finaly got my 340 dl (cvt) running ok...ish however after 10 min or so of running it begins to run poorly and even cuts out

when checking all the usual things i find that the spark plugs are soaked in fuel.. so i clean them up and it runs ok again for 10 min or so then same problem, thought it may be running to rich at the mix but if i make the mix any more lean it wont idle without foot on gas.... any thoughts anybody?

can you not lean it out, but increase the idle speed?

no.. if i increse the idle speed any more the transmission crunches when i change between n and drive and also if i increase it any more it tries to move when in drive and no gas applied wich a cvt should not do :S

have you setup the carb with a warmed up engine or cold?

when it was setup on a warm engine it sounds like you've just covered up a sympton by adjusting it;

what condition is:
- oil + filter
- valve clearence
- ignition parts (dizzy, rotorarm, leads, plugs)
and have you checked the carb for faulty gaskets; arleaks; poreus membrames, blocked jets, worn o-rings, loose copper rings, leaking floaterneedle, floaterheigt etc?

carb is good as it was recently re-built , oil, filter, plugs and leads are new....dizzy cap and rotor arm are in good condition.

ok... have just descovered that its only firing on 2 cylinders checking seems to show spark at each plug....any ideas what the cause could be?..... was thinking possible loss of compression due to failed head gasket as the 2 that arent firing are next to each other

Get a compression tester, they're not that much money. A good engine will give immediate good compression readings.

ok will do that...

if it is lack of compression in the 2 cylinders should i be looking at changing the head gasket you think?

if there is a really low compression on those cylinders than yes it's time to pop the head and inspect it

which cyl aren't firing? try cleaning the TDC sensor first or replace it with one you know is definatly ok

counting from the end nearest the dash.... its 1&2 that arent firing...... have checked and all plugs are firing.....so figure it must be a compression issue??

yeah possibly but i'm stunned; i have never heard of this before on the 1.4 and i know these engines from 76 till 92 and from running great till reving into destruction...

the 1.4 headgasket is very rare to fail compression wise; it could also be 2 broken liners but 2 at a time on a bone stock engine is just as rare.... in the "out of the box" thinking style; the camshaft has a weak point right after the distributor link, the cam could have broken just behind that due to non properly lubricated cam bearings on the first 2 cylinders...

that probably means engine=exit; but you can check this to be sure by removing the valve cover and rotating the crank a few times; if the valves on those cylinders aren't working you know enough

you do get fuel into those cylinders?

yes i get fuel to them..

ok. ive had the head off and descovered that one of the valves is stuck in the open position....woud this cause the poor running and anyone know how to fix this??

Is the valve seized? Is it attached at the top?