sudden 'lurches' at high speed

[craig r]

Hi everyone,

had my 2200TC out on the motorway last weekend. I only took it up to 60mph max and it seemed to handle it very well. However I did notice that when at around 50/60mph If i eased off the throttle, even very slightly, when I applied pressure again the car would make a couple of little 'lurches', as if it had cut out for a split second then fired again.

Any thoughts on what this could be? Is it common? Carb issue maybe?


Cheers,


Craig.

 

[pat180269]

Could be an air leak. If extra air is being dragged in at high rpm (not through the carb inlets) then it will lean out the mixture which can cause the hesitation you mention. Check you have oil in carb dashpots also

 

[craig r]

Could be an air leak. If extra air is being dragged in at high rpm (not through the carb inlets) then it will lean out the mixture which can cause the hesitation you mention. Check you have oil in carb dashpots also

Thanks Pat. The rocker cover is leaking and needs a new gasket, would this cause the extra air to get in?

I was going to take the dashpots off and give a wee spray of WD40 incase the piston was sticking. Should there be oil in there?


Craig.

 

[pat180269]

What you describe is likely caused by a weak mixture.

Check all pipes that go into the inlet manifold for splits and leaks; breathers , vac for servo, anti run on valve, distributor etc.

The oil in the dashpot and the piston act as a damper to slow the initial rise of the needle richening the mixture when the throttle is opened, similar to the enrichment effect of an accelerator pump in a conventional carb . If there is no oil in the dashpots the mixture can lean out when you snap open the throttle after cruising this will cause hesitation and misfire as you describe. Unscrew the plastic cap on the top of each carb and fill to within 1/2" of the bottom of the cap threads with engine oil.

Pat