I am not familier with the Carb models ut it doessound very much like either the ignition or fuel system that is breaking down.

Ignition. Go for the cheapest first so check the dizzy cap and rota arm for wear or cracks and tracking marks on the inside of the cap. If the rota arm is burnt at the end clean it on the wall of a tyre. If either look knackered then replace.

Leads are often ignored and breakdown over a number of years utill they fail. If you get a shock from them when the enine is running then the silicone insulation has prbably broken down. Check them for cracks and general deteriation. The carbon leads which are now used have small gaps in the carbon core that forces the power to jump and this increases its intencity. In damp weather moisture gets through old insulation and makes starting difficult and will cause power loss. There is a bloke on ebay selling new sets for under 12 quid so if in doubt replace them. Look at the state of the plugs and adjust or replace. Don't wire brush them as this buggers up the insulation of the inner terminal. If the deposits are black after a run then the car is running too rich. If the deposits are white then too weak. Each plug should have a sandy brown coloured deposit. Adjust the gaps and if any of the electrodes are eroded then replace the set. If any of the deposits are black and oiy then that cylinder is burning oil which will need further investigation.

Assuming these are all fine then check the ignition timing. Adjust if necesary. If the plugs were black with carbon then it MAY be that the timing is too far advanced making the car run rich, if they were white then the tming MAY be retarded making the engine run weak and hot. Isay may as this is one reason and you may find the tming spot on. Use a strobe to chck the timng marking the appropriate timing marks white on the pully and the appropriate fixed point timing belt cover area representing the degrees stated in the Manual or owners handbook. If these are lined up when the engine is running and the strobe pointed at them then the timing is. If they arnnt then loosten the retaining bolt at te base ofthe dissy and turn it eiter waygently until the marks align. Tighte the bolt and recheckthe marks with the strobe for allignment. Make sure youread the Manual to get the correct RPM for chacking and remove the vacuum advance tube if it says to. Once complete replace the tube and tighten the clamp on the dissy. If youfound tat you needed to adjust the timing or replace any igntion parts then run the car tosee ifthe roble persists. If it doesthe turn to the Carb.

ONCE YOU ARE SATISFIED THAT THE IGNITION SYSTEM IS OK THEN TURN TO THE CARB.
This part I am unfamilier with on Sportraks but more than familier on other normally aspirated cars. Again there will be amixture screw that will adjust the fue air mix andif you found that the timing was ok yet the plugs either white or black then the mixture will be ether too richor too lean and the mixture screw should be adjusted accordingly. Normally you turn the screw in by small amounts (The mixture screw has a tapered end that goes into the choke tube of the carb). Screw in utill the engine becomes a bit ruogh then gently screw it out until it runs smooth again screw a bit more out and it will run rough again. Allow the adjusted mix to settle momenterally before screwing in more or outmore. The best setting is in between the two. A colour tune plug would help with accuracy but because the plugs are so deep down I think it would be difficultt use. If you have an exhaust gas anayzer then this will do the job but you can do it by ear. It is possible that the float camber is flooding and forcing too much fuel into the carb. In mostcars this is like a toilet system wit a float and stop cock. If the pin on the end of the stop cock has worn with use then it allows petrol to overfill the float chamber and can lead to an enriched mixture. Carb spindles ware with age ca cause problems by not closing tightly. You can really only check this with the carb off the car. As I said I am not familier with the Carb on the Sportrak and my experience has been with SU and Zenith carbs and maybe copletely innaproprite to the Carb in question.

As for the head gasket, yesthe symptoms could be this but the car would tend to run hot and lose water.If you remove the oil filler cap and if it is full of "salad cream" then this is caused by oil and water mixing but in cold weather a sall amount of this can form due to condensation. Obviously if it is a large amount then it indicates water contamination in the oil.Look at the oil on the dipstick,is it grey?, or normal. Again grey or salad creamy points to water contamination and the head gasket.

I hope this has been of help to you and I am sure that if any part is incorrect then another forum member will correct it.

Good luck

OLDMINIMAN