet which seems a bit unusual to me, most slants of my experience have a little cam noise, especially when cold. Its also not unknown for the clearances not to be adjusted after a HGF (either through ignorance or incompetence) so, although a tappet is unlikely to tighten up in service, you can still have it happen.

Steve

Hi its tractor boy done compression tests with engine hot. All 4 cyls are the same with little or no variation between the cylinders. Also checked all valve clearances they are ok none are tight. could there be an air leak on the inlet manifold for no 3 cyl. Im beginning to suspect dizzy cap or leads it may be of dubious manufacture. Will see if i can locate an AC or lucas one. Any more ideas lads, thanks tractor boy.

1850 distributor caps and rotor arms don't tend to give much trouble due to the long electrical tracking distances. I know Jonners had the contact tab on the rotor arm break off once though.
Can you get a pair of large heavily insulated pliers and try pulling off each plug lead in turn until you find the one that makes no difference. That would give a clue as to which cylinder the problem is in.
For a standard 1850 my order of swapping things would be ....
* Points ( particularly if the rev; counter needle is jumping about.)
* Capacitor
* plug leads
Then I'd go back to fuel things.
An air leak can be detected around the inlet manifold by spraying WD4o at the joints.
Let us know how you get on.
Tony.

Its a very happy tractor boy, solved the problem.Previous owner had made his own inlet manifold/cyl head gasket from a cornflake box and it was leaking at no 3 cyl joint. Made a new one from proper thickness gasket material reassembled with wellseal and bingo everything is hunky dory. many thanks for all you help and suggestions. tractor boy.

Great news. Love a happy ending .